George H Rieke

Interests

No activities entered.

Courses

Scholarly Contributions

Books

• Rieke, G. H. (2020). Detection of Light. Cambridge University Press.
  More info

  I finished the manuscript for the third edition of "Detection of Light," which has become the standard textbook and overall reference for astronomical detectors (and mare general detector types - it is really a physics/engineering text). All chapters were reviewed and brought up to date regarding new detector types and improvements in existing ones. Particular attention was paid to superconducting detectors, which now merit a full chapter of their own. The remainder of the year and the first part of 2021 has involved reviewing various proofs and doing other checking. The book is due to be published officially in April, 2021.
• Rieke, G. H. (2012). Measuring the Universe: A Multiwavelength Perspective. Cambridge University Press.
  More info

  Graduate level textbook on astronomical instrumentation
• Rieke, G. H. (2006). The Last of the Great Observatories: Spitzer and the Era of Faster, Better, Cheaper at NASA. University of Arizona Press.
• Rieke, G. H. (2002). Detection of Light: From the Ultraviolet to the Submillimeter, Second Edition. Cambridge University Press.

Journals/Publications

• Defr{`ere}, D., Hinz, P., Kennedy, G., Stone, J., Rigley, J., Ertel, S., Gaspar, A., Bailey, V., Hoffmann, W., Mennesson, B., Millan-Gabet, R. .., Danchi, W., Absil, O., Arbo, P., Beichman, C., Bonavita, M., Brusa, G., Bryden, G., Downey, E., , Esposito, S., et al. (2021). "The HOSTS Survey: Evidence for an Extended Dust Disk and Constraints on the Presence of Giant Planets in the Habitable Zone of {ensuremath{beta} Leo}". aj, 161(4), 186.
• Gordon, K. D., Misselt, K. A., Bouwman, J., Clayton, G. C., Decleir, M., Hines, D. C., Pendleton, Y., Rieke, G., Smith, J., & Whittet, D. (2021). "Milky Way Mid-Infrared Spitzer Spectroscopic Extinction Curves: Continuum and Silicate Features". apj, 916(1), 33.
• G{'asp'ar}, A., Rieke, G. H., Guillard, P., Dicken, D., Gastaud, R., Alberts, S., Morrison, J., Ressler, M. E., Argyriou, I., & Glasse, A. (2021). "The Quantum Efficiency and Diffractive Image Artifacts of Si:As IBC mid-IR Detector Arrays at 5-10 {ensuremath{mu}m: Implications for the JWST/MIRI Detectors}". pasp, 133(1019), 014504.
• Hagan, J. B., Rieke, G., Fox, O. D., Noriega-Crespo, A., Hines, D. C., Cracraft, M., & Garc{'ia, M. M. (2021). "Cosmic-ray-related Signals from Detectors in Space: The Spitzer/IRAC Si:As IBC Devices". pasp, 133(1029), 114503.
• Krick, J. E., Lowrance, P., Carey, S., Laine, S., Grillmair, C., Van, D., Glaccum, W. J., Ingalls, J. G., Rieke, G., Hora, J. L., Fazio, G. G., Gordon, K. D., & Bohlin, R. C. (2021). "Spitzer IRAC Photometry of JWST Calibration Stars". aj, 161(4), 177.
• Leisawitz}, D., Amatucci, E., Allen, L., Arenberg, J., Armus, L., Battersby, C., Bauer, J., Bell, R., Benford, D., Bergin, E., Booth, J. T., Bradford, C. M., Bradley, D., Carey, S., Carter, R., Cooray, A., Corsetti, J., Dewell, L., DiPirro, M., , Drake, B. G., et al. (2021). "Origins Space Telescope: trades and decisions leading to the baseline mission concept". Journal of Astronomical Telescopes, Instruments, and Systems, 7, 011014.
• Lyu, J., & Rieke, G. H. (2021). "The Dusty Heart of NGC 4151 Revealed by {ensuremath{lambda} ensuremath{sim} 1-40 ensuremath{mu}m Reverberation Mapping and Variability: A Challenge to Current Clumpy Torus Models}". apj, 912(2), 126.
• Rieke, G., Su, K., Melis, C., & G{'asp'ar}, A. (2021). "Extreme Variability of the V488 Persei Debris Disk". apj, 918(2), 71.
• Alberts, S., Rujopakarn, W., Rieke, G. H., Jagannathan, P., & Nyland, K. (2020). "Completing the Census of AGN in GOODS-S/HUDF: New Ultradeep Radio Imaging and Predictions for JWST". apj, 901(2), 168.
• De, R. M., Rieke, G., Shivaei, I., Bromm, V., & Lyu, J. (2020). "Dust emission from the first massive galaxies". Boletin de la Asociacion Argentina de Astronomia La Plata Argentina, 61B, 180-182.
• Ertel, S., Defr{`ere}, D., Hinz, P., Mennesson, B., Kennedy, G., Danchi, W., Gelino, C., Hill, J., Hoffmann, W., Mazoyer, J., Rieke, G., Shannon, A., Stapelfeldt, K., Spalding, E., Stone, J., Vaz, A., Weinberger, A., Willems, P., Absil, O., , Arbo, P., et al. (2020). "The HOSTS Survey for Exozodiacal Dust: Observational Results from the Complete Survey". aj, 159(4), 177.
• Gaspar, A., & Rieke, G. (2020). "New HST data and modeling reveal a massive planetesimal collision around Fomalhaut". Proceedings of the National Academy of Science, 117(18), 9712-9722.
• Shivaei, I., Darvish, B., Sattari, Z., Chartab, N., Mobasher, B., Scoville, N., & Rieke, G. (2020). "Dependence of the IRX-{ensuremath{beta} Dust Attenuation Relation on Metallicity and Environment}". apjl, 903(2), L28.
• Shivaei, I., Reddy, N., Rieke, G., Shapley, A., Kriek, M., Battisti, A., Mobasher, B., Sanders, R., Fetherolf, T., Azadi, M., Coil, A. L., Freeman, W. R., Groot, L., Leung, G., Price, S. H., Siana, B., & Zick, T. (2020). "The MOSDEF Survey: The Variation of the Dust Attenuation Curve with Metallicity". apj, 899(2), 117.
• Su, K. Y., Rieke, G. H., Melis, C., Jackson, A. P., Smith, P. S., Meng, H. Y., & G{'asp'ar}, A. (2020). "Mid-infrared Studies of HD 113766 and HD 172555: Assessing Variability in the Terrestrial Zone of Young Exoplanetary Systems". apj, 898(1), 21.
• Lyu, J., Rieke, G. H., & Smith, P. S. (2019). Mid-IR Variability and Dust Reverberation Mapping of Low-z Quasars. I. Data, Methods, and Basic Results. apj, 886(1), 33.
• Meng, H. Y., Rieke, G., Kim, J. S., Sicilia-Aguilar, A., Cross, N., Esplin, T., Rebull, L., & Hodapp, K. W. (2019). Near-infrared Variability of Low-mass Stars in IC 1396A and Tr 37. apj, 878(1), 7.
• Rujopakarn, W., Daddi, E., Rieke, G., Puglisi, A., Schramm, M., P{'erez-Gonz'alez}, P., Magdis, G., Alberts, S., Bournaud, F., Elbaz, D., Franco, M., Kawinwanichakij, L., Kohno, K., Narayanan, D., Silverman, J., Wang, T., & Williams, C. (2019). ALMA 200 pc Resolution Imaging of Smooth Cold Dusty Disks in Typical z ̃ 3 Star-forming Galaxies. apj, 882(2), 107.
• Su, K. Y., Jackson, A. P., G{'asp'ar}, A., Rieke, G. H., Dong, R., Olofsson, J., Kennedy, G., Leinhardt, Z. M., Malhotra, R., Hammer, M., Meng, H. Y., Rujopakarn, W., Rodriguez, J. E., Pepper, J., Reichart, D., James, D., & Stassun, K. G. (2019). Extreme Debris Disk Variability: Exploring the Diverse Outcomes of Large Asteroid Impacts During the Era of Terrestrial Planet Formation. aj, 157(5), 202.
• Su, K., Rieke, G., & Sand, D. (2019). Infrared Brightening in HD 166191 - A Young Star with Active Terrestrial Debris. The Astronomer's Telegram, 12986, 1.
• Wilson, J., Hearty, F., Skrutskie, M., Majewski, S., Holtzman, J., Eisenstein, D., Gunn, J., Blank, B., Henderson, C., Smee, S., Nelson, M., Nidever, D., Arns, J., Barkhouser, R., Barr, J., Beland, S., Bershady, M., Blanton, M., Brunner, S., , Burton, A., et al. (2019). The Apache Point Observatory Galactic Evolution Experiment (APOGEE) Spectrographs. pasp, 131(999), 055001.
• De, R. M., Rieke, G., Shivaei, I., Bromm, V., & Lyu, J. (2018). The Far-infrared Emission of the First Massive Galaxies. apj, 869, 4.
• Ertel, S., Defr{`ere}, D., Hinz, P., Mennesson, B., Kennedy, G., Danchi, W., Gelino, C., Hill, J., Hoffmann, W., Rieke, G., Shannon, A., Spalding, E., Stone, J., Vaz, A., Weinberger, A., Willems, P., Absil, O., Arbo, P., Bailey, V., , Beichman, C., et al. (2018). The HOSTS SurveymdashExozodiacal Dust Measurements for 30 Stars. aj, 155, 194.
• Jackson, A., Su, K., Dong, R., Rieke, G., & Gaspar, A. (2018). Observing Giant, Planet Forming Impacts in Exoplanetary Systems. LPI Contributions, 2107, 2019.
• Lyu, J., & Rieke, G. (2018). Polar Dust, Nuclear Obscuration, and IR SED Diversity in Type-1 AGNs. apj, 866, 92.
• Rujopakarn, W., Nyland, K., Rieke, G., Barro, G., Elbaz, D., Ivison, R., Jagannathan, P., Silverman, J., Smol{v, c. V., & Wang, T. (2018). Cospatial Star Formation and Supermassive Black Hole Growth in z tilde 3 Galaxies: Evidence for In Situ Co-evolution. apjl, 854, L4.
• Su, K., Jackson, A., Dong, R., Rieke, G., & Gaspar, A. (2018). Short-Term Disk Flux Modulations due to the Orbital Evolution of Impact Produced Clouds of Dust in NGC2547-ID8. LPI Contributions, 2107, 2025.
• Ballering, N., Rieke, G., Su, K., & G{'asp'ar}, A. (2017). "What Sets the Radial Locations of Warm Debris Disks?". apj, 845, 120.
• Dunlop, J., McLure, R., Biggs, A., Geach, J., Micha{lowski}, M., Ivison, R., Rujopakarn, W., Kampen, E., Kirkpatrick, A., Pope, A., Scott, D., Swinbank, A., Targett, T., Aretxaga, I., Austermann, J., Best, P., Bruce, V., Chapin, E., Charlot, S., , Cirasuolo, M., et al. (2017). "A deep ALMA image of the Hubble Ultra Deep Field". mnras, 466, 861-883.
• Kirkpatrick, A., Alberts, S., Pope, A., Barro, G., Bonato, M., Kocevski, D., P{'erez-Gonz'alez}, P., Rieke, G., Rodr{'{i}guez-Mu~noz}, L., Sajina, A., Grogin, N., Mantha, K., Pandya, V., Pforr, J., Salvato, M., & Santini, P. (2017). "The AGN-Star Formation Connection: Future Prospects with JWST". apj, 849, 111.
• Lyu, J., & Rieke, G. (2017). "The Intrinsic Far-infrared Continua of Type-1 Quasars". apj, 841, 76.
• Lyu, J., Rieke, G., & Shi, Y. (2017). "Dust-deficient Palomar-Green Quasars and the Diversity of AGN Intrinsic IR Emission". apj, 835, 257.
• MacGregor, M., Matr{`a}, L., Kalas, P., Wilner, D., Pan, M., Kennedy, G., Wyatt, M., Duchene, G., Hughes, A., Rieke, G., Clampin, M., Fitzgerald, M., Graham, J., Holland, W., Pani{'c}, O., Shannon, A., & Su, K. (2017). "A Complete ALMA Map of the Fomalhaut Debris Disk". apj, 842, 8.
• Meng, H., Rieke, G., Dubois, F., Kennedy, G., Marengo, M., Siegel, M., Su, K., Trueba, N., Wyatt, M., Boyajian, T., Lisse, C., Logie, L., Rau, S., & Vanaverbeke, S. (2017). "Extinction and the Dimming of KIC 8462852". apj, 847, 131.
• Meng, H., Rieke, G., Su, K., & G{'asp'ar}, A. (2017). "The First 40 Million Years of Circumstellar Disk Evolution: The Signature of Terrestrial Planet Formation". apj, 836, 34.
• Schneider, G., Gaspar, A., Debes, J., Gull, T., Apai, D., & Rieke, G. H. (2017). Enabling Narrow(est) IWA Coronagraphy with STIS BAR5 and BAR10 Occulters. Space Telescope Science Institute Instrument Science Reports, 2017(003), 35.
• Su, K., De, B. J., Rieke, G., Krivov, A., L{"ohne}, T., Marengo, M., Stapelfeldt, K., Ballering, N., & Vacca, W. (2017). "The Inner 25 au Debris Distribution in the {$epsilon$ Eri System}". aj, 153, 226.
• {Ballering}, N., {Su}, K., {Rieke}, G., sp{'a}r}, A. (2016). "{A Comprehensive Dust Model Applied to the Resolved Beta Pictoris Debris Disk from Optical to Radio Wavelengths}". apj, 823, 108.
• {Balog}, Z., {Siegler}, N., {Rieke}, G., {Kiss}, L., {Muzerolle}, J., {Gutermuth}, R., {Bell}, C., {Vink{'o}}, J., {Su}, K., {Young}, E., sp{'a}r}, A. (2016). "{Protoplanetary and Transitional Disks in the Open Stellar Cluster IC 2395}". apj, 832, 87.
• {Defr{`e}re}, D., {Hinz}, P., {Mennesson}, B., {Hoffmann}, W., {Millan-Gabet}, R., {Skemer}, A., {Bailey}, V., {Danchi}, W., {Downey}, E., {Durney}, O., {Grenz}, P., {Hill}, J., {McMahon}, T., {Montoya}, M., {Spalding}, E., {Vaz}, A., {Absil}, O., {Arbo}, P., {Bailey}, H., , {Brusa}, G., et al. (2016). "{Nulling Data Reduction and On-sky Performance of the Large Binocular Telescope Interferometer}". apj, 824, 66.
• {G{'a}sp{'a}r}, A., {Rieke}, G., , N. (2016). "{The Correlation between Metallicity and Debris Disk Mass}". apj, 826, 171.
• {Kilpatrick}, C., {Andrews}, J., {Smith}, N., {Milne}, P., {Rieke}, G., {Zheng}, W., , A. (2016). "{An optical and near-infrared study of the Type Ia/IIn Supernova PS15si}". mnras, 463, 1088-1098.
• {Kilpatrick}, C., {Bieging}, J., , G. (2016). "{A Systematic Survey for Broadened CO Emission toward Galactic Supernova Remnants}". apj, 816, 1.
• {Lyu}, J., {Rieke}, G., , S. (2016). "{The Contribution of Host Galaxies to the Infrared Energy Output of z {gsim} 5.0 Quasars}". apj, 816, 85.
• {Meng}, H., {Plavchan}, P., {Rieke}, G., {Cody}, A., {G{"u}th}, T., {Stauffer}, J., {Covey}, K., {Carey}, S., {Ciardi}, D., {Duran-Rojas}, M., {Gutermuth}, R., {Morales-Calder{'o}n}, M., {Rebull}, L., , A. (2016). "{Photo-reverberation Mapping of a Protoplanetary Accretion Disk around a T Tauri Star}". apj, 823, 58.
• {Rieke}, G., {G{'a}sp{'a}r}, A., , N. (2016). "{Magnetic Grain Trapping and the Hot Excesses around Early-type Stars}". apj, 816, 50.
• {Rujopakarn}, W., {Dunlop}, J., {Rieke}, G., {Ivison}, R., {Cibinel}, A., {Nyland}, K., {Jagannathan}, P., {Silverman}, J., {Alexander}, D., {Biggs}, A., {Bhatnagar}, S., {Ballantyne}, D., {Dickinson}, M., {Elbaz}, D., {Geach}, J., {Hayward}, C., {Kirkpatrick}, A., {McLure}, R., {Micha{l}owski}, M., , {Miller}, N., et al. (2016). "{VLA and ALMA Imaging of Intense Galaxy-wide Star Formation in z {tilde} 2 Galaxies}". apj, 833, 12.
• {Shipley}, H., {Papovich}, C., {Rieke}, G., {Brown}, M., , J. (2016). "{A New Star Formation Rate Calibration from Polycyclic Aromatic Hydrocarbon Emission Features and Application to High-redshift Galaxies}". apj, 818, 60.
• {Skemer}, A., {Morley}, C., {Zimmerman}, N., {Skrutskie}, M., {Leisenring}, J., {Buenzli}, E., {Bonnefoy}, M., {Bailey}, V., {Hinz}, P., {Defr{'e}re}, D., {Esposito}, S., {Apai}, D., {Biller}, B., {Brandner}, W., {Close}, L., {Crepp}, J., {De Rosa}, R., {Desidera}, S., {Eisner}, J., , {Fortney}, J., et al. (2016). "{The LEECH Exoplanet Imaging Survey: Characterization of the Coldest Directly Imaged Exoplanet, GJ 504 b, and Evidence for Superstellar Metallicity}". apj, 817, 166.
• {Su}, K., {Rieke}, G., {Defr{'e}re}, D., {Wang}, K., {Lai}, S., {Wilner}, D., {van Lieshout}, R., , C. (2016). "{The Inner Debris Structure in the Fomalhaut Planetary System}". apj, 818, 45.
• {Zhang}, Z., {Shi}, Y., {Rieke}, G., {Xia}, X., {Wang}, Y., {Sun}, B., , L. (2016). "{Distributions of Quasar Hosts on the Galaxy Main Sequence Plane}". apjl, 819, L27.
• Defrere, D. (2015). First-light LBT Nulling Interferometric Observations: Warm Exozodiacal Dust Resolved within a Few AU of η Crv. Astrophysical Journal.
• Eisner, J. A. (2015). Time-monitoring observations of Brγ emission from young stars. MNRAS, 447.
• Kennedy, G. M. (2015). Exo-zodi Modeling for the Large Binocular Telescope Interferometer. Astrophysical Journal Supplements.
• Su, K. (2015). Debris Distribution in HD 95086—A Young Analog of HR 8799. Astrophysical Journal.
• Weinberger, A. J. (2015). Target Selection for the LBTI Exozodi Key Science Program. Astrophysical Journal Supplements, 216.
• {Boccaletti}, A., {Lagage}, P., {Baudoz}, P., {Beichman}, C., {Bouchet}, P., {Cavarroc}, C., {Dubreuil}, D., {Glasse}, A., {Glauser}, A., {Hines}, D., {Lajoie}, C., {Lebreton}, J., {Perrin}, M., {Pueyo}, L., {Reess}, J., {Rieke}, G., {Ronayette}, S., {Rouan}, D., {Soummer}, R., , G. (2015). "{The Mid-Infrared Instrument for the James Webb Space Telescope, V: Predicted Performance of the MIRI Coronagraphs}". pasp, 127, 633-645.
• {Glasse}, A., {Rieke}, G., {Bauwens}, E., {Garc{'{i}}a-Mar{'{i}}n}, M., {Ressler}, M., {Rost}, S., {Tikkanen}, T., {Vandenbussche}, B., , G. (2015). "{The Mid-Infrared Instrument for the James Webb Space Telescope, IX: Predicted Sensitivity}". pasp, 127, 686-695.
• {Gordon}, K., {Chen}, C., {Anderson}, R., {Azzollini}, R., {Bergeron}, L., {Bouchet}, P., {Bouwman}, J., {Cracraft}, M., {Fischer}, S., {Friedman}, S., {Garc{'{i}}a-Mar{'{i}}n}, M., {Glasse}, A., {Glauser}, A., {Goodson}, G., {Greene}, T., {Hines}, D., {Khorrami}, M., {Lahuis}, F., {Lajoie}, C., , {Meixner}, M., et al. (2015). "{The Mid-Infrared Instrument for the James Webb Space Telescope, X: Operations and Data Reduction}". pasp, 127, 696-711.
• {Kiminki}, M., {Kim}, J., {Bagley}, M., {Sherry}, W., , G. (2015). "{The O- and B-Type Stellar Population in W3: Beyond the High-Density Layer}". apj, 813, 42.
• {Lyu}, J., {Rieke}, G., , S. (2015). "{The Contribution of Host Galaxies to the Infrared Energy Output of $zgtrsim5.0$ QUASARS}". ArXiv e-prints.
• {Meng}, H., {Su}, K., {Rieke}, G., {Rujopakarn}, W., {Myers}, G., {Cook}, M., {Erdelyi}, E., {Maloney}, C., {McMath}, J., {Persha}, G., {Poshyachinda}, S., , D. (2015). "{Planetary Collisions Outside the Solar System: Time Domain Characterization of Extreme Debris Disks}". apj, 805, 77.
• {Ressler}, M., {Sukhatme}, K., {Franklin}, B., {Mahoney}, J., {Thelen}, M., {Bouchet}, P., {Colbert}, J., {Cracraft}, M., {Dicken}, D., {Gastaud}, R., {Goodson}, G., {Eccleston}, P., {Moreau}, V., {Rieke}, G., , A. (2015). "{The Mid-Infrared Instrument for the James Webb Space Telescope, VIII: The MIRI Focal Plane System}". pasp, 127, 675-685.
• {Rieke}, G. (2015). "{Infrared Astronomy{mdash}Seeing the Heat: From William Herschel to the Herschel Space Observatory}". American Journal of Physics, 83, 661-662.
• {Rieke}, G., {Ressler}, M., {Morrison}, J., {Bergeron}, L., {Bouchet}, P., {Garc{'{i}}a-Mar{'{i}}n}, M., {Greene}, T., {Regan}, M., {Sukhatme}, K., , H. (2015). "{The Mid-Infrared Instrument for the James Webb Space Telescope, VII: The MIRI Detectors}". pasp, 127, 665-674.
• {Rieke}, G., {Wright}, G., {B{"o}ker}, T., {Bouwman}, J., {Colina}, L., {Glasse}, A., {Gordon}, K., {Greene}, T., {G{"u}del}, M., {Henning}, T., {Justtanont}, K., {Lagage}, P., {Meixner}, M., {N{o}rgaard-Nielsen}, H., {Ray}, T., {Ressler}, M., {van Dishoeck}, E., , C. (2015). "{The Mid-Infrared Instrument for the James Webb Space Telescope, I: Introduction}". pasp, 127, 584-594.
• {Skemer}, A., {Skemer}, A., {Morley}, C., {Morley}, C., {Zimmerman}, N., {Zimmerman}, N., {Skrutskie}, M., {Skrutskie}, M., {Leisenring}, J., {Leisenring}, J., {Buenzli}, E., {Buenzli}, E., {Bonnefoy}, M., {Bonnefoy}, M., {Bailey}, V., {Bailey}, V., {Hinz}, P., {Hinz}, P., {Defr{'e}re}, D., , {Defr{'e}re}, D., et al. (2015). "{The LEECH Exoplanet Imaging Survey: Characterization of the Coldest Directly Imaged Exoplanet, GJ 504 b, and Evidence for Super-Stellar Metallicity}". ArXiv e-prints.
• {Su}, K., {Su}, K., {Rieke}, G., {Rieke}, G., {Defrere}, D., {Defrere}, D., {Wang}, K., {Wang}, K., {Lai}, S., {Lai}, S., {Wilner}, D., {Wilner}, D., {van Lieshout}, R., {van Lieshout}, R., {Lee}, C., , C. (2015). "{The Inner Debris Structure in the Fomalhaut Planetary System}". ArXiv e-prints.
• {Wright}, G., {Wright}, D., {Goodson}, G., {Rieke}, G., {Aitink-Kroes}, G., {Amiaux}, J., {Aricha-Yanguas}, A., {Azzollini}, R., {Banks}, K., {Barrado-Navascues}, D., {Belenguer-Davila}, T., {Bloemmart}, J., {Bouchet}, P., {Brandl}, B., {Colina}, L., {Detre}, {., {Diaz-Catala}, E., {Eccleston}, P., {Friedman}, S., , {Garc{'{i}}a-Mar{'{i}}n}, M., et al. (2015). "{The Mid-Infrared Instrument for the James Webb Space Telescope, II: Design and Build}". pasp, 127, 595-611.
• {Xu}, L., {Rieke}, G., {Egami}, E., {Haines}, C., {Pereira}, M., , G. (2015). "{The Relation between Luminous AGNs and Star Formation in Their Host Galaxies}". apj, 808, 159.
• {Xu}, L., {Rieke}, G., {Egami}, E., {Pereira}, M., {Haines}, C., , G. (2015). "{A Herschel Study of 24 {$mu$}{$mu$}m-Selected AGNs and Their Host Galaxies}". apjs, 219, 18.
• {Youdin}, A., {Youdin}, A., {Rieke}, G., , G. (2015). "{Planetesimals in Debris Disks}". ArXiv e-prints.
• Ballering, N. P. (2014). Probing the Terrestrial Regions of Planetary Systems: Warm Debris Disks with Emission Features. Astrophysical Journal.
• Ballering, N. P., Rieke, G. H., Su, K. Y., & Montiel, E. (2014). A trend between cold debris disk temperature and stellar type: Implications for the formation and evolution of wide-orbit planets. Proceedings of the International Astronomical Union, 8(S299), 326-327.
  More info

  Abstract: Cold debris disks have the potential to answer many outstanding questions in wide-orbit planet formation and evolution. We characterized the infrared excess SEDs of 174 cold debris disks with Spitzer IRS and MIPS. We found a trend between the temperature of the disks and the stellar type of the stars they orbit. This argues against the importance of strictly temperature-dependent processes (e.g. ice lines) in setting the dimensions of cold debris disks. We also found no evidence that delayed stirring causes the trend. The trend may result from outward planet migration that traces the extent of the primordial protoplanetary disk, or from planet formation that halts at an orbital radius limited by the efficiency of core accretion. For the full details of this work, see Ballering et al. (2013). Copyright © 2013, International Astronomical Union.
• Booth, M., Kennedy, G., Sibthorpe, B., Matthews, B. C., Wyatt, M. C., Duchêne, G., Kavelaars, J. J., Rodriguez, D., Greaves, J. S., Koning, A., Vican, L., Rieke, G. H., Y., K., Moro-Martín, A., & Kalas, P. (2014). Locating the dust in A star debris discs. Proceedings of the International Astronomical Union, 8(S299), 330-331.
  More info

  Abstract: Using photometry at just two wavelengths it is possible to fit a blackbody to the spectrum of infrared excess that is the signature of a debris disc. From this the location of the dust can be inferred. However, it is well known that dust in debris discs is not a perfect blackbody. By resolving debris discs we can find the actual location of the dust and compare this to that inferred from the blackbody fit. Using the Herschel Space Observatory we resolved many systems as part of the DEBRIS survey. Here we discuss a sample of 9 discs surrounding A stars and find that the discs are actually located between 1 and 2.5 times further from their star than predicted by blackbody fits to the spectral energy distribution (SED). The variation in this ratio is due to differences in stellar luminosities, location of the dust, size distribution and composition of the dust. Copyright © 2013, International Astronomical Union.
• Currie, T. (2014). A Deep Spitzer Survey of Circumstellar Disks in the Young Double Cluster, h and χ Persei. Astrophysical Journal, 796.
• Flaherty, K. M. (2014). Connecting X-Ray and Infrared Variability among Young Stellar Objects: Ruling out Potential Sources of Disk Fluctuations. Astrophysical Journal.
• Gáspár, A., & Rieke, G. H. (2014). The herschel cold debris disks: Confusion with the extragalactic background at 160 μm. Astrophysical Journal, 784(1).
  More info

  Abstract: The Herschel "DUst around NEarby Stars" (DUNES) survey has found a number of debris disk candidates that are apparently very cold, with temperatures near 22 K. It has proven difficult to fit their spectral energy distributions with conventional models for debris disks. Given this issue, we carefully examine the alternative explanation that the detections arise from confusion with infrared cirrus and/or background galaxies that are not physically associated with the foreground stars. We find that such an explanation is consistent with all of these detections. © 2014. The American Astronomical Society. All rights reserved..
• Kilpatrick, C. D. (2014). Interaction between Cassiopeia A and Nearby Molecular Clouds. Astrophysical Journal, 796.
• Meng, H. (2014). Large impacts around a solar-analog star in the era of terrestrial planet formation. Science.
• Shi, Y. (2014). Infrared Spectra and Photometry Of Complete Samples of Palomar-Green and Two Micron All Sky Survey Quasars. Astrophysical Journal.
• Sierchio, J. M., Rieke, G. H., Su, K. Y., & Gáspár, A. (2014). The decay of debris disks around solar-type stars. Astrophysical Journal, 785(1).
  More info

  Abstract: We present a Spitzer MIPS study of the decay of debris disk excesses at 24 and 70 μm for 255 stars of types F4-K2. We have used multiple tests, including consistency between chromospheric and X-ray activity and placement on the H-R diagram, to assign accurate stellar ages. Within this spectral type range, at 24 μm, 13.6% ± 2.8% of the stars younger than 1 Gyr have excesses at the 3σ level or more, whereas none of the older stars do, confirming previous work. At 70 μm, 22.5% ± 3.6% of the younger stars have excesses at ≥3σ significance, whereas only % of the older stars do. To characterize the far-infrared behavior of debris disks more robustly, we doubled the sample by including stars from the DEBRIS and DUNES surveys. For the F4-K4 stars in this combined sample, there is only a weak (statistically not significant) trend in the incidence of far-infrared excess with spectral type (detected fractions of 21.9, late F; 16.5, G; and 16.9, early K). Taking this spectral type range together, there is a significant decline between 3 and 4.5 Gyr in the incidence of excesses, with fractional luminosities just under 10-5. There is an indication that the timescale for decay of infrared excesses varies roughly inversely with the fractional luminosity. This behavior is consistent with theoretical expectations for passive evolution. However, more excesses are detected around the oldest stars than are expected from passive evolution, suggesting that there is late-phase dynamical activity around these stars. © 2014. The American Astronomical Society. All rights reserved..
• Sivanandam, S. (2014). Tracing Ram-pressure Stripping with Warm Molecular Hydrogen Emission. Astrophysical Journal, 796.
• Skemer, A., Apai, D., Bailey, V., Biller, B., Bonnefoy, M., Brandner, W., Buenzli, E., Close, L., Crepp, J., Defrere, D., Desidera, S., Eisner, J., Esposito, S., Fortney, J., Henning, T., Hinz, P., Hofmann, K., Leisenring, J., Males, J., , Millan-Gabet, R., et al. (2014). LEECH: A 100 night exoplanet imaging survey at the LBT. Proceedings of the International Astronomical Union, 8(S299), 70-71.
  More info

  Abstract: In February 2013, the LEECH (LBTI Exozodi Exoplanet Common Hunt) survey began its 100-night campaign from the Large Binocular Telescope atop Mount Graham in Arizona. LEECH neatly complements other high-contrast planet imaging efforts by observing stars in L' band (3.8 microns) as opposed to the shorter wavelength near-infrared bands (1-2.3 microns). This part of the spectrum offers deeper mass sensitivity for intermediate age (several hundred Myr-old) systems, since their Jovian-mass planets radiate predominantly in the mid-infrared. In this proceedings, we present the science goals for LEECH and a preliminary contrast curve from some early data. Copyright © 2013, International Astronomical Union.
• Su, K. Y., & Rieke, G. H. (2014). Signposts of multiple planets in debris disks. Proceedings of the International Astronomical Union, 8(S299), 318-321.
  More info

  Abstract: We review the nearby debris disk structures revealed by multi-wavelength images from Spitzer and Herschel, and complemented with detailed spectral energy distribution modeling. Similar to the definition of habitable zones around stars, debris disk structures should be identified and characterized in terms of dust temperatures rather than physical distances so that the heating power of different spectral type of stars is taken into account and common features in disks can be discussed and compared directly. Common features, such as warm (~150 K) dust belts near the water-ice line and cold (~50 K) Kuiper-belt analogs, give rise to our emerging understanding of the levels of order in debris disk structures and illuminate various processes about the formation and evolution of exoplanetary systems. In light of the disk structures in the debris disk twins (Vega and Fomalhaut), and the current limits on the masses of planetary objects, we suggest that the large gap between the warm and cold dust belts is the best signpost for multiple (low-mass) planets beyond the water-ice line. Copyright © 2013, International Astronomical Union.
• Tyler, K. (2014). Star Formation Trends in the Unrelaxed, Post-merger Cluster A2255. Astrophysical Journal.
• {Beichman}, C., {Benneke}, B., {Knutson}, H., {Smith}, R., {Lagage}, P., {Dressing}, C., {Latham}, D., {Lunine}, J., {Birkmann}, S., {Ferruit}, P., {Giardino}, G., {Kempton}, E., {Carey}, S., {Krick}, J., {Deroo}, P., {Mandell}, A., {Ressler}, M., {Shporer}, A., {Swain}, M., , {Vasisht}, G., et al. (2014). "{Observations of Transiting Exoplanets with the James Webb Space Telescope (JWST)}". pasp, 126, 1134-1173.
• Alonso-Herrero, A., Pereira-Santaella, M., Rieke, G. H., Diamond-Stanic, A. M., Wang, Y., Hernán-Caballero, A., & Rigopoulou, D. (2013). Local luminous infrared galaxies. III. co-evolution of black hole growth and star formation activity?. Astrophysical Journal, 765(2).
  More info

  Abstract: Local luminous infrared (IR) galaxies (LIRGs) have both high star formation rates (SFR) and a high AGN (Seyfert and AGN/starburst composite) incidence. Therefore, they are ideal candidates to explore the co-evolution of black hole (BH) growth and star formation (SF) activity, not necessarily associated with major mergers. Here, we use Spitzer/IRS spectroscopy of a complete volume-limited sample of local LIRGs (distances of
• Bailey, V., Hinz, P. M., Currie, T., Su, K. Y., Esposito, S., Hill, J. M., Hoffmann, W. F., Jones, T., Kim, J., Leisenring, J., Meyer, M., Murray-Clay, R., Nelson, M. J., Pinna, E., Puglisi, A., Rieke, G., Rodigas, T., Skemer, A., Skrutskie, M. F., , Vaitheeswaran, V., et al. (2013). A thermal infrared imaging study of very low mass, wide-separation brown dwarf companions to upper scorpius stars: Constraining circumstellar environments. Astrophysical Journal, 767(1).
  More info

  Abstract: We present a 3-5 μm LBT/MMT adaptive optics imaging study of three Upper Scorpius stars with brown dwarf (BD) companions with very low masses/mass ratios (MBD
• Ballering, N. P., Rieke, G. H., Y., K., & Montiel, E. (2013). A trend between cold debris disk temperature and stellar type: Implications for the formation and evolution of wide-orbit planets. Astrophysical Journal, 775(1).
  More info

  Abstract: Cold debris disks trace the limits of planet formation or migration in the outer regions of planetary systems, and thus have the potential to answer many of the outstanding questions in wide-orbit planet formation and evolution. We characterized the infrared excess spectral energy distributions of 174 cold debris disks around 546 main-sequence stars observed by both the Spitzer Infrared Spectrograph and the Multiband Imaging Photometer for Spitzer. We found a trend between the temperature of the inner edges of cold debris disks and the stellar type of the stars they orbit. This argues against the importance of strictly temperature-dependent processes (e.g., non-water ice lines) in setting the dimensions of cold debris disks. Also, we found no evidence that delayed stirring causes the trend. The trend may result from outward planet migration that traces the extent of the primordial protoplanetary disk, or it may result from planet formation that halts at an orbital radius limited by the efficiency of core accretion. © 2013. The American Astronomical Society. All rights reserved.
• Booth, M., Kennedy, G., Sibthorpe, B., Matthews, B. C., Wyatt, M. C., Ducĥene, G., Kavelaars, J. J., Rodriguez, D., Greaves, J. S., Koning, A., Vican, L., Rieke, G. H., Y., K., Moro-Mart́in, A., & Kalas, P. (2013). Resolved debris discs around a stars in the herschel DEBRIS survey. Monthly Notices of the Royal Astronomical Society, 428(2), 1263-1280.
  More info

  Abstract: The majority of debris discs discovered so far have only been detected through infrared excess emission above stellar photospheres. While disc properties can be inferred from unresolved photometry alone under various assumptions for the physical properties of dust grains, there is a degeneracy between disc radius and dust temperature that depends on the grain size distribution and optical properties. By resolving the disc we can measure the actual location of the dust. The launch of Herschel, with an angular resolution superior to previous far-infrared telescopes, allows us to spatially resolve more discs and locate the dust directly. Here we present the nine resolved discs around A stars between 20 and 40 pc observed by the Disc Emission via a Bias-free Reconnaissance in the Infrared/Submillimetre (DEBRIS) survey. We use these data to investigate the disc radii by fitting narrowringmodels to images at 70, 100 and 160μm and by fitting blackbodies to full spectral energy distributions. We do this with the aim of finding an improved way of estimating disc radii for unresolved systems. The ratio between the resolved and blackbody radii varies between 1 and 2.5. This ratio is inversely correlated with luminosity and any remaining discrepancies are most likely explained by differences to the minimum size of grain in the size distribution or differences in composition. We find that three of the systems are well fit by a narrow ring, two systems are borderline cases and the other four likely require wider or multiple rings to fully explain the observations, reflecting the diversity of planetary systems. © 2012 The Authors Published by Oxford University Press on behalf of the Royal Astronomical Society.
• Broekhoven-Fiene, H., Matthews, B. C., Kennedy, G. M., Booth, M., Sibthorpe, B., Lawler, S. M., Kavelaars, J. J., Wyatt, M. C., Chenruo, Q. i., Koning, A., Y., K., Rieke, G. H., Wilner, D. J., & Greaves, J. S. (2013). The debris disk around γ doradus resolved with Herschel. Astrophysical Journal, 762(1).
  More info

  Abstract: We present observations of the debris disk around γ Doradus, an F1V star, from the Herschel Key Programme DEBRIS (Disc Emission via Bias-free Reconnaissance in the Infrared/Submillimetre). The disk is well resolved at 70, 100, and 160 μm, resolved along its major axis at 250 μm, detected but not resolved at 350 μm, and confused with a background source at 500 μm. It is one of our best resolved targets and we find it to have a radially broad dust distribution. The modeling of the resolved images cannot distinguish between two configurations: an arrangement of a warm inner ring at several AU (best fit 4 AU) and a cool outer belt extending from ∼55 to 400 AU or an arrangement of two cool, narrow rings at ∼70 AU and ∼190 AU. This suggests that any configuration between these two is also possible. Both models have a total fractional luminosity of ∼10-5 and are consistent with the disk being aligned with the stellar equator. The inner edge of either possible configuration suggests that the most likely region to find planets in this system would be within ∼55 AU of the star. A transient event is not needed to explain the warm dust's fractional luminosity. © 2013. The American Astronomical Society. All rights reserved.
• Eisner, J. A., Rieke, G. H., Rieke, M. J., Flaherty, K. M., Arnold, T. J., Stone, J. M., Cortes, S. R., Cox, E., Hawkins, C., Cole, A., Zajac, S., & Rudolph, A. L. (2013). Time-monitoring observations of the ro-vibrational overtone CO bands in young stars. Monthly Notices of the Royal Astronomical Society, 434(1), 407-414.
  More info

  Abstract: We present near-infrared spectra of a sample of T Tauri, Herbig Ae/Be and FU Ori objects. Using the FSPEC instrument on the Bok 90-inch telescope, we obtained K-band spectra with a resolution of ≈3500. Here, we present spectra of the δv = 2-0 and δv = 3-1 bandheads of ro-vibrational transitions of carbon monoxide. We observed these spectra over multiple epochs spaced by a few days and approximately one month. Several of our targets show CO emission or absorption features. However, we see little evidence of variability in these features across multiple epochs. We compare our results with previous observations and discuss the physical implications of non-variable CO emission across the sampled time-scales. © 2013 The Authors Published by Oxford University Press on behalf of the Royal Astronomical Society.
• Flaherty, K. M., Muzerolle, J., Rieke, G., Gutermuth, R., Balog, Z., Herbst, W., & Megeath, S. T. (2013). Kinks and dents in protoplanetary disks: Rapid infrared variability as evidence for large structural perturbations. Astronomical Journal, 145(3).
  More info

  Abstract: We report on synoptic observations at 3.6 and 4.5 μm of young stellar objects in IC 348 with 38 epochs covering 40 days. We find that among the detected cluster members, 338 at [3.6] and 269 at both [3.6] and [4.5], many are variable on daily to weekly timescales with typical fluctuations of ∼0.1 mag. The fraction of variables ranges from 20% for the diskless pre-main sequence stars to 60% for the stars still surrounded by infalling envelopes. We also find that stars in the exposed cluster core are less variable than the stars in the dense, slightly younger, southwestern ridge. This trend persists even after accounting for the underlying correlation with infrared spectral energy distribution type, suggesting that the change in variable fraction is not simply a reflection of the change in relative fraction of class I versus class II sources across the cloud, but instead reflects a change in variability with age. We also see a strong correlation between infrared variability and X-ray luminosity among the class II sources. The observed variability most likely reflects large changes in the structure of the inner wall located at the dust sublimation radius. We explore the possibility that these structural perturbations could be caused by a hot spot on the star heating dust above the sublimation temperature, causing it to evaporate rapidly, and increasing the inner radius for a portion of the disk. Under a number of simplifying assumptions we show that this model can reproduce the size and timescale of the 3.6 and 4.5 μm fluctuations. Regardless of its source, the infrared variability indicates that the inner disk is not a slowly evolving entity, but instead is a bubbling, warped, dented mass of gas and dust whose global size and shape fluctuate in a matter of days. © 2013. The American Astronomical Society. All rights reserved.
• Gáspár, A., Rieke, G. H., & Balog, Z. (2013). The collisional evolution of debris disks. Astrophysical Journal, 768(1).
  More info

  Abstract: We explore the collisional decay of disk mass and infrared emission in debris disks. With models, we show that the rate of the decay varies throughout the evolution of the disks, increasing its rate up to a certain point, which is followed by a leveling off to a slower value. The total disk mass falls off ∝t -0.35 at its fastest point (where t is time) for our reference model, while the dust mass and its proxy - the infrared excess emission - fades significantly faster (∝t -0.8). These later level off to a decay rate of M tot (t) t -0.08 and M dust (t) or L ir (t) t -0.6. This is slower than the ∝t -1 decay given for all three system parameters by traditional analytic models. We also compile an extensive catalog of Spitzer and Herschel 24, 70, and 100 μm observations. Assuming a log-normal distribution of initial disk masses, we generate model population decay curves for the fraction of stars harboring debris disks detected at 24 μm. We also model the distribution of measured excesses at the far-IR wavelengths (70-100 μm) at certain age regimes. We show general agreement at 24 μm between the decay of our numerical collisional population synthesis model and observations up to a Gyr. We associate offsets above a Gyr to stochastic events in a few select systems. We cannot fit the decay in the far-infrared convincingly with grain strength properties appropriate for silicates, but those of water ice give fits more consistent with the observations (other relatively weak grain materials would presumably also be successful). The oldest disks have a higher incidence of large excesses than predicted by the model; again, a plausible explanation is very late phases of high dynamical activity around a small number of stars. Finally, we constrain the variables of our numerical model by comparing the evolutionary trends generated from the exploration of the full parameter space to observations. Amongst other results, we show that erosive collisions are dominant in setting the timescale of the evolution and that planetesimals on the order of 100 km in diameter are necessary in the cascades for our population synthesis models to reproduce the observations. © 2013. The American Astronomical Society. All rights reserved.
• Oemler Jr., A., Dressler, A., Gladders, M. G., Rigby, J. R., Bai, L., Kelson, D., Villanueva, E., Fritz, J., Rieke, G., Poggianti, B. M., & Vulcani, B. (2013). The imacs cluster building survey. I. description of the survey and analysis methods. Astrophysical Journal, 770(1).
  More info

  Abstract: The IMACS Cluster Building Survey uses the wide field spectroscopic capabilities of the IMACS spectrograph on the 6.5 m Baade Telescope to survey the large-scale environment surrounding rich intermediate-redshift clusters of galaxies. The goal is to understand the processes which may be transforming star-forming field galaxies into quiescent cluster members as groups and individual galaxies fall into the cluster from the surrounding supercluster. This first paper describes the survey: the data taking and reduction methods. We provide new calibrations of star formation rates (SFRs) derived from optical and infrared spectroscopy and photometry. We demonstrate that there is a tight relation between the observed SFR per unit B luminosity, and the ratio of the extinctions of the stellar continuum and the optical emission lines. With this, we can obtain accurate extinction-corrected colors of galaxies. Using these colors as well as other spectral measures, we determine new criteria for the existence of ongoing and recent starbursts in galaxies. © 2013. The American Astronomical Society. All rights reserved.
• Rujopakarn, W., Rieke, G. H., Weiner, B. J., Pérez-González, P., Rex, M., Walth, G. L., & Kartaltepe, J. S. (2013). Mid-infrared determination of total infrared luminosity and star formation rates of local and high-redshift galaxies. Astrophysical Journal, 767(1).
  More info

  Abstract: We demonstrate estimating the total infrared luminosity, L(TIR), and star formation rates (SFRs) of star-forming galaxies at redshift 0 < z < 2.8 from single-band 24 μm observations, using local spectral energy distribution (SED) templates without introducing additional free parameters. Our method is based on characterizing the SEDs of galaxies as a function of their L(TIR) surface density, which is motivated by the indications that the majority of IR luminous star-forming galaxies at 1 < z < 3 have extended star-forming regions, in contrast to the strongly nuclear concentrated, merger-induced starbursts in local luminous and ultraluminous IR galaxies. We validate our procedure for estimating L(TIR) by comparing the resulting L(TIR) with those measured from far-IR observations, such as those from Herschel in the Extended Chandra Deep Field South (ECDFS) and Hubble Deep Field North (HDFN), as well as L(TIR) measured from stacked far-IR observations at redshift 0 < z < 2.8. Active galactic nuclei were excluded using X-ray and 3.6-8.0 μm observations, which are generally available in deep cosmological survey fields. The Gaussian fits to the distribution of the discrepancies between the L(TIR) measurements from single-band 24 μm and Herschel observations in the ECDFS and HDFN samples have σ < 0.1 dex, with ∼10% of objects disagreeing by more than 0.2 dex. Since the 24 μm estimates are based on SEDs for extended galaxies, this agreement suggests that ∼90% of IR galaxies at high z are indeed much more physically extended than local counterparts of similar L(TIR), consistent with recent independent studies of the fractions of galaxies forming stars in the main-sequence and starburst modes, respectively. Because we have not introduced empirical corrections to enhance these estimates, in principle, our method should be applicable to lower luminosity galaxies. This will enable use of the 21 μm band of the Mid-Infrared Instrument on board the James Webb Space Telescope to provide an extremely sensitive tracer of obscured SFR in individual star-forming galaxies across the peak of the cosmic star formation history. © 2013. The American Astronomical Society. All rights reserved..
• Tyler, K. D., Rieke, G. H., & Bai, L. (2013). Star-forming galaxy evolution in nearby rich clusters. Astrophysical Journal, 773(2).
  More info

  Abstract: Dense environments are known to quench star formation in galaxies, but it is still unknown what mechanism(s) are directly responsible. In this paper, we study the star formation of galaxies in A2029 and compare it to that of Coma, combining indicators at 24 μm, Hα, and UV down to rates of 0.03 M ⊙ yr-1. We show that A2029's star-forming galaxies follow the same mass-SFR relation as the field. The Coma cluster, on the other hand, has a population of galaxies with star formation rates (SFRs) significantly lower than the field mass-SFR relation, indicative of galaxies in the process of being quenched. Over half of these galaxies also host active galactic nuclei. Ram-pressure stripping and starvation/strangulation are the most likely mechanisms for suppressing the star formation in these galaxies, but we are unable to disentangle which is dominating. The differences we see between the two clusters' populations of star-forming galaxies may be related to their accretion histories, with A2029 having accreted its star-forming galaxies more recently than Coma. Additionally, many early-type galaxies in A2029 are detected at 24 μm and/or in the far-UV, but this emission is not directly related to star formation. Similar galaxies have probably been classified as star forming in previous studies of dense clusters, possibly obscuring some of the effects of the cluster environment on true star-forming galaxies. © 2013. The American Astronomical Society. All rights reserved.
• Y., K., Rieke, G. H., Malhotra, R., Stapelfeldt, K. R., Hughes, A. M., Bonsor, A., Wilner, D. J., Balog, Z., Watson, D. M., Werner, M. W., & Misselt, K. A. (2013). Asteroid belts in debris disk twins: Vega and fomalhaut. Astrophysical Journal, 763(2).
  More info

  Abstract: Vega and Fomalhaut are similar in terms of mass, ages, and global debris disk properties; therefore, they are often referred to as "debris disk twins." We present Spitzer 10-35 μm spectroscopic data centered at both stars and identify warm, unresolved excess emission in the close vicinity of Vega for the first time. The properties of the warm excess in Vega are further characterized with ancillary photometry in the mid-infrared and resolved images in the far-infrared and submillimeter wavelengths. The Vega warm excess shares many similar properties with the one found around Fomalhaut. The emission shortward of 30 μm from both warm components is well described as a blackbody emission of 170 K. Interestingly, two other systems, ε Eri and HR 8799, also show such an unresolved warm dust using the same approach. These warm components may be analogous to the solar system's zodiacal dust cloud, but of far greater mass (fractional luminosity of 10-5 to 10-6 compared to 10-8 to 10-7). The dust temperature and tentative detections in the submillimeter suggest that the warm excess arises from dust associated with a planetesimal ring located near the water-frost line and presumably created by processes occurring at similar locations in other debris systems as well. We also review the properties of the 2 μm hot excess around Vega and Fomalhaut, showing that the dust responsible for the hot excess is not spatially associated with the dust we detected in the warm belt. We suggest it may arise from hot nano grains trapped in the magnetic field of the star. Finally, the separation between the warm and cold belt is rather large with an orbital ratio ≳10 in all four systems. In light of the current upper limits on the masses of planetary objects and the large gap, we discuss the possible implications for their underlying planetary architecture and suggest that multiple, low-mass planets likely reside between the two belts in Vega and Fomalhaut. © 2013. The American Astronomical Society. All rights reserved.
• Alonso-Herrero, A., Pereira-Santaella, M., Rieke, G. H., & Rigopoulou, D. (2012). Local luminous infrared galaxies. II. Active galactic nucleus activity from spitzer/infrared spectrograph spectra. Astrophysical Journal, 744(1).
  More info

  Abstract: We quantify the active galactic nucleus (AGN) contribution to the mid-infrared (mid-IR) and the total infrared (IR, 8-1000 μm) emission in a complete volume-limited sample of 53 local luminous infrared galaxies (LIRGs, L IR = 1011-1012 L ⊙). We decompose the Spitzer Infrared Spectrograph low-resolution 5-38 μm spectra of the LIRGs into AGN and starburst components using clumpy torus models and star-forming galaxy templates, respectively. We find that 50% (25/50) of local LIRGs have an AGN component detected with this method. There is good agreement between these AGN detections through mid-IR spectral decomposition and other AGN indicators, such as the optical spectral class, mid-IR spectral features, and X-ray properties. Taking all the AGN indicators together, the AGN detection rate in the individual nuclei of LIRGs is 62%. The derived AGN bolometric luminosities are in the range L bol(AGN) = (0.4-50) × 10 43 erg s-1. The AGN bolometric contribution to the IR luminosities of the galaxies is generally small, with 70% of LIRGs having L bol[AGN]/L IR ≤ 0.05. Only ≃ 8% of local LIRGs have a significant AGN bolometric contribution L bol[AGN]/L IR > 0.25. From the comparison of our results with literature results of ultraluminous infrared galaxies (L IR = 10 12-1013 L ⊙), we confirm that in the local universe the AGN bolometric contribution to the IR luminosity increases with the IR luminosity of the galaxy/system. If we add up the AGN bolometric luminosities we find that AGNs only account for of the total IR luminosity produced by local LIRGs (with and without AGN detections). This proves that the bulk of the IR luminosity of local LIRGs is due to star formation activity. Taking the newly determined IR luminosity density of LIRGs in the local universe, we then estimate an AGN IR luminosity density of ΩAGNIR = 3 × 105 L ⊙ Mpc-3 in LIRGs.
• Diamond-Stanic, A. M., & Rieke, G. H. (2012). The relationship between black hole growth and star formation in seyfert galaxies. Astrophysical Journal, 746(2).
  More info

  Abstract: We present estimates of black hole accretion rates (BHARs) and nuclear, extended, and total star formation rates for a complete sample of Seyfert galaxies. Using data from the Spitzer Space Telescope, we measure the active galactic nucleus (AGN) luminosity using the [O IV] λ25.89 μm emission line and the star-forming luminosity using the 11.3 μm aromatic feature and extended 24 μm continuum emission. We find that black hole growth is strongly correlated with nuclear (r < 1kpc) star formation, but only weakly correlated with extended (r > 1kpc) star formation in the host galaxy. In particular, the nuclear star formation rate (SFR) traced by the 11.3 μm aromatic feature follows a relationship with the BHAR of the form SFR ∞ M · 0.8BH, with an observed scatter of 0.5 dex. This SFR-BHAR relationship persists when additional star formation in physically matched r = 1kpc apertures is included, taking the form SFR ∞ M · 0.8BH. However, the relationship becomes almost indiscernible when total SFRs are considered. This suggests a physical connection between the gas on sub-kiloparsec and sub-parsec scales in local Seyfert galaxies that is not related to external processes in the host galaxy. It also suggests that the observed scaling between star formation and black hole growth for samples of AGNs will depend on whether the star formation is dominated by a nuclear or an extended component. We estimate the integrated black hole and bulge growth that occurs in these galaxies and find that an AGN duty cycle of 5%-10% would maintain the ratio between black hole and bulge masses seen in the local universe. © 2012. The American Astronomical Society. All rights reserved.
• Flaherty, K. M., Muzerolle, J., Rieke, G., Gutermuth, R., Balog, Z., Herbst, W., Megeath, S. T., & Kun, M. (2012). Infrared variability of evolved protoplanetary disks: Evidence for scale height variations in the inner disk. Astrophysical Journal, 748(1).
  More info

  Abstract: We present the results of a multi-wavelength multi-epoch survey of five evolved protoplanetary disks in the IC348 cluster that show significant infrared variability. Using 3-8 μm and 24 μm photometry along with 5-40 μm spectroscopy from the Spitzer Space Telescope, as well as ground-based 0.8-5 μm spectroscopy, optical spectroscopy, and near-infrared photometry, covering timescales of days to years, we examine the variability in the disk, stellar, and accretion flux. We find substantial variations (10%-60%) at all infrared wavelengths on timescales of weeks to months for all of these young stellar objects. This behavior is not unique when compared to other cluster members and is consistent with changes in the structure of the inner disk, most likely scale height fluctuations on a dynamical timescale. Previous observations, along with our near-infrared photometry, indicate that the stellar fluxes are relatively constant; stellar variability does not appear to drive the large changes in the infrared fluxes. Based on our near-infrared spectroscopy of the Paβ and Brγ lines we find that the accretion rates are variable in most of the evolved disks but the overall rates are probably too small to cause the infrared variability. We discuss other possible physical causes for the variability, including the influence of a companion, magnetic fields threading the disk, and X-ray flares. © 2012 The American Astronomical Society. All rights reserved.
• Gáspár, A., Psaltis, D., Rieke, G. H., & Özel, F. (2012). Modeling collisional cascades in debris disks: Steep dust-size distributions. Astrophysical Journal, 754(1).
  More info

  Abstract: We explore the evolution of the mass distribution of dust in collision-dominated debris disks, using the collisional code introduced in our previous paper. We analyze the equilibrium distribution and its dependence on model parameters by evolving over 100 models to 10Gyr. With our numerical models, we confirm that systems reach collisional equilibrium with a mass distribution that is steeper than the traditional solution by Dohnanyi. Our model yields a quasi-steady-state slope of n(m) m -1.88 [n(a) a -3.65] as a robust solution for a wide range of possible model parameters. We also show that a simple power-law function can be an appropriate approximation for the mass distribution of particles in certain regimes. The steeper solution has observable effects in the submillimeter and millimeter wavelength regimes of the electromagnetic spectrum. We assemble data for nine debris disks that have been observed at these wavelengths and, using a simplified absorption efficiency model, show that the predicted slope of the particle-mass distribution generates spectral energy distributions that are in agreement with the observed ones. © 2012. The American Astronomical Society. All rights reserved..
• Gáspár, A., Psaltis, D., Zel, F., Rieke, G. H., & Cooney, A. (2012). Modeling collisional cascades in debris disks: The numerical method. Astrophysical Journal, 749(1).
  More info

  Abstract: We develop a new numerical algorithm to model collisional cascades in debris disks. Because of the large dynamical range in particle masses, we solve the integro-differential equations describing erosive and catastrophic collisions in a particle-in-a-box approach, while treating the orbital dynamics of the particles in an approximate fashion. We employ a new scheme for describing erosive (cratering) collisions that yields a continuous set of outcomes as a function of colliding masses. We demonstrate the stability and convergence characteristics of our algorithm and compare it with other treatments. We show that incorporating the effects of erosive collisions results in a decay of the particle distribution that is significantly faster than with purely catastrophic collisions. © 2012 The American Astronomical Society. All rights reserved.
• Rawle, T. D., Chung, S. M., Fadda, D., Rex, M., Egami, E., Perez-Gonzalez, P. G., Altieri, B., Blain, A. W., Bridge, C. R., Fiedler, A. K., Gonzalez, A. H., Pereira, M. J., Richard, J., Smail, I., Valtchanov, I., Zemcov, M., Appleton, P. N., Bock, J. J., Boone, F., , Clement, B., et al. (2012). Deep Herschel view of obscured star formation in the Bullet cluster. ASTRONOMY & ASTROPHYSICS, 518.
  More info

  We use deep, five band (100-500 mu m) data from the Herschel Lensing Survey (HLS) to fully constrain the obscured star formation rate, SFR(FIR), of galaxies in the Bullet cluster (z = 0.296), and a smaller background system (z = 0.35) in the same field. Herschel detects 23 Bullet cluster members with a total SFRFIR = 144 +/- 14 M(circle dot) yr(-1). On average, the background system contains brighter far-infrared (FIR) galaxies, with similar to 50% higher SFRFIR (21 galaxies; 207 +/- 9 M(circle dot) yr(-1)). SFRs extrapolated from 24 mu m flux via recent templates (SFR(24) mu m) agree well with SFRFIR for similar to 60% of the cluster galaxies. In the remaining similar to 40%, SFR(24) mu m underestimates SFRFIR due to a significant excess in observed S(100)/S(24) (rest frame S(75)/S(18)) compared to templates of the same FIR luminosity.
• Rujopakarn, W., Rieke, G. H., Papovich, C. J., Weiner, B. J., Rigby, J. R., Rex, M., Bian, F., Kuhn, O. P., & Thompson, D. (2012). Large binocular telescope and spitzer spectroscopy of star-forming galaxies at 1 Astrophysical Journal, 755(2).
  More info

  Abstract: We present spectroscopic observations in the rest-frame optical and near- to mid-infrared wavelengths of four gravitationally lensed infrared (IR) luminous star-forming galaxies at redshift 1
• Serjeant, S., Dye, S., Mortier, A., Peacock, J., Egami, E., Cirasuolo, M., Rieke, G., Borys, C., Chapman, S., Clements, D., Coppin, K., Dunlop, J., Eales, S., Farrah, D., Halpern, M., Mauskopf, P., Pope, A., Rowan-Robinson, M., Scott, D., , Smail, I., et al. (2012). The SCUBA Half Degree Extragalactic Survey (SHADES) - IX. The environment, mass and redshift dependence of star formation. MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, 386(4), 1907-1921.
  More info

  We present a comparison between the SCUBA (Submillimetre Common User Bolometer Array) Half Degree Extragalactic Survey (SHADES) at 450 and 850 mu m in the Lockman Hole East with a deep Spitzer Space Telescope survey at 3.6-24 mu m conducted in guaranteed time. Using stacking analyses we demonstrate a striking correspondence between the galaxies contributing the submm extragalactic background light, with those likely to dominate the backgrounds at Spitzer wavelengths. Using a combination BRIzK plus Spitzer photometric redshifts, we show that at least a third of the Spitzer-identified submm galaxies at 1 < z < 1.5 appear to reside in overdensities when the density field is smoothed at 0.5-2 Mpc comoving diameters, supporting the high-redshift reversal of the local star formation-galaxy density relation. We derive the dust-shrouded cosmic star formation history of galaxies as a function of assembled stellar masses. For model stellar masses < 10(11) M(circle dot), this peaks at lower redshifts than the ostensible z similar to 2.2 maximum for submm point sources, adding to the growing consensus for 'downsizing' in star formation. Our surveys are also consistent with 'downsizing' in mass assembly. Both the mean star formation rates < dM(*)/dt > and specific star formation rates are in striking disagreement with some semi-analytic predictions from the Millenium Simulation. The discrepancy could either be resolved with a top-heavy initial mass function, or a significant component of the submm flux heated by the interstellar radiation field.
• Stansberry, J. A., Grundy, W. M., Mueller, M., Benecchi, S. D., Rieke, G. H., Noll, K. S., Buie, M. W., Levison, H. F., Porter, S. B., & Roe, H. G. (2012). Physical properties of trans-neptunian binaries (120347) Salacia-Actaea and (42355) Typhon-Echidna. Icarus, 219(2), 676-688.
  More info

  Abstract: We report new Hubble Space Telescope and Spitzer Space Telescope results concerning the physical properties of the trans-neptunian object (TNO) binaries (120347) Salacia-Actaea (formerly 2004 SB 60), and (42355) Typhon-Echidna (formerly 2002 CR 46). The mass of the (120347) Salacia-Actaea system is 4.66±0.22×10 20kg. The semi-major axis, period, and eccentricity of the binary orbit are a=5619±87km, P=5.49380±0.00016days, and e=0.0084±0.0076, respectively. In terms of the ratio of the semimajor axis to the radius of the Hill sphere, a/r H, (120347) Salacia-Actaea is the tightest TNO binary system with a known orbit. Based on hybrid Standard Thermal Model (hybrid-STM) fits to the data, the effective diameter and V-band geometric albedo of the system are D=954±109km (making it one of the largest known TNOs), and pV=3.57-0.72+1.03%. Thermophysical models for (120347) Salacia suggest that it probably has a thermal inertia ≤5Jm -2s -1/2K -1, although we cannot rule out values as high as 30Jm -2s -1/2K -1. Based on the magnitude difference between Salacia and Actaea, δ=2.37±0.06, we estimate their individual diameters to be d 1=905±103km and d 2=303±35km. The mass density of the components is ρ=1.16-0.36+0.59 g/cm 3. Hybrid-STM fits to new Spitzer data for Typhon-Echidna give an effective diameter and V-band geometric albedo for the system of D=157±34km, and pV=6.00-2.08+4.10%. Thermophysical models for (42355) Typhon suggest somewhat lower albedos (probably no higher than about 8.2%, as compared to the hybrid-STM upper limit of 10.1%). Taken together with the previously reported mass, this diameter indicates a density of ρ=0.60-0.29+0.72g/cm3, consistent with the very low densities of most other TNOs smaller than 500km diameter. Both objects must have significant amounts of void space in their interiors, particularly if they contain silicates as well as water-ice (as is expected). The ensemble of binary-TNO densities suggests a trend of increasing density with size, with objects smaller than 400km diameter all having densities less than 1g/cm 3, and those with diameters greater than 800km all having densities greater than 1g/cm 3. If the eccentricity of the binary orbit of (42355) Typhon-Echidna is not due to recent perturbations, considerations of tidal evolution suggest that (42355) Typhon-Echidna must have a rigidity close to that of solid water ice, otherwise the orbital eccentricity of the system would have been damped by now. © 2012 Elsevier Inc.
• Urban, L. E., Rieke, G., Kate, S. u., & Trilling, D. E. (2012). The incidence of debris disks at 24 μm and 670 Myr. Astrophysical Journal, 750(2).
  More info

  Abstract: We use Spitzer Space Telescope 24 μm data to search for debris disks among 122 AFGKM stars from the ∼670 Myr clusters Hyades, Coma Ber, and Praesepe, utilizing a number of advances in data reduction and determining the intrinsic colors of main-sequence stars. For our sample, the 1σ dispersion about the main-sequence V-K S , K S -[24] locus is approximately 3.1%. We identify seven debris disks at 10% or more (≥3σ confidence level) above the expected K S -[24] for purely photospheric emission. The incidence of excesses of 10% or greater in our sample at this age is 5.7 +3.1- 1.7%. Combining with results from the literature, the rate is 7.8 +4.2- 2.1% for early-type (B9-F4) stars and 2.7 +3.3- 1.7% for solar-like (F5-K9) stars. Our primary sample has strict criteria for inclusion to allow comparison with other work; when we relax these criteria, three additional debris disks are detected. They are all around stars of solar-like type and hence reinforce our conclusion that disks around such stars are still relatively common at 670 Myr and are similar to the rate around early-type stars. The apparently small difference in decay rates between early-type and solar-like stars is inconsistent with the first-order theoretical predictions that the later type stellar disks would decay an order of magnitude more quickly than the earlier type ones. © 2012. The American Astronomical Society. All rights reserved.
• Wilson, J. C., Hearty, F., Skrutskie, M. F., Majewski, S. R., Schiavon, R., Eisenstein, D., Gunn, J., Holtzman, J., Nidever, D., Gillespie, B., Weinberg, D., Blank, B., Henderson, C., Smee, S., Barkhouser, R., Harding, A., Hope, S., Fitzgerald, G., Stolberg, T., , Arns, J., et al. (2012). Performance of the apache point observatory galactic evolution experiment (APOGEE) high-resolution near-infrared multi-object fiber spectrograph. Proceedings of SPIE - The International Society for Optical Engineering, 8446.
  More info

  Abstract: The Apache Point Observatory Galactic Evolution Experiment (APOGEE) uses a dedicated 300-fiber, narrow-band near-infrared (1.51-1.7 μm), high resolution (R~22,500) spectrograph to survey approximately 100,000 giant stars across the Milky Way. This three-year survey, in operation since late-summer 2011 as part of the Sloan Digital Sky Survey III (SDSS III), will revolutionize our understanding of the kinematical and chemical enrichment histories of all Galactic stellar populations. We present the performance of the instrument from its first year in operation. The instrument is housed in a separate building adjacent to the 2.5-m SDSS telescope and fed light via approximately 45-meter fiber runs from the telescope. The instrument design includes numerous innovations including a gang connector that allows simultaneous connection of all fibers with a single plug to a telescope cartridge that positions the fibers on the sky, numerous places in the fiber train in which focal ratio degradation had to be minimized, a large mosaic-VPH (290 mm x 475 mm elliptically-shaped recorded area), an f/1.4 six-element refractive camera featuring silicon and fused silica elements with diameters as large as 393 mm, three near-infrared detectors mounted in a 1 x 3 mosaic with sub-pixel translation capability, and all of these components housed within a custom, LN2-cooled, stainless steel vacuum cryostat with dimensions 1.4-m x 2.3-m x 1.3-m. © 2012 SPIE.
• Wyatt, M. C., Kennedy, G., Sibthorpe, B., Moro-Martín, A., Lestrade, J. -., Ivison, R. J., Matthews, B., Udry, S., Greaves, J. S., Kalas, P., Lawler, S., Su, K. Y., Rieke, G. H., Booth, M., Bryden, G., Horner, J., Kavelaars, J. J., & Wilner, D. (2012). Herschel imaging of 61Vir: Implications for the prevalence of debris in low-mass planetary systems. Monthly Notices of the Royal Astronomical Society, 424(2), 1206-1223.
  More info

  Abstract: This paper describes Herschel observations of the nearby (8.5pc) G5V multi-exoplanet host star 61Vir at 70, 100, 160, 250, 350 and 500m carried out as part of the DEBRIS survey. These observations reveal emission that is significantly extended out to a distance of >15arcsec with a morphology that can be fitted by a nearly edge-on (77° inclination) radially broad (from 30au out to at least 100au) debris disc of fractional luminosity 2.7 × 10 -5, with two additional (presumably unrelated) sources nearby that become more prominent at longer wavelengths. Chance alignment with a background object seen at 1.4GHz provides potential for confusion, however, the star's 1.4arcsecyr -1 proper motion allows archival Spitzer 70m images to confirm that what we are interpreting as disc emission really is circumstellar. Although the exact shape of the disc's inner edge is not well constrained, the region inside 30au must be significantly depleted in planetesimals. This is readily explained if there are additional planets outside those already known (i.e. in the 0.5-30au region), but is also consistent with collisional erosion. We also find tentative evidence that the presence of detectable debris around nearby stars correlates with the presence of the lowest mass planets that are detectable in current radial velocity surveys. Out of an unbiased sample of the nearest 60G stars, 11 are known to have planets, of which six (including 61Vir) have planets that are all less massive than Saturn, and four of these have evidence for debris. The debris towards one of these planet hosts (HD20794) is reported here for the first time. This fraction (4/6) is higher than that expected for nearby field stars (15per cent), and implies that systems that form low-mass planets are also able to retain bright debris discs. We suggest that this correlation could arise because such planetary systems are dynamically stable and include regions that are populated with planetesimals in the formation process where the planetesimals can remain unperturbed over Gyr time-scales. © 2012 The Authors Monthly Notices of the Royal Astronomical Society © 2012 RAS.
• Y., H., Rieke, G. H., Y., K., Ivanov, V. D., Vanzi, L., & Rujopakarn, W. (2012). Variability of the infrared excess of extreme debris disks. Astrophysical Journal Letters, 751(1).
  More info

  Abstract: Debris disks with extremely large infrared excesses (fractional luminosities >10-2) are rare. Those with ages between 30 and 130Myr are of interest because their evolution has progressed well beyond that of protoplanetary disks (which dissipate with a timescale of order 3Myr), yet they represent a period when dynamical models suggest that terrestrial planet building may still be progressing through large, violent collisions that could yield large amounts of debris and large infrared excesses. For example, our Moon was formed through a violent collision of two large protoplanets during this age range. We report two disks around the solar-like stars ID8 and HD23514 in this age range where the 24 μm infrared excesses vary on timescales of a few years, even though the stars are not variable in the optical. Variations this rapid are difficult to understand if the debris is produced by collisional cascades, as it is for most debris disks. It is possible that the debris in these two systems arises in part from condensates from silicate-rich vapor produced in a series of violent collisions among relatively large bodies. If their evolution is rapid, the rate of detection of extreme excesses would indicate that major collisions may be relatively common in this age range. © 2012. The American Astronomical Society. All rights reserved..
• Backman, D., Marengo, M., Stapelfeldt, K., Su, K., Wilner, D., Dowell, C. D., Watson, D., Stansberry, J., Rieke, G., Megeath, T., Fazio, G., & Werner, M. (2011). EPSILON ERIDANI'S PLANETARY DEBRIS DISK: STRUCTURE AND DYNAMICS BASED ON SPITZER AND CALTECH SUBMILLIMETER OBSERVATORY OBSERVATIONS. ASTROPHYSICAL JOURNAL, 690(2), 1522-1538.
  More info

  Spitzer and Caltech Submillimeter Observatory images and spectrophotometry of epsilon Eridani at wavelengths from 3.5 to 350 mu m reveal new details of its bright debris disk. The 350 mu m map confirms the presence of a ring at r = 11 '' - 28 ''(35-90 AU), observed previously at longer sub-mm wavelengths. The Spitzer mid-IR and far-IR images do not show the ring, but rather a featureless disk extending from within a few arcsec of the star across the ring to r similar to 34 '' (110 AU). The spectral energy distribution (SED) of the debris system implies a complex structure. A model constrained by the surface brightness profiles and the SED indicates that the sub-mm ring emission is primarily from large (a similar to 135 mu m) grains, with smaller (a similar to 15 mu m) grains also present in and beyond the ring. The Spitzer Infrared Spectrograph and Multiband Imaging Photometer for Spitzer SED-mode spectrophotometry data clearly show the presence of spatially compact excess emission at lambda greater than or similar to 15 mu m that requires the presence of two additional narrow belts of dust within the sub-mm ring's central void. The innermost belt at r similar to 3 AU is composed of silicate dust. A simple dynamical model suggests that dust produced collisionally by a population of about 11 M(circle plus) of planetesimals in the sub-mm ring could be the source of the emission from both in and beyond the sub- mm ring. Maintaining the inner belts and the inner edge to the sub-mm ring may require the presence of three planets in this system including the candidate radial velocity object.
• Bohlin, R. C., Gordon, K. D., Rieke, G. H., Ardila, D., Carey, S., Deustua, S., Engelbracht, C., Ferguson, H. C., Flanagan, K., Kalirai, J., Meixner, M., Noriega-Crespo, A., Su, K. Y., & Tremblay, P. -. (2011). Absolute flux calibration of the IRAC instrument on the spitzer space telescope using hubble space telescope flux standards. Astronomical Journal, 141(5).
  More info

  Abstract: The absolute flux calibration of the James Webb Space Telescope (JWST) will be based on a set of stars observed by the Hubble and Spitzer Space Telescopes. In order to cross-calibrate the two facilities, several A, G, and white dwarf stars are observed with both Spitzer and Hubble and are the prototypes for a set of JWST calibration standards. The flux calibration constants for the four Spitzer IRAC bands 1-4 are derived from these stars and are 2.3%, 1.9%, 2.0%, and 0.5% lower than the official cold-mission IRAC calibration of Reach et al., i.e., in agreement within their estimated errors of 2%. The causes of these differences lie primarily in the IRAC data reduction and secondarily in the spectral energy distributions of our standard stars. The independent IRAC 8 μm band-4 fluxes of Rieke et al. are about 1.5% 2% higher than those of Reach et al. and are also in agreement with our 8 μm result. © 2011. The American Astronomical Society. All rights reserved.
• Churcher, L. J., Wyatt, M. C., Duchêne, G., Sibthorpe, B., Kennedy, G., Matthews, B. C., Kalas, P., Greaves, J., Su, K., & Rieke, G. (2011). Multiwavelength modelling of the β Leo debris disc: One, two or three planetesimal populations?. Monthly Notices of the Royal Astronomical Society, 417(3), 1715-1734.
  More info

  Abstract: In this paper we present a model of the β Leo debris disc, with an emphasis on modelling the resolved Photodetector Array Camera and Spectrometer (PACS) images obtained as a part of the Herschel key programme DEBRIS. We also present new Spectral and Photometric Imaging REceiver (SPIRE) images of the disc at 250μm, as well as new constraints on the disc from SCUBA-2, mid-infrared (mid-IR) and scattered light imaging. Combining all the available observational constraints, we find three possible models for the β Leo (HD 102647) debris disc: (i) a two-component model, comprised of a hot component at 2 au and a cold component from 15 to 70 au; (ii) a three-component model with hot dust at 2 au, warm dust at 9 au and a cold component from 30 to 70 au, is equally valid since the cold emission is not resolved within 30 au; (iii) a somewhat less likely possibility is that the system consists of a single very eccentric planetesimal population, with pericentres at 2 au and apocentres at 65 au. Thus, despite the wealth of observational constraints significant ambiguities remain; deep mid-IR and scattered light imaging of the dust distribution within 30 au seems to be the most promising method to resolve the degeneracy. We discuss the implications for the possible planetary system architecture, e.g. the two-component model suggests that planets may exist at 2-15 au, while the three-component model suggests planets between 2 and 30 au with a stable region containing the dust belt at 9 au, and there should be no planets between 2 and 65 au in the eccentric planetesimal model. We suggest that the hot dust may originate in the disintegration of comets scattered in the cold disc, and examine all A stars known to harbour both hot and cold dust to consider the possibility that the ratio of hot and cold dust luminosities is indicative of the intervening planetary system architecture. © 2011 The Authors. Monthly Notices of the Royal Astronomical Society © 2011 RAS.
• Currie, T., Lisse, C. M., Sicilia-Aguilar, A., Rieke, G. H., & Y., K. (2011). Spitzer infrared spectrograph spectroscopy of the 10Myr old EF Cha debris disk: Evidence for phyllosilicate-rich dust in the terrestrial zone. Astrophysical Journal, 734(2).
  More info

  Abstract: We describe Spitzer Infrared Spectrograph spectroscopic observations of the ∼10Myr old star, EF Cha. Compositional modeling of the spectra from 5 μm to 35 μm confirms that it is surrounded by a luminous debris disk with LD /L⊙ ∼ 10-3, containing dust with temperatures between 225 K and 430 K, characteristic of the terrestrial zone. The EF Cha spectrum shows evidence for many solid-state features, unlike most cold, low-luminosity debris disks but like some other 10-20Myr old luminous, warm debris disks (e.g., HD 113766A). The EF Cha debris disk is unusually rich in a species or combination of species whose emissivities resemble that of finely powdered, laboratory-measured phyllosilicate species (talc, saponite, and smectite), which are likely produced by aqueous alteration of primordial anhydrous rocky materials. The dust and, by inference, the parent bodies of the debris also contain abundant amorphous silicates and metal sulfides, and possibly water ice. The dust's total olivine to the pyroxene ratio of ∼2 also provides evidence of aqueous alteration. The large mass volume of grains with sizes comparable to or below the radiation blow-out limit implies that planetesimals may be colliding at a rate high enough to yield the emitting dust but not so high as to devolatize the planetesimals via impact processing. Because phyllosilicates are produced by the interactions between anhydrous rock and warm, reactive water, EF Cha's disk is a likely signpost for water delivery to the terrestrial zone of a young planetary system. © 2011. The American Astronomical Society. All rights reserved.
• Donley, J. L., Rieke, G. H., Alexander, D. M., Egami, E., & Perez-Gonzalez, P. G. (2011). THE AGN, STAR-FORMING, AND MORPHOLOGICAL PROPERTIES OF LUMINOUS IR-BRIGHT/OPTICALLY-FAINT GALAXIES. ASTROPHYSICAL JOURNAL, 719(2), 1393-1407.
  More info

  We present the active galactic nucleus (AGN), star-forming, and morphological properties of a sample of 13 MIR-luminous (f(24) greater than or similar to 700 mu Jy) IR-bright/optically-faint galaxies (IRBGs, f(24)/f(R) greater than or similar to 1000). While these z similar to 2 sources were drawn from deep Chandra fields with >200 ks X-ray coverage, only seven are formally detected in the X-ray and four lack X-ray emission at even the 2 sigma level. Spitzer InfraRed Spectrograph (IRS) spectra, however, confirm that all of the sources are AGN-dominated in the mid-IR, although half have detectable polycyclic aromatic hydrocarbon (PAH) emission responsible for similar to 25% of their mid-infrared flux density. When combined with other samples, this indicates that at least 30%-40% of luminous IRBGs have star formation rates in the ultraluminous infrared galaxy (ULIRG) range (similar to 100-2000 M(circle dot) yr(-1)). X-ray hardness ratios and MIR to X-ray luminosity ratios indicate that all members of the sample contain heavily X-ray obscured AGNs, 80% of which are candidates to be Compton thick. Furthermore, the mean X-ray luminosity of the sample, log L(2-10) (keV)(erg s(-1)) similar to 44.6, indicates that these IRBGs are Type 2 QSOs, at least from the X-ray perspective. While those sources most heavily obscured in the X-ray are also those most likely to display strong silicate absorption in the mid-IR, silicate absorption does not always accompany X-ray obscuration. Finally, similar to 70% of the IRBGs are merger candidates, a rate consistent with that of sub-mm galaxies (SMGs), although SMGs appear to be physically larger than IRBGs. These characteristics are consistent with the proposal that these objects represent a later, AGN-dominated, and more relaxed evolutionary stage following soon after the star-formation-dominated one represented by the SMGs.
• Eisenstein, D. J., Weinberg, D. H., Agol, E., Aihara, H., Prieto, C. A., Anderson, S. F., Arns, J. A., Aubourg, E., Bailey, S., Balbinot, E., Barkhouser, R., Beers, T. C., Berlind, A. A., Bickerton, S. J., Bizyaev, D., Blanton, M. R., Bochanski, J. J., Bolton, A. S., Bosman, C. T., , Bovy, J., et al. (2011). SDSS-III: Massive spectroscopic surveys of the distant Universe, the MILKY WAY, and extra-solar planetary systems. Astronomical Journal, 142(3).
  More info

  Abstract: Building on the legacy of the Sloan Digital Sky Survey (SDSS-I and II), SDSS-III is a program of four spectroscopic surveys on three scientific themes: dark energy and cosmological parameters, the history and structure of the Milky Way, and the population of giant planets around other stars. In keeping with SDSS tradition, SDSS-III will provide regular public releases of all its data, beginning with SDSS Data Release 8 (DR8), which was made public in 2011 January and includes SDSS-I and SDSS-II images and spectra reprocessed with the latest pipelines and calibrations produced for the SDSS-III investigations. This paper presents an overview of the four surveys that comprise SDSS-III. The Baryon Oscillation Spectroscopic Survey will measure redshifts of 1.5 million massive galaxies and Lyα forest spectra of 150,000 quasars, using the baryon acoustic oscillation feature of large-scale structure to obtain percent-level determinations of the distance scale and Hubble expansion rate at z < 0.7 and at z ≈ 2.5. SEGUE-2, an already completed SDSS-III survey that is the continuation of the SDSS-II Sloan Extension for Galactic Understanding and Exploration (SEGUE), measured medium-resolution (R = λ/Δλ 1800) optical spectra of 118,000 stars in a variety of target categories, probing chemical evolution, stellar kinematics and substructure, and the mass profile of the dark matter halo from the solar neighborhood to distances of 100 kpc. APOGEE, the Apache Point Observatory Galactic Evolution Experiment, will obtain high-resolution (R 30,000), high signal-to-noise ratio (S/N ≥ 100 per resolution element), H-band (1.51 μm < λ < 1.70 μm) spectra of 105 evolved, late-type stars, measuring separate abundances for 15 elements per star and creating the first high-precision spectroscopic survey of all Galactic stellar populations (bulge, bar, disks, halo) with a uniform set of stellar tracers and spectral diagnostics. The Multi-object APO Radial Velocity Exoplanet Large-area Survey (MARVELS) will monitor radial velocities of more than 8000 FGK stars with the sensitivity and cadence (10-40 m s -1, 24 visits per star) needed to detect giant planets with periods up to two years, providing an unprecedented data set for understanding the formation and dynamical evolution of giant planet systems. As of 2011 January, SDSS-III has obtained spectra of more than 240,000 galaxies, 29,000 z ≥ 2.2 quasars, and 140,000 stars, including 74,000 velocity measurements of 2580 stars for MARVELS. © 2011. The American Astronomical Society. All rights reserved.
• Flaherty, K. M., Muzerolle, J., Rieke, G., Gutermuth, R., Balog, Z., Herbst, W., Megeath, S. T., & Kun, M. (2011). The highly dynamic behavior of the innermost dust and gas in the transition disk variable LRLL 31. Astrophysical Journal, 732(2).
  More info

  Abstract: We describe extensive synoptic multi-wavelength observations of the transition disk LRLL 31 in the young cluster IC 348. We combined 4 epochs of IRS spectra, 9 epochs of MIPS photometry, 7 epochs of cold-mission IRAC photometry, and 36 epochs of warm-mission IRAC photometry along with multi-epoch near-infrared spectra, optical spectra, and polarimetry to explore the nature of the rapid variability of this object. We find that the inner disk, as traced by the 2-5 μm excess, stays at the dust sublimation radius while the strength of the excess changes by a factor of eight on weekly timescales, and the 3.6 and 4.5 μm photometry show a drop of 0.35 mag in 1week followed by a slow 0.5 mag increase over the next 3 weeks. The accretion rate, as measured by Paβ and Brγ emission lines, varies by a factor of five with evidence for a correlation between the accretion rate and the infrared excess. While the gas and dust in the inner disk are fluctuating, the central star stays relatively static. Our observations allow us to put constraints on the physical mechanism responsible for the variability. The variable accretion, and wind, are unlikely to be causes of the variability, but are both effects of the same physical process that disturbs the disk. The lack of periodicity in our infrared monitoring indicates that it is unlikely that there is a companion within ∼0.4 AU that is perturbing the disk. The most likely explanation is either a companion beyond ∼0.4 AU or a dynamic interface between the stellar magnetic field and the disk leading to a variable scale height and/or warping of the inner disk. © 2011. The American Astronomical Society. All rights reserved.
• Golimowski, D. A., Krist, J. E., Stapelfeldt, K. R., Chen, C. H., Ardila, D. R., Bryden, G., Clampin, M., Ford, H. C., Illingworth, G. D., Plavchan, P., Rieke, G. H., & Su, K. Y. (2011). Hubble and spitzer space telescope observations of the debris disk around the nearby K dwarf HD92945. Astronomical Journal, 142(1).
  More info

  Abstract: We present the first resolved images of the debris disk around the nearby K dwarf HD92945, obtained with the Hubble Space Telescope's (HST 's) Advanced Camera for Surveys. Our F606W (Broad V) and F814W (Broad I) coronagraphic images reveal an inclined, axisymmetric disk consisting of an inner ring about 20-30 (43-65AU) from the star and an extended outer disk whose surface brightness declines slowly with increasing radius approximately 30-51 (65-110AU) from the star. A precipitous drop in the surface brightness beyond 110AU suggests that the outer disk is truncated at that distance. The radial surface-density profile is peaked at both the inner ring and the outer edge of the disk. The dust in the outer disk scatters neutrally but isotropically, and it has a low V-band albedo of 0.1. This combination of axisymmetry, ringed and extended morphology, and isotropic neutral scattering is unique among the 16 debris disks currently resolved in scattered light. We also present new infrared photometry and spectra of HD92945 obtained with the Spitzer Space Telescope's Multiband Imaging Photometer and InfraRed Spectrograph. These data reveal no infrared excess from the disk shortward of 30μm and constrain the width of the 70μm source to ≲180AU. Assuming that the dust comprises compact grains of astronomical silicate with a surface-density profile described by our scattered-light model of the disk, we successfully model the 24-350μm emission with a minimum grain size of a min = 4.5μm and a size distribution proportional to a -3.7 throughout the disk, but with maximum grain sizes of 900μm in the inner ring and 50μm in the outer disk. Together, our HST and Spitzer observations indicate a total dust mass of ∼0.001M ⊕. However, our observations provide contradictory evidence of the dust's physical characteristics: its neutral V-I color and lack of 24μm emission imply grains larger than a few microns, but its isotropic scattering and low albedo suggest a large population of submicron-sized grains. If grains smaller than a few microns are absent, then stellar radiation pressure may be the cause only if the dust is composed of highly absorptive materials like graphite. The dynamical causes of the sharply edged inner ring and outer disk are unclear, but recent models of dust creation and transport in the presence of migrating planets support the notion that the disk indicates an advanced state of planet formation around HD92945. © 2011. The American Astronomical Society. All rights reserved.
• Greenhouse, M. A., Mather, J. C., Clampin, M., Doyon, R., Flanagan, K. A., Franx, M., Hammel, H. B., Hutchings, J. B., Jakobsen, P., Lilly, S. J., Lunine, J. I., McCaughrean, M. J., Mountain, M., Rieke, G. H., Rieke, M. J., Sonneborn, G., Stiavelli, M., Windhorst, R., & Wright, G. S. (2011). The James Webb space telescope: Mission overview and status. 2nd International Conference on Space Technology, ICST 2011.
  More info

  Abstract: The James Webb Space Telescope (JWST) is the infrared successor to the Hubble Space Telescope. It is a cryogenic infrared space observatory with a 25 m2 aperture (6 m class) telescope yielding diffraction limited angular resolution at a wavelength of 2 um. The science instrument payload includes three passively cooled near-infrared instruments providing broad- and narrow-band imagery, coronagraphy, as well as multi-object and integral-field spectroscopy over the 0.6 < λ < 5.0 um spectrum. An actively cooled mid-infrared instrument provides broad-band imagery, coronagraphy, and integral-field spectroscopy over the 5.0 < λ < 29 um spectrum. The JWST is being developed by NASA, in partnership with the European and Canadian Space Agencies, as a general user facility with science observations to be proposed by the international astronomical community in a manner similar to the Hubble Space Telescope. Technology development and mission design are complete, and construction is underway in all areas of the program. © 2011 IEEE.
• Luhman, K., Stauffer, ., Muench, A., Rieke, G., Lada, E., Bouvier, J., & Lada, C. (2011). A census of the young cluster IC 348. ASTROPHYSICAL JOURNAL, 593(2), 1093-1115.
  More info

  We present a new census of the stellar and substellar members of the young cluster IC 348. We have obtained images at I and Z for a 42' x 28' field encompassing the cluster and have combined these measurements with previous optical and near-infrared photometry. From spectroscopy of candidate cluster members appearing in these data, we have identified 122 new members, 15 of which have spectral types of M6.5-M9, corresponding to masses of similar to0.08-0.015 M-circle dot by recent evolutionary models. The latest census for IC 348 now contains a total of 288 members, 23 of which are later than M6 and thus are likely to be brown dwarfs. From an extinction-limited sample of members (A(V) less than or equal to 4) for a 16' x 14' field centered on the cluster, we construct an initial mass function (IMF) that is unbiased in mass and nearly complete for M/M-circle dot greater than or equal to 0.03 (less than or similar toM8). In logarithmic units where the Salpeter slope is 1.35, the mass function for IC 348 rises from high masses down to a solar mass, rises more slowly down to a maximum at 0.1-0.2 M-circle dot, and then declines into the substellar regime. In comparison, the similarly derived IMF for Taurus from Briceno et al. and Luhman et al. rises quickly to a peak near 0.8 M-circle dot and steadily declines to lower masses. The distinctive shapes of the IMFs in IC 348 and Taurus are reflected in the distributions of spectral types, which peak at M5 and K7, respectively. These data provide compelling, model-independent evidence for a significant variation of the IMF with star-forming conditions.
• Morales, F. Y., Rieke, G. H., Werner, M. W., Bryden, G., Stapelfeldt, K. R., & Su, K. Y. (2011). Common warm dust temperatures around main-sequence stars. Astrophysical Journal Letters, 730(2 PART II).
  More info

  Abstract: We compare the properties of warm dust emission from a sample of main-sequence A-type stars (B8-A7) to those of dust around solar-type stars (F5-K0) with similar Spitzer Space Telescope Infrared Spectrograph/MIPS data and similar ages. Both samples include stars with sources with infrared spectral energy distributions that show evidence of multiple components. Over the range of stellar types considered, we obtain nearly the same characteristic dust temperatures (190 K and 60 K for the inner and outer dust components, respectively) - slightly above the ice evaporation temperature for the inner belts. The warm inner dust temperature is readily explained if populations of small grains are being released by sublimation of ice from icy planetesimals. Evaporation of low-eccentricity icy bodies at 150 K can deposit particles into an inner/warm belt, where the small grains are heated to T dust 190 K. Alternatively, enhanced collisional processing of an asteroid belt-like system of parent planetesimals just interior to the snow line may account for the observed uniformity in dust temperature. The similarity in temperature of the warmer dust across our B8-K0 stellar sample strongly suggests that dust-producing planetesimals are not found at similar radial locations around all stars, but that dust production is favored at a characteristic temperature horizon. © 2011. The American Astronomical Society. All rights reserved.
• Pereira-Santaella, M., Alonso-Herrero, A., Santos-Lleo, M., Colina, L., Jiménez-Bailón, E., Longinotti, A. L., Rieke, G. H., Ward, M., & Esquej, P. (2011). The X-ray emission of local luminous infrared galaxies. Astronomy and Astrophysics, 535.
  More info

  Abstract: We study the X-ray emission of a representative sample of 27 local luminous infrared galaxies (LIRGs). The median IR luminosity of our sample is log L IR/L⊙ = 11.2, therefore the low-luminosity end of the LIRG class is well represented. We used new XMM-Newton data as well as Chandra and XMM-Newton archive data. The soft X-ray (0.5-2? keV) emission of most of the galaxies (>80%), including LIRGs hosting a Seyfert 2 nucleus, is dominated by star-formation-related processes. These LIRGs follow the star-formation rate (SFR) versus soft X-ray luminosity correlation observed in local starbursts. We find that ∼15% of the non-Seyfert LIRGs (3 out of 20) have an excessively hard X-ray emission relative to that expected from star-formation, which might indicate the presence of an obscured AGN. The rest of the non-Seyfert LIRGs follow the SFR versus hard X-ray (2-10? keV) luminosity correlation of local starbursts. The non-detection of the 6.4? keV Fe? Kα emission line in the non-Seyfert LIRGs allows us to put an upper limit on the bolometric luminosity of an obscured AGN, Lbol
• Rex, M., Rawle, T. D., Egami, E., Perez-Gonzalez, P. G., Zemcov, M., Aretxaga, I., Chung, S. M., Fadda, D., Gonzalez, A. H., Hughes, D. H., Horellou, C., Johansson, D., Kneib, J. -., Richard, J., Altieri, B., Fiedler, A. K., Pereira, M. J., Rieke, G. H., Smail, I., , Valtchanov, I., et al. (2011). The far-infrared/submillimeter properties of galaxies located behind the Bullet cluster. ASTRONOMY & ASTROPHYSICS, 518.
  More info

  The Herschel Lensing Survey (HLS) takes advantage of gravitational lensing by massive galaxy clusters to sample a population of high-redshift galaxies which are too faint to be detected above the confusion limit of current far-infrared/submillimeter telescopes. Measurements from 100-500 mu m bracket the peaks of the far-infrared spectral energy distributions of these galaxies, characterizing their infrared luminosities and star formation rates. We introduce initial results from our science demonstration phase observations, directed toward the Bullet cluster (1E0657-56). By combining our observations with LABOCA 870 mu m and AzTEC 1.1 mm data we fully constrain the spectral energy distributions of 19 MIPS 24 mu m-selected galaxies which are located behind the cluster. We find that their colors are best fit using templates based on local galaxies with systematically lower infrared luminosities. This suggests that our sources are not like local ultra-luminous infrared galaxies in which vigorous star formation is contained in a compact highly dust-obscured region. Instead, they appear to be scaled up versions of lower luminosity local galaxies with star formation occurring on larger physical scales.
• Rujopakarn, W., Rieke, G. H., Eisenstein, D. J., & Juneau, S. (2011). Morphology and size differences between local and high-redshift luminous infrared galaxies. Astrophysical Journal, 726(2).
  More info

  Abstract: We show that the star-forming regions in high-redshift luminous and ultraluminous infrared galaxies (LIRGs and ULIRGs) and submillimeter galaxies (SMGs) have similar physical scales to those in local normal star-forming galaxies. To first order, their higher infrared (IR) luminosities result from higher luminosity surface density. We also find a good correlation between the IR luminosity and IR luminosity surface density in starburst galaxies across over five orders of magnitude of IR luminosity from local normal galaxies to z ∼ 2 SMGs. The intensely star-forming regions of local ULIRGs are significantly smaller than those in their high-redshift counterparts and hence diverge significantly from this correlation, indicating that the ULIRGs found locally are a different population from the high-redshift ULIRGs and SMGs. Based on this relationship, we suggest that luminosity surface density should serve as a more accurate indicator for the IR emitting environment, and hence the observable properties, of star-forming galaxies than their IR luminosity. We demonstrate this approach by showing that ULIRGs at z ∼ 1 and a lensed galaxy at z ∼ 2.5 exhibit aromatic features agreeing with local LIRGs that are an order of magnitude less luminous, but have similar IR luminosity surface density. A consequence of this relationship is that the aromatic emission strength in star-forming galaxies will appear to increase at z > 1 for a given IR luminosity compared to their local counterparts. © 2011 The American Astronomical Society. All rights reserved.
• Seymour, N., Huynh, M., Dwelly, T., Symeonidis, M., Hopkins, A., McHardy, I. M., Page, M. J., & Rieke, G. (2011). Investigating the far-IR/radio correlation of star-forming Galaxies to z=3. MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, 398(3), 1573-1581.
  More info

  In order to examine the far-infrared (far-IR)/radio correlation at high redshift, we have studied the Spitzer 70 mu m/far-IR properties of sub-mJy radio sources from the 13(H) XMM-Newton/Chandra Deep Field by redshift and galaxy type: active galactic nucleus (AGN) or star-forming galaxy (SFG). We directly detect 70 mu m counterparts (at > 3 sigma significance) for 22.5 per cent (92/408) of the radio sources, while for the rest we perform stacking analysis by redshift and galaxy type. For the sources detected at 70 mu m, we find that the median and scatter of the observed flux density ratio, q(70), are similar to previous results in the literature, but with a slight decrease in q(70) towards higher redshifts. Of the radio sources detected at 70 mu m 8/92 were already classified as AGN, but two of which maybe SFGs. For the stacked sources, we obtain a detection for the SFGs at every redshift bin which implies they have mean flux densities a factor similar to 5 below the original 70 mu m detection limit. For the stacked AGN, we obtain a detection only in our highest redshift bin (1
• Tyler, K. D., Rieke, G. H., Wilman, D. J., McGee, S. L., Bower, R. G., Bai, L., Mulchaey, J. S., Parker, L. C., Shi, Y., & Pierini, D. (2011). The nature of star formation at 24 μm in the group environment at 0.3 ≲ z ≲ 0.55. Astrophysical Journal, 738(1).
  More info

  Abstract: Galaxy star formation rates (SFRs) are sensitive to the local environment; for example, the high-density regions at the cores of dense clusters are known to suppress star formation. It has been suggested that galaxy transformation occurs largely in groups, which are the intermediate step in density between field and cluster environments. In this paper, we use deep MIPS 24 μm observations of intermediate-redshift (0.3 ≲ z ≲ 0.55) group and field galaxies from the Group Environment and Evolution Collaboration (GEEC) subset of the Second Canadian Network for Observational Cosmology (CNOC2) survey to probe the moderate-density environment of groups, wherein the majority of galaxies are found. The completeness limit of our study is log (L TIR(L ∞)) ≳ 10.5, corresponding to SFR ≳2.7 M ∞ yr-1. We find that the group and field galaxies have different distributions of morphologies and mass. However, individual group galaxies have star-forming properties comparable to those of field galaxies of similar mass and morphology; that is, the group environment does not appear to modify the properties of these galaxies directly. There is a relatively large number of massive early-type group spirals, along with E/S0 galaxies, that are forming stars above our detection limit. These galaxies account for the nearly comparable level of star-forming activity in groups as compared with the field, despite the differences in mass and morphology distributions between the two environments. The distribution of specific SFRs (SFR/M *) is shifted to lower values in the groups, reflecting the fact that groups contain a higher proportion of massive and less active galaxies. Considering the distributions of morphology, mass, and SFR, the group members appear to lie between field and cluster galaxies in overall properties. © 2011. The American Astronomical Society. All rights reserved.
• Alonso-Herrero, A., Pereira-Santaella, M., Rieke, G. H., Colina, L., Engelbracht, C. W., Pérez-González, P. G., Díaz-Santos, T., & Smith, J. -. (2010). Local luminous infrared galaxies: Spatially resolved mid-infrared observations with Spitzer/IRS. Advances in Space Research, 45(1), 99-111.
  More info

  Abstract: Luminous Infrared (IR) Galaxies (LIRGs, LIR = 1011 s(-) 1012 Lȯ) are an important cosmological class of galaxies as they are the main contributors to the co-moving star formation rate density of the universe at z = 1. In this paper we present a guaranteed time observation (GTO) Spitzer InfraRed Spectrograph (IRS) program aimed to obtain spectral mapping of a sample of 14 local (d < 76 Mpc) LIRGs. The data cubes map, at least, the central 20 arcsec × 20 arcsec to 30 arcsec × 30 arcsec regions of the galaxies, and use all four IRS modules covering the full 5 s(-) 38 μ m spectral range. The final goal of this project is to characterize fully the mid-IR properties of local LIRGs as a first step to understanding their more distant counterparts. In this paper we present the first results of this GTO program. The IRS spectral mapping data allow us to build spectral maps of the bright mid-IR emission lines (e.g., [Ne ii]12.81 μ m, [Ne iii]15.56 μ m, [S iii]18.71 μ m, H2 at 17 μ m), continuum, the 6.2 and 11.3 μ m polycyclic aromatic hydrocarbon (PAH) features, and the 9.7 μ m silicate feature, as well as to extract 1D spectra for regions of interest in each galaxy. The IRS data are used to obtain spatially resolved measurements of the extinction using the 9.7 μ m silicate feature, and to trace star forming regions using the neon lines and the PAH features. We also investigate a number of active galactic nuclei (AGN) indicators, including the presence of high excitation emission lines and a strong dust continuum emission at around 6 μ m. We finally use the integrated Spitzer/IRS spectra as templates of local LIRGs. We discuss several possible uses for these templates, including the calibration of the star formation rate of IR-bright galaxies at high redshift. We also predict the intensities of the brightest mid-IR emission lines for LIRGs as a function of redshift, and compare them with the expected sensitivities of future space IR missions. © 2009 COSPAR.
• Austermann, J. E., Dunlop, J. S., Perera, T. A., Scott, K. S., Wilson, G. W., Aretxaga, I., Hughes, D. H., Almaini, O., Chapin, E. L., Chapman, S. C., Cirasuolo, M., Clements, D. L., Coppin, K. E., Dunne, L., Dye, S., Eales, S. A., Egami, E., Farrah, D., Ferrusca, D., , Flynn, S., et al. (2010). AzTEC half square degree survey of the SHADES fields - I. Maps, catalogues and source counts. Monthly Notices of the Royal Astronomical Society, 401(1), 160-176.
  More info

  Abstract: We present the first results from the largest deep extragalactic mm-wavelength survey undertaken to date. These results are derived from maps covering over 0.7 deg 2, made at λ = 1.1 mm, using the AzTEC continuum camera mounted on the James Clerk Maxwell Telescope. The maps were made in the two fields originally targeted at λ = 850 μm with the Submillimetre Common-User Bolometer Array (SCUBA) in the SCUBA Half-Degree Extragalactic Survey (SHADES) project, namely the Lockman Hole East (mapped to a depth of 0.9-1.3 mJy rms) and the Subaru/XMM-Newton Deep Field (mapped to a depth of 1.0-1.7 mJy rms). The wealth of existing and forthcoming deep multifrequency data in these two fields will allow the bright mm source population revealed by these new wide-area 1.1 mm images to be explored in detail in subsequent papers. Here, we present the maps themselves, a catalogue of 114 high-significance submillimetre galaxy detections, and a thorough statistical analysis leading to the most robust determination to date of the 1.1 mm source number counts. These new maps, covering an area nearly three times greater than the SCUBA SHADES maps, currently provide the largest sample of cosmological volumes of the high-redshift Universe in the mm or sub-mm. Through careful comparison, we find that both the Cosmic Evolution Survey (COSMOS) and the Great Observatories Origins Deep Survey (GOODS) North fields, also imaged with AzTEC, contain an excess of mm sources over the new 1.1 mm source-count baseline established here. In particular, our new AzTEC/SHADES results indicate that very luminous high-redshift dust enshrouded starbursts (S 1.1mm > 3 mJy) are 25-50 per cent less common than would have been inferred from these smaller surveys, thus highlighting the potential roles of cosmic variance and clustering in such measurements. We compare number count predictions from recent models of the evolving mm/sub-mm source population to these sub-mm bright galaxy surveys, which provide important constraints for the ongoing refinement of semi-analytic and hydrodynamical models of galaxy formation, and find that all available models overpredict the number of bright submillimetre galaxies found in this survey. © 2009 RAS.
• Diamond-Stanic, A. M., & Rieke, G. H. (2010). The effect of active galactic nuclei on the mid-infrared aromatic features. Astrophysical Journal Letters, 724(1), 140-153.
  More info

  Abstract: We present Spitzer measurements of the aromatic (also known as polycyclic aromatic hydrocarbon) features for 35 Seyfert galaxies from the revised Shapley-Ames sample and find that the relative strengths of the features differ significantly from those observed in star-forming galaxies. Specifically, the features at 6.2, 7.7, and 8.6 μm are suppressed relative to the 11.3 μm feature in Seyferts. Furthermore, we find an anti-correlation between the L(7.7 μm)/L(11.3 μm) ratio and the strength of the rotational H2 emission, which traces shocked gas. This suggests that shocks suppress the short-wavelength features by modifying the structure of the aromatic molecules or destroying the smallest grains. Most Seyfert nuclei fall on the relationship between aromatic emission and [Ne ii] emission for star-forming galaxies, indicating that aromatic-based estimates of the star formation rate are generally reasonable in galaxies hosting active galactic nuclei. For the outliers from this relationship, which have small L(7.7 μm)/L(11.3 μm) ratios and strong H2 emission, the 11.3 μm feature still provides a valid measure of the star formation rate. © 2010. The American Astronomical Society. All Rights Reserved.
• Donley, J. L., Rieke, G. H., Alexander, D. M., Egami, E., & Pérez-González, P. (2010). The AGN, star-forming, and morphological properties of luminous IR-bright/optically-faint galaxies. Astrophysical Journal Letters, 719(2), 1393-1407.
  More info

  Abstract: We present the active galactic nucleus (AGN), star-forming, and morphological properties of a sample of 13 MIR-luminous (f24 ≳ 700 μJy) IR-bright/optically-faint galaxies (IRBGs, f24/fR ≳ 1000). While these z ∼ 2 sources were drawn from deep Chandra fields with >200 ks X-ray coverage, only seven are formally detected in the X-ray and four lack X-ray emission at even the 2σ level. Spitzer InfraRed Spectrograph (IRS) spectra, however, confirm that all of the sources are AGN-dominated in the mid-IR, although half have detectable polycyclic aromatic hydrocarbon (PAH) emission responsible for ∼25% of their mid-infrared flux density. When combined with other samples, this indicates that at least 30%-40% of luminous IRBGs have star formation rates in the ultraluminous infrared galaxy (ULIRG) range (∼100-2000 Mȯ yr-1). X-ray hardness ratios and MIR to X-ray luminosity ratios indicate that all members of the sample contain heavily X-ray obscured AGNs, 80% of which are candidates to be Compton thick. Furthermore, the mean X-ray luminosity of the sample, log L2-10keV(erg s-1) ∼44.6, indicates that these IRBGs are Type 2 QSOs, at least from the X-ray perspective. While those sources most heavily obscured in the X-ray are also those most likely to display strong silicate absorption in the mid-IR, silicate absorption does not always accompany X-ray obscuration. Finally, ∼70% of the IRBGs are merger candidates, a rate consistent with that of sub-mm galaxies (SMGs), although SMGs appear to be physically larger than IRBGs. These characteristics are consistent with the proposal that these objects represent a later, AGN-dominated, and more relaxed evolutionary stage following soon after the star-formation-dominated one represented by the SMGs. © 2010. The American Astronomical Society. All rights reserved. Printed in the U.S.A.
• Dressler, A., Rigby, J., Oemler, A., Fritz, J., Poggianti, B. M., Rieke, G., & Bai, L. (2010). SPITZER 24 mu m DETECTIONS OF STARBURST GALAXIES IN ABELL 851. ASTROPHYSICAL JOURNAL, 693(1), 140-151.
  More info

  Spitzer-MIPS 24 mu m observations and ground-based optical imaging and spectroscopy of the rich galaxy cluster Abell 851 at z = 0.41 are used to derive and compare star formation rates from the mid-IR 24 mu m and from [O II] lambda lambda 3727 emission. Many cluster galaxies have star formation rates SFR(24 mu m)/SFR([O II]) >> 1, indicative of star formation in regions highly obscured by dust. We focus on the substantial minority of A851 cluster members where strong Balmer absorption points to a starburst on a 10(8)-10(9) year timescale. As is typical, two types of galaxies with strong Balmer absorption are found in A851: with optical emission (starforming), and without optical emission (post-starburst). Our principal result is that the starforming variety, so-called e(a) galaxies, are mostly detected (9 out of 12) at 24 mu m-for these we find typically SFR(24 mu m)/SFR([O II]) similar to 4. Strong Balmer absorption and high values of SFR(24 mu m)/SFR([O II]) indicate moderately active starbursts (SB); both observations support the picture that e(a) galaxies are the active starbursts that feed the post-starburst population. While 24 mu m detections are frequent with Balmer-strong objects (even 6 out of 18 of the supposedly "post-starburst" galaxies are detected), only two out of seven of the continuously starforming 'e(c)' galaxies (with weak Balmer absorption) are detected-for them, SFR(24 mu m)/SFR([O II]) similar to 1. Their optical spectra resemble present-epoch spirals that dominate today's universe; we strengthen this association by showing that SFR(24 mu m)/SFR([O II]) similar to 1 is the norm today. That is, not just the amount of star formation but also its mode has evolved strongly from z similar to 0.4 to the present. We fit spectrophotometric models in order to measure the strength and duration of the bursts and to quantify the evolutionary sequence from active to post-starburst. Our results harden the evidence that moderately active starbursts are the defining feature of starforming cluster galaxies at z similar to 0.4.
• Egami, E., Rex, M., Rawle, T. D., Perez-Gonzalez, P. G., Richard, J., Kneib, J. -., Schaerer, D., Altieri, B., Valtchanov, I., Blain, A. W., Fadda, D., Zemcov, M., Bock, J. J., Boone, F., Bridge, C. R., Clement, B., Combes, F., Dessauges-Zavadsky, M., Dowell, C. D., , Ilbert, O., et al. (2010). The Herschel Lensing Survey (HLS): Overview. ASTRONOMY & ASTROPHYSICS, 518.
  More info

  The Herschel Lensing Survey (HLS) will conduct deep PACS and SPIRE imaging of similar to 40 massive clusters of galaxies. The strong gravitational lensing power of these clusters will enable us to penetrate through the confusion noise, which sets the ultimate limit on our ability to probe the Universe with Herschel. Here we present an overview of our survey and a summary of the major results from our science demonstration phase (SDP) observations of the Bullet cluster (z = 0.297). The SDP data are rich and allow us to study not only the background high-redshift galaxies (e. g., strongly lensed and distorted galaxies at z = 2.8 and 3.2) but also the properties of cluster-member galaxies. Our preliminary analysis shows a great diversity of far-infrared/submillimeter spectral energy distributions (SEDs), indicating that we have much to learn with Herschel about the properties of galaxy SEDs. We have also detected the Sunyaev-Zel'dovich (SZ) effect increment with the SPIRE data. The success of this SDP program demonstrates the great potential of the Herschel Lensing Survey to produce exciting results in a variety of science areas.
• Egami, E., Rex, M., Rawle, T. D., Pérez-González, P., Richard, J., Kneib, J. -., Schaerer, D., Altieri, B., Valtchanov, I., Blain, A. W., Fadda, D., Zemcov, M., Bock, J. J., Boone, F., Bridge, C. R., Clement, B., Combes, F., Dessauges-Zavadsky, M., Dowell, C. D., , Ilbert, O., et al. (2010). The Herschel Lensing Survey (HLS): Overview. Astronomy and Astrophysics, 518(7-8).
  More info

  Abstract: The Herschel Lensing Survey (HLS) will conduct deep PACS and SPIRE imaging of ~40 massive clusters of galaxies. The strong gravitational lensing power of these clusters will enable us to penetrate through the confusion noise, which sets the ultimate limit on our ability to probe the Universe with Herschel. Here we present an overview of our survey and a summary of the major results from our science demonstration phase (SDP) observations of the Bullet cluster (z = 0.297). The SDP data are rich and allow us to study not only the background high-redshift galaxies (e.g., strongly lensed and distorted galaxies at z = 2.8 and 3.2) but also the properties of cluster-member galaxies. Our preliminary analysis shows a great diversity of far-infrared/submillimeter spectral energy distributions (SEDs), indicating that we have much to learn with Herschel about the properties of galaxy SEDs. We have also detected the Sunyaev-Zel'dovich (SZ) effect increment with the SPIRE data. The success of this SDP program demonstrates the great potential of the Herschel Lensing Survey to produce exciting results in a variety of science areas. © 2010 ESO.
• Glasse, A. C., Bauwens, E., Bouwman, J., Detre, Ö., Fischer, S., Garcia-Marin, M., Justannont, K., Labiano, A., Nakos, T., Ressler, M., Rieke, G., Scheithauer, S., Wells, M., & Wright, G. S. (2010). The throughput and sensitivity of the JWST mid-infrared instrument. Proceedings of SPIE - The International Society for Optical Engineering, 7731.
  More info

  Abstract: The Verification Model (VM) of MIRI has recently completed an extensive programme of cryogenic testing, with the Flight Model (FM) now being assembled and made ready to begin performance testing in the next few months. By combining those VM test results which relate to MIRI's scientific performance with measurements made on FM components and sub-assemblies, we have been able to refine and develop the existing model of the instrument's throughput and sensitivity. We present the main components of the model, its correlation with the existing test results and its predictions for MIRI's performance on orbit. © 2010 SPIE.
• Krist, J. E., Stapelfeldt, K. R., Geoffrey, B., Rieke, G. H., Su, K. Y., Chen, C. C., Beichman, C. A., Hines, D. C., Rebull, L. M., Angelle, T., Trilling, D. E., Mark, C., & András, G. (2010). HST and Spitzer observations of the HD 207129 debris ring. Astronomical Journal, 140(4), 1051-1061.
  More info

  Abstract: A debris ring around the star HD 207129 (G0V; d = 16.0 pc) has been imaged in scattered visible light with the ACS coronagraph on the Hubble Space Telescope (HST) and in thermal emission using MIPS on the Spitzer Space Telescope at λ = 70 μ. (resolved) and 160 μ (unresolved). Spitzer IRS (λ, = 7-35 μm) and MIPS (λ = 55-90 μm) spectrographs measured disk emission at A > 28 μm. In the HST image the disk appears as a ∼30 AU wide ring with a mean radius of ∼163 AU and is inclined by 60° from pole-on. At 70 μm, it appears partially resolved and is elongated in the same direction and with nearly the same size as seen with HST in scattered light. At 0.6 μm, the ring shows no significant brightness asymmetry, implying little or no forward scattering by its constituent dust. With a mean surface brightness of V = 23.7 mag arcsec-2, it is the faintest disk imaged to date in scattered light. We model the ring's infrared spectral energy distribution (SED) using a dust population fixed at the location where HST detects the scattered light. The observed SED is well fit by this model, with no requirement for additional unseen debris zones. The firm constraint on the dust radial distance breaks the usual grain size-distance degeneracy that exists in modeling of spatially unresolved disks, and allows us to infer a minimum grain size of ∼2.8 μm and a dust size distribution power-law spectral index of -3.9. An albedo of ∼5% is inferred from the integrated brightness of the ring in scattered light. The low-albedo and isotropic scattering properties are inconsistent with Mie theory for astronomical silicates with the inferred grain size and show the need for further modeling using more complex grain shapes or compositions. Brightness limits are also presented for six other main-sequence stars with strong Spitzer excess around which HST detects no circumstellar nebulosity (HD 10472, HD 21997, HD 38206, HD 82943, HD 113556, and HD 138965). © 2010. The American Astronomical Society. All rights reserved.
• Moro-Martín, A., Malhotra, R., Bryden, G., Rieke, G. H., Y., K., Beichman, C. A., & Lawler, S. M. (2010). Locating planetesimal belts in the multiple-planet systems HD 128311, HD 202206, HD 82943, and HR 8799. Astrophysical Journal Letters, 717(2), 1123-1139.
  More info

  Abstract: In addition to the Sun, six other stars are known to harbor multiple planets and debris disks: HD 69830, HD 38529, HD 128311, HD 202206, HD 82943, and HR 8799. In this paper, we set constraints on the location of the dust-producing planetesimals around the latter four systems. We use a radiative transfer model to analyze the spectral energy distributions of the dust disks (including two new Spitzer IRS spectra presented in this paper), and a dynamical model to assess the long-term stability of the planetesimals' orbits. As members of a small group of stars that show evidence of harboring a multiple planets and planetesimals, their study can help us learn about the diversity of planetary systems. © 2010. The American Astronomical Society. All rights reserved.
• Moro-Martín, A., Rieke, G. H., & Su, K. Y. (2010). Could the planets around HR 8799 be brown dwarfs?. Astrophysical Journal Letters, 721(2 PART 2), L199-L202.
  More info

  Abstract: We consider the limiting case for orbital stability of the companions to HR 8799. This case is only consistent with ages for the system of ∼100 Myr, not with the 1 Gyr age proposed from asteroseismology. The discrepancy probably arises because the inclination of the star is smaller than assumed in analyzing the asteroseismology data. Given this young age, the best estimates of the companion masses place them by a small margin on the planet side of the division between planets and brown dwarfs. ©2010. The American Astronomical Society. All rights reserved.
• Pereira-Santaella, M., Alonso-Herrero, A., Rieke, G. H., Colina, L., Díaz-Santos, T., Smith, J. -., Pérez-Gonzlez, P. G., & Engelbracht, C. W. (2010). Local luminous infrared galaxies. I. Spatially resolved observations with the Spitzer infrared spectrograph. Astrophysical Journal, Supplement Series, 188(2), 447-472.
  More info

  Abstract: We present results from the Spitzer Infrared Spectrograph spectral mapping observations of 15 local luminous infrared galaxies (LIRGs). In this paper, we investigate the spatial variations of the mid-IR emission which includes fine structure lines, molecular hydrogen lines, polycyclic aromatic features (PAHs), continuum emission, and the 9.7 μm silicate feature. We also compare the nuclear and integrated spectra. We find that the star formation takes place in extended regions (several kpc) as probed by the PAH emission, as well as the [Ne II]12.81 μm and [Ne III]15.56 μm emissions. The behavior of the integrated PAH emission and 9.7 μm silicate feature is similar to that of local starburst galaxies. We also find that the minima of the [Ne III]15.56 μm/[Ne II]12.81 μm ratio tends to be located at the nuclei and its value is lower than that of H II regions in our LIRGs and nearby galaxies. It is likely that increased densities in the nuclei of LIRGs are responsible for the smaller nuclear [Ne III]15.56 μm/[Ne II]12.81 μm ratios. This includes the possibility that some of the most massive stars in the nuclei are still embedded in ultracompact H II regions. In a large fraction of our sample, the 11.3 μm PAH emission appears more extended than the dust 5.5 μm continuum emission. We find a dependency of the 11.3 μm PAH/7.7 μm PAH and [Ne II]12.81 μm/11.3 μm PAH ratios with the age of the stellar populations. Smaller and larger ratios, respectively, indicate recent star formation. The estimated warm (300K
• Pereira-Santaella, M., Alonso-Herrero, A., Santos-Lleo, M., Colina, L., Jimenez-Bailon, E., Longinotti, A. L., Rieke, G. H., Ward, M., & Esquej, P. (2010). The X-ray emission of local luminous infrared galaxies. ASTRONOMY & ASTROPHYSICS, 535.
  More info

  We study the X-ray emission of a representative sample of 27 local luminous infrared galaxies (LIRGs). The median IR luminosity of our sample is log L-IR/L-circle dot = 11.2, therefore the low-luminosity end of the LIRG class is well represented. We used new XMM-Newton data as well as Chandra and XMM-Newton archive data. The soft X-ray (0.5-2 keV) emission of most of the galaxies (>80%), including LIRGs hosting a Seyfert 2 nucleus, is dominated by star-formation-related processes. These LIRGs follow the star-formation rate (SFR) versus soft X-ray luminosity correlation observed in local starbursts. We find that similar to 15% of the non-Seyfert LIRGs (3 out of 20) have an excessively hard X-ray emission relative to that expected from star-formation, which might indicate the presence of an obscured AGN. The rest of the non-Seyfert LIRGs follow the SFR versus hard X-ray (2-10 keV) luminosity correlation of local starbursts. The non-detection of the 6.4 keV Fe K alpha emission line in the non-Seyfert LIRGs allows us to put an upper limit on the bolometric luminosity of an obscured AGN, L-bol < 10(43) erg s(-1). That is, if these galaxies were hosting a low-luminosity AGN, its contribution to the total luminosity would be less than 10%. Finally we estimate that the AGN contribution to the total luminosity for our sample of local LIRGs is between 7% and 10%.
• Pereira-Santaella, M., Diamond-Stanic, A. M., Alonso-Herrero, A., & Rieke, G. H. (2010). The mid-infrared high-ionization lines from active galactic nuclei and star-forming galaxies. Astrophysical Journal Letters, 725(2), 2270-2280.
  More info

  Abstract: We used Spitzer/Infrared Spectrograph spectroscopic data on 426 galaxies including quasars, Seyferts, LINERs, and Hii galaxies to investigate the relationship among the mid-IR emission lines. There is a tight linear correlation between the [Ne v]14.3 μm and 24.3 μm (97.1 eV) and the [Oiv]25.9 μm (54.9 eV) high-ionization emission lines. The correlation also holds for these high-ionization emission lines and the [Ne iii]15.56 μm (41 eV) emission line, although only for active galaxies. We used these correlations to calculate the [Ne iii] excess due to star formation in Seyfert galaxies. We also estimated the [Oiv] luminosity due to star formation in active galaxies and determined that it dominates the [Oiv] emission only if the contribution of the active nucleus to the total luminosity is below 5%. We find that the active galactic nucleus dominates the [Oiv] emission in most Seyfert galaxies, whereas star formation adequately explains the observed [Oiv] emission in optically classified Hii galaxies. Finally, we computed photoionization models to determine the physical conditions of the narrow-line region where these high-ionization lines originate. The estimated ionization parameter range is -2.8 < log U < -2.5 and the total hydrogen column density range is 20 < log nH (cm-2) < 21. © 2010 The American Astronomical Society. All rights reserved.
• Pérez-González, P., Egami, E., Rex, M., Rawle, T. D., Kneib, J. -., Richard, J., Johansson, D., Altieri, B., Blain, A. W., Bock, J. J., Boone, F., Bridge, C. R., Chung, S. M., Clément, B., Clowe, D., Combes, F., Cuby, J. -., Dessauges-Zavadsky, M., Dowell, C. D., , Espino-Briones, N., et al. (2010). Improving the identification of high- z Herschel sources with position priors and optical/NIR and FIR/mm photometric redshifts. Astronomy and Astrophysics, 518(4).
  More info

  Abstract: We present preliminary results about the detection of high redshift (U)LIRGs in the Bullet cluster field by the PACS and SPIRE instruments within the Herschel Lensing Survey (HLS) Program. We describe in detail a photometric procedure designed to recover robust fluxes and deblend faint Herschel sources near the confusion noise. The method is based on the use of the positions of Spitzer/MIPS 24 μm sources as priors. Our catalogs are able to reliably (5σ) recover galaxies with fluxes above 6 and 10 mJy in the PACS 100 and 160 μm channels, respectively, and 12 to 18 mJy in the SPIRE bands. We also obtain spectral energy distributions covering the optical through the far-infrared/millimeter spectral ranges of all the Herschel detected sources, and analyze them to obtain independent estimations of the photometric redshift based on either stellar population or dust emission models. We exemplify the potential of the combined use of Spitzer position priors plus independent optical and IR photometric redshifts to robustly assign optical/NIR counterparts to the sources detected by Herschel and other (sub-)mm instruments. © ESO 2010.
• Pérez-González, P., Egami, E., Rex, M., Rawle, T. D., Kneib, J. -., Richard, J., Johansson, D., Altieri, B., Blain, A. W., Bock, J. J., Boone, F., Bridge, C. R., Chung, S. M., Clément, B., Clowe, D., Combes, F., Cuby, J. -., Dessauges-Zavadsky, M., Dowell, C. D., , Espino-Briones, N., et al. (2010). Improving the identification of high-z Herschel sources with position priors and optical/NIR and FIR/mm photometric redshifts. Astronomy and Astrophysics, 518(1).
  More info

  Abstract: We present preliminary results about the detection of high redshift (U)LIRGs in the Bullet cluster field by the PACS and SPIRE instruments within the Herschel Lensing Survey (HLS) Program. We describe in detail a photometric procedure designed to recover robust fluxes and deblend faint Herschel sources near the confusion noise. The method is based on the use of the positions of Spitzer/MIPS 24 μm sources as priors. Our catalogs are able to reliably (5σ) recover galaxies with fluxes above 6 and 10 mJy in the PACS 100 and 160 μm channels, respectively, and 12 to 18 mJy in the SPIRE bands. We also obtain spectral energy distributions covering the optical through the far-infrared/millimeter spectral ranges of all the Herschel detected sources, and analyze them to obtain independent estimations of the photometric redshift based on either stellar population or dust emission models. We exemplify the potential of the combined use of Spitzer position priors plus independent optical and IR photometric redshifts to robustly assign optical/NIR counterparts to the sources detected by Herschel and other (sub-)mm instruments. © 2010 ESO.
• RIX, H., CARLETON, N., RIEKE, G., & RIEKE, M. (2010). PROBING INTERMEDIATE SEYFERT-GALAXIES BY PA-BETA SPECTROSCOPY. ASTROPHYSICAL JOURNAL, 363(2), 480-487.
• Rawle, T. D., Chung, S. M., Fadda, D., Rex, M., Egami, E., Pérez-González, P., Altieri, B., Blain, A. W., Bridge, C. R., Fiedler, A. K., Gonzalez, A. H., Pereira, M. J., Richard, J., Smail, I., Valtchanov, I., Zemcov, M., Appleton, P. N., Bock, J. J., Boone, F., , Clement, B., et al. (2010). Deep Herschel view of obscured star formation in the Bullet cluster. Astronomy and Astrophysics, 518(2).
  More info

  Abstract: We use deep, five band (100-500 μm) data from the Herschel Lensing Survey (HLS) to fully constrain the obscured star formation rate, SFR FIR, of galaxies in the Bullet cluster (z = 0.296), and a smaller background system (z = 0.35) in the same field. Herschel detects 23 Bullet cluster members with a total SFRFIR = 144±14 odot yr -1. On average, the background system contains brighter far-infrared (FIR) galaxies, with ~50% higher SFRFIR (21 galaxies; 207± 9 odotyr-1). SFRs extrapolated from 24 μm flux via recent templates (SFR24 μm) agree well with SFRFIR for ∼60% of the cluster galaxies. In the remaining ∼40%, SFR24 μm underestimates SFRFIR due to a significant excess in observed S 100/S24 (rest frame S75/S18) compared to templates of the same FIR luminosity. © 2010 ESO.
• Rex, M., Rawle, T. D., Egami, E., Pérez-González, P., Zemcov, M., Aretxaga, I., Chung, S. M., Fadda, D., Gonzalez, A. H., Hughes, D. H., Horellou, C., Johansson, D., Kneib, J. -., Richard, J., Altieri, B., Fiedler, A. K., Pereira, M. J., Rieke, G. H., Smail, I., , Valtchanov, I., et al. (2010). The far-infrared/submillimeter properties of galaxies located behind the Bullet cluster. Astronomy and Astrophysics, 518(7-8).
  More info

  Abstract: The Herschel Lensing Survey (HLS) takes advantage of gravitational lensing by massive galaxy clusters to sample a population of high-redshift galaxies which are too faint to be detected above the confusion limit of current far-infrared/submillimeter telescopes. Measurements from 100-500 μm bracket the peaks of the far-infrared spectral energy distributions of these galaxies, characterizing their infrared luminosities and star formation rates. We introduce initial results from our science demonstration phase observations, directed toward the Bullet cluster (1E0657-56). By combining our observations with LABOCA 870 μm and AzTEC 1.1 mm data we fully constrain the spectral energy distributions of 19 MIPS 24 μm-selected galaxies which are located behind the cluster. We find that their colors are best fit using templates based on local galaxies with systematically lower infrared luminosities. This suggests that our sources are not like local ultra-luminous infrared galaxies in which vigorous star formation is contained in a compact highly dust-obscured region. Instead, they appear to be scaled up versions of lower luminosity local galaxies with star formation occurring on larger physical scales. © 2010 ESO.
• Roussel, H., Helou, G., Smith, J. D., Draine, B. T., Hollenbach, D. J., Moustakas, J., Spoon, H. W., Kennicutt, R. C., Rieke, G. H., Walter, F., Armus, L., Dale, D. A., Sheth, K., Bendo, G. J., Engelbracht, C. W., Gordon, K. D., Meyer, M. J., Regan, M. W., & Murphy, E. J. (2010). The opaque nascent starburst in NGC 1377: Spitzer SINGS observations. ASTROPHYSICAL JOURNAL, 646(2), 841-857.
  More info

  We analyze extensive data on NGC 1377 from the Spitzer Infrared Nearby Galaxies Survey (SINGS). Within the category of nascent starbursts that we previously selected as having infrared-to-radio continuum ratios in large excess of the average and containing hot dust, NGC 1377 has the largest infrared excess yet measured. Optical imaging reveals a morphological distortion suggestive of a recent accretion event. Infrared spectroscopy reveals a compact and opaque source dominated by a hot, self-absorbed continuum(tau similar to 20 in the 10 mu m silicate band). We provide physical evidence against nonstellar activity being the heating source. H II regions are detected through the single [Ne II] line, probing < 1% of the ionizing radiation. Not only is the optical depth in different gas and dust phases very high, but > 85% of ionizing photons are suppressed by dust. The only other detected emission features are molecular hydrogen lines, arguably excited mainly by shocks, besides photodissociation regions, and weak aromatic bands. The new observations support our interpretation in terms of an extremely young starburst (< 1 Myr). More generally, galaxies deficient in radio synchrotron emission are likely observed within a few Myr of the onset of a starburst and after a long quiescence, prior to the replenishment of the interstellar medium with cosmic rays. The similar infrared-radio properties of NGC 1377 and some infrared-luminous galaxies suggest that NGC 1377 constitutes an archetype that will be useful to better understand starburst evolution. Although rare locally because observed in a brief evolutionary stage, nascent starbursts may represent a nonnegligible fraction of merger-induced starbursts that dominate deep infrared counts. Since they differ dramatically from usual starburst templates, they have important consequences for the interpretation of deep surveys.
• Seymour, N., Symeonidis, M., Page, M. J., Huynh, M., Dwelly, T., McHardy, I. M., & Rieke, G. (2010). The comoving infrared luminosity density: Domination of cold galaxies across 0 < z < 1. Monthly Notices of the Royal Astronomical Society, 402(4), 2666-2670.
  More info

  Abstract: In this paper, we examine the contribution of galaxies with different infrared (IR) spectral energy distributions (SEDs) to the comoving IR luminosity density (IRLD), a proxy for the comoving star formation rate (SFR) density. We characterize galaxies as having either a cold or hot IR SED depending on whether the rest-frame wavelength of their peak IR energy output is above or below 90 μm. Our work is based on a far-IR selected sample both in the local Universe and at high redshift, the former consisting of IRAS60 μm-selected galaxies at z < 0.07 and the latter of Spitzer70 μm selected galaxies across0.1 < z≤ 1. We find that the total IR luminosity densities for each redshift/luminosity bin agree well with results derived from other deep mid-/far-IR surveys. Atz < 0.07, we observe the previously known results that moderate luminosity galaxies(LIR < 1011 L⊙) dominate the total luminosity density and that the fraction of cold galaxies decreases with increasing luminosity, becoming negligible at the highest luminosities. Conversely, abovez= 0.1, we find that luminous IR galaxies(LIR > 1011 L⊙), the majority of which are cold, dominate the IRLD. We therefore infer that cold galaxies dominate the IRLD across the whole0 < z < 1 range, hence appear to be the main driver behind the increase in SFR density up toz∼ 1 whereas local luminous galaxies are not, on the whole, representative of the high-redshift population. © 2010 The Authors. Journal compilation © 2010 RAS.
• Sheehan, C. K., Greaves, J. S., Bryden, G., Rieke, G. H., Su, K. Y., Wyatt, M. C., & Beichman, C. A. (2010). Forming the first planetary systems: Debris around Galactic thick disc stars. Monthly Notices of the Royal Astronomical Society: Letters, 408(1), L90-L94.
  More info

  Abstract: The thick disc contains stars formed within the first Gyr of Galactic history, and little is known about their planetary systems. The Spitzer MIPS instrument was used to search 11 of the closest of these old low-metal stars for circumstellar debris, as a signpost that bodies at least as large as planetesimals were formed. A total of 22 thick disc stars has now been observed, after including archival data, but dust is not found in any of the systems. The data rule out a high incidence of debris among star systems from early in the Galaxy's formation. However, some stars of this very old population do host giant planets, at possibly more than the general incidence among low-metal Sun-like stars. As the Solar system contains gas giants but little cometary dust, the thick disc could host analogue systems that formed many Gyr before the Sun. © 2010 The Authors. Journal compilation © 2010 RAS.
• Shi, Y., Rieke, G. H., Smith, P., Rigby, J., Hines, D., Donley, J., Schmidt, G., & Diamond-Stanic, A. M. (2010). Unobscured type 2 active galactic nuclei. Astrophysical Journal Letters, 714(1), 115-129.
  More info

  Abstract: Type 2 active galactic nuclei (AGNs) with intrinsically weak broad emission lines (BELs) would be exceptions to the unified model. After examining a number of proposed candidates critically, we find that the sample is contaminated significantly by objects with BELs of strengths indicating that they actually contain intermediate-type AGNs, plus a few Compton-thick sources as revealed by extremely low ratios of X-ray to nuclear IR luminosities. We develop quantitative metrics that show two (NGC3147 and NGC4594) of the remaining candidates to have BELs 2-3 orders of magnitude weaker than those of typical type1 AGNs. Several more galaxies remain as candidates to have anomalously weak BELs, but this status cannot be confirmed with the existing information. Although the parent sample is poorly defined, the two confirmed objects are well under 1% of its total number of members, showing that the absence of a BEL is possible, but very uncommon in AGN. We evaluate these two objects in detail using multi-wavelength measurements including new IR data obtained with Spitzer and ground-based optical spectropolarimeteric observations. They have little X-ray extinction with N H < ∼ 1021cm-2. Their IR spectra show strong silicate emission (NGC4594) or weak aromatic features on a generally power-law continuum with a suggestion of silicates in emission (NGC3147). No polarized BEL is detected in NGC3147. These results indicate that the two unobscured type2 objects have circumnuclear tori that are approximately face-on. Combined with their X-ray and optical/UV properties, this behavior implies that we have an unobscured view of the nuclei and thus that they have intrinsically weak BELs. We compare their properties with those of the other less-extreme candidates. We then compare the distributions of bolometric luminosities and accretion rates of these objects with theoretical models that predict weak BELs. © 2010. The American Astronomical Society. All rights reserved.
• Sierchio, J. M., Rieke, G. H., Su, K. Y., Plavchan, P., Stauffer, J. R., & Gorlova, N. I. (2010). Debris disks around solar-type stars: Observations of the pleiades with the spitzer space telescope. Astrophysical Journal Letters, 712(2), 1421-1432.
  More info

  Abstract: We present Spitzer MIPS observations at 24μm of 37 solar-type stars in the Pleiades and combine them with previous observations to obtain a sample of 71 stars. We report that 23 stars, or 32% ± 6.8%, have excesses at 24μm at least 10% above their photospheric emission. We compare our results with studies of debris disks in other open clusters and with a study of A stars to show that debris disks around solar-type stars at 115Myr occur at nearly the same rate as around A-type stars. We analyze the effects of binarity and X-ray activity on the excess flux. Stars with warm excesses tend not to be in equal-mass binary systems, possibly due to clearing of planetesimals by binary companions in similar orbits. We find that the apparent anti-correlations in the incidence of excess and both the rate of stellar rotation and also the level of activity as judged by X-ray emission are statistically weak. © 2010. The American Astronomical Society. All rights reserved.
• Sivanandam, S., Rieke, M. J., & Rieke, G. H. (2010). A warm molecular hydrogen tail due to ram-pressure stripping of a cluster galaxy. Astrophysical Journal Letters, 717(1), 147-162.
  More info

  Abstract: We have discovered a remarkable warm (130-160 K) molecular hydrogen tail with a H2 mass of approximately 4 × 107 M ® extending 20 kpc from a cluster spiral galaxy, ESO 137-001, in Abell 3627. At least half of this gas is lost permanently to the intracluster medium, as the tail extends beyond the tidal radius of the galaxy. We also detect a hot (400-550 K) component in the tail that is approximately 1% of the mass. The large H2 line to IR continuum luminosity ratio in the tail indicates that star formation is not a major excitation source and that the gas is possibly shock-heated. This discovery confirms that the galaxy is currently undergoing ram-pressure stripping, as also indicated by its previously discovered X-ray and Hα tails. We estimate that the galaxy is losing its warm H2 gas at a rate of ∼2-3 M ® yr-1. The true mass-loss rate is likely higher if we account for cold molecular gas and atomic gas. We predict that the galaxy will lose most of its gas in a single pass through the core and place a strong upper limit on the ram-pressure timescale of 1 Gyr. We also study the star-forming properties of the galaxy and its tail. We identify most of the previously discovered external Hα sources within the tail in our 8 μm data but not in our 3.6 μm data; IRS spectroscopy of the region containing these Hα sources also reveals aromatic features typically associated with star formation. From the positions of these H II regions, it appears that star formation is not occurring throughout the molecular hydrogen tail but only immediately downstream of the galaxy. Some of these H II regions lie outside the tidal radius of the galaxy, indicating that ram-pressure stripping can be a source of intracluster stars. © 2010. The American Astronomical Society. All rights reserved..
• Stock, N. D., Y., K., Liu, W., Hinz, P. M., Rieke, G. H., Marengo, M., Stapelfeldt, K. R., Hines, D. C., & Trilling, D. E. (2010). The structure of the β leonis debris disk. Astrophysical Journal Letters, 724(2), 1238-1255.
  More info

  Abstract: We combine nulling interferometry at 10 μm using the MMT and Keck Telescopes with spectroscopy, imaging, and photometry from 3 to 100 μm using Spitzer to study the debris disk around β Leo over a broad range of spatial scales, corresponding to radii of 0.1 to ∼100 AU. We have also measured the close binary star o Leo with both Keck and MMT interferometers to verify our procedures with these instruments. The β Leo debris system has a complex structure: (1) relatively little material within 1 AU; (2) an inner component with a color temperature of ∼600 K, fitted by a dusty ring from about 2-3 AU; and (3) a second component with a color temperature of ∼120 K fitted by a broad dusty emission zone extending from about ∼5 AU to ∼55 AU. Unlike many other A-type stars with debris disks, β Leo lacks a dominant outer belt near 100 AU. © 2010. The American Astronomical Society.
• Whitmore, B. C., Chandar, R., Schweizer, F., Rothberg, B., Leitherer, C., Rieke, M., Rieke, G., Blair, W. P., Mengel, S., & Alonso-Herrero, A. (2010). The antennae galaxies (NGC 4038/4039) Revisited: Advanced camera for surveys and nicmos observations of a prototypical merger. Astronomical Journal, 140(1), 75-109.
  More info

  Abstract: The Advanced Camera for Surveys and the Near Infrared Camera and Multi-Object Spectrometer (NICMOS) have been used to obtain new Hubble Space Telescope images of NGC 4038/4039 ("The Antennae"). These new observations allow us to better differentiate compact star clusters from individual stars, based on both size and color. We use this ability to extend the cluster luminosity function (LF) by approximately 2mag over our previous WFPC2 results, and find that it continues as a single power law, dN/dL L α with α = -2.13 ± 0.07, down to the observational limit of MV ≈-7. Similarly, the mass function (MF) is a single power law dN/dM M β with β = -2.10 ± 0.20 for clusters with ages 3mag. © 2010. The American Astronomical Society. All rights reserved.
• Willmer, C. N., Rieke, G. H., Le Floc'h, E., Hinz, J. L., Engelbracht, C. W., Marcillac, D., & Gordon, K. D. (2010). SPITZER OBSERVATIONS OF COLD DUST GALAXIES. ASTRONOMICAL JOURNAL, 138(1), 146-158.
  More info

  We combine new Spitzer Space Telescope observations in the mid-infrared and far-infrared ( FIR) with SCUBA 850 mu m observations to improve the measurement of dust temperatures, masses, and luminosities for 11 galaxies of the SCUBA Local Universe Galaxy Survey. By fitting dust models we measure typical dust masses of 10(7.9) M(circle dot) and dust luminosities of similar to 10(10) L(circle dot), for galaxies with modest star formation rates. The data presented in this paper combined with previous observations show that cold dust is present in all types of spiral galaxies and is a major contributor to their total luminosity. Because of the lower dust temperature of the SCUBA sources measured in this paper, they have flatter FIR nu F(nu)(160 mu m)/nu F(nu)(850 mu m) slopes than the larger Spitzer Infrared Nearby Galaxies Survey (SINGS), the sample that provides the best measurements of the dust properties of galaxies in the nearby universe. The new data presented here added to SINGS extend the parameter space that is well covered by local galaxies, providing a comprehensive set of templates that can be used to interpret the observations of nearby and distant galaxies.
• Wilson, J. C., Hearty, F., Skrutskie, M. F., Majewski, S., Schiavon, R., Eisenstein, D., Gunn, J., Blank, B., Henderson, C., Smee, S., Barkhouser, R., Harding, A., Fitzgerald, G., Stolberg, T., Arns, J., Nelson, M., Brunner, S., Burton, A., Walker, E., , Lam, C., et al. (2010). The Apache Point Observatory Galactic Evolution Experiment (APOGEE) high-resolution near-infrared multi-object fiber spectrograph. Proceedings of SPIE - The International Society for Optical Engineering, 7735(PART 1).
  More info

  Abstract: The Apache Point Observatory Galactic Evolution Experiment (APOGEE) will use a dedicated 300-fiber, narrow-band (1.5-1.7 micron), high resolution (R∼30,000), near-infrared spectrograph to survey approximately 100,000 giant stars across the Milky Way. This survey, conducted as part of the Sloan Digital Sky Survey III (SDSS III), will revolutionize our understanding of kinematical and chemical enrichment histories of all Galactic stellar populations. The instrument, currently in fabrication, will be housed in a separate building adjacent to the 2.5 m SDSS telescope and fed light via approximately 45-meter fiber runs from the telescope. The instrument design includes numerous technological challenges and innovations including a gang connector that allows simultaneous connection of all fibers with a single plug to a telescope cartridge that positions the fibers on the sky, numerous places in the fiber train in which focal ratio degradation must be minimized, a large (290 mm x 475 mm elliptically-shaped recorded area) mosaic-VPH, an f/1.4 sixelement refractive camera featuring silicon and fused silica elements with diameters as large as 393 mm, three near-within a custom, LN2-cooled, stainless steel vacuum cryostat with dimensions 1.4 m x 2.3 m x 1.3 m. © 2010 Copyright SPIE - The International Society for Optical Engineering.
• Wright, G. S., Rieke, G., Boeker, T., Colina, L., Dishoeck, E. V., Driggers, P., Friedman, S., Glasse, A., Goodson, G., Greene, T., Guedel, M., Henning, T., Lagage, P. -., Lorenzo-Alvarez, J., Meixner, M., Norgaard-Nielsen, H., Oloffson, G., Ray, T., Ressler, M., , Sukhatme, K., et al. (2010). Progress with the design and development of MIRI, the mid-IR instrument for JWST. Proceedings of SPIE - The International Society for Optical Engineering, 7731.
  More info

  Abstract: MIRI is one of four instruments to be built for the James Webb Space Telescope. It provides imaging, coronography and integral field spectroscopy over the 5-28.5um wavelength range. MIRI is the only instrument which is cooked to 7K by a dedicated cooker, much lower than the passively cooled 40K of the rest of JWST, and consists of both an Optical System and a Cooler System. This paper will describe the key features of the overall instrument design and then concentrate on the status of the MIRI Optical System development. The flight model design and manufacture is complete, and final assembly and test of the integrated instrument is now underway. Prior to integration, all of the major subassemblies have undergone individual environmental qualification and performance tests and end-end testing of a flight representative model has been carried out. The paper will provide an overview of results from this testing and describe the current status of the flight model build and the plan for performance verification and ground calibration. © 2010 SPIE.
• Zemcov, M., Rex, M., Rawle, T. D., Bock, J. J., Egami, E., Altieri, B., Blain, A. W., Boone, F., Bridge, C. R., Clement, B., Combes, F., Dowell, C. D., Dessauges-Zavadsky, M., Fadda, D., Ilbert, O., Ivison, R. J., Jauzac, M., Kneib, J. -., Lutz, D., , Pelló, R., et al. (2010). First detection of the Sunyaev Zel'dovich effect increment at λ < 650 μ m. Astronomy and Astrophysics, 518(7-8).
  More info

  Abstract: The Sunyaev-Zel'dovich (SZ) effect is a spectral distortion of the cosmic microwave background as observed through the hot plasma in galaxy clusters. This distortion is a decrement in the CMB intensity for λ > 1.3 mm, an increment at shorter wavelengths, and small again by λ ∼ 250 μm. As part of the Herschel Lensing Survey (HLS) we have mapped 1E0657-56 (the Bullet cluster) with SPIRE with bands centered at 250, 350 and 500 μm and have detected the SZ effect at the two longest wavelengths. The measured SZ effect increment central intensities are ΔI0 = 0.097 ± 0.019 MJy sr-1 at 350 μm and ΔI0 = 0.268 ± 0.031 MJy sr-1 at 500 μm, consistent with the SZ effect spectrum derived from previous measurements at 2 mm. No other diffuse emission is detected. The presence of the finite temperature SZ effect correction is preferred by the SPIRE data at a significance of 2.1σ, opening the possibility that the relativistic SZ effect correction can be constrained by SPIRE in a sample of clusters. The results presented here have important ramifications for both sub-mm measurements of galaxy clusters and blank field surveys with SPIRE. © 2010 ESO.
• Alonso-Herrero, A., Díaz-Santos, T., García-Marín, M., Colina, L., Arribas, S., & Rieke, G. H. (2009). Massive star formation in local luminous infrared galaxies. Astrophysics and Space Science, 324(2), 333-336.
  More info

  Abstract: Luminous infrared galaxies (LIRGs) provide insights into star formation (SF) and nuclear activity (AGN) under extreme conditions. We are carrying out a multiwavelength (X-rays, ultraviolet through mid-infrared, and radio) program to obtain high angular resolution observations of a volume-limited sample of local LIRGs. The typical distances to these LIRGs (D = 35-75 Mpc) allow us to identify star clusters and H II regions on scales of tens to hundreds of parsecs.We present here recent results on properties of the massive star-forming regions and star clusters in two LIRGs in our sample, Arp 299 and NGC7469. © Springer Science+Business Media B.V. 2009.
• Alonso-Herrero, A., Rieke, G. H., Colina, L., Pereira-Santaella, M., García-Marín, M., Smith, J. -., Brandl, B., Charmandaris, V., & Armus, L. (2009). The extreme star formation activity of Aarp 299 revealed by spitzer IRS spectral mapping. Astrophysical Journal Letters, 697(1), 660-675.
  More info

  Abstract: We present Spitzer/IRS spectral mapping observations of the luminous infrared galaxy Arp 299 (IC 694 + NGC 3690) covering the central 45″ 9 kpc. The integrated mid-IR spectrum of Arp 299 is similar to that of local starbursts despite its strongly interacting nature and high-IR luminosity, L IR 6 × 1011 L ⊙. This is explained because the star formation (probed by, e.g., high [Ne III]15.56 μm/[Ne II]12.81 μm line ratios) is spread across at least 6-8kpc. Moreover, a large fraction of this star formation is taking place in young regions of moderate mid-IR optical depths such as the C+C′ complex in the overlap region between the two galaxies and in H II regions in the disks of the galaxies. It is only source A, the nuclear region of IC 694, which shows the typical mid-IR characteristics of ultraluminous infrared galaxies (ULIRGs; L IR > 1012 L ⊙), that is, very compact (less than 1kpc) and dust-enshrouded star formation resulting in a deep silicate feature and moderate equivalent widths of the polycyclic aromatic hydrocarbons. The nuclear region of NGC 3690, known as source B1, hosts a low-luminosity active galactic nucleus (AGN) and is surrounded by regions of star formation. Although the high-excitation [Ne V]14.32 μm line typical of AGN is not detected in B1, its upper limit is consistent with the value expected from the X-ray luminosity. The AGN emission is detected in the form of a strong hot-dust component that accounts for 80%-90% of the 6 μm luminosity of B1. The similarity between the Arp 299 integrated mid-IR spectrum and those of high-z ULIRGs suggests that Arp 299 may represent a local example, albeit with lower IR luminosity and possibly higher metallicity, of the star formation processes occurring at high-z. © 2009. The American Astronomical Society. All rights reserved.
• BEALL, J., KNIGHT, F., SMITH, H., WOOD, K., LEBOFSKY, M., & RIEKE, G. (2009). INFRARED-EMISSION FROM ACCRETION DISKS - DETECTABILITY AND VARIABILITY. ASTROPHYSICAL JOURNAL, 284(2), 745-750.
• Backman, D., Marengo, M., Stapelfeldt, K., Su, K., Wilner, D., Dowell, C. D., Watson, D., Stansberry, J., Rieke, G., Megeath, T., Fazio, G., & Werner, M. (2009). Epsilon Eridani's planetary debris disk: Structure and dynamics based on spitzer and Caltech Submillimeter Observatory observations. Astrophysical Journal Letters, 690(2), 1522-1538.
  More info

  Abstract: Spitzer and Caltech Submillimeter Observatory images and spectrophotometry of ε Eridani at wavelengths from 3.5 to 350 μm reveal new details of its bright debris disk. The 350 μm map confirms the presence of a ring at r = 11″-28″(35-90 AU), observed previously at longer sub-mm wavelengths. The Spitzer mid-IR and far-IR images do not show the ring, but rather a featureless disk extending from within a few arcsec of the star across the ring to r 34″ (110 AU). The spectral energy distribution (SED) of the debris system implies a complex structure. A model constrained by the surface brightness profiles and the SED indicates that the sub-mm ring emission is primarily from large (a 135 μm) grains, with smaller (a 15 μm) grains also present in and beyond the ring. The Spitzer Infrared Spectrograph and Multiband Imaging Photometer for Spitzer SED-mode spectrophotometry data clearly show the presence of spatially compact excess emission at λ ≳ 15 μm that requires the presence of two additional narrow belts of dust within the sub-mm ring's central void. The innermost belt at r 3 AU is composed of silicate dust. A simple dynamical model suggests that dust produced collisionally by a population of about 11 M ⊕ of planetesimals in the sub-mm ring could be the source of the emission from both in and beyond the sub-mm ring. Maintaining the inner belts and the inner edge to the sub-mm ring may require the presence of three planets in this system including the candidate radial velocity object. © 2009. The American Astronomical Society. All rights reserved.
• Bai, L., Rieke, G. H., Rieke, M. J., Christlein, D., & Zabludoff, A. I. (2009). The infrared luminosity functions of rich clusters. Astrophysical Journal, 693(2), 1840-1850.
  More info

  Abstract: We present Multiband Imaging Photometer observations of the cluster A3266. About 100 spectroscopic cluster members have been detected at 24 μm. The infrared (IR) luminosity function (LF) in A3266 is very similar to that in the Coma cluster down to the detection limit LIR ∼ 1043 erg s-1, suggesting a universal form of the bright-end IR LF for local rich clusters with M ∼ 1015M. The shape of the bright end of the A3266-Coma composite IR LF is not significantly different from that of nearby field galaxies, but the fraction of IR-bright galaxies (star formation rate (SFR) >0.2 M yr-1) in both clusters increases with cluster-centric radius. The decrease of the blue galaxy fraction toward the high-density cores only accounts for part of the trend; the fraction of red galaxies with moderate SFRs (0.2 M yr-1 < SFR < 1 M yr-1) also decreases with increasing galaxy density. These results suggest that for the IR-bright galaxies nearby rich clusters are distinguished from the field by a lower star forming galaxy fraction, but not by a change in L*IR. The composite IR LF of Coma and A3266 shows strong evolution when compared with the composite IR LF of two z ∼ 0.8 clusters, MS 1054 and RX J0152, with and . This L*IR evolution is indistinguishable from that in the field, and the Φ*IR evolution is stronger, but still consistent with that in the field. The similarity of the evolution of the bright-end IR LF in very different cluster and field environments suggests either this evolution is driven by the mechanism that works in both environments, or clusters continually replenish their star forming galaxies from the field, yielding an evolution in the IR LF that is similar to the field. The mass-normalized integrated SFRs of clusters within 0.5R 200 also evolve strongly with redshift as (1 + z)5.3. © 2009. The American Astronomical Society. All rights reserved..
• Barmby, P., Ashby, M. L., Bianchi, L., Engelbracht, C. W., Gehrz, R. D., Gordon, K. D., Hinz, J. L., Huchra, J. P., Humphreys, R. M., Pahre, M. A., Perez-Gonzalez, P. G., Polomski, E. F., Rieke, G. H., Thilker, D. A., Willner, S. P., & Woodward, C. E. (2009). Dusty waves on a starry sea: The mid-infrared view of M31. ASTROPHYSICAL JOURNAL, 650(1), L45-L49.
  More info

  Mid-infrared observations of the Andromeda galaxy, M31, obtained with the Infrared Array Camera on board the Spitzer Space Telescope are presented. The image mosaics cover areas of approximately and include 3 degrees.7 x 1 degrees.6 the satellite galaxies M32 and NGC 205. The appearance of M31 varies dramatically in the different mid-infrared bands, from the smooth bulge and disk of the old stellar population seen at 3.6 mu m to the well-known "10 kpc ring" dominating the 8 mu m image. The similarity of the 3.6 mm and optical isophotes and the nearly constant optical-mid-infrared color over the inner 400" confirm that there is no significant extinction at optical wavelengths in M31's bulge. The nuclear colors indicate the presence of dust but not an infrared-bright active galactic nucleus. The integrated 8 mu m nonstellar luminosity implies a star formation rate of 0.4 M-circle dot, yr(-1), consistent with other indicators that show M31 to be a quiescent galaxy.
• Beichman, C., Bryden, G., Gautier, T., Stapelfeldt, K., Werner, M., Misselt, K., Rieke, G., Stansberry, J., & Trilling, D. (2009). An excess due to small grains around the nearby K0V star HD 69830: Asteroid or cometary debris?. ASTROPHYSICAL JOURNAL, 626(2), 1061-1069.
  More info

  Spitzer photometry and spectroscopy of the star HD 69830 reveal an excess of emission relative to the stellar photosphere between 8 and 35 mu m dominated by strong features attributable to crystalline silicates with an emitting surface area more than 1000 times that of our zodiacal cloud. The spectrum closely resembles that of the comet C/1995 O1 (Hale-Bopp). Since no excess is detected at 70 mu m, the emitting material must be quite warm, be confined within a few AU of the star, and originate in grains with low, long-wavelength emissivity, i.e., grains much smaller than 70 mu m/2 pi similar to 10 mu m. The strong mineralogical features are evidence for even smaller, possibly submicronsized grains. This small grain size is in direct contrast to the 10-100 mu m grains that dominate the relatively featureless spectra of our zodiacal dust cloud and most other main-sequence stars with excesses. The upper limit at 70 mu m also implies that any Kuiper Belt analog must be either very cold or less massive than similar to 5 times our own Kuiper Belt. With collisional and Poynting-Robertson drag times of less than 1000 yr for small grains, the emitting material must either (1) be created through continual grinding down of material in a dense asteroid belt, or ( 2) originate in cometary debris arising from either a single "supercomet" or a very large number of individual comets arriving from a distant reservoir. In the case of a cometary origin for the emission, the mass requirements for continuous generation by many individual comets are unreasonable, and we favor the capture of a single super comet into a 0.5-1 AU orbit, where it can evolve a large number of small grains over a 2 Myr period.
• Bryden, G., Beichman, C. A., Carpenter, J. M., Rieke, G. H., Stapelfeldt, K. R., Werner, M. W., Tanner, A. M., Lawler, S. M., Wyatt, M. C., Trilling, D. E., Su, K. Y., Blaylock, M., & Stansberry, J. A. (2009). Planets and debris disks: Results from a SPITZER/MIPS search for infrared excess. Astrophysical Journal Letters, 705(2), 1226-1236.
  More info

  Abstract: Using the MIPS camera on the Spitzer Space Telescope, we have searched for debris disks around 104 stars known from radial velocity studies to have one or more planets. Combining this new data with 42 already published observations of planet-bearing stars, we find that 14 of the 146 systems have IR excess at 24 and/or 70 μm. Only one star, HD 69830, has IR excess exclusively at 24 μm, indicative of warm dust in the inner system analogous to that produced by collisions in the solar system's asteroid belt. For the other 13 stars with IR excess the emission is stronger at 70 μm, consistent with cool dust (
• Diamond-Stanic, A. M., Rieke, G. H., & Rigby, J. R. (2009). Isotropic luminosity indicators in a complete AGN sample. Astrophysical Journal Letters, 698(1), 623-631.
  More info

  Abstract: The [O IV] λ25.89 μm line has been shown to be an accurate indicator of active galactic nucleus (AGN) intrinsic luminosity in that it correlates well with hard (10-200 keV) X-ray emission. We present measurements of [O IV] for 89 Seyfert galaxies from the unbiased revised Shapley-Ames (RSA) sample. The [O IV] luminosity distributions of obscured and unobscured Seyferts are indistinguishable, indicating that their intrinsic AGN luminosities are quite similar and that the RSA sample is well suited for tests of the unified model. In addition, we analyze several commonly used proxies for AGN luminosity, including [O III] λ5007 , 6 cm radio, and 2-10keV X-ray emission. We find that the radio luminosity distributions of obscured and unobscured AGNs show no significant difference, indicating that radio luminosity is a useful isotropic luminosity indicator. However, the observed [O III] and 2-10keV luminosities are systematically smaller for obscured Seyferts, indicating that they are not emitted isotropically. © 2009. The American Astronomical Society. All rights reserved.
• Draine, B. T., Dale, D. A., Bendo, G., Gordon, K. D., Smith, J. D., Armus, L., Engelbracht, C. W., Helou, G., Kennicutt, R. C., Li, A., Roussel, H., Walter, F., Calzetti, D., Moustakas, J., Murphy, E. J., Rieke, G. H., Bot, C., Hollenbach, D. J., Sheth, K., & Teplitz, H. I. (2009). Dust masses, PAH abundances, and starlight intensities in the SINGS galaxy sample. ASTROPHYSICAL JOURNAL, 663(2), 866-894.
  More info

  Physical dust models are presented for 65 galaxies in SINGS that are strongly detected in the four IRAC bands and three MIPS bands. For each galaxy we estimate ( 1) the total dust mass, ( 2) the fraction of the dust mass contributed by PAHs, and ( 3) the intensity of the starlight heating the dust grains. We find that spiral galaxies have dust properties resembling the dust in the local region of the MilkyWay, with similar dust- to- gas ratio and similar PAH abundance. The observed SEDs, including galaxies with SCUBA photometry, can be reproduced by dust models that do not require `` cold'' ( T less than or similar to 10 K) dust. The dust- to- gas ratio is observed to be dependent on metallicity. In the interstellar media of galaxies with A(O) equivalent to 12 + log(10)( O/ H) > 8: 1, grains contain a substantial fraction of interstellar Mg, Si, and Fe. Galaxies with AO < 8: 1 and extended H I envelopes in some cases appear to have global dust- to- gas ratios that are low for their measured oxygen abundance, but the dust- to- gas ratio in the regions where infrared emission is detected generally appears to be consistent with a substantial fraction of interstellar Mg, Si, and Fe being contained in dust. The PAH index qPAH, the fraction of the dust mass in the form of PAHs, correlates with metallicity. The nine galaxies in our sample with AO < 8: 1 have a median qPAH 1: 0%, whereas galaxies with AO > 8: 1 have a median qPAH 3: 55%. The derived dust masses favor a value XCO approximate to 4.1020 cm(-2) ( K km s(-1))(-1) for the CO- to- H-2 conversion factor. Except for some starbursting systems ( Mrk 33, Tol 89, NGC 3049), dust in the diffuse ISMdominates the IR power.
• Dressler, A., Rigby, J., Oemler, A., Fritz, J., Poggianti, B. M., Rieke, G., & Bai, L. (2009). Spitzer 24 μm detections of starburst galaxies in abell 851. Astrophysical Journal, 693(1), 140-151.
  More info

  Abstract: Spitzer-MIPS 24 μm observations and ground-based optical imaging and spectroscopy of the rich galaxy cluster Abell 851 at z = 0.41 are used to derive and compare star formation rates from the mid-IR 24 μm and from [O II] λλ3727 emission. Many cluster galaxies have star formation rates SFR(24μm)/SFR([O II]) ≫ 1, indicative of star formation in regions highly obscured by dust. We focus on the substantial minority of A851 cluster members where strong Balmer absorption points to a starburst on a 108-10 9 year timescale. As is typical, two types of galaxies with strong Balmer absorption are found in A851: with optical emission (starforming), and without optical emission (post-starburst). Our principal result is that the starforming variety, so-called e(a) galaxies, are mostly detected (9 out of 12) at 24 μm - for these we find typically SFR(24 μm)/SFR([O II]) 4. Strong Balmer absorption and high values of SFR(24 μm)/SFR([O II]) indicate moderately active starbursts (SB); both observations support the picture that e(a) galaxies are the active starbursts that feed the post-starburst population. While 24 μm detections are frequent with Balmer-strong objects (even 6 out of 18 of the supposedly "post-starburst" galaxies are detected), only two out of seven of the continuously starforming 'e(c)' galaxies (with weak Balmer absorption) are detected - for them, SFR(24 μm)/SFR([O II]) 1. Their optical spectra resemble present-epoch spirals that dominate today's universe; we strengthen this association by showing that SFR(24 μm)/SFR([O II]) 1 is the norm today. That is, not just the amount of star formation but also its mode has evolved strongly from z 0.4 to the present. We fit spectrophotometric models in order to measure the strength and duration of the bursts and to quantify the evolutionary sequence from active to post-starburst. Our results harden the evidence that moderately active starbursts are the defining feature of starforming cluster galaxies at z 0.4. © 2009. The American Astronomical Society. All rights reserved..
• Gautier, T. N., Rieke, G. H., Stansberry, J., Bryden, G. C., Stapelfeldt, K. R., Werner, M. W., Beichman, C. A., Chen, C., Su, K., Trilling, D., Patten, B. M., & Roellig, T. L. (2009). Far-infrared properties of M dwarfs. ASTROPHYSICAL JOURNAL, 667(1), 527-536.
  More info

  We report the mid- and far-infrared properties of nearby M dwarfs. Spitzer MIPS measurements were obtained for a sample of 62 stars at 24 mu m, with subsamples of 41 and 20 stars observed at 70 and 160 mu m, respectively. We compare the results with current models of M star photospheres and look for indications of circumstellar dust in the form of significant deviations of K-[24 mu m] colors and 70 mu m/24 mu m flux ratios from the average M star values. At 24 mu m, all 62 of the targets were detected; 70 mu m detections were achieved for 20 targets in the subsample observed, and no detections were seen in the 160 mu m subsample. No clear far-infrared excesses were detected in our sample. The average far-infrared excess relative to the photospheric emission of the M stars is at least 4 times smaller than the similar average for a sample of solar-type stars. However, this limit allows the average fractional infrared luminosity in the M-star sample to be similar to that for more massive stars. We have also set low limits (10(-4) to 10(-9) M-circle times depending on location) for the maximum mass of dust possible around our stars.
• Gáspár, A., Rieke, G. H., Su, K. Y., Balog, Z., Trilling, D., Muzzerole, J., Apai, D., & Kelly, B. C. (2009). The low level of debris disk activity at the time of the late heavy bombardment: A spitzer study of praesepe. Astrophysical Journal Letters, 697(2), 1578-1596.
  More info

  Abstract: We present 24 μm photometry of the intermediate-age open cluster Praesepe. We assemble a catalog of 193 probable cluster members that are detected in optical databases, the Two Micron All Sky Survey (2MASS), and at 24 μm, within an area of 2.47 deg2. Mid-IR excesses indicating debris disks are found for one early-type and for three solar-type stars. Corrections for sampling statistics yield a 24 μm excess fraction (debris disk fraction) of 6.5% 4.1% for luminous and 1.9% 1.2% for solar-type stars. The incidence of excesses is in agreement with the decay trend of debris disks as a function of age observed for other cluster and field stars. The values also agree with those for older stars, indicating that debris generation in the zones that emit at 24 μm falls to the older 1-10 Gyr field star sample value by roughly 750Myr. We discuss our results in the context of previous observations of excess fractions for early- and solar-type stars. We show that solar-type stars lose their debris disk 24 μm excesses on a shorter timescale than early-type stars. Simplistic Monte Carlo models suggest that, during the first Gyr of their evolution, up to 15%-30% of solar-type stars might undergo an orbital realignment of giant planets such as the one thought to have led to the Late Heavy Bombardment, if the length of the bombardment episode is similar to the one thought to have happened in our solar system. In the Appendix, we determine the cluster's parameters via bootstrap Monte Carlo isochrone fitting, yielding an age of 757Myr (36Myr at 1σ confidence) and a distance of 179 pc (2 pc at 1σ confidence), not allowing for systematic errors. © 2009. The American Astronomical Society. All rights reserved.
• Martin, D. C., Small, T., Schiminovich, D., Wyder, T. K., Perez-Gonzalez, P. G., Johnson, B., Wolf, C., Barlow, T. A., Forster, K., Friedman, P. G., Morrissey, P., Neff, S. G., Seibert, M., Welsh, B. Y., Bianchi, L., Donas, J., Heckman, T. M., Lee, Y., Madore, B. F., , Milliard, B., et al. (2009). The star formation and extinction coevolution of UV-selected galaxies over 0.05 < z < 1.2. ASTROPHYSICAL JOURNAL SUPPLEMENT SERIES, 173(2), 415-431.
  More info

  We use a new stacking technique to obtain mean mid-IR and far-IR to far-UV flux ratios over the rest-frame near-UV, near-IR color-magnitude diagram. We employ COMBO-17 redshifts and COMBO-17 optical, GALEX far- and near-UV, and Spitzer IRAC and MIPS mid-IR photometry. This technique permits us to probe the infrared excess (IRX), the ratio of far-IR to far-UV luminosity, and the specific star formation rate (SSFR) and their coevolution over 2 orders of magnitude of stellar mass and over redshift 0.1 < z < 1.2. We find that the SSFR and the characteristic mass (M-0) above which the SSFR drops increase with redshift (downsizing). At any given epoch, the IRX is an increasing function of mass up to M-0. Above this mass the IRX falls, suggesting gas exhaustion. In a given mass bin below M-0, the IRX increases with time in a fashion consistent with enrichment. We interpret these trends using a simple model with a Schmidt-Kennicutt law and extinction that tracks gas density and enrichment. We find that the average IRX and SSFR follow a galaxy age parameter xi, which is determined mainly by the galaxy mass and time since formation. We conclude that blue-sequence galaxies have properties which show simple, systematic trends with mass and time such as the steady buildup of heavy elements in the interstellar media of evolving galaxies and the exhaustion of gas in galaxies that are evolving off the blue sequence. The IRX represents a tool for selecting galaxies at various stages of evolution.
• Martínez-Galarza, J., Kamp, I., Su, K. Y., Gspr, A., Rieke, G., & Mamajek, E. E. (2009). Infrared emission by dust around λ bootis stars: Debris disks or thermally emitting nebulae?. Astrophysical Journal Letters, 694(1), 165-173.
  More info

  Abstract: We present a model that describes stellar infrared excesses due to heating of the interstellar (IS) dust by a hot star passing through a diffuse IS cloud. This model is applied to six λ Bootis stars with infrared excesses. Plausible values for the IS medium (ISM) density and relative velocity between the cloud and the star yield fits to the excess emission. This result is consistent with the diffusion/accretion hypothesis that λ Bootis stars (A- to F-type stars with large underabundances of Fe-peak elements) owe their characteristics to interactions with the ISM. This proposal invokes radiation pressure from the star to repel the IS dust and excavate a paraboloidal dust cavity in the IS cloud, while the metal-poor gas is accreted onto the stellar photosphere. However, the measurements of the infrared excesses can also be fit by planetary debris disk models. A more detailed consideration of the conditions to produce λ Bootis characteristics indicates that the majority of infrared-excess stars within the Local Bubble probably have debris disks. Nevertheless, more distant stars may often have excesses due to heating of IS material such as in our model. © 2009 The American Astronomical Society.
• Morales, F. Y., Rieke, G. H., Werner, M. W., Bryden, G., Stapelfeldt, K. R., & Su, K. Y. (2009). COMMON WARM DUST TEMPERATURES AROUND MAIN-SEQUENCE STARS. ASTROPHYSICAL JOURNAL LETTERS, 730(2).
  More info

  We compare the properties of warm dust emission from a sample of main-sequence A-type stars (B8-A7) to those of dust around solar-type stars (F5-K0) with similar Spitzer Space Telescope Infrared Spectrograph/MIPS data and similar ages. Both samples include stars with sources with infrared spectral energy distributions that show evidence of multiple components. Over the range of stellar types considered, we obtain nearly the same characteristic dust temperatures (similar to 190 K and similar to 60 K for the inner and outer dust components, respectively)-slightly above the ice evaporation temperature for the inner belts. The warm inner dust temperature is readily explained if populations of small grains are being released by sublimation of ice from icy planetesimals. Evaporation of low-eccentricity icy bodies at similar to 150 K can deposit particles into an inner/warm belt, where the small grains are heated to T-dust similar to 190 K. Alternatively, enhanced collisional processing of an asteroid belt-like system of parent planetesimals just interior to the snow line may account for the observed uniformity in dust temperature. The similarity in temperature of the warmer dust across our B8-K0 stellar sample strongly suggests that dust-producing planetesimals are not found at similar radial locations around all stars, but that dust production is favored at a characteristic temperature horizon.
• Morales, F. Y., Werner, M. W., Bryden, G., Plavchan, P., Stapelfeldt, K. R., Rieke, G. H., Su, K. Y., Beichman, C. A., Chen, C. H., Grogan, K., Kenyon, S. J., Moro-Martin, A., & Wolf, S. (2009). Spitzer mid-ir spectra of dust debris around a and late b type stars: Asteroid belt analogs and power-law dust distributions. Astrophysical Journal Letters, 699(2), 1067-1086.
  More info

  Abstract: Using the Spitzer/Infrared Spectrograph (IRS) low-resolution modules covering wavelengths from 5 to 35 μm, we observed 52 main-sequence A and late B type stars previously seen using Spitzer/Multiband Imaging Photometer (MIPS) to have excess infrared emission at 24 μm above that expected from the stellar photosphere. The mid-IR excess is confirmed in all cases but two. While prominent spectral features are not evident in any of the spectra, we observed a striking diversity in the overall shape of the spectral energy distributions. Most of the IRS excess spectra are consistent with single-temperature blackbody emission, suggestive of dust located at a single orbital radius - a narrow ring. Assuming the excess emission originates from a population of large blackbody grains, dust temperatures range from 70 to 324 K, with a median of 190 K corresponding to a distance of 10 AU. Thirteen stars however, have dust emission that follows a power-law distribution, F ν = F 0λα, with exponent α ranging from 1.0 to 2.9. The warm dust in these systems must span a greater range of orbital locations - an extended disk. All of the stars have also been observed with Spitzer/MIPS at 70 μm, with 27 of the 50 excess sources detected (signal-to-noise ratio > 3). Most 70 μm fluxes are suggestive of a cooler, Kuiper Belt-like component that may be completely independent of the asteroid belt-like warm emission detected at the IRS wavelengths. Fourteen of 37 sources with blackbody-like fits are detected at 70 μm. The 13 objects with IRS excess emission fit by a power-law disk model, however, are all detected at 70 μm (four above, three on, and six below the extrapolated power law), suggesting that the mid-IR IRS emission and far-IR 70 μm emission may be related for these sources. Overall, the observed blackbody and power-law thermal profiles reveal debris distributed in a wide variety of radial structures that do not appear to be correlated with spectral type or stellar age. An additional 43 fainter A and late B type stars without 70 μm photometry were also observed with Spitzer/IRS; results are summarized in Appendix B. © 2009. The American Astronomical Society.
• Muzerolle, J., Flaherty, K., Balog, Z., Furlan, E., Smith, P. S., Allen, L., Calvet, N., D'Alessio, P., Megeath, S. T., Muench, A., Rieke, G. H., & Sherry, W. H. (2009). Evidence for dynamical changes in a transitional protoplanetary disk with mid-infrared variability. Astrophysical Journal Letters, 704(1 PART 2), L15-L19.
  More info

  Abstract: We present multi-epoch Spitzer Space Telescope observations of the transitional disk LRLL 31 in the 2-3 Myr old star-forming region IC 348. Our measurements show remarkable mid-infrared variability on timescales as short as one week. The infrared continuum emission exhibits systematic wavelength-dependent changes that suggest corresponding dynamical changes in the inner disk structure and variable shadowing of outer disk material. We propose several possible sources for the structural changes, including a variable accretion rate or a stellar or planetary companion embedded in the disk. Our results indicate that variability studies in the infrared can provide important new constraints on protoplanetary disk behavior. © 2009. The American Astronomical Society. All rights reserved.
• Rieke, G. H. (2009). History of infrared telescopes and astronomy. Experimental Astronomy, 25(1-3), 125-141.
  More info

  Abstract: The first attempts to measure the infrared outputs of stars preceded by nearly a century the permanent establishment of infrared astronomy as an important aspect of the field. There were a number of false starts in that century, significant efforts that had little impact on the astronomical community at large. Why did these efforts fizzle out? What was different in the start that did not fizzle, in the 1960s? I suggest that the most important advances were the success of radio astronomy in demonstrating interesting phenomena outside of the optical regime, and the establishment virtually simultaneously in the United States of a number of research groups that could support each other and compete against one another in their approach to infrared astronomy. © Springer Science + Business Media B.V. 2009.
• Rieke, G. H., Alonso-Herrero, A., Weiner, B. J., Pérez-González, P., Blaylock, M., Donley, J. L., & Marcillac, D. (2009). Determining star formation rates for infrared galaxies. Astrophysical Journal, 692(1), 556-573.
  More info

  Abstract: We show that measures of star formation rates (SFRs) for infrared galaxies using either single-band 24 μm or extinction-corrected Paα luminosities are consistent in the total infrared luminosity = L(TIR) ∼ 1010 L⊙ range. MIPS 24 μm photometry can yield SFRs accurately from this luminosity upward: SFR(M⊙ yr-1) = 7.8 × 10-10 L(24 μm, L⊙) from L(TIR) = 5× 109 L ⊙ to 1011 L ⊙ and SFR = 7.8 × 10-10 L(24 μm, L ⊙)(7.76 × 10-11 L(24))0.048 for higher L(TIR). For galaxies with L(TIR) ≥ 1010 L ⊙, these new expressions should provide SFRs to within 0.2 dex. For L(TIR) ≥ 1011 L ⊙, we find that the SFR of infrared galaxies is significantly underestimated using extinction-corrected Paα (and presumably using any other optical or near-infrared recombination lines). As a part of this work, we constructed spectral energy distribution templates for eleven luminous and ultraluminous purely star forming infrared galaxies and over the spectral range 0.4 μm to 30 cm. We use these templates and the SINGS data to construct average templates from 5 μm to 30 cm for infrared galaxies with L(TIR) = 5× 109 to 1013 L ⊙. All of these templates are made available online. © 2009. The American Astronomical Society. All rights reserved.
• Rieke, G. H., Blaylock, M., Decin, L., Engelbracht, C., Ogle, P., Avrett, E., Carpenter, J., Cutri, R. M., Armus, L., Gordon, K., Gray, R. O., Hinz, J., Su, K., & Willmer, C. N. (2009). Absolute physical calibration in the infrared. ASTRONOMICAL JOURNAL, 135(6), 2245-2263.
  More info

  We determine an absolute calibration for the Multiband Imaging Photometer for Spitzer 24 mu m band and recommend adjustments to the published calibrations for Two Micron All Sky Survey (2MASS), Infrared Array Camera (IRAC), and IRAS photometry to put them on the same scale. We show that consistent results are obtained by basing the calibration on either an average A0V star spectral energy distribution (SED), or by using the absolutely calibrated SED of the Sun in comparison with solar-type stellar photometry (the solar analog method). After the rejection of a small number of stars with anomalous SEDs (or bad measurements), upper limits of similar to 1.5% root mean square (rms) are placed on the intrinsic infrared (IR) SED variations in both A-dwarf and solar-type stars. These types of stars are therefore suitable as general-purpose standard stars in the IR. We provide absolutely calibrated SEDs for a standard zero magnitude A star and for the Sun to allow extending this work to any other IR photometric system. They allow the recommended calibration to be applied from 1 to 25 mu m with an accuracy of similar to 2%, and with even higher accuracy at specific wavelengths such as 2.2, 10.6, and 24 mu m, near which there are direct measurements. However, we confirm earlier indications that Vega does not behave as a typical A0V star between the visible and the IR, making it problematic as the defining star for photometric systems. The integration of measurements of the Sun with those of solar-type stars also provides an accurate estimate of the solar SED from 1 through 30 mu m, which we show agrees with theoretical models.
• Rigopoulou, D., Mainieri, V., Almaini, O., Alonso-Herrero, A., Huang, J. -., Hasinger, G., Rieke, G., Dunlop, J., & Lehmann, I. (2009). Spectral energy distributions of type 2 quasi-stellar objects: Obscured star formation at high redshifts. Monthly Notices of the Royal Astronomical Society, 400(3), 1199-1207.
  More info

  Abstract: We present new mid-infrared and submillimetre observations for a sample of eight high-redshift type 2 quasi-stellar objects (QSOs) located in the Chandra Deep Field-South. The sources are X-ray absorbed with luminosities in excess of 1044 erg s-1. Two of the targets have robust detections, S/N > 4, while further three targets are marginally detected with S/N ≥ 2.5. All sources are detected in multiple mid-infrared bands with the Spitzer Space Telescope. The multiwavelength spectral energy distributions (SEDs) of the type 2 QSOs are compared to those of two local ultraluminous galaxies (Arp220 and IR22491) in order to assess contributions from a star-forming component in various parts of the SED. We suggest that their submm emission is possibly due to a starburst while a large fraction of the mid-infrared energy is likely to originate in the obscured central quasar. Using the mid-infrared and submm observations, we derive infrared luminosities which are found to be in excess of L > 1012 L⊙. The submm (850 μm) to X-ray (2 keV) spectral indices (αSX) span a wide range. About half of the type 2 QSOs have values typical for a Compton-thick active galactic nuclei with only 1 per cent of the nuclear emission seen through scattering, and the remaining with values typical of submm-bright galaxies. Combining the available observational evidence, we outline a possible scenario for the early stages of evolution of these sources. © 2009 RAS.
• Seymour, N., Huynh, M., Dwelly, T., Symeonidis, M., Hopkins, A., McHardy, I. M., Page, M. J., & Rieke, G. (2009). Investigating the far-IR/radio correlation of star-forming Galaxies to z = 3. Monthly Notices of the Royal Astronomical Society, 398(3), 1573-1581.
  More info

  Abstract: In order to examine the far-infrared (far-IR)/radio correlation at high redshift, we have studied the Spitzer 70 μm/far-IR properties of sub-mJy radio sources from the 13H XMM-Newton/Chandra Deep Field by redshift and galaxy type: active galactic nucleus (AGN) or star-forming galaxy (SFG). We directly detect 70 μm counterparts (at >3σ significance) for 22.5 per cent (92/408) of the radio sources, while for the rest we perform stacking analysis by redshift and galaxy type. For the sources detected at 70 μm, we find that the median and scatter of the observed flux density ratio, q 70, are similar to previous results in the literature, but with a slight decrease in q70 towards higher redshifts. Of the radio sources detected at 70 μm 8/92 were already classified as AGN, but two of which maybe SFGs. For the stacked sources, we obtain a detection for the SFGs at every redshift bin which implies they have mean flux densities a factor ∼5 below the original 70 μm detection limit. For the stacked AGN, we obtain a detection only in our highest redshift bin (1 ≤ z ≤ 5) where we may be sampling hot dust associated with the AGN at rest frame 12-35 μm. The combined observed mean value of q70 for the SFGs (detected and non-detected at 70 μm) decreases gradually with redshift, consistent with tracks derived from empirical spectral energy distributions (SEDs) of local SFGs. Upon closer inspection and when comparing with tracks of appropriate luminosity, the values of q70 broadly agree at low redshift. However, at z ∼ 1, the observed q70 [for ultraluminous infrared galaxies (ULIRGs)] is 2 σ below the value seen for local ULIRGs tracks, implying a difference in the SED between local and z ∼ 1 ULIRGs. At higher redshifts, the convergence of the tracks and the higher uncertainties in q70 do not allow us to determine if such a difference persists. © 2009 RAS.
• Shi, Y., Rieke, G. H., Ogle, P., Jiang, L., & Diamond-Stanic, A. M. (2009). Cosmic evolution of star formation in type-1 quasar hosts since z = 1. Astrophysical Journal Letters, 703(1), 1107-1122.
  More info

  Abstract: We present Spitzer Infrared Spectrograph observations of a complete sample of 57 Sloan Digital Sky Survey type-1 quasars at z ∼ 1. Aromatic features at 6.2 and/or 7.7 μm are detected in about half of the sample and show profiles similar to those seen in normal galaxies at both low and high redshift, indicating a star formation origin for the features. Based on the ratio of aromatic to star formation infrared (SFIR) luminosities for normal star-forming galaxies at z ∼ 1, we have constructed the SFIR luminosity function (LF) of z ∼ 1 quasars. As we found earlier for low-redshift Palomar-Green (PG) quasars, these z ∼ 1 quasars show a flatter SFIR LF than do z ∼ 1 field galaxies, implying the quasar host galaxy population has on average a higher star formation rate (SFR) than the field galaxies do. As measured from their SFIR LF, individual quasar hosts have on average LIRG-level SFRs, which mainly arise in the circumnuclear regions. By comparing with similar measurements of low-redshift PG quasars, we find that the comoving SFIR luminosity density in quasar hosts shows a much larger increase with redshift than that in field galaxies. The behavior is consistent with pure density evolution since the average SFR and the average SFR/BH accretion rate in quasar hosts show little evolution with redshift. For individual quasars, we have found a correlation between the aromatic-based SFR and the luminosity of the nuclear radiation, consistent with predictions of some theoretical models. We propose that type-1 quasars reside in a distinct galaxy population that shows elliptical morphology but that harbors a significant fraction of intermediate-age stars and is experiencing intense circumnuclear star formation. © 2009. The American Astronomical Society. All rights reserved.
• Shi, Y., Rieke, G., Lotz, J., & Perez-Gonzalez, P. G. (2009). ROLE OF GALAXY MERGERS IN COSMIC STAR FORMATION HISTORY. ASTROPHYSICAL JOURNAL, 697(2), 1764-1783.
  More info

  We present a morphology study of intermediate-redshift (0.2 < z < 1.2) luminous infrared galaxies (LIRGs) and general field galaxies in the GOODS fields using a revised asymmetry measurement method optimized for deep fields. By taking careful account of the importance of the underlying sky-background structures, our new method does not suffer from systematic bias and offers small uncertainties. By redshifting local LIRGs and low-redshift GOODS galaxies to different higher redshifts, we have found that the redshift dependence of the galaxy asymmetry due to surface-brightness dimming is a function of the asymmetry itself, with larger corrections for more asymmetric objects. By applying redshift-, infrared (IR)-luminosity- and optical-brightness-dependent asymmetry corrections, we have found that intermediate-redshift LIRGs generally show highly asymmetric morphologies, with implied merger fractions similar to 50% up to z = 1.2, although they are slightly more symmetric than local LIRGs. For general field galaxies, we find an almost constant relatively high merger fraction (20%-30%). The B-band luminosity functions (LFs) of galaxy mergers are derived at different redshifts up to z = 1.2 and confirm the weak evolution of the merger fraction after breaking the luminosity-density degeneracy. The IR LFs of galaxy mergers are also derived, indicating a larger merger fraction at higher IR luminosity. The integral of the merger IR LFs indicates a dramatic evolution of the merger-induced IR energy density [(1 + z)(similar to(5-6))], and that galaxy mergers start to dominate the cosmic IR energy density at z greater than or similar to 1.
• Shi, Y., Rieke, G., Lotz, J., & Perez-Gonzalez, P. G. (2009). Role of galaxy mergers in cosmic star formation history. Astrophysical Journal Letters, 697(2), 1764-1783.
  More info

  Abstract: We present a morphology study of intermediate-redshift (0.2 < z
• Stansberry, J. A., Gordon, K. D., Bhattacharya, B., Engelbracht, C. W., Rieke, G. H., Marleau, F. R., Fadda, D., Frayer, D. T., Noriega-Crespo, A., Wachter, S., Young, E. T., Mueller, T. G., Kelly, D. M., Blaylock, M., Henderson, D., Neugebauer, G., Beeman, J. W., & Haller, E. E. (2009). Absolute calibration and characterization of the multiband imaging photometer for spitzer. III. An asteroid-based calibration of MIPS at 160 mu m. PUBLICATIONS OF THE ASTRONOMICAL SOCIETY OF THE PACIFIC, 119(859), 1038-1051.
  More info

  We describe the absolute calibration of the Multiband Imaging Photometer for Spitzer (MIPS) 160 mu m channel. After the on-orbit discovery of a near-IR ghost image that dominates the signal for sources hotter than about 2000 K, we adopted a strategy utilizing asteroids to transfer the absolute calibrations of the MIPS 24 and 70 mu m channels to the 160 mu m channel. Near-simultaneous observations at all three wavelengths are taken, and photometry at the two shorter wavelengths is fit using the standard thermal model. The 160 mu m flux density is predicted from those fits and compared with the observed 160 mu m signal to derive the conversion from instrumental units to surface brightness. The calibration factor we derive is 41.7 MJy sr(-1) MIPS160(-1) (MIPS160 being the instrumental units). The scatter in the individual measurements of the calibration factor, as well as an assessment of the external uncertainties inherent in the calibration, lead us to adopt an uncertainty of 5.0 MJy sr(-1) MIPS160(-1) (12%) for the absolute uncertainty on the 160 mu m flux density of a particular source as determined from a single measurement. For sources brighter than about 2 Jy, nonlinearity in the response of the 160 mu m detectors produces an underestimate of the flux density: for objects as bright as 4 Jy, measured flux densities are likely to be similar or equal to 20% too low. This calibration has been checked against that of the ISO ( using ULIRGs) and IRAS ( using IRAS-derived diameters), and is consistent with those at the 5% level.
• Stutz, A. M., Bourke, T. L., Rieke, G. H., Bieging, J. H., Misselt, K. A., Myers, P. C., & Shirley, Y. L. (2009). Spitzer observations of L429: A near-collapse or collapsing starless core. Astrophysical Journal Letters, 690(1 PART 2), L35-L38.
  More info

  Abstract: We present Spitzer infrared (IR) observations of the starless core L429. The IR images of this core show an absorption feature, caused by the dense core material, at wavelengths ≤ 70 μm. The core has a steep density profile, and reaches AV > 35 mag near the center. We show that L429 is either collapsing or in a near-collapse state. © 2009. The American Astronomical Society. All rights reserved. Printed in the U.S.A.
• Stutz, A. M., Rieke, G. H., Bieging, J. H., Balog, Z., Heitsch, F., Kang, M., Peters, W. L., Shirley, Y. L., & Werner, M. W. (2009). Spitzer and heinrich hertz telescope observations of starless cores: Masses and environments. Astrophysical Journal Letters, 707(1), 137-166.
  More info

  Abstract: We present Spitzer observations of a sample of 12 starless cores selected to have prominent 24 μm shadows. The Spitzer images show 8 μm and 24 μm shadows and in some cases 70 μm shadows; these spatially resolved absorption features trace the densest regions of the cores. We have carried out a 12CO (2-1) and 13CO (2-1) mapping survey of these cores with the Heinrich Hertz Telescope (HHT). We use the shadow features to derive optical depth maps. We derive molecular masses for the cores and the surrounding environment; we find that the 24 μm shadow masses are always greater than or equal to the molecular masses derived in the same region, a discrepancy likely caused by CO freezeout onto dust grains. We combine this sample with two additional cores that we studied previously to bring the total sample to 14 cores. Using a simple Jeans mass criterion, we find that ∼ 2/3 of the cores selected to have prominent 24 μm shadows are collapsing or near collapse, a result that is supported by millimeter line observations. Of this subset at least half have indications of 70 μm shadows. All cores observed to produce absorption features at 70 μm are close to collapse. We conclude that 24 μm shadows, and even more so the 70 μm ones, are useful markers of cloud cores that are approaching collapse. © 2009. The American Astronomical Society. All rights reserved.
• Symeonidis, M., Page, M. J., Seymour, N., Dwelly, T., Coppin, K., McHardy, I., Rieke, G. H., & Huynh, M. (2009). The link between SCUBA and Spitzer: Cold galaxies at z ≲ 1. Monthly Notices of the Royal Astronomical Society, 397(4), 1728-1738.
  More info

  Abstract: We show that the far-IR properties of distant Luminous and UltraLuminous InfraRed Galaxies (LIRGs and ULIRGs, respectively) are on average divergent from analogous sources in the local Universe. Our analysis is based on Spitzer Multiband Imaging Photometer (MIPS) and Infrared Array Camera (IRAC) data of LIR > 1010 L⊙, 70 μm selected objects in the 0.1 < z < 2 redshift range and supported by a comparison with the IRAS Bright Galaxy Sample. The majority of the objects in our sample are described by spectral energy distributions (SEDs) which peak at longer wavelengths than local sources of equivalent total infrared luminosity. This shift in SED peak wavelength implies a noticeable change in the dust and/or star-forming properties from z ∼ 0 to the early Universe, tending towards lower dust temperatures, indicative of strong evolution in the cold dust, 'cirrus', component. We show that these objects are potentially the missing link between the well-studied local IR-luminous galaxies, Spitzer IR populations and SCUBA sources - the z < 1 counterparts of the cold z > 1 SubMillimetre Galaxies (SMGs) discovered in blank-field submillimetre surveys. The Herschel Space Observatory is well placed to fully characterize the nature of these objects, as its coverage extends over a major part of the far-IR/sub-mm SED for a wide redshift range. © 2009 The Authors. Journal compilation © 2009 RAS.
• Teixeira, P., Lada, C., Young, E., Marengo, M., Muench, A., Muzerolle, J., Siegler, N., Rieke, G., Hartmann, L., Megeath, S., & Fazio, G. (2009). Identifying primordial substructure in NGC 2264. ASTROPHYSICAL JOURNAL, 636(1), L45-L48.
  More info

  We present new Spitzer Space Telescope observations of the young cluster NGC 2264. Observations at 24 mm with the Multiband Imaging Photometer have enabled us to identify the most highly embedded and youngest objects in NGC 2264. This Letter reports on one particular region of NGC 2264 where bright 24 mm sources are spatially configured in curious linear structures with quasi-uniform separations. The majority of these sources (similar to 60%) are found to be protostellar in nature, with Class I spectral energy distributions. Comparison of their spatial distribution with submillimeter data from Wolf-Chase et al. and millimeter data from Peretto et al. shows a close correlation between the dust filaments and the linear spatial configurations of the protostars, indicating that star formation is occurring primarily within dense, dusty filaments. Finally, the quasi-uniform separations of the protostars are found to be comparable in magnitude to the expected Jeans length, suggesting thermal fragmentation of the dense filamentary material.
• Weiner, B. J., Coil, A. L., Prochaska, J. X., Newman, J. A., Cooper, M. C., Bundy, K., Conselice, C. J., Dutton, A. A., Faber, S. M., Koo, D. C., Lotz, J. M., Rieke, G. H., & Rubin, K. H. (2009). Ubiquitous outflows in DEEP2 spectra of star-forming galaxies at z = 1.4. Astrophysical Journal, 692(1), 187-211.
  More info

  Abstract: Galactic winds are a prime suspect for the metal enrichment of the intergalactic medium (IGM) and may have a strong influence on the chemical evolution of galaxies and the nature of QSO absorption-line systems. We use a sample of 1406 galaxy spectra at z ∼ 1.4 from the DEEP2 redshift survey to show that blueshifted Mg IYI λλ 2796, 2803 absorption is ubiquitous in star-forming galaxies at this epoch. This is the first detection of frequent outflowing galactic winds at z ∼ 1. The presence and depth of absorption are independent of active galactic nuclei spectral signatures or galaxy morphology; major mergers are not a prerequisite for driving a galactic wind from massive galaxies. Outflows are found in co-added spectra of galaxies spanning a range of 30 times in stellar mass and 10 times in star formation rate (SFR), calibrated from K-band and from the Multiband Imaging Photometer for Spitzer IR fluxes. The outflows have column densities of order NH ∼ 1020 cm-2 and characteristic velocities of ∼ 300-500 km s-1, with absorption seen out to 1000 km s-1 in the most massive, highest SFR galaxies. The velocities suggest that the outflowing gas can escape into the IGM and that massive galaxies can produce cosmologically and chemically significant outflows. Both the Mg II equivalent width and the outflow velocity are larger for galaxies of higher stellar mass and SFR, with Vwind ∼ SFR0.3, similar to the scaling in low redshift IR-luminous galaxies. The high frequency of outflows in the star-forming galaxy population at z ∼ 1 indicates that galactic winds occur in the progenitors of massive spirals as well as those of ellipticals. The increase of outflow velocity with mass and SFR constrains theoretical models of galaxy evolution that include feedback from galactic winds, and may favor momentum-driven models for the wind physics. © 2009. The American Astronomical Society. All rights reserved.
• Willmer, C. N., Rieke, G. H., Floc'H, E. L., Hinz, J. L., Engelbracht, C. W., Marcillac, D., & Gordon, K. D. (2009). Spitzer observations of cold dust galaxies. Astronomical Journal, 138(1), 146-158.
  More info

  Abstract: We combine new Spitzer Space Telescope observations in the mid-infrared and far-infrared (FIR) with SCUBA 850 μm observations to improve the measurement of dust temperatures, masses, and luminosities for 11 galaxies of the SCUBA Local Universe Galaxy Survey. By fitting dust models we measure typical dust masses of 107.9 M⊙ and dust luminosities of 1010 L⊙, for galaxies with modest star formation rates. The data presented in this paper combined with previous observations show that cold dust is present in all types of spiral galaxies and is a major contributor to their total luminosity. Because of the lower dust temperature of the SCUBA sources measured in this paper, they have flatter FIR νFν(160 μm)/νF ν(850 μm) slopes than the larger Spitzer Infrared Nearby Galaxies Survey (SINGS), the sample that provides the best measurements of the dust properties of galaxies in the nearby universe. The new data presented here added to SINGS extend the parameter space that is well covered by local galaxies, providing a comprehensive set of templates that can be used to interpret the observations of nearby and distant galaxies. © 2009. The American Astronomical Society. All rights reserved.
• Yusef-Zadeh, F., Hewitt, J. W., Arendt, R. G., Whitney, B., Rieke, G., Wardle, M., Hinz, J. L., Stolovy, S., Lang, C. C., Burton, M. G., & Ramirez, S. (2009). Star formation in the central 400 PC of the milky way: Evidence for a population of massive young stellar objects. Astrophysical Journal Letters, 702(1), 178-225.
  More info

  Abstract: The central kpc of the Milky Way might be expected to differ significantly from the rest of the Galaxy with regard to gasdynamics and the formation of young stellar objects (YSOs). We probe this possibility with mid-infrared observations obtained with Infrared Array Camera and Multiband Imaging Photometer on Spitzer and with Midcourse Space Experiment. We use color-color diagrams and spectral energy distribution (SED) fits to explore the nature of YSO candidates (including objects with 4.5μm excesses possibly due to molecular emission). There is an asymmetry in the distribution of the candidate YSOs, which tend to be found at negative Galactic longitudes; this behavior contrasts with that of the molecular gas, approximately 2/3 of which is at positive longitudes. The small-scale height of these objects suggests that they are within the Galactic center region and are dynamically young. They lie between two layers of infrared dark clouds and may have originated from these clouds. We identify new sites for this recent star formation by comparing the mid-IR, radio, submillimeter, and methanol maser data. The methanol masers appear to be associated with young, embedded YSOs characterized by 4.5μm excesses. We use the SEDs of these sources to estimate their physical characteristics; their masses appear to range from 10 to 20 M. Within the central 400 × 50 pc (|l| < 13 and |b| < 10′) the star formation rate (SFR) based on the identification of Stage I evolutionary phase of YSO candidates is about 0.14M yr-1. Given that the majority of the sources in the population of YSOs are classified as Stage I objects, we suggest that a recent burst of star formation took place within the last 105 yr. This suggestion is also consistent with estimates of SFRs within the last 107 yr showing a peak around 105 yr ago. Lastly, we find that the Schmidt-Kennicutt Law applies well in the central 400 pc of the Galaxy. This implies that star formation does not appear to be dramatically affected by the extreme physical conditions in the Galactic center region. © 2009. The American Astronomical Society. All rights reserved.
• Zheng, X. Z., Bell, E. F., Somerville, R. S., Rix, H. -., Jahnke, K., Fontanot, F., Rieke, G. H., Schiminovich, D., & Meisenheimer, K. (2009). Observational constraints on the co-evolution of supermassive black holes and galaxies. Astrophysical Journal Letters, 707(2), 1566-1577.
  More info

  Abstract: The star formation rate (SFR) and black hole accretion rate (BHAR) functions are measured to be proportional to each other at z≲ 3. This close correspondence between SF and BHA would naturally yield a BH mass-galaxy mass correlation, whereas a BH mass-bulge mass correlation is observed. To explore this apparent contradiction, we study the SF in spheroid-dominated galaxies between z = 1 and the present day. We use 903 galaxies from the COMBO-17 survey with M* > 2 × 1010 M⊙, ultraviolet and infrared-derived SFRs from Spitzer and Galaxy Evolution Explorer, and morphologies from GEMS Hubble Space Telescope/Advanced Camera for Surveys imaging. Using stacking techniques, we find that 2.5), while the BHAR that we would expect if the global scalings held is 3 times higher. This rules out the simplest picture of co-evolution, in which SF and BHA trace each other at all times. These results could be explained if SF and BHA occur in the same events, but offset in time, for example at different stages of a merger event. However, one would then expect to see the corresponding star formation activity in early-stage mergers, in conflict with observations. We conclude that the major episodes of SF and BHA occur in different events, with the bulk of SF happening in isolated disks and most BHA occurring in major mergers. The apparent global co-evolution results from the regulation of the BH growth by the potential well of the galactic spheroid, which includes a major contribution from disrupted disk stars. © 2009. The American Astronomical Society. All rights reserved.
• Alonso-Herrero, A., Pérez-González, P. G., Rieke, G. H., Alexander, D. M., Rigby, J. R., Papovich, C., Donley, J. L., & Rigopoulou, D. (2008). The host galaxies and black holes of typical z ∼ 0.5-1.4 AGNs. Astrophysical Journal, 677(1), 127-136.
  More info

  Abstract: We study the stellar and star formation properties of the host galaxies of 58 X-ray-selected AGNs in the GOODS portion of the Chandra Deep Field South (CDF-S) region at z ∼ 0.5-1.4. The AGNs are selected such that their rest-frame UV to near-infrared spectral energy distributions (SEDs) are dominated by stellar emission; i.e., they show a prominent 1.6 μm bump, thus minimizing the AGN emission "contamination." This AGN population comprises approximately 50% of the X-ray-selected AGNs at these redshifts. We find that AGNs reside in the most massive galaxies at the redshifts probed here. Their characteristic stellar masses (M*, ∼ 7.8 × 10 10 and M* ∼ 1.2 × 1011 M⊙ at median redshifts of 0.67 and 1.07, respectively) appear to be representative of the X-ray-selected AGN population at these redshifts and are intermediate between those of local type 2 AGNs and high-redshift (z ∼ 2) AGNs. The inferred black hole masses (MBH ∼ 2 × 108 M ⊙) of typical AGNs are similar to those of optically identified quasars at similar redshifts. Since the AGNs in our sample are much less luminous (L2-10 kev < 1044 erg s-1) than quasars, typical AGNs have low Eddington ratios (η ∼ 0.01-0.001). This suggests that, at least at intermediate redshifts, the cosmic AGN "downsizing" is due to both a decrease in the characteristic stellar mass of typical host galaxies and less efficient accretion. Finally, there is no strong evidence in AGN host galaxies for either highly suppressed star formation (expected if AGNs played a role in quenching star formation) or elevated star formation when compared to mass-selected (i.e., IRAC-selected) galaxies of similar stellar masses and redshifts. © 2008. The American Astronomical Society. All rights reserved.
• Austermann, J. E., Dunlop, J. S., Perera, T. A., Scott, K. S., Wilson, G. W., Aretxaga, I., Hughes, D. H., Almaini, O., Chapin, E. L., Chapman, S. C., Cirasuolo, M., Clements, D. L., Coppin, K. E., Dunne, L., Dye, S., Eales, S. A., Egami, E., Farrah, D., Ferrusca, D., , Flynn, S., et al. (2008). AzTEC half square degree survey of the SHADES fields - I. Maps, catalogues and source counts. MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, 401(1), 160-176.
  More info

  We present the first results from the largest deep extragalactic mm-wavelength survey undertaken to date. These results are derived from maps covering over 0.7 deg2, made at lambda = 1.1 mm, using the AzTEC continuum camera mounted on the James Clerk Maxwell Telescope. The maps were made in the two fields originally targeted at lambda = 850 mu m with the Submillimetre Common-User Bolometer Array (SCUBA) in the SCUBA Half-Degree Extragalactic Survey (SHADES) project, namely the Lockman Hole East (mapped to a depth of 0.9-1.3 mJy rms) and the Subaru/XMM-Newton Deep Field (mapped to a depth of 1.0-1.7 mJy rms). The wealth of existing and forthcoming deep multifrequency data in these two fields will allow the bright mm source population revealed by these new wide-area 1.1 mm images to be explored in detail in subsequent papers. Here, we present the maps themselves, a catalogue of 114 high-significance submillimetre galaxy detections, and a thorough statistical analysis leading to the most robust determination to date of the 1.1 mm source number counts. These new maps, covering an area nearly three times greater than the SCUBA SHADES maps, currently provide the largest sample of cosmological volumes of the high-redshift Universe in the mm or sub-mm. Through careful comparison, we find that both the Cosmic Evolution Survey (COSMOS) and the Great Observatories Origins Deep Survey (GOODS) North fields, also imaged with AzTEC, contain an excess of mm sources over the new 1.1 mm source-count baseline established here. In particular, our new AzTEC/SHADES results indicate that very luminous high-redshift dust enshrouded starbursts (S(1.1mm) > 3 mJy) are 25-50 per cent less common than would have been inferred from these smaller surveys, thus highlighting the potential roles of cosmic variance and clustering in such measurements. We compare number count predictions from recent models of the evolving mm/sub-mm source population to these sub-mm bright galaxy surveys, which provide important constraints for the ongoing refinement of semi-analytic and hydrodynamical models of galaxy formation, and find that all available models overpredict the number of bright submillimetre galaxies found in this survey.
• Balog, Z., Rieke, G. H., Muzerolle, J., Bally, J., Y., K., Misselt, K., & Gáspár, A. (2008). Photoevaporation of protoplanetary disks. Astrophysical Journal, 688(1), 408-417.
  More info

  Abstract: We present HST NICMOS Paschen α (Paα) images and low- and high-resolution IRS spectra of photoevaporating disk-tail systems originally detected at 24 μm near O stars. We find no Paα emission in any of the systems. The resulting upper limits correspond to about (2-3) × 10 -6 M⊙ of mass in hydrogen in the tails, suggesting that the gas is severely depleted. The IRAC data and the low-resolution 5-12 μm IRS spectra provide evidence for an inner disk, while high-resolution long-wavelength (14-30 μm) IRS spectra confirm the presence of a gas-free tail that consists of ∼0.01 to ∼ 1 μm dust grains originating in the outer parts of the circumstellar disks. Overall, our observations support theoretical predictions in which photoevaporation removes the gas relatively quickly (≤ 105 yr) from the outer region of a protoplanetary disk, but leaves an inner, more robust, and possibly gas-rich disk component of radius 5-10 AU. With the gas gone, larger solid bodies in the outer disk can experience a high rate of collisions and produce elevated amounts of dust. This dust is being stripped from the system by the photon pressure of the O star to form a gas-free dusty tail. © 2008. The American Astronomical Society. All rights reserved.
• Beichman, C. A., Bryden, G., Stapelfeldt, K. R., Gautier, T. N., Grogan, K., Shao, M., Velusamy, T., Lawler, S. M., Blaylock, M., Rieke, G. H., Lunine, J. I., Fischer, D. A., Marcy, G. W., Greaves, J. S., Wyatt, M. C., Holland, W. S., & Dent, W. R. (2008). New debris disks around nearby main-sequence stars: Impact on the direct detection of planets. ASTROPHYSICAL JOURNAL, 652(2), 1674-1693.
  More info

  Using the MIPS instrument on Spitzer, we have searched for infrared excesses around a sample of 82 stars, mostly F, G, and K main-sequence field stars, along with a small number of nearby M stars. These stars were selected for their suitability for future observations by a variety of planet-finding techniques. These observations provide information on the asteroidal and cometary material orbiting these stars, data that can be correlated with any planets that may eventually be found. We have found significant excess 70 mu m emission toward 12 stars. Combined with an earlier study, we find an overall 70 mu m excess detection rate of 13% +/- 3% for mature cool stars. Unlike the trend for planets to be found preferentially toward stars with high metallicity, the incidence of debris disks is uncorrelated with metallicity. By newly identifying four of these stars as having weak 24 mu m excesses (fluxes similar to 10% above the stellar photosphere), we confirm a trend found in earlier studies wherein a weak 24 mu m excess is associated with a strong 70 mu m excess. Interestingly, we find no evidence for debris disks around 23 stars cooler than K1, a result that is bolstered by a lack of excess around any of the 38 K1-M6 stars in two companion surveys. One motivation for this study is the fact that strong zodiacal emission can make it hard or impossible to detect planets directly with future observatories such as the Terrestrial Planet Finder (TPF). The observations reported here exclude a few stars with very high levels of emission, > 1000 times the emission of our zodiacal cloud, from direct planet searches. For the remainder of the sample, we set relatively high limits on dust emission from asteroid belt counterparts.
• Bradford, C. M., Kenyon, M., Holmes, W., Bock, J., Koch, T., Day, P., Nguyen, H., Werner, M., Cofield, R., Paine, C., Irwin, K., Harwit, M., Stacey, G., Helou, G., Armus, L., Smith, J. D., Chapman, S., Rieke, G., Lester, D., , Nakagawa, T., et al. (2008). Sensitive far-IR survey spectroscopy: BLISS for SPICA. Proceedings of SPIE - The International Society for Optical Engineering, 7020.
  More info

  Abstract: We present a concept for BLISS, a sensitive far-IR-submillimeter spectrograph for SPICA. SPICA is a JAXA-led mission featuring a 3.5-meter telescope actively cooled to below 5K, envisioned for launch in 2017. The low-background platform is especially compelling for moderate-resolution survey spectroscopy, for which BLISS is designed. The BLISS / SPICA combination will offer line sensitivities below 10-20Wm-2 in modest integrations, enabling rapid survey spectroscopy of galaxies out to redshift 5. The far-IR fine-structure and molecular transitions which BLISS / SPICA will measure are immune to dust extinction, and will unambiguously reveal these galaxies' redshifts, stellar and AGN contents, gas properties, and heavy-element abundances. Taken together, such spectra will reveal the history of galaxies from 1 GY after the Big Bang to the present day. BLISS is comprised of five sub-bands, each with two R ∼ 700 grating spectrometer modules. The modules are configured with polarizing and dichroic splitters to provide complete instantaneous spectral coverage in two sky positions. To approach background-limited performance, BLISS detectors must have sensitivities at or below 5 × 10-20WHz-1/2, and the format is 10 arrays of several hundred pixels each. It is anticipated that these requirements can be met on SPICA's timescale with leg-isolated superconducting (TES) bolometers cooled with a 50 mK magnetic refrigerator.
• Brown, M., Brand, K., Dey, A., Jannuzi, B., Cool, R., Le Floc'h, E., Kochanek, C., Armus, L., Bian, C., Higdon, J., Higdon, S., Papovich, C., Rieke, G., Rieke, M., Smith, J., Soifer, B., & Weedman, D. (2008). The 1 < z < 5 infrared luminosity function of type I quasars. ASTROPHYSICAL JOURNAL, 638(1), 88-99.
  More info

  We determine the rest-frame 8 mu m luminosity function of type I quasars over the redshift range 1 < z < 5. Our sample consists of 292 24 mu m sources brighter than 1 mJy selected from 7.17 deg(2) of the Spitzer Space Telescope MIPS survey of the NOAO DeepWide-Field Survey Bootes field. The AGN and Galaxy Evolution Survey (AGES) has measured redshifts for 270 of the R < 21.7 sources, and we estimate that the contamination of the remaining 22 sources by stars and galaxies is low. We are able to select quasars missed by ultraviolet excess quasar surveys, including reddened type I quasars and 2.2 < z < 3.0 quasars with optical colors similar to main-sequence stars. We find that reddened type I quasars comprise similar to 20% of the type I quasar population. Nonetheless, the shape, normalization, and evolution of the rest-frame 8 mu m luminosity function are comparable to those of quasars selected from optical surveys. The 8 mu m luminosity function of type I quasars is well approximated by a power law with index -2.75 +/- 0.14. We directly measure the peak of the quasar space density to be at z = 2.6 +/- 0.3.
• Currie, T., Kenyon, S. J., Balog, Z., Rieke, G., Bragg, A., & Bromley, B. (2008). The rise and fall of debris disks: MIPS observations of h and χ Persei and the evolution of mid-IR emission from planet formation. Astrophysical Journal, 672(1), 558-574.
  More info

  Abstract: We describe Spitzer MIPS observations of the double cluster, h and χ Persei, covering a ∼0.6 deg2 area surrounding the cores of both clusters. The data are combined with IRAC and 2MASS data to investigate ∼616 sources from 1.25-24 μm. We use the long-baseline Ks - [24] color to identify two populations with IR excess indicative of circumstellar material: Be stars with 24 μm excess from optically thin free-free emission, and 17 fainter sources (J ∼ 14-15) with [24] excess consistent with a circumstellar disk. The frequency of IR excess for the fainter sources increases from 4.5 to 24 μm. The IR excess is likely due to debris from the planet formation process. The wavelength-dependent behavior is consistent with an inside-out clearing of circumstellar disks. A comparison of the 24 μm excess population in h and χ Per sources with results for other clusters shows that 24 μm emission from debris disks "rises" from 5 to 10 Myr, peaks at ∼10-15 Myr, and then "falls" from ∼15-20 Myr to 1 Gyr. © 2008. The American Astronomical Society. All rights reserved.
• Donley, J. L., Rieke, G. H., Pérez-González, P., & Barro, G. (2008). Spitzer's contribution to the AGN population. Astrophysical Journal, 687(1), 111-132.
  More info

  Abstract: Infrared selection is a potentially powerful way to identify heavily obscured AGNs missed in even the deepest X-ray surveys. Using a 24 μm-selected sample in GOODS-S, we test the reliability and completeness of three infrared AGN selection methods: (1) IRAC color-color selection, (2) IRAC power-law selection, and (3) IR-excess selection; we also evaluate a number of IR-excess approaches. We find that the vast majority of non-power-law IRAC color-selected AGN candidates in GOODS-S have colors consistent with those of star-forming galaxies. Contamination by star-forming galaxies is most prevalent at low 24 μm flux densities (∼100 μJy) and high redshifts (z ∼ 2), but the fraction of potential contaminants is still high (∼50%) at 500 μJy, the highest flux density probed reliably by our survey. AGN candidates selected via a simple, physically motivated power-law criterion ("power-law galaxies," or PLGs), however, appear to be reliable. We confirm that the IR-excess methods successfully identify a number of AGNs, but we also find that such samples may be significantly contaminated by star-forming galaxies. Adding only the secure Spitzer-selected PLG, color-selected, IR-excess, and radio/IR-selected AGN candidates to the deepest X-ray-selected AGN samples directly increases the number of known X-ray AGNs (84) by 54%-77%, and implies an increase to the number of 24 μm-detected AGNs of 71%-94%. Finally, we show that the fraction of MIR sources dominated by an AGN decreases with decreasing MIR flux density, but only down to f24 μm = 300 μJy. Below this limit, the AGN fraction levels out, indicating that a nonnegligible fraction (∼10%) of faint 24 μm sources (the majority of which are missed in the X-ray) are powered not by star formation, but by the central engine. The fraction of all AGNs (regardless of their MIR properties) exceeds 15% at all 24 μm flux densities. © 2008. The American Astronomical Society. All rights reserved.
• Dye, S., Eales, S. A., Aretxaga, I., Serjeant, S., Dunlop, J. S., Babbedge, T. S., Chapman, S. C., Cirasuolo, M., Clements, D. L., Coppin, K. E., Dunne, L., Egami, E., Farrah, D., Ivison, R. J., Kampen, E. V., Pope, A., Priddey, R., Rieke, G. H., Schael, A. M., , Scott, D., et al. (2008). The SCUBA HAlf Degree Extragalactic Survey (SHADES) - VII. Optical/IR photometry and stellar masses of submillimetre galaxies. Monthly Notices of the Royal Astronomical Society, 386(2), 1107-1130.
  More info

  Abstract: We present estimates of the photometric redshifts, stellar masses and star formation histories of sources in the Submillimetre Common-User Bolometer Array (SCUBA) HAlf Degree Extragalactic Survey (SHADES). This paper describes the 60 SCUBA sources detected in the Lockman Hole covering an area of ∼320 arcmin2. Using photometry spanning the B band to 8 μm, we find that the average SCUBA source forms a significant fraction of its stars in an early period of star formation and that most of the remainder forms in a shorter more intense burst around the redshift it is observed. This trend does not vary significantly with source redshift. However, the sources show a clear increase in stellar mass with redshift, consistent with downsizing. In terms of spectral energy distribution types, only two out of the 51 sources we have obtained photometric redshifts for are best fitted by a quasar-like spectrum, with approximately 80 per cent of the sources being best fitted with late-type spectra (Sc, Im and starburst). By including photometry at 850 μm, we conclude that the average SCUBA source is forming stars at a rate somewhere between 6 and 30 times the rate implied from the rest-frame optical in a dust obscured burst and that this burst creates 15-65 per cent of the total stellar mass. Using a simplistic calculation, we estimate from the average star formation history that between one in five and one in 15 bright (L* + 2 < Loptical < L* - 1 mag) galaxies in the field over the interval 0 < z < 3 will at some point in their lifetime experience a similar energetic dusty burst of star formation. Finally, we compute the evolution of the star formation rate density and find it peaks around z ∼ 2. © 2008 The Authors.
• Engelbracht, C. W., Rieke, G. H., Gordon, K. D., Smith, J. -., Werner, M. W., Moustakas, J., Willmer, C. N., & Vanzi, L. (2008). Erratum: Metallicity effects on dust properties in starbursting galaxies (The Astrophysical Journal (2008) 678 (804)). Astrophysical Journal, 685(1), 678-.
• Engelbracht, C. W., Rieke, G. H., Gordon, K. D., Smith, J. -., Werner, M. W., Moustakas, J., Willmer, C. N., & Vanzi, L. (2008). Metallicity effects on dust properties in starbursting galaxies. Astrophysical Journal, 678(2), 804-827.
  More info

  Abstract: We present infrared observations of 66 starburst galaxies over the full range of oxygen abundances observed in local star-forming galaxies, from 12 + log(O/H) = 7.1 to 8.9. The data include imaging and spectroscopy from the Spitzer Space Telescope, supplemented by ground-based near-infrared imaging. We confirm a strong correlation of aromatic emission with metallicity, with a threshold at 12 + log (O/H) ∼ 8. We show that the far-infrared color temperature of the large dust grains increases toward lower metallicity, peaking at a metallicity of 8 before turning over. We compute dust masses and compare them to H I masses from the literature to derive the ratio of atomic gas to dust, which increases by nearly 3 orders of magnitude between solar metallicity and a metallicity of 8, below which it flattens out. The abrupt change in aromatic emission at mid-infrared wavelengths thus appears to be reflected in the far-infrared properties, indicating that metallicity changes affect the composition of the full range of dust grain sizes that dominate the infrared emission. Although the great majority of galaxies show similar patterns of behavior as described above, there are three exceptions, SBS 0335-052E, Haro 11, and SHOC 391. Their infrared SEDs are dominated energetically by the mid-IR near 24 μm rather than by the 60-200 μm region. In addition, they have very weak near-infrared outputs and their SEDs are dominated by emission by dust at wavelengths as short as 1.8 μm. The latter behavior indicates that the dominant star-forming episodes in them are extremely young. The component of the ISM responsible for the usual far-infrared emission appears to be either missing or inefficiently heated in these three galaxies. © 2008. The American Astronomical Society. All rights reserved.
• Gordon, K. D., Engelbracht, C. W., Rieke, G. H., Misselt, K. A., Smith, J. -., & Kennicutt Jr., R. C. (2008). The behavior of the aromatic features in M101 H II regions: Evidence for dust processing. Astrophysical Journal, 682(1), 336-354.
  More info

  Abstract: The aromatic features in M101 were studied spectroscopically and photometrically using observations from all three instruments on the Spitzer Space Telescope. The global SED of M101 shows strong aromatic feature (commonly called PAH feature) emission. The spatially resolved spectral and photometric measurements of the aromatic feature emission show strong variations with significantly weaker emission at larger radii. We compare these variations with changes in the ionization index (asmeasured by [Ne III]/[Ne II] and [S IV/S III], which range from 0.03 to 20 and 0.044 to 15, respectively) and metallicity [expressed as log (O/H) + 12, which ranges from 8.1 to 8.8]. Over these ranges, the spectroscopic equivalent widths of the aromatic features fromseven H II regions and the nucleus were found to correlate better with ionization index than metallicity. This implies that theweakening of the aromatic emission in massive star-forming regions is due primarily to processing of the dust grains in these environments, not to differences in how they form. The behavior of the aromatic feature versus ionization index correlation can be described as a constant equivalent width until a threshold in ionization index is reached ([Ne III][Ne II]∼1), above which the equivalent widths decreasewith a power-law dependence. This behavior is also seen for the starburst galaxy sample presented in the companion study by Engelbracht and coworkers, which expands the range of [Ne III]/[Ne II] ratios to 0.03-25 and log (O/H) + 12 values to 7.1-8.8. The form of the correlation explains seemingly contradictory results present in the literature. The behavior of the ratios of different aromatic features versus ionization index does not follow the predictions of existing PAH models of the aromatic features, implying a more complex origin of the aromatic emission in massive star-forming regions. © 2008. The American Astronomical Society. All rights reserved.
• Gáspár, A., Su, K. Y., Rieke, G. H., Balog, Z., Kamp, I., Martínez-Galarza, J., & Stapelfeldt, K. (2008). Modeling the infrared bow shock at δ Velorum: Implications for studies of debris disks and λ boötis stars. Astrophysical Journal, 672(2), 974-983.
  More info

  Abstract: We have discovered a bow shock shaped mid-infrared excess region in front of δ Velorum using 24 μm observations obtained with the Multiband Imaging Photometer for Spitzer ( MIPS). Although the bow shock morphology was only detected in the 24 μm observations, its excess was also resolved at 70 μm. We show that the stellar heating of an ambient interstellar medium (ISM) cloud can produce the measured flux. Since δ Velorum was classified as a debris disk star previously, our discovery may call into question the same classification of other stars. We model the interaction of the star and ISM, producing images that show the same geometry and surface brightness as is observed. The modeled ISM is ∼15 times overdense relative to the average Local Bubble value, which is surprising considering the close proximity (24 pc) of δ Velorum. The abundance anomalies of λ Boötis stars have been previously explained as arising from the same type of interaction of stars with the ISM. Low-resolution optical spectra of δ Velorum show that it does not belong to this stellar class. The star therefore is an interesting testbed for the ISM accretion theory of the λ Boötis phenomenon. © 2008. The American Astronomical Society. All rights reserved.
• Hinz, J. L., & Rieke, G. H. (2008). Dynamical masses in luminous infrared galaxies. ASTROPHYSICAL JOURNAL, 646(2), 872-880.
  More info

  We have studied the dynamics and masses of a sample of 10 nearby luminous and ultraluminous infrared galaxies (LIRGs and ULIRGs, respectively) using 2.3 mu m (12)CO-absorption line spectroscopy and near-infrared H- and K(s)-band imaging. By combining velocity dispersions derived from the spectroscopy, disk scale lengths obtained from the imaging, and a set of likely model density profiles, we calculate dynamical masses for each LIRG. For the majority of the sample, it is difficult to reconcile our mass estimates with the large amounts of gas derived from millimeter observations and from a standard conversion between (12)CO emission and H(2) mass. Our results imply that LIRGs do not have huge amounts of molecular gas (10(10)-10(11) M(circle dot)) at their centers and support previous indications that the standard conversion of (12)CO to H(2) probably overestimates the gas masses and cannot be used in these environments. This in turn suggests much more modest levels of extinction in the near-infrared for LIRGs than previously predicted (A(V) similar to 10-20 vs. A(V) similar to 100-1000). The lower gas mass estimates indicated by our observations imply that the star formation efficiency in these systems is very high and is triggered by cloud-cloud collisions, shocks, and winds rather than by gravitational instabilities in circumnuclear gas disks.
• KIRKPATRICK, J., KELLY, D., RIEKE, G., LIEBERT, J., ALLARD, F., & WEHRSE, R. (2008). M-DWARF SPECTRA FROM 0.6 TO 1.5 MICRONS - A SPECTRAL SEQUENCE, MODEL ATMOSPHERE FITTING, AND THE TEMPERATURE SCALE. ASTROPHYSICAL JOURNAL, 402(2), 643-654.
  More info

  Red/infrared (0.6-1.5 mum) spectra are presented for a sequence of well-studied M dwarfs ranging from M2 through M9. A variety of temperature-sensitive features useful for spectral classification are identified. Using these features the spectral data are compared to recent theoretical models, from which a temperature scale is assigned. The red portion of the model spectra provide reasonably good fits for dwarfs earlier than M6. For later types, the infrared region provides a more reliable fit to the observations. In each case, the wavelength region used includes the broad peak of the energy distribution. For a given spectral type, the derived temperature sequence assigns higher temperatures than have earlier studies-the difference becoming more pronounced at lower luminosities. The positions of M dwarfs on the H-R diagram are, as a result, in closer agreement with theoretical tracks of the lower main sequence.
• Kamp, I., Martínez-Galarza, J., Paunzen, E., Su, K. Y., Gáspár, A., & Rieke, G. H. (2008). λ Bootis stars: Current status and new insights from Spitzer. Contributions of the Astronomical Observatory Skalnate Pleso, 38(2), 147-156.
  More info

  Abstract: The group of λ Bootis type stars comprises late B- to early F-type, Population I objects which are basically metal weak, in particular the Fe group elements, but with the clear exception of C, N, O and S. We present a spectroscopical definition for the group membership by using the light element versus metal abundance pattern. One of the current explanations for the λ Bootis peculiarity is the accretion of interstellar material as the star travels through a diffuse interstellar cloud. We will review this hypothesis in the context of ESO high resolution spectra and Spitzer imaging and photometry. The Na I D lines provide simultaneously stellar abundances and physical properties of interstellar material along the line of sight. The new Spitzer results shed light on the presence of dust around these stars, its composition and geometric distribution.
• Kim, Y., Rieke, G. H., Krause, O., Misselt, K., Indebetouw, R., & Johnson, K. E. (2008). Structure of the interstellar medium around Cas A. ASTROPHYSICAL JOURNAL, 678(1), 287-296.
  More info

  We present a 3 yr series of observations at 24 mu m with the Spitzer Space Telescope of the interstellar material in a 200' x 200' square area centered on Cassiopeia A. Interstellar dust heated by the outward light pulse from the supernova explosion emits in the form of compact, moving features. Their sequential outward movements allow us to study the complicated three- dimensional structure of the interstellar medium ( ISM) behind and near Cassiopeia A. The ISM consists of sheets and filaments, with many structures on a scale of a parsec or less. The spatial power spectrum of the ISM appears to be similar to that of fractals with a spectral index of 3.5. The filling factor for the small structures above the spatial wavenumber k similar to 0. 5 cycles pc(-1) is only similar to 0.4%.
• Kim, Y., Rieke, G. H., Krause, O., Misselt, K., Indebetouw, R., & Johnson, K. E. (2008). Structure of the interstellar medium around cas A. Astrophysical Journal, 678(1), 287-296.
  More info

  Abstract: We present a 3yr series of observations at 24 μm with the Spitzer Space Telescope of the interstellar material in a 200′ × 200′ square area centered on Cassiopeia A. Interstellar dust heated by the outward light pulse from the supernova explosion emits in the form of compact, moving features. Their sequential outward movements allow us to study the complicated three-dimensional structure of the interstellar medium (ISM) behind and near Cassiopeia A. The ISM consists of sheets and filaments, with many structures on a scale of a parsec or less. The spatial power spectrum of the ISM appears to be similar to that of fractals with a spectral index of 3.5. The filling factor for the small structures above the spatial wavenumber k ∼0.5 cycles pc -1 is only ∼0.4%. © 2008. The American Astronomical Society. All rights reserved.
• Krause, O., Birkmann, S. M., Usuda, T., Hattori, T., Goto, M., Rieke, G. H., & Misselt, K. A. (2008). The cassiopeia A supernova was of type IIb. Science, 320(5880), 1195-1197.
  More info

  PMID: 18511684;Abstract: Cassiopeia A is the youngest supernova remnant known in the Milky Way and a unique laboratory for supernova physics. We present an optical spectrum of the Cassiopeia A supernova near maximum brightness, obtained from observations of a scattered light echo more than three centuries after the direct light of the explosion swept past Earth. The spectrum shows that Cassiopeia A was a type IIb supernova and originated from the collapse of the helium core of a red supergiant that had lost most of its hydrogen envelope before exploding. Our finding concludes a long-standing debate on the Cassiopeia A progenitor and provides new insight into supernova physics by linking the properties of the explosion to the wealth of knowledge about its remnant.
• Lotz, J. M., Davis, M., Faber, S. M., Guhathakurta, P., Gwyn, S., Huang, J., Koo, D. C., Floc'H, E. L., Lin, L., Newman, J., Noeske, K., Papovich, C., Willmer, C. N., Coil, A., Conselice, C. J., Cooper, M., Hopkins, A. M., Metevier, A., Primack, J., , Rieke, G., et al. (2008). The evolution of galaxy mergers and morphology at z < 1.2 in the extended groth strip. Astrophysical Journal, 672(1), 177-197.
  More info

  Abstract: We present the quantitative rest-frame B morphological evolution and galaxy merger fraction at 0.2 < z < 1.2 as observed by the All-Wavelength Extended Groth Strip International Survey (AEGIS). We use the Gini coefficient and M20 to identify major mergers and classify galaxy morphology for a volume-limited sample of 3009 galaxies brighter than 0 4L*B, assuming pure luminosity evolution. We find that the merger fraction remains roughly constant at 10% ± 2% for 0.2 < z < 1.2. The fraction of E/S0/Sa galaxies increases from 21% ± 3% at z ∼ 1.1 to 44% ±9% at z ∼ 0.3, while the fraction of Sb-Ir galaxies decreases from 64% ± 6% at z ∼ 1.1 to 47% ± 9% at z ∼ 0.3. The majority ofz < 1.2 Spitzer MIPS 24 μm sources with L(IR) > 1011 L ⊙ are disk galaxies, and only ∼15% are classified as major merger candidates. Edge-on and dusty disk galaxies (Sb-Ir) are almost a third of the red sequence at z ∼ 1.1, while E/S0/Samake up over 90% of the red sequence at z ∼ 0.3. Approximately 2% of our full sample are red mergers. We conclude (1) the merger rate does not evolve strongly between 0.2 < z < 1.2; (2) the decrease in the volume-averaged star formation rate density since z ∼ 1 is a result of declining star formation in disk galaxies rather than a disappearing population of major mergers; (3) the build-up of the red sequence at z < 1 can be explained by a doubling in the number of spheroidal galaxies since z ∼ 1.2. © 2008. The American Astronomical Society. All rights reserved.
• Marcillac, D., Rieke, G. H., Papovich, C., Willmer, C. N., Weiner, B. J., Coil, A. L., Cooper, M. C., Gerke, B. F., Woo, J., Newman, J. A., Georgakakis, A., Laird, E. S., Nandra, K., Fazio, G. G., Huang, J. -., & Koo, D. C. (2008). The environment on a few Mpc scales of infrared luminous galaxies at redshift z ∼ 1. Astrophysical Journal, 675(2), 1156-1170.
  More info

  Abstract: We investigate the environment of infrared-luminous galaxies [Z IR(8-1000 μm) >1011 L⊙]. We focus on the redshift range 0.7 ≤ z ≤ 1, where these galaxies dominate the star formation activity and play a significant role in galaxy evolution. We employ MIPS 24 μm data to identify infrared galaxies in the Extended Groth Strip (EGS). We use a local density indicator to probe the environment on a few Mpc scales and a group member catalog, both of which make use of the DEEP2 spectroscopic redshift catalog, to quantify the environment of these galaxies. We find that the local environment of LIRGs and ULIRGs is intermediate between that of blue and red galaxies. LIRGs and ULIRGs avoid underdense environments and inhabit local environments that are more dense on average than those of other DEEP2 galaxies at similar redshifts. However, when the comparison sample of the non-IR DEEP2 galaxies is restricted to have the same range of stellar mass, color, or luminosity as the IR galaxies, there is no longer any significant difference in environment: the IR galaxies follow the same trends in the color-environment and luminosity-environment relations observed at z ∼ 1. We also find that about 30% of the LIRGs and ULIRGs belong to groups, associated with a minimum dark matter halo of 6 × 1012 M ⊙ h-1. The group members constitute 20% of the sources responsible for the IR star formation rate density and comoving energy density at z ∼ 1. © 2008. The American Astronomical Society. All rights reserved.
• Marcillac, D., Rigby, J. R., Rieke, G. H., & Kelly, D. M. (2008). Strong dusty bursts of star formation in galaxies falling into the cluster RX J0152.7-1357. ASTROPHYSICAL JOURNAL, 654(2), 825-834.
  More info

  We have observed the cluster RX J0152.7 - 1357 (z similar to 0.83) at 24 mu m with the Multiband Imaging Photometer for Spitzer (MIPS). We detected 22 sources associated with spectroscopically confirmed cluster members, while 10 more have photometric redshifts compatible with membership. Two of the 32 likely cluster members contain obvious active nuclei, while the others are associated with dusty star formation. The median IR-determined star formation rate among the remaining galaxies is estimated at 22 M-. yr(-1), significantly higher than in previous estimates from optical data. Most of the mid-infrared (MIR) emitting galaxies also have optical emission lines, but a few do not and hence have completely hidden bursts of star formation or AGN activity. An excess of MIR-emitting galaxies is seen in the cluster, compared to the field at the same redshift. The MIR cluster members are more associated with previously detected infalling late-type galaxies rather than triggered by the ongoing merging of bigger X-ray clumps. Rough estimates also show that ram pressure may not be capable of stripping the gas away from cluster outskirt galaxies, but it may disturb the gas enough to trigger the star formation activity. Harassment can also play a role if, for example, these galaxies belong to poor galaxy groups. Thus, bursts of star formation occur in the cluster environment and could also help consume the galaxy gas content, in addition to ram pressure, harassment, or galaxy-galaxy strong interactions.
• Nanyao, L. u., Smith, P. S., Engelbracht, C. W., Noriega-Crespo, A., Morrison, J., Gordon, K. D., Stansberry, J., Marleau, F. R., Rieke, G. H., Paladini, R., Padgett, D. L., Keene, J., Latter, W. B., Fadda, D., & Rho, J. (2008). Absolute calibration and characterization of the multiband imaging photometer for Spitzer. IV. The spectral energy distribution mode. Publications of the Astronomical Society of the Pacific, 120(865), 328-338.
  More info

  Abstract: The spectral energy distribution (SED) mode of the Multiband Imaging Photometer for Spitzer (MIPS) aboard the Spitzer Space Telescope provides low-spectral resolution (R ≈ 15-25) spectroscopy in the far-infrared using the MIPS 70 μm detector. A reflective grating provides a dispersion of 1.7 μm per pixel, and an effective wavelength coverage of 52.8-98.7 μm over detector rows 1-27. The final 5 detector rows are contaminated by second-order diffracted light and are left uncalibrated. The flux calibration is based on observations of MIPS calibration stars with 70 μm flux densities of 0.5-15 Jy. The point-source flux calibration accuracy is estimated to be 10% or better down to about 0.5 Jy at the blue end of the spectrum and to ∼2 Jy near the red end. With additional uncertainties from the illumination and aperture corrections included, the surface brightness calibration of extended sources is accurate to ∼15%. Repeatability of better than 5% is found for the SED mode through multiple measurements of several calibration stars. © 2008. The Astronomical Society of the Pacific. All rights reserved.
• Noeske, K. G., Weiner, B. J., Faber, S. M., Papovich, C., Koo, D. C., Somerville, R. S., Bundy, K., Conselice, C. J., Newman, J. A., Schiminovich, D., Le Floc'h, E., Coil, A. L., Rieke, G. H., Lotz, J. M., Primack, J. R., Barmby, P., Cooper, M. C., Davis, M., Ellis, R. S., , Fazio, G. G., et al. (2008). Star formation in AEGIS field galaxies since z=1.1: The dominance of gradually declining star formation, and the main sequence of star-forming galaxies. ASTROPHYSICAL JOURNAL, 660(1), L43-L46.
  More info

  We analyze star formation (SF) as a function of stellar mass (M-*) and redshift z in the All-Wavelength Extended M * Groth Strip International Survey. For 2905 field galaxies, complete to 10(10)(10(10.8)) M-circle dot at z < 0.7( 1), spectroscopic redshifts out to z = 1.1, we compile SF rates (SFRs) from emission lines, GALEX, and Spitzer MIPS 24 mu m photometry, optical-NIR M-* measurements, and HST morphologies. Galaxies with reliable signs of SF form a distinct "main sequence" (MS), with a limited range of SFRs at a given M-* and z (1 sigma less than or similar to +/- 0.3 dex), and log (SFR) approximately proportional to log M-*. The range of log (SFR) remains constant to z > 1, while the MS as a whole moves to higher SFR as z increases. The range of the SFR along the MS constrains the amplitude of episodic variations of SF and the effect of mergers on the SFR. Typical galaxies spend similar to 67%( 95%) of their lifetime since z = 1 within a factor of less than or similar to 2(4) of their average SFR at a given M-* and z. The dominant mode of the evolution z similar to 1 is apparently a gradual decline of the average SFR in most individual galaxies, not a decreasing frequency of starburst episodes, or a decreasing factor by which SFRs are enhanced in starbursts. LIRGs at z similar to 1 seem to mostly reflect the high SFR typical for massive galaxies at that epoch. The smooth MS may reflect that the same set of few physical processes governs SF prior to additional quenching processes. A gradual process like gas exhaustion may play a dominant role.
• Park, S. Q., Barmby, P., Fazio, G. G., Nandra, K., Laird, E. S., Georgakakis, A., Rosario, D., Willner, S. P., Rieke, G. H., Ashby, M. L., Ivison, R. J., Coil, A. L., & Miyazaki, S. (2008). AEGIS: Radio and mid-infrared selection of obscured AGN candidates. Astrophysical Journal, 678(2), 744-750.
  More info

  Abstract: The application of multiwavelength selection techniques is crucial for discovering a complete and unbiased set of active galactic nuclei (AGNs). Here, we select a sample of 72 AGN candidates in the extended Groth strip (EGS) using deep radio and mid-infrared (mid-IR) data from the Very Large Array (VLA) and the Spitzer Space Telescope, and analyze their properties across other wavelengths. Only 30% of these sources are detected in deep 200 ks Chandra X-Ray Observatory pointings. The X-ray-detected sources demonstrate moderate obscuration with column densities of NH ≳ 1022 cm-2. A stacked image of sources undetected by Chandra shows low levels of X-ray activity, suggesting they may be faint or obscured AGNs. Less than 40% of our sample are selected as AGNs with optical broad lines, mid-IR power laws, or X-ray detections. Thus, if our candidates are indeed AGNs, then the radio/mid-IR selection criteria we use provide a powerful tool for identifying sources missed by other surveys. © 2008. The American Astronomical Society. All rights reserved.
• Pérez-González, P. G., Rieke, G. H., Villar, V., Barro, G., Blaylock, M., Egami, E., Gallego, J., Gil, A., Pascual, S., Zamorano, J., & Donley, J. L. (2008). The stellar mass assembly of galaxies from z = 0 to z = 4: Analysis of a sample selected in the rest-frame near-infrared with Spitzer. Astrophysical Journal, 675(1), 234-261.
  More info

  Abstract: Using a sample of ∼28,000 sources selected at 3.6-4.5 μm with Spitzer observations of the Hubble Deep Field North, the Chandra Deep Field South, and the Lockman Hole (surveyed area ∼664 arcmin2), we study the evolution of the stellar mass content of the universe at 0 < z < 4. We calculate stellar masses and photometric redshifts, based on ∼2000 templates built with stellar population and dust emission models fitting the ultraviolet to mid-infrared spectral energy distributions of galaxies with spectroscopic redshifts. We estimate stellar mass functions for different redshift intervals. We find that 50% of the local stellar mass density was assembled at 0 < z < 1 (average star formation rate [SFR] 0.048 M⊙ yr-1 Mpc-3), and at least another 40% at 1 < z < 4 (average SFR 0.074 M⊙ yr-1 Mpc-3). Our results confirm and quantify the "downsizing" scenario of galaxy formation. The most massive galaxies (M > 1012.0 M⊙ ) assembled the bulk of their stellar content rapidly (in 1-2 Gyr) beyond z ∼ 3 in very intense star formation events (producing high specific SFRs). Galaxies with 10 11.5 < M < 1012.0 M⊙ assembled half of their stellar mass beforez ∼ 1.5, and more than 90% of theirmass was already in place atz ∼ 0.6. Galaxies with M < 1011.5M⊙ evolved more slowly (presenting smaller specific SFRs), assembling half of their stellar mass below z ∼ 1. About 40% of the local stellar mass density of 10 9.0 < M < 1011.0 M⊙ galaxies was assembled below z ∼ 0.4, most probably through accretion of small satellites producing little star formation. The cosmic stellar mass density atz > 2.5 is dominated by optically faint (R ≳ 25) red galaxies (distant red galaxies or BzK sources), which account for ∼30% of the global population of galaxies, but contribute at least 60% of the cosmic stellar mass density. Bluer galaxies (e.g., Lyman break galaxies) are more numerous but less massive, contributing less than 50% of the global stellar mass density at high redshift. © 2008. The American Astronomical Society. All rights reserved.
• Rieke, G. H., Blaylock, M., Decin, L., Engelbracht, C., Ogle, P., Avrett, E., Carpenter, J., Cutri, R. M., Armus, L., Gordon, K., Gray, R. O., Hinz, J., Su, K., & N., C. (2008). Absolute physical calibration in the infrared. Astronomical Journal, 135(6), 2245-2263.
  More info

  Abstract: We determine an absolute calibration for the Multiband Imaging Photometer for Spitzer 24 μm band and recommend adjustments to the published calibrations for Two Micron All Sky Survey (2MASS), Infrared Array Camera (IRAC), and IRAS photometry to put them on the same scale. We show that consistent results are obtained by basing the calibration on either an average A0V star spectral energy distribution (SED), or by using the absolutely calibrated SED of the Sun in comparison with solar-type stellar photometry (the solar analog method). After the rejection of a small number of stars with anomalous SEDs (or bad measurements), upper limits of 1.5% root mean square (rms) are placed on the intrinsic infrared (IR) SED variations in both A-dwarf and solar-type stars. These types of stars are therefore suitable as general-purpose standard stars in the IR. We provide absolutely calibrated SEDs for a standard zero magnitude A star and for the Sun to allow extending this work to any other IR photometric system. They allow the recommended calibration to be applied from 1 to 25 μm with an accuracy of 2%, and with even higher accuracy at specific wavelengths such as 2.2, 10.6, and 24 μm, near which there are direct measurements. However, we confirm earlier indications that Vega does not behave as a typical A0V star between the visible and the IR, making it problematic as the defining star for photometric systems. The integration of measurements of the Sun with those of solar-type stars also provides an accurate estimate of the solar SED from 1 through 30 μm, which we show agrees with theoretical models. © 2008. The American Astronomical Society. All rights reserved.
• Rieke, G., Young, E., Engelbracht, C., Kelly, D., Low, F., Haller, E., Beeman, J., Gordon, K., Stansberry, J., Misselt, K., Cadien, J., Morrison, J., Rivlis, G., Latter, W., Noriega-Crespo, A., Padgett, D., Stapelfeldt, K., Hines, D., Egami, E., , Muzerolle, J., et al. (2008). The Multiband Imaging Photometer for Spitzer (MIPS). ASTROPHYSICAL JOURNAL SUPPLEMENT SERIES, 154(1), 25-29.
  More info

  The Multiband Imaging Photometer for Spitzer (MIPS) provides long-wavelength capability for the mission in imaging bands at 24, 70, and 160 mum and measurements of spectral energy distributions between 52 and 100 mum at a spectral resolution of about 7%. By using true detector arrays in each band, it provides both critical sampling of the Spitzer point-spread function and relatively large imaging fields of view, allowing for substantial advances in sensitivity, angular resolution, and efficiency of areal coverage compared with previous space far-infrared capabilities. The 24 mum array has excellent photometric properties, and measurements with rms relative errors of about 1% can be obtained. The two longer-wavelength arrays use detectors with poor photometric stability, but a system of onboard stimulators used for relative calibration, combined with a unique data pipeline, produce good photometry with rms relative errors of less than 10%.
• Rigby, J. R., Marcillac, D., Egami, E., Rieke, G. H., Richard, J., Kneib, J. -., Fadda, D., Willmer, C. N., Borys, C., Van, P., Pérez-González, P., Knudsen, K. K., & Papovich, C. (2008). Mid-infrared spectroscopy of lensed galaxies at 1 < z < 3: The nature of sources near the mips confusion limit. Astrophysical Journal, 675(1), 262-280.
  More info

  Abstract: We present Spitzer 1RS mid-infrared spectra for 15 gravitationally lensed, 24 μm-selected galaxies, and combine the results with four additional very faint galaxies with IRS spectra in the literature. The median intrinsic 24 μm flux density of the sample is 130 μJy, enabling a systematic survey of the spectral properties of the very faint 24 μm sources that dominate the number counts of Spitzer cosmological surveys. Six of the 19 galaxy spectra (32%) show the strong mid-IR continuua expected of AGNs; X-ray detections confirm the presence of AGNs in three of these cases, and reveal AGNs in two other galaxies. These results suggest that nuclear accretion may contribute more flux to faint 24 μm-selected samples than previously assumed. Almost all the spectra show some aromatic (PAH) emission features; the measured aromatic flux ratios do not show evolution from z = 0. In particular, the high signal-to-noise mid-IR spectrum of SMM J163554.2-661225 agrees remarkably well with low-redshift, lower luminosity templates. We compare the rest-frame 8 μm and total infrared luminosities of star-forming galaxies, and find that the behavior of this ratio with total IR luminosity has evolved modestly from z = 2 to z = 0. Since the high aromatic-to-continuum flux ratios in these galaxies rule out a dominant contribution by AGNs, this finding implies systematic evolution in the structure and/or metallicity of infrared sources with redshift. It also has implications for the estimates of star-forming rates inferred from 24 μm measurements, in the sense that at z ∼ 2, a given observed frame 24 μm luminosity corresponds to a lower bolometric luminosity than would be inferred from low-redshift templates of similar luminosity at the corresponding rest wavelength. © 2008. The American Astronomical Society. AU rights reserved.
• Serjeant, S., Dye, S., Mortier, A., Peacock, J., Egami, E., Cirasuolo, M., Rieke, G., Borys, C., Chapman, S., Clements, D., Coppin, K., Dunlop, J., Eales, S., Farrah, D., Halpern, M., Mauskopf, P., Pope, A., Rowan-Robinson, M., Scott, D., , Smail, I., et al. (2008). The SCUBA Half Degree Extragalactic Survey (SHADES) - IX. the environment, mass and redshift dependence of star formation. Monthly Notices of the Royal Astronomical Society, 386(4), 1907-1921.
  More info

  Abstract: We present a comparison between the SCUBA (Submillimetre Common User Bolometer Array) Half Degree Extragalactic Survey (SHADES) at 450 and 850 μm in the Lockman Hole East with a deep Spitzer Space Telescope survey at 3.6-24 μm conducted in guaranteed time. Using stacking analyses we demonstrate a striking correspondence between the galaxies contributing the submm extragalactic background light, with those likely to dominate the backgrounds at Spitzer wavelengths. Using a combination BRIzK plus Spitzer photometric redshifts, we show that at least a third of the Spitzer-identified submm galaxies at 1 < z < 1.5 appear to reside in overdensities when the density field is smoothed at 0.5-2 Mpc comoving diameters, supporting the high-redshift reversal of the local star formation-galaxy density relation. We derive the dust-shrouded cosmic star formation history of galaxies as a function of assembled stellar masses. For model stellar masses
• Seymour, N., Dwelly, T., Moss, D., McHardy, I., Zoghbi, A., Rieke, G., Page, M., Hopkins, A., & Loaring, N. (2008). The star formation history of the Universe as revealed by deep radio observations. Monthly Notices of the Royal Astronomical Society, 386(3), 1695-1708.
  More info

  Abstract: Discerning the exact nature of the sub-mJy radio population has been historically difficult due to the low luminosity of these sources at most wavelengths. Using deep ground based optical follow-up and observations from the Spitzer Space Telescope we are able to disentangle the radio-selected active galactic nuclei (AGN) and star-forming galaxy (SFG) populations for the first time in a deep multifrequency VLA/MERLIN Survey of the 13H XMM-Newton/Chandra Deep Field. The discrimination diagnostics include radio morphology, radio spectral index, radio/near-infrared (near-IR) and mid-IR/radio flux density ratios. We are now able to calculate the extragalactic Euclidean normalized source counts separately for AGN and SFGs. We find that while SFGs dominate at the faintest flux densities and account for the majority of the upturn in the counts, AGN still make up around one quarter of the counts at ∼50 μJy (1.4 GHz). Using radio luminosity as an unobscured star formation rate (SFR) measure we are then able to examine the comoving SFR density of the Universe up to z = 3 which agrees well with measures at other wavelengths. We find a rough correlation of SFR with stellar mass for both the sample presented here and a sample of local radio-selected SFGs from the 6df-NVSS survey. This work also confirms the existence of, and provides alternative evidence for, the evolution of distribution of star formation by galaxy mass: 'downsizing'. As both these samples are SFR-selected, this result suggests that there is a maximum SFR for a given galaxy that depends linearly on its stellar mass. The low 'characteristic times' (inverse specific SFR) of the SFGs in our sample are similar to those of the 6dF-NVSS sample, implying that most of these sources are in a current phase of enhanced star formation. © 2008 RAS.
• Seymour, N., Symeonidis, M., Page, M. J., Huynh, M., Dwelly, T., McHardy, I. M., & Rieke, G. (2008). The comoving infrared luminosity density: domination of cold galaxies across 0 < z < 1. MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, 402(4), 2666-2670.
  More info

  sIn this paper, we examine the contribution of galaxies with different infrared (IR) spectral energy distributions (SEDs) to the comoving IR luminosity density (IRLD), a proxy for the comoving star formation rate (SFR) density. We characterize galaxies as having either a cold or hot IR SED depending on whether the rest-frame wavelength of their peak IR energy output is above or below 90 mu m. Our work is based on a far-IR selected sample both in the local Universe and at high redshift, the former consisting of IRAS 60 mu m-selected galaxies at z < 0.07 and the latter of Spitzer 70 mu m selected galaxies across 0.1 < z 10(11) L(circle dot)), the majority of which are cold, dominate the IRLD. We therefore infer that cold galaxies dominate the IRLD across the whole 0 < z < 1 range, hence appear to be the main driver behind the increase in SFR density up to z similar to 1 whereas local luminous galaxies are not, on the whole, representative of the high-redshift population.
• Shi, Y., Rieke, G., Donley, J., Cooper, M., Willmer, C., & Kirby, E. (2008). Black hole accretion in low-mass galaxies since z ∼ 1. Astrophysical Journal, 688(2), 794-806.
  More info

  Abstract: We have selected a sample of X-ray-emitting active galactic nuclei (AGNs) in low-mass host galaxies (∼5 × 109-2 × 10 10 M⊙) out to z ∼ 1. By comparing to AGNs in more massive hosts, we have found that the AGN spatial number density and the fraction of galaxies hosting AGNs depends strongly on the host mass, with the AGN host mass function peaking at intermediate mass and with the AGN fraction increasing with host mass. AGNs in low-mass hosts show strong cosmic evolution in comoving number density, the fraction of such galaxies hosting active nuclei, and the comoving X-ray energy density. The integrated X-ray luminosity function is used to estimate the amount of the accreted black hole mass in these AGNs and places a strong lower limit of 12% to the fraction of local low-mass galaxies hosting black holes, although a more likely value is probably much higher (>50%) once the heavily obscured objects missed in current X-ray surveys are accounted for. © 2008. The American Astronomical Society. All rights reserved.
• Stutz, A. M., Rubin, M., Werner, M. W., Rieke, G. H., Bieging, J. H., Keene, J., Kang, M., Shirley, Y. L., Su, K. Y., Velusamy, T., & Wilner, D. J. (2008). Spitzer and HHT observations of Bok globule B335: Isolated star formation efficiency and cloud structure. Astrophysical Journal, 687(1), 389-405.
  More info

  Abstract: We present infrared and millimeter observations of Barnard 335, the prototypical isolated Bok globule with an embedded protostar. Using Spitzer data we measure the source luminosity accurately; we also constrain the density profile of the innermost globule material near the protostar using the observation of an 8.0 μm shadow. Heinrich Hertz Telescope (HHT) observations of 12CO 2-1 confirm the detection of a flattened molecular core with diameter ∼10,000 AU and the same orientation as the circumstellar disk (∼100 to 200 AU in diameter). This structure is probably the same as that generating the 8.0 μm shadow and is expected from theoretical simulations of collapsing embedded protostars. We estimate the mass of the protostar to be only ∼5% of the mass of the parent globule.
• Su, K. Y., Rieke, G. H., Stansberry, J. A., Bryden, G., Stapelfeldt, K. R., Trilling, D. E., Muzerolle, J., Beichman, C. A., Moro-Martin, A., Hines, D. C., & Werner, M. W. (2008). Debris disk evolution around a stars. ASTROPHYSICAL JOURNAL, 653(1), 675-689.
  More info

  We report 24 and/or 70 mu m measurements of similar to 160 A-type main-sequence stars using the Multiband Imaging Photometer for Spitzer (MIPS). Their ages range from 5 to 850 Myr, based on estimates from the literature (cluster or moving group associations) or from the H-R diagram and isochrones. The thermal infrared excess is identified by comparing the deviation (similar to 3% and similar to 15% at the 1 sigma or level at 24 and 70 mu m, respectively) between the measurements and the synthetic Kurucz photospheric predictions. Stars showing excess infrared emission due to strong emission lines or extended nebulosity seen at 24 mu m are excluded from our sample; therefore, the remaining infrared excesses are likely to arise from circumstellar debris disks. At the 3 sigma, confidence level, the excess rate at 24 and 70 mu m is 32% and >= 33% (with an uncertainty of 5%), considerably higher than what has been found for old solar analogs and M dwarfs. Our measurements place constraints on the fractional dust luminosities and temperatures in the disks. We find that older stars tend to have lower fractional dust luminosity than younger ones. While the fractional luminosity from the excess infrared emission follows a general 1/t relationship, the values at a given stellar age vary by at least 2 orders of magnitude. We also find that (1) older stars possess a narrow range of temperature distribution peaking at colder temperatures, and (2) the disk emission at 70 mu m persists longer than that at 24 pm. Both results suggest that the debris disk clearing process is more effective in the inner regions.
• Su, K. Y., Rieke, G. H., Stapelfeldt, K. R., Smith, P. S., Bryden, G., Chen, C. H., & Trilling, D. E. (2008). The exceptionally large debris disk around γ ophiuchi. Astrophysical Journal, 679(2 PART 2), L125-L129.
  More info

  Abstract: Spitzer images resolve the debris disk around γ Ophiuchi at both 24 and 70 μm. The resolved images suggest a disk radius of ∼520 AU at 70 μm and ≥S260 AU at 24 μm. The images, along with a consistent fit to the spectral energy distribution of the disk from 20 to 350 μm, show that the primary disk structure is inclined by ∼50° from the plane of the sky at a position angle of 55° ± 2°. Among a group of 12 debris disks that have similar host star spectral types, ages, and infrared fractional luminosities, the observed sizes in the infrared and color temperatures indicate that evolution of the debris disks is influenced by multiple parameters in addition to the protoplanetary disk initial mass © 2008, The American Astronomical Society, All rights reserved.
• Trilling, D. E., Bryden, G., Beichman, C. A., Rieke, G. H., Su, K. Y., Stansberry, J. A., Blaylock, M., Stapelfeldt, K. R., Beeman, J. W., & Haller, E. E. (2008). Debris disks around Sun-like stars. ASTROPHYSICAL JOURNAL, 674(2), 1086-1105.
  More info

  We have observed nearly 200 FGK stars at 24 and 70 mu m with the Spitzer Space Telescope. We identify excess infrared emission, including a number of cases where the observed flux is more than 10 times brighter than the predicted photospheric flux, and interpret these signatures as evidence of debris disks in those systems. We combine this sample of FGK stars with similar published results to produce a sample of more than 350 main sequence AFGKM stars. The incidence of debris disks is 4.2(-1.1)(+2.0)% at 24 mu m for a sample of 213 Sun-like (FG) stars and 16.4(-2.9)(+2.8)% at 70 mu m for 225 Sun-like (FG) stars. We find that the excess rates for A, F, G, and K stars are statistically indistinguishable, but with a suggestion of decreasing excess rate toward the later spectral types; this may be an age effect. The lack of strong trend among FGK stars of comparable ages is surprising, given the factor of 50 change in stellar luminosity across this spectral range. We also find that the incidence of debris disks declines very slowly beyond ages of 1 billion years.
• Trilling, D. E., Bryden, G., Beichman, C. A., Rieke, G. H., Su, K. Y., Stansberry, J. A., Blaylock, M., Stapelfeldt, K. R., Beeman, J. W., & Haller, E. E. (2008). Debris disks around Sun-like stars. Astrophysical Journal, 674(2), 1086-1105.
  More info

  Abstract: We have observed nearly 200 FGK stars at 24 and 70 μm with the Spitzer Space Telescope. We identify excess infrared emission, including a number of cases where the observed flux is more than 10 times brighter than the predicted photospheric flux, and interpret these signatures as evidence of debris disks in those systems. We combine this sample of FGK stars with similar published results to produce a sample of more than 350 main sequence AFGKM stars. The incidence of debris disks is 4.2-1.1-2.0% at 24 μm for a sample of 213 Sun-like (FG) stars and 16.4-2.9-2.8 at 70 μm for 225 Sun-like (FG) stars. We find that the excess rates for A, F, G, and K stars are statistically indistinguishable, but with a suggestion of decreasing excess rate toward the later spectral types; this may be an age effect. The lack of strong trend among FGK stars of comparable ages is surprising, given the factor of 50 change in stellar luminosity across this spectral range. We also find that the incidence of debris disks declines very slowly beyond ages of 1 billion years. © 2008. The American Astronomical Society. All rights reserved.
• ULRICH, M., KINMAN, T., LYNDS, C., RIEKE, G., & EKERS, R. (2008). NONTHERMAL CONTINUUM RADIATION IN 3 ELLIPTICAL GALAXIES. ASTROPHYSICAL JOURNAL, 198(2), 261-266.
• Whitmore, B. C., Chandar, R., Schweizer, F., Rothberg, B., Leitherer, C., Rieke, M., Rieke, G., Blair, W. P., Mengel, S., & Alonso-Herrero, A. (2008). THE ANTENNAE GALAXIES (NGC 4038/4039) REVISITED: ADVANCED CAMERA FOR SURVEYS AND NICMOS OBSERVATIONS OF A PROTOTYPICAL MERGER. ASTRONOMICAL JOURNAL, 140(1), 75-109.
  More info

  The Advanced Camera for Surveys and the Near Infrared Camera and Multi-Object Spectrometer (NICMOS) have been used to obtain new Hubble Space Telescope images of NGC 4038/4039 ("The Antennae"). These new observations allow us to better differentiate compact star clusters from individual stars, based on both size and color. We use this ability to extend the cluster luminosity function (LF) by approximately 2 mag over our previous WFPC2 results, and find that it continues as a single power law, dN/dL proportional to L(alpha) with alpha = -2.13 +/- 0.07, down to the observational limit of M(V) approximate to -7. Similarly, the mass function (MF) is a single power law dN/dM proportional to M beta with beta = -2.10 +/- 0.20 for clusters with ages 3 mag.
• Alonso-Herrero, A., Donley, J. L., Rieke, G. H., Rigby, J. R., & Pérez-González, P. (2007). The quest for obscured AGN at cosmological distances: Infrared power-law galaxies. Highlights of Spanish Astrophysics IV - Proceedings of the 7th Scientific Meeting of the Spanish Astronomical Society, SEA 2006, 143-155.
  More info

  Abstract: We summarize multiwavelength properties of a sample of galaxies in the CDF-N and CDF-S whose spectral energy distributions (SEDs) exhibit the characteristic power-law behavior expected for AGN in the Spitzer/IRAC 3.6-8 μm bands. AGN selected this way tend to comprise the majority of high x-ray luminosity AGN, whereas AGN selected via other IRAC color-color criteria might contain more starformation dominated galaxies. Approximately half of these IR power-law galaxies in the CDF-S are detected in deep (1 Ms) Chandra x-ray imaging, although in the CDF-N (2 Ms) about 77% are detected at the 3 σlevel. The SEDs and x-ray upper limits of the sources not detected in x-rays are consistent with those of obscured AGN, and are significantly different from those of massive star-forming galaxies. About 40% of IR power-law galaxies detected in x-rays have SEDs resembling that of an optical QSO and morphologies dominated by bright point source emission. The remaining 60% have SEDs whose UV and optical continuum are much steeper (obscured) and more extended morphologies than those detected in x-rays. Most of the IR power-law galaxies not detected in x-rays have IR (8?1000 μm) above 1012 L, and x-ray (upper limits) to mid-IR ratios similar to those of local warm (i.e. hosting an AGN) ULIRGs. The SED shapes of power-law galaxies are consistent with the obscured fraction (4:1) as derived from the x-ray column densities, if we assume that all the sources not detected in x-rays are heavily absorbed. IR power-law galaxies may account for between 20% and 50% of the predicted number density of mid-IR detected obscured AGN. The remaining obscured AGN probably have rest-frame SEDs dominated by stellar emission. © 2007 Springer.
• Bai, L., Marcillac, D., Rieke, G. H., Rieke, M. J., Tran, K. H., Hinz, J. L., Rudnick, G., Kelly, D. M., & Blaylock, M. (2007). IR observations of MS 1054-03: Star formation and its evolution in rich galaxy clusters. Astrophysical Journal, 664(1 I), 181-197.
  More info

  Abstract: We study the IR properties of galaxies in the cluster MS 1054-03 at z = 0.83 by combining MIPS 24 μm data with spectra of more than 400 galaxies and a very deep K-band-selected catalog. Nineteen IR cluster members are selected spectroscopically, and an additional 15 are selected by their photometric redshifts. We derive the IR luminosity function of the cluster and find strong evolution compared to the similar-mass Coma Cluster. The best-fitting Schechter function gives LIR* = 11.49-0.29+0.30L⊙ with a fixed faint-end slope, about 1 order of magnitude larger than that in Coma. The rate of evolution of the IR luminosity from Coma to MS 1054-03 is consistent with that found in field galaxies, and it suggests that some internal mechanism, e.g., the consumption of the gas fuel, is responsible for the general decline of the cosmic SFR in different environments. The mass-normalized integrated SFR within 0.5R 200 in MS 1054-03 also shows evolution compared with other rich clusters at lower redshifts, but the trend is less conclusive if the mass selection effect is considered. A nonnegligible fraction (13% ± 3%) of cluster members are forming stars actively, and the overdensity of IR galaxies is about 20 compared to the field. It is unlikely that clusters only passively accrete starforming galaxies from the surrounding fields and have their star formation quenched quickly afterward; instead, many cluster galaxies still have large amounts of gas, and their star formation may be enhanced by the interaction with the cluster. © 2007. The American Astronomical Society. All rights reserved.
• Bai, L., Rieke, G. H., & Rieke, M. J. (2007). A search for infrared emission from intracluster dust in Abell 2029. Astrophysical Journal, 668(1 PART 2), L5-L8.
  More info

  Abstract: We have searched for IR emission from the intracluster dust (ICD) in the galaxy cluster A2029. Weak signals of enhanced extended emission in the cluster are detected at 24 and 70 μm. However, the signals are indistinguishable from the foreground fluctuations. The 24 μm versus 70 μm color map does not discriminate the dust emission in the cluster from the cirrus emission. After excluding the contamination from the point sources, we obtain upper limits for the extended ICD emission in A2029, 5 × 103 Jy sr-1 at 14 μm and 5 × 104 Jy sr-1 1 70 μm. The upper limits are generally consistent with the expectation from theoretical calculations and support a dust deficiency in the cluster compared to the interstellar medium (ISM) of our Galaxy. Our results suggest that even with the much improved sensitivity of current IR telescopes, a clear detection of the IR emission from ICD may be difficult due to cirrus noise. © 2007. The American Astronomical Society.
• Balog, Z., Muzerolle, J., Rieke, G. H., Su, K. Y., Young, E. T., & Megeath, S. T. (2007). Spitzer/IRAC-MIPS survey of NGC 2244: Protostellar disk survival in the vicinity of hot stars. ASTROPHYSICAL JOURNAL, 660(2), 1532-1540.
  More info

  We present the results from a survey of NGC 2244 from 3.6 to 24 mu m with the Spitzer Space Telescope. The 24 mu m- 8 mu m-3.6 mu m color composite image of the region shows that the central cavity surrounding the multiple O and B stars of NGC 2244 contains a large amount of cool dust visible only at 24 mu m. Our survey gives a detailed look at disk survivability within the hot-star-dominated environment in this cavity. Using mid-infrared two-color diagrams ( [ 3: 6 ]- [4. 5] vs. [5. 8] - [8.0]), we identified 337 class II and 25 class I objects out of 1084 objects detected in all four of these bands with photometric uncertainty better than 10%. Including the 24 -m data, we found 213 class II and 20 class I sources out of 279 stars also detected at this latter band. The center of the class II density contours is in very good agreement with the center of the cluster detected in the 2MASS images. We studied the distribution of the class II sources relative to the O stars and found that the effect of high-mass stars on the circumstellar disks is significant only in their immediate vicinity.
• Balog, Z., Muzerolle, J., Rieke, G. H., Y., K., Young, E. T., & Megeath, S. T. (2007). Spitzer/IRAC-mips survey of NGC 2244: Protostellar disk survival in the vicinity of hot stars. Astrophysical Journal, 660(2 I), 1532-1540.
  More info

  Abstract: Department of Optics and Quantum Electronics, University of Szeged, H-6720, Szeged, Hungary We present the results from a survey of NGC 2244 from 3.6 to 24 μm with the Spitzer Space Telescope. The 24 μm-8 μm-3.6 μm color composite image of the region shows that the central cavity surrounding the multiple O and B stars of NGC 2244 contains a large amount of cool dust visible only at 24 μm. Our survey gives a detailed look at disk survivability within the hot-star-dominated environment in this cavity. Using mid-infrared two-color diagrams ([3.6] - [4.5] vs. [5.8] - [8.0]), we identified 337 class II and 25 class I objects out of 1084 objects detected in all four of these bands with photometric uncertainty better than 10%. Including the 24 μm data, we found 213 class II and 20 class I sources out of 279 stars also detected at this latter band. The center of the class II density contours is in very good agreement with the center of the cluster detected in the 2MASS images. We studied the distribution of the class II sources relative to the 0 stars and found that the effect of high-mass stars on the circumstellar disks is significant only in their immediate vicinity. © 2007. The American Astronomical Society, All rights reserved.
• Barmby, P., Ashby, M. L., Bianchi, L., Engelbracht, C. W., Gehrz, R. D., Gordon, K. D., Hinz, J. L., Huchra, J. P., Humphreys, R. M., Pahre, M. A., Pérez-González, P., Polomski, E. F., Rieke, G. H., Thilker, D. A., Willner, S. P., & Woodward, C. E. (2007). Erratum: Dusty waves on a starry sea: The mid-infrared view of M31 (Astrophysical Journal (2006) 650 (L45)). Astrophysical Journal, 655(1 II), L61.
• Bryden, G., Beichman, C. A., Carpenter, J. M., Rieke, G. H., Stapelfeldt, K. R., Werner, M. W., Tanner, A. M., Lawler, S. M., Wyatt, M. C., Trilling, D. E., Su, K. Y., Blaylock, M., & Stansberry, J. A. (2007). PLANETS AND DEBRIS DISKS: RESULTS FROM A SPITZER/MIPS SEARCH FOR INFRARED EXCESS. ASTROPHYSICAL JOURNAL, 705(2), 1226-1236.
  More info

  Using the MIPS camera on the Spitzer Space Telescope, we have searched for debris disks around 104 stars known from radial velocity studies to have one or more planets. Combining this new data with 42 already published observations of planet-bearing stars, we find that 14 of the 146 systems have IR excess at 24 and/or 70 mu m. Only one star, HD 69830, has IR excess exclusively at 24 mu m, indicative of warm dust in the inner system analogous to that produced by collisions in the solar system's asteroid belt. For the other 13 stars with IR excess the emission is stronger at 70 mu m, consistent with cool dust (< 100 K) located beyond 10 AU, well outside of the orbital location of the known planets. Selection effects inhibit detection of faint disks around the planet-bearing stars (e. g., the stars tend to be more distant), resulting in a lower detection rate for IR excess than in a corresponding control sample of nearby stars not known to have planets (9% +/- 3% versus 14% +/- 3%). Even taking into account the selection bias, we find that the difference between the dust emission around stars with planets and stars without known planets is not statistically significant.
• Burgarella, D., Floc'H, E. L., Takeuchi, T. T., Huang, J. S., Buat, V., Rieke, G. H., & Tyler, K. D. (2007). Lyman break galaxies at z ∼ 1 and the evolution of dust attenuation in star-forming galaxies with redshift. Monthly Notices of the Royal Astronomical Society, 380(3), 986-998.
  More info

  Abstract: Ultraviolet (UV) galaxies have been selected from the Galaxy Evolution Explorer deep imaging survey. The presence of a far-UV (FUV) drop-out in their spectral energy distributions (SEDs) proved to be a very complete (83.3 per cent) but not very efficient (21.4 per cent) tool for identifying Lyman break galaxies (LBGs) at z ∼ 1. In this paper, we explore the physical properties of these galaxies and how they contribute to the total star formation rate (SFR). We divide the LBG sample into two subclasses: red LBGs (RLBGs) detected at λ = 24 μm which are mainly luminous infrared (IR) galaxies (LIRGs) and blue LBGs (BLBGs) undetected at λ = 24 μm down to the MIPS/GTO limiting flux density of 83 μJy. Two of the RLBGs are also detected at 70 μm. The median SED of the RLBGs is similar (above λ ∼ 1 μm) to that of a luminous dusty starburst at z ∼ 1.44, HR10. However, unlike local luminous and ultraluminous IR galaxies, RLBGs are UV bright objects. We suggest that these objects contain a large amount of dust but that some bare stellar populations are also directly visible. The median SED of the BLBGs is consistent with their containing the same stellar population as the RLBGs (i.e. a 250-500 Myr old, exponentially decaying star formation history) but with a lower dust content. The luminosity function (LF) of our LBG sample at z ∼ 1 is similar to the LF of near-UV (NUV) selected galaxies at the same redshift. The integrated luminosity densities of z ∼ 1 LBGs and NUV-selected galaxies are very consistent. Making use of the RLBG sample, we show that SFRs estimated from UV measurements and corrected using the IRX-β method provide average total SFRTOT in agreement with the sum of the UV and IR contributions: SFR UV + SFR dust. However, IRX-β-based SFR TOT shows a large dispersion. Summing up the detected UV (1150-Å rest-frame) and IR-based SFRs of the detected objects, we find that only one-third of the total (i.e. UV + dust) LBG SFR resides in BLBGs and two-thirds in RLBGs, even though most LBGs at z ∼ 1 are BLBGs. On the other hand, the total SFR of LBGs accounts for only 11 per cent of the total SFR at z ∼ 1. Finally, we observe a regular decrease in the luminosity ratio L dust/LFUV from z = 0 to z ≈ 2 for UV-selected samples. © 2007 RAS.
• Burgarella, D., Le Floc'h, E., Takeuchi, T. T., Huang, J. S., Buat, V., Rieke, G. H., & Tyler, K. D. (2007). Lyman break galaxies at z similar to 1 and the evolution of dust attenuation in star-forming galaxies with redshift. MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, 380(3), 986-998.
  More info

  Ultraviolet (UV) galaxies have been selected frorn the Galaxy Evolution Explorer deep imaging survey. The presence of a far-UV (FUV) drop-out in their spectral energy distributions (SEDs) proved to be a very complete (83.3 per cent) but not very efficient (21.4 per cent) tool for identifying Lyman break galaxies (LBGs) at z similar to 1. In this paper, we explore the physical properties of these galaxies and how they contribute to the total star formation rate (SFR). We divide the LBG sample into two subclasses: red LBGs (RLBGs) detected at lambda = 24 mu m which are mainly luminous infrared (IR) galaxies (LIRGs) and blue LBGs (BLBGs) undetected at, = 24 mu m down to the MIPS/GTO limiting flux density of 83 mu Jy. Two of the RLBGs are also detected at 70 mu m. The median SED of the RLBGs is similar (above lambda similar to 1 mu m) to that of a luminous dusty starburst at z similar to 1.44, HR 10. However, unlike local luminous and ultraluminous IR galaxies, RLBGs are UV bright objects. We suggest that these objects contain a large amount of dust but that some bare stellar populations are also directly visible. The median SED of the BLBGs is consistent with their containing the same stellar population as the RLBGs (i.e. a 250-500 Myr old, exponentially decaying star formation history) but with a lower dust content. The luminosity function (LF) of our LBG sample at z similar to I is similar to the LF of near-UV (NUV) selected galaxies at the same redshift. The integrated luminosity densities of z similar to I LBGs and NUV-selected galaxies are very consistent. Making use of the RLBG sample, we 1 p show that SFRs estimated from UV measurements and corrected using the IRX-beta method provide average total SFRTOT in agreement with the sum of the UV and IR contributions: SFRuv + SFR (dust). However, IRX-beta-based SFRTOT shows a large dispersion. Summing up the detected UV (1150-angstrom rest-frame) and IR-based SFRs of the detected objects, we find that only one-third of the total (i.e. UV + dust) LBG SFR resides in BLBGs and two-thirds in RLBGs, even though most LBGs at z similar to I are BLBGs. On the other hand, the total SFR of LBGs accounts for only I I per cent of the total SFR at z similar to 1. Finally, we observe a regular decrease in the luminosity ratio L-dust/L-FUV from z = 0 to z approximate to 2 for UV-selected samples.
• Calzetti, D., Kennicutt, R. C., Engelbracht, C. W., Leitherer, C., Draine, B. T., Kewley, L., Moustakas, J., Sosey, M., Dale, D. A., Gordon, K. D., Helou, G. X., Hollenbach, D. J., Armus, L., Bendo, G., Bot, C., Buckalew, B., Jarrett, T., Li, A., Meyer, M., , Murphy, E. J., et al. (2007). The calibration of mid-infrared star formation rate indicators. Astrophysical Journal, 666(2 I), 870-895.
  More info

  Abstract: With the goal of investigating the degree to which the MIR emission traces the SFR, we analyze Spitzer 8 and 24 ßm data of star-forming regions in a sample of 33 nearby galaxies with available HST NICMOS images in the Pan ( 1.8756 μm) emission line. The galaxies are drawn from the SINGS sample and cover a range of morphologies and a factor ∼ 10 in oxygen abundance. Published data on local low-metallicity starburst galaxies and LIRGs are also included in the analysis. Both the stellar continuum-subtracted 8 μ emission and the 24 μm emission correlate with the extinction-corrected Paa line emission, although neither relationship is linear, Simple models of stellar populations and dust extinction and emission are able to reproduce the observed nonlinear trend of the 24 //m emission versus number of ionizing photons, including the modest deficiency of 24 μm emission in the low-metallicity regions, which results from a combination of decreasing dust opacity and dust temperature at low luminosities. Conversely, the trend of the 8 μm emission as a function of the number of ionizing photons is not well reproduced by the same models. The 8 μm emission is contributed, in larger measure than the 24 μm emission, by dust heated by nonionizing stellar populations, in addition to the ionizing ones, in agreement with previous findings. Two SFR calibrations, one using the 24 μm emission and the other using a combination of the 24 μm and Ha luminosities (Kennicutt and coworkers), are presented. No calibration is presented for the 8 μm emission because of its significant dependence on both metallicity and environment. The calibrations presented here should be directly applicable to systems dominated by ongoing star formation. © 2007. The American Astronomical Society. All rights reserved.
• Chen, C. H., Li, A., Bohac, C., Kim, K. H., Watson, D. M., Cleve, J. V., Houck, J., Stapelfeldt, K., Werner, M. W., Rieke, G., Su, K., Marengo, M., Backman, D., Beichman, C., & Fazio, G. (2007). The dust and gas around β pictoris. Astrophysical Journal, 666(1 I), 466-474.
  More info

  Abstract: We have obtained Spitzer IRS 5.5-35 μm spectroscopy of the debris disk around β Pictoris. In addition to the 10 μm silicate emission feature originally observed from the ground, we also detect the crystalline silicate emission bands at 28 and 33.5 μm. This is the first time that the silicate bands at wavelengths longer than 10 μm have ever been seen in the β Pictoris disk. The observed dust emission is well reproduced by a dust model consisting of fluffy cometary and crystalline olivine aggregates. We searched for line emission from molecular hydrogen and atomic [S I], Fe II, and Si II gas but detected none. We place a 3 σ upper limit of < 17 M ⊕ on the H2 S(1) gas mass, assuming an excitation temperature of Tex = 100 K. This suggests that there is less gas in this system than is required to form the envelope of Jupiter. We hypothesize that some of the atomic Na I gas observed in Keplerian rotation around β Pictoris may be produced by photon-stimulated desorption from circumstellar dust grains. © 2007. The American Astronomical Society. All rights reserved.
• Cortese, L., Marcillac, D., Richard, J., Bravo-Alfaro, H., Kneib, J. -., Rieke, G., Covone, G., Egami, E., Rigby, J., Czoske, O., & Davies, J. (2007). The strong transformation of spiral galaxies infalling into massive clusters at z ap; 0.2. Monthly Notices of the Royal Astronomical Society, 376(1), 157-172.
  More info

  Abstract: We describe two peculiar galaxies falling into the massive galaxy clusters Abell 1689 (z ≈ 0.18) and Abell 2667 (z ≈ 0.23), respectively. Hubble Space Telescope (HST) images show extraordinary trails composed of bright blue knots (-16.5 < M < -11.5 mag) and stellar streams associated with each of these systems. Combining optical, near- and mid-infrared and radio observations we prove that while both galaxies show similar extended trails of star-forming knots, their recent star formation histories are different. One (≈L*) is experiencing a strong burst of star formation, appearing as a rare example of a luminous infrared cluster galaxy. In comparison, the other (≈0.1L*) has recently ceased its star formation activity. Our model suggests that the morphologies and star formation in these galaxies have been influenced by the combined action of tidal interaction (likely with the cluster potential) and of ram pressure with the intracluster medium (ICM). These results can be used to gain more insights to the origin of S0s, dwarf and ultracompact dwarf (UCD) cluster galaxies. © 2007 RAS.
• Currie, T., Balog, Z., Kenyon, S. J., Rieke, G., Prato, L., Young, E. T., Muzerolle, J., Clemens, D. P., Buie, M., Sarcia, D., Grabu, A., Tollestrup, E. V., Taylor, B., Dunham, E., & Mace, G. (2007). Spitzer IRAC and JHK_S observations of h and _χ persei: Constraints on protoplanetary disk and massive cluster evolution at ∼10⁷ years. Astrophysical Journal, 659(1 I), 599-615.
  More info

  Abstract: We describe IRAC 3.6-8 μm observations and ground-based near-IR JHK S photometry from Mimir and 2MASS of the massive double cluster h and χ Persei complete to J = 15.5 (M ∼ 1.3 M⊙). Within 25′ of the cluster centers we detect ∼11,000 sources with J ≤ 15.5, ∼7000 sources with [4.5] ≤ 15, and ∼5000 sources with [8] ≤ 14.5. In both clusters the surface density profiles derived from the 2MASS data decline with distance from the cluster centers as expected for a bound cluster. Within 15′ of the cluster centers, ∼50% of the stars lie on a reddened ∼13 Myr isochrone; at 15′-25′ from the cluster centers, ∼40% lie on this isochrone. Thus, the optical/2MASS color-magnitude diagrams indicate that h and χ Per are accompanied by a halo population with roughly the same age and distance as the two dense clusters. The double cluster lacks any clear IR excess sources for J ≤ 13.5 (∼2.7 M⊙). Therefore, disks around high-mass stars disperse prior to ∼107 yr. At least 2%-3% of the fainter cluster stars have strong IR excess at both [5.8] and [8]. About 4%-8% of sources slightly more massive than the Sun (∼1.4 M⊙) have IR excesses at [8]. Combined with the lack of detectable excesses for brighter stars, this result suggests that disks around lower mass stars have longer lifetimes. The IR excess population also appears to be larger at longer IRAC bands ([5.8], [8]) than at shorter IRAC/2MASS bands (KS, [4.5]), a result consistent with an inside-out clearing of disks. © 2007. The American Astronomical Society. All rights reserved.
• Currie, T., Kenyon, S. J., Rieke, G., Balog, Z., & Bromley, B. C. (2007). Terrestrial zone debris disk candidates in h and χ persei. Astrophysical Journal, 663(2 II), L105-L108.
  More info

  Abstract: We analyze eight sources with strong mid-infrared excesses in the 13 Myr old double cluster h and \Persei. New optical spectra and broadband spectral energy distributions (SEDs; 0.36-8 μm) are consistent with cluster membership. We show that the material with T ∼ 300-400 K and L d/L* ∼ 10-4 to 10-3 produces the excesses in these sources. Optically thick blackbody disk models, including those with large inner holes, do not match the observed SEDs. The SEDs of optically thin debris disks produced from terrestrial planet formation calculations match the observations well. Thus, some h and χ Persei stars may have debris from terrestrial zone planet formation. © 2007. The American Astronomical Society. All rights reserved.
• Davis, M., Guhathakurta, P., Konidaris, N. P., Newman, J. A., Ashby, M. L., Biggs, A. D., Barmby, P., Bundy, K., Chapman, S. C., Coil, A. L., Conselice, C. J., Cooper, M. C., Croton, D. J., Eisenhardt, P. R., Ellis, R. S., Faber, S. M., Fang, T., Fazio, G. G., Georgakakis, A., , Gerke, B. F., et al. (2007). The all-wavelength extended groth strip international survey (AEGIS) data sets. Astrophysical Journal, 660(1 II), L1-L6.
  More info

  Abstract: In this the first of a series of Letters, we present a panchromatic data set in the Extended Groth Strip region of the sky. Our survey, the All-Wavelength Extended Groth Strip International Survey (AEGIS), aims to study the physical properties and evolutionary processes of galaxies at z ∼ 1. It includes the following deep, wide-field imaging data sets: Chandra/ACIS X-ray, GALEX ultraviolet, CFHT/MegaCam Legacy Survey optical, CFHT/CFH12K optical, Hubble Space Telescope/ACS optical and NICMOS near-infrared, Palomar/WIRC near-infrared, Spitzer/IRAC mid-infrared, Spitzer/MIPS far-infrared, and VLA radio continuum. In addition, this region of the sky has been targeted for extensive spectroscopy using the Deep Imaging Multi-Object Spectrograph (DEIMOS) on the Keck II 10 m telescope. Our survey is compared to other large multiwavelength surveys in terms of depth and sky coverage. © 2007. The American Astronomical Sociey, All rights reserved.
• Donley, J. L., Rieke, G. H., Pérez-González, P., Rigby, J. R., & Alonso-Herrero, A. (2007). Spitzer power-law active galactic nucleus candidates in the Chandra Deep Field-North. Astrophysical Journal, 660(1 I), 167-190.
  More info

  Abstract: We define a sample of 62 galaxies in the Chandra Deep Field-North whose Spitzer IRAC SEDs exhibit the characteristic power-law emission expected of luminous AGNs. We study the multiwavelength properties of this sample and compare the AGNs selected in this way to those selected via other Spitzer color-color criteria. Only 55% of the power-law galaxies are detected in the X-ray catalog at exposures of >0.5 Ms, although a search for faint emission results in the detection of 85% of the power-law galaxies at the ≥2.5 σ detection level. Most of the remaining galaxies are likely to host AGNs that are heavily obscured in the X-ray. Because the power-law selection requires the AGNs to be energetically dominant in the near- and mid-infrared, the power-law galaxies comprise a significant fraction of the S/Hfeer-detected AGN population at high luminosities and redshifts. The high 24 μm detection fraction also points to a luminous population. The power-law galaxies comprise a subset of color-selected AGN candidates. A comparison with various mid-infrared color selection criteria demonstrates that while the color-selected samples contain a larger fraction of the X-ray-luminous AGNs, there is evidence that these selection techniques also suffer from a higher degree of contamination by star-forming galaxies in the deepest exposures. Considering only those power-law galaxies detected in the X-ray catalog, we derive an obscured fraction of 68% (2:1). Including all of the power-law galaxies suggests an obscured fraction of
• Draine, B. T., Dale, D. A., Bendo, G., Gordon, K. D., Smith, J. D., Armus, L., Engelbracht, C. W., Helou, G., Kennicutt Jr., R. C., Li, A., Roussel, H., Walter, F., Calzetti, D., Moustakas, J., Murphy, E. J., Rieke, G. H., Bot, C., Hollenbach, D. J., Sheth, K., & Teplitz, H. I. (2007). Dust masses, pah abundances, and starlight intensities in the sings galaxy sample. Astrophysical Journal, 663(2 I), 866-894.
  More info

  Abstract: Physical dust models are presented for 65 galaxies in SINGS that are strongly detected in the four IRAC bands and three MIPS bands. For each galaxy we estimate (1) the total dust mass, (2) the fraction of the dust mass contributed by PAHs, and (3) the intensity of the starlight heating the dust grains. We find that spiral galaxies have dust properties resembling the dust in the local region of the Milky Way, with similar dust-to-gas ratio and similar PAH abundance. The observed SEDs, including galaxies with SCUBA photometry, can be reproduced by dust models that do not require "cold" (T ≳ 10 K) dust. The dust-to-gas ratio is observed to be dependent on metallicity. In the interstellar media of galaxies with AO = 12 + log 10(O/H) > 8.1, grains contain a substantial fraction of interstellar Mg, Si, and Fe. Galaxies with AO < 8.1 and extended H I envelopes in some cases appear to have global dust-to-gas ratios that are low for their measured oxygen abundance, but the dust-to-gas ratio in the regions where infrared emission is detected generally appears to be consistent with a substantial fraction of interstellar Mg, Si, and Fe being contained in dust. The PAH index qpAH, the fraction of the dust mass in the form of PAHs, correlates with metallicity. The nine galaxies in our sample with AO < 8.1 have a median qPAH = 1.0%, whereas galaxies with A O > 8.1 have a median qPAH = 3.55%. The derived dust masses favor a value XCo ≈ 4 × 1020 cm -2 (K kms-1)-1 for the CO-to-H2 conversion factor. Except for some starbursting systems (Mrk 33, Toi 89, NGC 3049), dust in the diffuse ISM dominates the IR power. © 2007. The American Astronomical Society. All rights reserved.
• Engelbracht, C. W., Blaylock, M., Su, K. Y., Rho, J., Rieke, G. H., Muzerolle, J., Padgett, D. L., Hines, D. C., Gordon, K. D., Fadda, D., Noriega-Crespo, A., Kelly, D. M., Latter, W. B., Hinz, J. L., Misselt, K. A., Morrison, J. E., Stansberry, J. A., Shupe, D. L., Stolovy, S., , Wheaton, W. A., et al. (2007). Absolute calibration and characterization of the multiband imaging photometer for spitzer. I. The stellar calibrator sample and the 24 mu m calibration. PUBLICATIONS OF THE ASTRONOMICAL SOCIETY OF THE PACIFIC, 119(859), 994-1018.
  More info

  We present the stellar calibrator sample and the conversion from instrumental to physical units for the 24 mm channel of the Multiband Imaging Photometer for Spitzer (MIPS). The primary calibrators are A stars, and the calibration factor based on those stars is 4.54 x 10(-2) MJy sr(-1) (DN s(-1))(-1), with a nominal uncertainty of 2%. We discuss the data reduction procedures required to attain this accuracy; without these procedures, the calibration factor obtained using the automated pipeline at the Spitzer Science Center is lower. We 1.6% +/- 0.6% extend this work to predict 24 mu m flux densities for a sample of 238 stars that covers a larger range of flux densities and spectral types. We present a total of 348 measurements of 141 stars at 24 mm. This sample covers a factor of similar to 460 in 24 mm flux density, from 8.6 mJy up to 4.0 Jy. We show that the calibration is linear over that range with respect to target flux and background level. The calibration is based on observations made using 3 s exposures; a preliminary analysis shows that the calibration factor may be 1% and 2% lower for 10 and 30 s exposures, respectively. We also demonstrate that the calibration is very stable: over the course of the mission, repeated measurements of our routine calibrator, HD 159330, show a rms scatter of only 0.4%. Finally, we show that the point-spread function (PSF) is well measured and allows us to calibrate extended sources accurately; Infrared Astronomy Satellite (IRAS) and MIPS measurements of a sample of nearby galaxies are identical within the uncertainties.
• Engelbracht, C. W., Blaylock, M., Su, K. Y., Rho, J., Rieke, G. H., Muzerolle, J., Padgett, D. L., Hines, D. C., Gordon, K. D., Fadda, D., Noriega-Crespo, A., Kelly, D. M., Latter, W. B., Hinz, J. L., Misselt, K. A., Morrison, J. E., Stansberry, J. A., Shupe, D. L., Stolovy, S., , Wheaton, W., et al. (2007). Absolute calibration and characterization of the multiband imaging photometer for Spitzer. I. The stellar calibrator sample and the 24 μm calibration. Publications of the Astronomical Society of the Pacific, 119(859), 994-1018.
  More info

  Abstract: We present the stellar calibrator sample and the conversion from instrumental to physical units for the 24 μm channel of the Multiband Imaging Photometer for Spitzer (MIPS). The primary calibrators are A stars, and the calibration factor based on those stars is 4.54 × 10 -2 MJy sr -1 (DN s -1) -1 with a nominal uncertainty of 2%. We discuss the data reduction procedures required to attain this accuracy; without these procedures, the calibration factor obtained using the automated pipeline at the Spitzer Science Center is 1.6% ± 0.6% lower. We extend this work to predict 24 μm flux densities for a sample of 238 stars that covers a larger range of flux densities and spectral types. We present a total of 348 measurements of 141 stars at 24 μm. This sample covers a factor of ∼460 in 24 μm flux density, from 8.6 mJy up to 4.0 Jy. We show that the calibration is linear over that range with respect to target flux and background level. The calibration is based on observations made using 3 s exposures; a preliminary analysis shows that the calibration factor may be 1% and 2% lower for 10 and 30 s exposures, respectively. We also demonstrate that the calibration is very stable: over the course of the mission, repeated measurements of our routine calibrator, HD 159330, show a rms scatter of only 0.4%. Finally, we show that the point-spread function (PSF) is well measured and allows us to calibrate extended sources accurately; Infrared Astronomy Satellite (IRAS) and MIPS measurements of a sample of nearby galaxies are identical within the uncertainties. © 2007. The Astronomical Society of the Pacific. All rights reserved.
• Flaherty, K. M., Muzerolle, J., Rieke, G., Gutermuth, R., Balog, Z., Herbst, W., Megeath, S. T., & Kun, M. (2007). INFRARED VARIABILITY OF EVOLVED PROTOPLANETARY DISKS: EVIDENCE FOR SCALE HEIGHT VARIATIONS IN THE INNER DISK. ASTROPHYSICAL JOURNAL, 748(1).
  More info

  We present the results of a multi-wavelength multi-epoch survey of five evolved protoplanetary disks in the IC 348 cluster that show significant infrared variability. Using 3-8 mu m and 24 mu m photometry along with 5-40 mu m spectroscopy from the Spitzer Space Telescope, as well as ground-based 0.8-5 mu m spectroscopy, optical spectroscopy, and near-infrared photometry, covering timescales of days to years, we examine the variability in the disk, stellar, and accretion flux. We find substantial variations (10%-60%) at all infrared wavelengths on timescales of weeks to months for all of these young stellar objects. This behavior is not unique when compared to other cluster members and is consistent with changes in the structure of the inner disk, most likely scale height fluctuations on a dynamical timescale. Previous observations, along with our near-infrared photometry, indicate that the stellar fluxes are relatively constant; stellar variability does not appear to drive the large changes in the infrared fluxes. Based on our near-infrared spectroscopy of the Pa beta and Br gamma lines we find that the accretion rates are variable in most of the evolved disks but the overall rates are probably too small to cause the infrared variability. We discuss other possible physical causes for the variability, including the influence of a companion, magnetic fields threading the disk, and X-ray flares.
• Floc'h, E. L., Willmer, C. N., Noeske, K., Konidaris, N. P., Laird, E. S., Koo, D. C., Nandra, K., Bundy, K., Salim, S., Maiolino, R., Conselice, C. J., Lotz, J. M., Papovich, C., Smith, J. D., Bai, L., Coil, A. L., Barmby, P., Ashby, M. L., Huang, J. -., , Blaylock, M., et al. (2007). Far-infrared characterization of an ultraluminous starburst associated with a massively accreting black hole at z = 1.15. Astrophysical Journal, 660(1 II), L65-L68.
  More info

  Abstract: As part of the All-Wavelength Extended Groth Strip International Survey (AEGIS), we describe the panchromatic characterization of an X-ray-luminous active galactic nucleus (AGN) in a merging galaxy at z = 1.15. This object is detected at infrared (8, 24, 70, and 160 μm), submillimeter (850 μm), and radio wavelengths, from which we derive a bolometric luminosity Lboi ∼ 9 × 1012 L⊙. We find that the AGN clearly dominates the hot dust emission below 40 μm but its total energetic power inferred from the hard X-rays is substantially less than the bolometric output of the system. About 50% of the infrared luminosity is indeed produced by a cold dust component that probably originates from enshrouded star formation in the host galaxy. In the context of a coeval growth of stellar bulges and massive black holes, this source might represent a "transition" object, sharing properties with both quasars and luminous starbursts. Study of such composite galaxies will help address how the star formation and disk-accretion phenomena may have regulated each other at high redshift and how this coordination may have participated in the buildup of the relationship observed locally between the masses of black holes and stellar spheroids. © 2007. The American Astronomical Society. All rights reserved.
• Gehrz, R. D., Roellig, T. L., Werner, M. W., Fazio, G. G., Houck, J. R., Low, F. J., Rieke, G. H., Soifer, B. T., Levine, D. A., & Romana, E. A. (2007). The NASA spitzer space telescope. Review of Scientific Instruments, 78(1).
  More info

  PMID: 17503900;Abstract: The National Aeronautics and Space Administration's Spitzer Space Telescope (formerly the Space Infrared Telescope Facility) is the fourth and final facility in the Great Observatories Program, joining Hubble Space Telescope (1990), the Compton Gamma-Ray Observatory (1991-2000), and the Chandra X-Ray Observatory (1999). Spitzer, with a sensitivity that is almost three orders of magnitude greater than that of any previous ground-based and space-based infrared observatory, is expected to revolutionize our understanding of the creation of the universe, the formation and evolution of primitive galaxies, the origin of stars and planets, and the chemical evolution of the universe. This review presents a brief overview of the scientific objectives and history of infrared astronomy. We discuss Spitzer's expected role in infrared astronomy for the new millennium. We describe pertinent details of the design, construction, launch, in-orbit checkout, and operations of the observatory and summarize some science highlights from the first two and a half years of Spitzer operations. More information about Spitzer can be found at http://spitzer.caltech.edu/. © 2007 American Institute of Physics.
• Golimowski, D. A., Krist, J. E., Stapelfeldt, K. R., Chen, C. H., Ardila, D. R., Bryden, G., Clampin, M., Ford, H. C., Illingworth, G. D., Plavchan, P., Rieke, G. H., & Su, K. Y. (2007). HUBBLE AND SPITZER SPACE TELESCOPE OBSERVATIONS OF THE DEBRIS DISK AROUND THE NEARBY K DWARF HD 92945. ASTRONOMICAL JOURNAL, 142(1).
  More info

  We present the first resolved images of the debris disk around the nearby K dwarf HD 92945, obtained with the Hubble Space Telescope's (HST's) Advanced Camera for Surveys. Our F606W (Broad V) and F814W (Broad I) coronagraphic images reveal an inclined, axisymmetric disk consisting of an inner ring about 2 ''.0-3.'' 0 (43-65 AU) from the star and an extended outer disk whose surface brightness declines slowly with increasing radius approximately 3.'' 0-5.'' 1 (65-110 AU) from the star. A precipitous drop in the surface brightness beyond 110 AU suggests that the outer disk is truncated at that distance. The radial surface-density profile is peaked at both the inner ring and the outer edge of the disk. The dust in the outer disk scatters neutrally but isotropically, and it has a low V-band albedo of 0.1. This combination of axisymmetry, ringed and extended morphology, and isotropic neutral scattering is unique among the 16 debris disks currently resolved in scattered light. We also present new infrared photometry and spectra of HD 92945 obtained with the Spitzer Space Telescope's Multiband Imaging Photometer and InfraRed Spectrograph. These data reveal no infrared excess from the disk shortward of 30 mu m and constrain the width of the 70 mu m source to less than or similar to 180 AU. Assuming that the dust comprises compact grains of astronomical silicate with a surface-density profile described by our scattered-light model of the disk, we successfully model the 24-350 mu m emission with a minimum grain size of a(min) = 4.5 mu m and a size distribution proportional to a-(3.7) throughout the disk, but with maximum grain sizes of 900 mu m in the inner ring and 50 mu m in the outer disk. Together, our HST and Spitzer observations indicate a total dust mass of similar to 0.001M circle plus. However, our observations provide contradictory evidence of the dust's physical characteristics: its neutral V-I color and lack of 24 mu m emission imply grains larger than a few microns, but its isotropic scattering and low albedo suggest a large population of submicron-sized grains. If grains smaller than a few microns are absent, then stellar radiation pressure may be the cause only if the dust is composed of highly absorptive materials like graphite. The dynamical causes of the sharply edged inner ring and outer disk are unclear, but recent models of dust creation and transport in the presence of migrating planets support the notion that the disk indicates an advanced state of planet formation around HD 92945.
• Gordon, K. D., Engelbracht, C. W., Fadda, D., Stansberry, J., Wachter, S., Frayer, D. T., Rieke, G., Noriega-Crespo, A., Latter, W. B., Young, E., Neugebauer, G., Balog, Z., Beeman, J. W., Dole, H., Egami, E., Haller, E. E., Hines, D., Kelly, D., Marleau, F., , Misselt, K., et al. (2007). Absolute calibration and characterization of the multiband imaging photometer for Spitzer. II. 70 μm imaging. Publications of the Astronomical Society of the Pacific, 119(859), 1019-1037.
  More info

  Abstract: The absolute calibration and characterization of the Multiband Imaging Photometer for Spitzer (MIPS) 70 μm coarse- and fine-scale imaging modes are presented based on over 2.5 yr of observations. Accurate photometry (especially for faint sources) requires two simple processing steps beyond the standard data reduction to remove long-term detector transients. Point-spread function (PSF) fitting photometry is found to give more accurate flux densities than aperture photometry. Based on the PSF fitting photometry, the calibration factor shows no strong trend with flux density, background, spectral type, exposure time, or time since anneals. The coarse-scale calibration sample includes observations of stars with flux densities from 22 mJy to 17 Jy, on backgrounds from 4 to 26 MJy sr -1, and with spectral types from B to M. The coarse-scale calibration is 702 ± 35 MJy sr -1 MIPS70 -1 (5% uncertainty) and is based on measurements of 66 stars. The instrumental units of the MIPS 70 μm coarse- and fine-scale imaging modes are called MIPS70 and MIPS70F, respectively. The photometric repeatability is calculated to be 4.5% from two stars measured during every MIPS campaign and includes variations on all timescales probed. The preliminary fine-scale calibration factor is 2894 ± 294 MJy sr -1 MIPS70F -1 (10% uncertainty) based on 10 stars. The uncertainties in the coarse- and finescale calibration factors are dominated by the 4.5% photometric repeatability and the small sample size, respectively. The 5 σ, 500 s sensitivity of the coarse-scale observations is 6-8 mJy. This work shows that the MIPS 70 μm array produces accurate, well-calibrated photometry and validates the MIPS 70 μm operating strategy, especially the use of frequent stimulator flashes to track the changing responsivities of the Ge:Ga detectors. © 2007. The Astronomical Society of the Pacific. All rights reserved.
• Gordon, K. D., Engelbracht, C. W., Fadda, D., Stansberry, J., Wachter, S., Frayer, D. T., Rieke, G., Noriega-Crespo, A., Latter, W. B., Young, E., Neugebauer, G., Balog, Z., Beeman, J. W., Dole, H., Egami, E., Haller, E. E., Hines, D., Kelly, D., Marleau, F., , Misselt, K., et al. (2007). Absolute calibration and characterization of the multiband imaging photometer for spitzer. II. 70 mu m imaging. PUBLICATIONS OF THE ASTRONOMICAL SOCIETY OF THE PACIFIC, 119(859), 1019-1037.
  More info

  The absolute calibration and characterization of the Multiband Imaging Photometer for Spitzer (MIPS) 70 mu m coarse- and fine-scale imaging modes are presented based on over 2.5 yr of observations. Accurate photometry ( especially for faint sources) requires two simple processing steps beyond the standard data reduction to remove long-term detector transients. Point-spread function (PSF) fitting photometry is found to give more accurate flux densities than aperture photometry. Based on the PSF fitting photometry, the calibration factor shows no strong trend with flux density, background, spectral type, exposure time, or time since anneals. The coarse- scale calibration sample includes observations of stars with flux densities from 22 mJy to 17 Jy, on backgrounds from 4 to 26 MJy sr(-1), and with spectral types from B to M. The coarse- scale calibration is 702 +/- 35 MJy sr(-1) MIPS70(-1) (5% uncertainty) and is based on measurements of 66 stars. The instrumental units of the MIPS 70 mm coarse- and fine-scale imaging modes are called MIPS70 and MIPS70F, respectively. The photometric repeatability is calculated to be 4.5% from two stars measured during every MIPS campaign and includes variations on all timescales probed. The preliminary fine-scale calibration factor is 2894 +/- 294 MJy sr(-1) MIPS70F(-1) (10% uncertainty) based on 10 stars. The uncertainties in the coarse- and fine-scale calibration factors are dominated by the 4.5% photometric repeatability and the small sample size, respectively. The 5 sigma, 500 s sensitivity of the coarse- scale observations is 6-8 mJy. This work shows that the 5 sigma MIPS 70 mm array produces accurate, well-calibrated photometry and validates the MIPS 70 mu m operating strategy, especially the use of frequent stimulator flashes to track the changing responsivities of the Ge:Ga detectors.
• Gordon, K. D., Engelbracht, C. W., Rieke, G. H., Misselt, K. A., Smith, J. -., & Kennicutt, R. C. (2007). The behavior of the aromatic features in M101 HII regions: Evidence for dust processing. ASTROPHYSICAL JOURNAL, 682(1), 336-354.
  More info

  The aromatic features in M101 were studied spectroscopically and photometrically using observations from all three instruments on the Spitzer Space Telescope. The global SED of M101 shows strong aromatic feature (commonly called PAH feature) emission. The spatially resolved spectral and photometric measurements of the aromatic feature emission show strong variations with significantly weaker emission at larger radii. We compare these variations with changes in the ionization index (as measured by [Ne III]/[Ne II] and [S IV/S III], which range from 0.03 to 20 and 0.044 to 15, respectively) and metallicity [expressed as log (O/H) + 12, which ranges from 8.1 to 8.8]. Over these ranges, the spectroscopic equivalent widths of the aromatic features from seven H II regions and the nucleus were found to correlate better with ionization index than metallicity. This implies that the weakening of the aromatic emission in massive star-forming regions is due primarily to processing of the dust grains in these environments, not to differences in how they form. The behavior of the aromatic feature versus ionization index correlation can be described as a constant equivalent width until a threshold in ionization index is reached ([Ne III]/[Ne II] similar to 1), above which the equivalent widths decrease with a power law dependence. This behavior is also seen for the star burst galaxy sample presented in the companion study by Engelbracht and coworkers, which expands the range of [Ne III]/[Ne II] ratios to 0.03-25 and log (O/H) + 12 values to 7.1-8.8. The form of the correlation explains seemingly contradictory results present in the literature. The behavior of the ratios of different aromatic features versus ionization index does not follow the predictions of existing PAH models of the aromatic features, implying a more complex origin of the aromatic emission in massive star-forming regions.
• Gorlova, N., Balog, Z., Rieke, G. H., Muzerolle, J., Su, K. Y., Ivanov, V. D., & Young, E. T. (2007). Debris disks in NGC 2547. ASTROPHYSICAL JOURNAL, 670(1), 516-535.
  More info

  We have surveyed the 30 Myr old cluster NGC 2547 for planetary debris disks using Spitzer. At 4.5-8 mu m we are sensitive to the photospheric level down to mid-M stars (0.2M circle dot), and at 24 mu m to early G stars (1.2 M circle dot). We find only two to four stars with excesses at 8 mu m out of similar to 400-500 cluster members, resulting in an excess fraction less than or similar to 1% at this wavelength. By contrast, the excess fraction at 24 mu m is similar to 40% (for B-F types). Out of four late-type stars with excesses at 8 mu m two marginal ones are consistent with asteroid- like debris disks. Among stars with strong 8 mu m excesses one is possibly from a transitional disk, while another one can be a result of a catastrophic collision. Our survey demonstrates that the inner 0.1-1 AU parts of disks around solar- type stars clear out very thoroughly by 30 Myr of age. Comparingwith the much slower decay of excesses at 24 and 70 mu m, disks clear from the inside out, of order 10 Myr for the inner zones probed at 8 mu m, compared with 100 or more megayears for those probed with the two longer wavelengths.
• Gorlova, N., Balog, Z., Rieke, G. H., Muzerolle, J., Su, K. Y., Ivanov, V. D., & Young, E. T. (2007). Debris disks in NGC 2547¹. Astrophysical Journal, 670(1), 516-535.
  More info

  Abstract: We have surveyed the 30 Myr old cluster NGC 2547 for planetary debris disks using Spitzer. At 4.5-8 μm we are sensitive to the photospheric level down to mid-M stars (0.2 M⊙), and at 24 μm to early G stars (1.2 M⊙). We find only two to four stars with excesses at 8 μ,m out of ∼400-500 cluster members, resulting in an excess fraction ≤% at this wavelength. By contrast, the excess fraction at 24 μm is ∼40% (for B-F types). Out of four late-type stars with excesses at 8 μm two marginal ones are consistent with asteroid-like debris disks. Among stars with strong 8 μm excesses one is possibly from a transitional disk, while another one can be a result of a catastrophic collision. Our survey demonstrates that the inner 0.1-1 AU parts of disks around solar-type stars clear out very thoroughly by 30 Myr of age. Comparing with the much slower decay of excesses at 24 and 70 μm, disks clear from the inside out, of order 10 Myr for the inner zones probed at 8 μm, compared with 100 or more megayears for those probed with the two longer wavelengths. © 2007. The American Astronomical Society. All rights reserved.
• Helou, G., Roussel, H., Appleton, P., Frayer, D., Stolovy, S., Storrie-Lombardi, L., Hurt, R., Lowrance, P., Makovoz, D., Masci, F., Surace, J., Gordon, K., Alonso-Herrero, A., Engelbracht, C., Misselt, K., Rieke, G., Rieke, M., Willner, S., Pahre, M., , Ashby, M., et al. (2007). The anatomy of star formation in NGC 300. ASTROPHYSICAL JOURNAL SUPPLEMENT SERIES, 154(1), 253-258.
  More info

  The Spitzer Space Telescope was used to study the mid-to far-infrared properties of NGC 300 and to compare dust emission to Halpha to elucidate the heating of the interstellar medium (ISM) and the star formation cycle at scales smaller than 100 pc. The new data allow us to discern clear differences in the spatial distribution of 8 mum dust emission with respect to 24 mum dust and to H II regions traced by Halpha light. The 8 mum emission highlights the rims of H II regions, and the 24 mum emission is more strongly peaked in star-forming regions than 8 mum. We confirm the existence and approximate amplitude of interstellar dust emission at 4.5 mum, detected statistically in Infrared Space Observatory (ISO) data, and conclude it arises in star-forming regions. When averaging over regions larger than similar to1 kpc, the ratio of Halpha to aromatic feature emission in NGC 300 is consistent with the values observed in disks of spiral galaxies. The mid-to far-infrared spectral energy distribution of dust emission is generally consistent with pre-Spitzer models.
• Hinz, J. L., Rieke, M. J., Rieke, G. H., Willmer, C. N., Misselt, K., Engelbracht, C. W., Blaylock, M., & Pickering, T. E. (2007). Spitzer observations of low-luminosity isolated and low surface brightness galaxies. Astrophysical Journal, 663(2 I), 895-907.
  More info

  Abstract: We examine the infrared properties of five low surface brightness galaxies (LSBGs) and compare them with related but higher surface brightness galaxies, using Spitzer Space Telescope images and spectra. All the LSBGs are detected in the 3.6 and 4.5 μm bands, representing the stellar population. All but one are detected at 5.8 and 8.0 μm, revealing emission from hot dust and aromatic molecules, although many are faint or pointlike at these wavelengths. Detections of LSBGs at the far-infrared wavelengths of 24,70, and 160 μm are varied in morphology and brightness, with only two detections at 160 μm, resulting in highly varied spectral energy distributions. Consistent with previous expectations for these galaxies, we find that detectable dust components exist for only some LSBGs, with the strength of dust emission dependent on the existence of bright star-forming regions. However, the far-infrared emission may be relatively weak compared with normal star-forming galaxies. © 2007. The American Astronomical Society. All rights reserved.
• Ivison, R. J., Greve, T. R., Dunlop, J. S., Peacock, J. A., Egami, E., Smail, I., Ibar, E., Kampen, E. V., Aretxaga, I., Babbedge, T., Biggs, A. D., Blain, A. W., Chapman, S. C., Clements, D. L., Coppin, K., Farrah, D., Halpern, M., Hughes, D. H., Jarvis, M. J., , Jenness, T., et al. (2007). The SCUBA HAlf Degree Extragalactic Survey - III. Identification of radio and mid-infrared counterparts to submillimetre galaxies. Monthly Notices of the Royal Astronomical Society, 380(1), 199-228.
  More info

  Abstract: Determining an accurate position for a submillimetre (submm) galaxy (SMG) is the crucial step that enables us to move from the basic properties of an SMG sample - source counts and 2D clustering - to an assessment of their detailed, multiwavelength properties, their contribution to the history of cosmic star formation and their links with present-day galaxy populations. In this paper, we identify robust radio and/or infrared (IR) counterparts, and hence accurate positions, for over two-thirds of the SCUBA HAlf-Degree Extragalactic Survey (SHADES) Source Catalogue, presenting optical, 24-μm and radio images of each SMG. Observed trends in identification rate have given no strong rationale for pruning the sample. Uncertainties in submm position are found to be consistent with theoretical expectations, with no evidence for significant additional sources of error. Employing the submm/radio redshift indicator, via a parametrization appropriate for radio-identified SMGs with spectroscopic redshifts, yields a median redshift of 2.8 for the radio-identified subset of SHADES, somewhat higher than the median spectroscopic redshift. We present a diagnostic colour-colour plot, exploiting Spitzer photometry, in which we identify regions commensurate with SMGs at very high redshift. Finally, we find that significantly more SMGs have multiple robust counterparts than would be expected by chance, indicative of physical associations. These multiple systems are most common amongst the brightest SMGs and are typically separated by 2-6 arcsec, at z ∼ 2, consistent with early bursts seen in merger simulations. © 2007 RAS.
• Lagache, G., Dole, H., Puget, J., Perez-Gonzalez, P., Le Floc'h, E., Rieke, G., Papovich, C., Egami, E., Alonso-Herrero, A., Engelbracht, C., Gordon, K., Misselt, K., & Morrison, J. (2007). Polycyclic aromatic hydrocarbon contribution to the infrared output energy of the universe at z similar or equal to 2. ASTROPHYSICAL JOURNAL SUPPLEMENT SERIES, 154(1), 112-117.
  More info

  We present an updated phenomenological galaxy evolution model to fit the Spitzer 24, 70, and 160 mum number counts, as well as all the previous mid- and far-infrared observations. Only a minor change of the comoving luminosity density distribution in the previous model (Lagache, Dole, & Puget), combined with a slight modification of the starburst template spectra mainly between 12 and 30 mum, are required to fit all the data available. We show that the peak in the Spitzer Multiband Imaging Photometer 24 mum counts is dominated by galaxies with redshift between 1 and 2, with a nonnegligible contribution from the z greater than or equal to 2 galaxies ( similar to 30% at S = 0.2 mJy). The very close agreement between the model and number counts at 15 and 24 mum strikingly implies that ( 1) the polycyclic aromatic hydrocarbon features remain prominent in the redshift band 0.5 - 2.5 and (2) the IR energy output has to be dominated by similar to3 x 10(11) L-. to similar to 3 x 10(12) L-. galaxies from redshift 0.5 to 2.5. Combining Spitzer with Infrared Space Observatory deep cosmological surveys gives for the first time an unbiased view of the infrared universe from z = 0 to 2.5.
• Le Floc'h, E., Willmer, C. N., Noeske, K., Konidaris, N. P., Laird, E. S., Koo, D. C., Nandra, K., Bundy, K., Salim, S., Maiolino, R., Conselice, C. J., Lotz, J. M., Papovich, C., Smith, J. D., Bai, L., Coil, A. L., Barmby, P., Ashby, M. L., Huang, J., , Blaylock, M., et al. (2007). Far-infrared characterization of an ultraluminous starburst associated with a massively accreting black hole at z=1.15. ASTROPHYSICAL JOURNAL, 660(1), L65-L68.
  More info

  As part of the All-Wavelength Extended Groth Strip International Survey (AEGIS), we describe the panchromatic characterization of an X-ray-luminous active galactic nucleus (AGN) in a merging galaxy at z = 1.15. This object is detected at infrared (8, 24, 70, and 160 mu m), submillimeter (850 mu m), and radio wavelengths, from which we derive a bolometric luminosity L-bol similar to 9 x 10(12) L-circle dot. We find that the AGN clearly dominates the hot dust emission below 40 mu m but its total energetic power inferred from the hard X-rays is substantially less than the bolometric output of the system. About 50% of the infrared luminosity is indeed produced by a cold dust component that probably originates from enshrouded star formation in the host galaxy. In the context of a coeval growth of stellar bulges and massive black holes, this source might represent a "transition" object, sharing properties with both quasars and luminous starbursts. Study of such composite galaxies will help address how the star formation and disk-accretion phenomena may have regulated each other at high redshift and how this coordination may have participated in the buildup of the relationship observed locally between the masses of black holes and stellar spheroids.
• Low, F. J., Rieke, G. H., & Gehrz, R. D. (2007). The beginning of modern infrared astronomy. Annual Review of Astronomy and Astrophysics, 45, 43-75.
  More info

  Abstract: I came to the attention of astronomers through inventing the low temperature bolometer at Texas Instruments. I was quickly drawn into pioneering infrared (IR) astronomy. I soon transferred to the National Radio Astronomy Observatory and then to the University of Arizona to make astronomy my focus. Parallel programs were getting under way at the California Institute of Technology, Cornell, the Universities of Minnesota and of California, San Diego. Although our methods were crude, discoveries were easy and exciting. I was involved in many of them because I could supply good detectors and invented a number of new techniques. Eventually, I supplied detector systems and instruments through founding of a small company. By the early 1970s, systematic IR astronomy was under way on many important problems that are still active research topics. This rapid success led to investments in large new telescopes and in the IRAS survey satellite. Copyright © 2007 by Annual Reviews. All rights reserved.
• Marcillac, D., Rigby, J. R., Rieke, G. H., & Kelly, D. M. (2007). Strong dusty bursts of star formation in galaxies falling into the cluster RX J0152.7-1357. Astrophysical Journal, 654(2 I), 825-834.
  More info

  Abstract: We have observed the cluster RX J0152.7-1357 (z ∼ 0.83) at 24 μm with the Multiband Imaging Photometer for Spitzer (MIPS). We detected 22 sources associated with spectroscopically confirmed cluster members, while 10 more have photometric redshifts compatible with membership. Two of the 32 likely cluster members contain obvious active nuclei, while the others are associated with dusty star formation. The median IR-determined star formation rate among the remaining galaxies is estimated at 22 M⊙ yr-1, significantly higher than in previous estimates from optical data. Most of the mid-infrared (MIR) emitting galaxies also have optical emission lines, but a few do not and hence have completely hidden bursts of star formation or AGN activity. An excess of MIR-emitting galaxies is seen in the cluster, compared to the field at the same redshift. The MIR cluster members are more associated with previously detected infalling late-type galaxies rather than triggered by the ongoing merging of bigger X-ray clumps. Rough estimates also show that ram pressure may not be capable of stripping the gas away from cluster outskirt galaxies, but it may disturb the gas enough to trigger the star formation activity. Harassment can also play a role if, for example, these galaxies belong to poor galaxy groups. Thus, bursts of star formation occur in the cluster environment and could also help consume the galaxy gas content, in addition to ram pressure, harassment, or galaxy-galaxy strong interactions. © 2007. The American Astronomical Society. All rights reserved.
• Marleau, F. R., Noriega-Crespo, A., Misselt, K. A., Gordon, K. D., Engelbracht, C. W., Rieke, G. H., Barmby, P., Willner, S. P., Mould, J., Gehrz, R. D., & Woodward, C. E. (2007). Mapping and mass measurement of the cold dust in NGC 205 with Spitzer. ASTROPHYSICAL JOURNAL, 646(2), 929-938.
  More info

  We present observations at 3.6, 4.5, 5.8, 8, 24, 70, and 160 mu m of NGC 205, the dwarf elliptical companion of M31, obtained with the Spitzer Space Telescope. The point-source-subtracted images at 8 and 24 mu m display a complex and fragmented infrared emission coming from both very small dust particles and larger grains. The extended dust emission is spatially concentrated in three main emission regions, seen at all wavelengths from 8 to 160 mu m. These regions lie approximately along NGC 205's semimajor axis and range from similar to 100 to 300 pc in size. On the basis of our mid-/far-infrared flux density measurements alone, we derive a total dust mass estimate on the order of 3.2 x 10(4) M-circle dot, mainly at a temperature of similar to 20 K. The gas mass associated with this component matches the predicted mass returned by the dying stars from the last burst of star formation in NGC 205 (similar to 0.5 Gyr ago). Analysis of the Spitzer data combined with previous 1.1 mm observations over a small central or "Core'' region (18" diameter) suggests the presence of very cold (T similar to 12 K) dust and a dust mass about 16 times higher than is estimated from the Spitzer measurements alone. Assuming a gas-to-dust mass ratio of 100, these two data sets, i.e., with and without the millimeter observations, suggest a total gas mass in the range from 3.2 x 10(6) to 5 x 10(7) M-circle dot.
• Marston, A., Reach, W., Noriega-Crespo, A., Rho, J., Smith, H., Melnick, G., Fazio, G., Rieke, G., Carey, S., Rebull, L., Muzerolle, J., Egami, E., Watson, D., Pipher, J., Latter, W., & Stapelfeldt, K. (2007). DR 21: A major star formation site revealed by Spitzer. ASTROPHYSICAL JOURNAL SUPPLEMENT SERIES, 154(1), 333-338.
  More info

  We have obtained images of the obscured massive star-forming region DR 21 using both the Infrared Array Camera (IRAC) and Multiband Imaging Photometer for Spitzer (MIPS) instruments aboard the Spitzer Space Telescope. Our images cover an area of more than half a square degree. The unprecedented high sensitivity and resolution of both IRAC and MIPS allow us to reveal the complexity of this region for the first time. Our images show extended outflows from a dense disk of material. Previously observed molecular outflows from the center of DR 21 are clearly visible in our images and are embedded in a much larger region of diffuse filaments apparently flowing out from DR 21. Many of the point sources in the region seen by Spitzer at 8 and 24 mum are both very obscured and intrinsically red. We discuss the properties of some of these extremely red objects and indicate that they are likely to be Class I or earlier protostars. Other features observed include mid-infrared dark clouds that occasionally appear as swept up features from extremely red objects, including a 15 pc long north-south filament to the south of DR 21 itself.
• Martin, D. C., Small, T., Schiminovich, D., Wyder, T. K., Pérez-González, P. G., Johnson, B., Wolf, C., Barlow, T. A., Forster, K., Friedman, P. G., Morrissey, P., Neff, S. G., Seibert, M., Welsh, B. Y., Bianchi, L., Donas, J., Heckman, T. M., Lee, Y., Madore, B. F., , Milliard, B., et al. (2007). The star formation and extinction coevolution of UV-selected galaxies over 0.05 < z < 1.2. Astrophysical Journal, Supplement Series, 173(2), 415-431.
  More info

  Abstract: We use a new stacking technique to obtain mean mid-IR and far-IR to far-UV flux ratios over the rest-frame near-UV, near-IR color-magnitude diagram. We employ COMBO-17 redshifts and COMBO-17 optical, GALEX far- and near-UV, and Spitzer IRAC and MIPS mid-IR photometry. This technique permits us to probe the infrared excess (IRX), the ratio of far-IR to far-UV luminosity, and the specific star formation rate (SSFR) and their coevolution over 2 orders of magnitude of stellar mass and over redshift 0.1 < z < 1.2. We find that the SSFR and the characteristic mass (M0) above which the SSFR drops increase with redshift (downsizing). At any given epoch, the IRX is an increasing function of mass up to M0. Above this mass the IRX falls, suggesting gas exhaustion. In a given mass bin below M0, the IRX increases with time in a fashion consistent with enrichment. We interpret these trends using a simple model with a Schmidt-Kennicutt law and extinction that tracks gas density and enrichment. We find that the average IRX and SSFR follow a galaxy age parameter ξ, which is determined mainly by the galaxy mass and time since formation. We conclude that blue-sequence galaxies have properties which show simple, systematic trends with mass and time such as the steady buildup of heavy elements in the interstellar media of evolving galaxies and the exhaustion of gas in galaxies that are evolving off the blue sequence. The IRX represents a tool for selecting galaxies at various stages of evolution. © 2007. The American Astronomical Society. All rights reserved.
• Morales, F. Y., Werner, M. W., Bryden, G., Plavchan, P., Stapelfeldt, K. R., Rieke, G. H., Su, K. Y., Beichman, C. A., Chen, C. H., Grogan, K., Kenyon, S. J., Moro-Martin, A., & Wolf, S. (2007). SPITZER MID-IR SPECTRA OF DUST DEBRIS AROUND A AND LATE B TYPE STARS: ASTEROID BELT ANALOGS AND POWER-LAW DUST DISTRIBUTIONS. ASTROPHYSICAL JOURNAL, 699(2), 1067-1086.
  More info

  Using the Spitzer/Infrared Spectrograph (IRS) low-resolution modules covering wavelengths from 5 to 35 mu m, we observed 52 main-sequence A and late B type stars previously seen using Spitzer/Multiband Imaging Photometer (MIPS) to have excess infrared emission at 24 mu m above that expected from the stellar photosphere. The mid-IR excess is confirmed in all cases but two. While prominent spectral features are not evident in any of the spectra, we observed a striking diversity in the overall shape of the spectral energy distributions. Most of the IRS excess spectra are consistent with single-temperature blackbody emission, suggestive of dust located at a single orbital radius-a narrow ring. Assuming the excess emission originates from a population of large blackbody grains, dust temperatures range from 70 to 324 K, with a median of 190 K corresponding to a distance of 10 AU. Thirteen stars however, have dust emission that follows a power-law distribution, F(nu) = F(0)lambda(alpha), with exponent alpha ranging from 1.0 to 2.9. The warm dust in these systems must span a greater range of orbital locations-an extended disk. All of the stars have also been observed with Spitzer/MIPS at 70 mu m, with 27 of the 50 excess sources detected (signal-to-noise ratio > 3). Most 70 mu m fluxes are suggestive of a cooler, Kuiper Belt-like component that may be completely independent of the asteroid belt-like warm emission detected at the IRS wavelengths. Fourteen of 37 sources with blackbody-like fits are detected at 70 mu m. The 13 objects with IRS excess emission fit by a power-law disk model, however, are all detected at 70 mu m (four above, three on, and six below the extrapolated power law), suggesting that the mid-IR IRS emission and far-IR 70 mu m emission may be related for these sources. Overall, the observed blackbody and power-law thermal profiles reveal debris distributed in a wide variety of radial structures that do not appear to be correlated with spectral type or stellar age. An additional 43 fainter A and late B type stars without 70 mu m photometry were also observed with Spitzer/IRS; results are summarized in Appendix B.
• N., T., Rieke, G. H., Stansberry, J., Bryden, G. C., Stapelfeldt, K. R., Werner, M. W., Beichman, C. A., Chen, C., Kate, S. u., Trilling, D., Patten, B. M., & Roellig, T. L. (2007). Far-infrared properties of M dwarfs. Astrophysical Journal, 667(1 I), 527-536.
  More info

  Abstract: We report the mid- and far-infrared properties of nearby M dwarfs. Spitzer MIPS measurements were obtained for a sample of 62 stars at 24 μm, with subsamples of 41 and 20 stars observed at 70 and 160 μm, respectively. We compare the results with current models of M star photospheres and look for indications of circumstellar dust in the form of significant deviations of K- [24 μm] colors and 70 μm/24 μm flux ratios from the average M star values. At 24 μm, all 62 of the targets were detected; 70 μm detections were achieved for 20 targets in the subsample observed, and no detections were seen in the 160 μm subsample. No clear far-infrared excesses were detected in our sample. The average far-infrared excess relative to the photospheric emission of the M stars is at least 4 times smaller than the similar average for a sample of solar-type stars. However, this limit allows the average fractional infrared luminosity in the M-star sample to be similar to that for more massive stars. We have also set low limits (10-4 to 10-9 M⊕ depending on location) for the maximum mass of dust possible around our stars. © 2007. The American Astronomical Society. All rights reserved.
• Noeske, K. G., Faber, S. M., Weiner, B. J., Koo, D. C., Primack, J. R., Dekel, A., Papovich, C., Conselice, C. J., Floc'h, E. L., Rieke, G. H., Coil, A. L., Lotz, J. M., Somerville, R. S., & Bundy, K. (2007). Star formation in AEGIS field galaxies since z = 1.1: Staged galaxy formation and a model of mass-dependent gas exhaustion. Astrophysical Journal, 660(1 II), L47-L50.
  More info

  Abstract: We analyze star formation (SF) as a function of stellar mass (M*) and redshift z in the All-Wavelength Extended Groth Strip International Survey, for star-forming field galaxies with M* ≳ 1010 M ̇ out to z = 1.1. The data indicate that the high specific SF rates (SFRs) of many less massive galaxies do not represent late, irregular or recurrent, starbursts in evolved galaxies. They rather seem to reflect the onset (initial burst) of the dominant SF episode of galaxies, after which SF gradually declines on gigayear timescales to z = 0 and forms the bulk of a galaxy's M*. With decreasing mass, this onset of major SF shifts to decreasing z for an increasing fraction of galaxies (staged galaxy formation). This process may be an important component of the "downsizing" phenomenon. We find that the predominantly gradual decline of SFRs described by Noeske et al. can be reproduced by exponential SF histories (τ models), if less massive galaxies have systematically longer e-folding times τ, and a later onset of SF (zf). Our model can provide a first parameterization of SFR as a function of M* and z, and quantify mass dependences of τ and zf, from direct observations of M* and SFRs up to z > 1. The observed evolution of SF in galaxies can plausibly reflect the dominance of gradual gas exhaustion. The data are also consistent with the history of cosmological accretion onto dark matter halos. © 2007. The American Astronomical Society. All rights reserved.
• Noeske, K. G., Faber, S. M., Weiner, B. J., Koo, D. C., Primack, J. R., Dekel, A., Papovich, C., Conselice, C. J., Le Floc'h, E., Rieke, G. H., Coil, A. L., Lotz, J. M., Somerville, R. S., & Bundy, K. (2007). Star formation in AEGIS field galaxies since z=1.1: Staged galaxy formation and a model of mass-dependent gas exhaustion. ASTROPHYSICAL JOURNAL, 660(1), L47-L50.
  More info

  We analyze star formation (SF) as a function of stellar mass (M-*) and redshift z in the All-Wavelength Extended Groth Strip International Survey, for star-forming field galaxies with M-* less than or similar to 10(10) M-circle dot out to z = 1.1. The data indicate that the high specific SF rates (SFRs) of many less massive galaxies do not represent late, irregular or recurrent, starbursts in evolved galaxies. They rather seem to reflect the onset (initial burst) of the dominant SF episode of galaxies, after which SF gradually declines on gigayear timescales to z = 0 and forms the bulk of a galaxy's M-*. With decreasing mass, this onset of major SF shifts to decreasing z for an increasing fraction of galaxies (staged galaxy formation). This process may be an important component of the "downsizing" phenomenon. We find that the predominantly gradual decline of SFRs described by Noeske et al. can be reproduced by exponential SF histories (tau models), if less massive galaxies have systematically longer e-folding times tau, and a later onset of SF (z(f)). Our model can provide a first parameterization of SFR as a function of M-* and z, and quantify mass dependences of t and, from direct observations of and SFRs up to z > 1. The observed evolution of SF in galaxies can plausibly reflect the dominance of gradual gas exhaustion. The data are also consistent with the history of cosmological accretion onto dark matter halos.
• Noeske, K. G., Weiner, B. J., Faber, S. M., Papovich, C., Koo, D. C., Somerville, R. S., Bundy, K., Conselice, C. J., Newman, J. A., Schiminovich, D., Floc'h, E. L., Coil, A. L., Rieke, G. H., Lotz, J. M., Primack, J. R., Barmby, P., Cooper, M. C., Davis, M., Ellis, R. S., , Fazio, G. G., et al. (2007). Star formation in AEGIS field galaxies since z = 1.1: The dominance of gradually declining star formation, and the main sequence of star-forming galaxies. Astrophysical Journal, 660(1 II), L43-L46.
  More info

  Abstract: We analyze star formation (SF) as a function of stellar mass (M*) and redshift z in the All-Wavelength Extended Groth Strip International Survey. For 2905 field galaxies, complete to 1010(1010.8) M ⊙ at z < 0.7(1), with Keck spectroscopic redshifts out to z = 1.1, we compile SF rates (SFRs) from emission lines, GALEX, and Spitzer MIPS 24 μm photometry, optical-NIR M* measurements, and HST morphologies. Galaxies with reliable signs of SF form a distinct "main sequence" (MS), with a limited range of SFRs at a given M* and z (1 σ ≲ ±0.3 dex), and log (SFR) approximately proportional to log M*. The range of log (SFR) remains constant to z > 1, while the MS as a whole moves to higher SFR as z increases. The range of the SFR along the MS constrains the amplitude of episodic variations of SF and the effect of mergers on the SFR. Typical galaxies spend ∼67%(95%) of their lifetime since z = 1 within a factor of ≲2(4) of their average SFR at a given M* and z. The dominant mode of the evolution of SF since z ∼ 1 is apparently a gradual decline of the average SFR in most individual galaxies, not a decreasing frequency of starburst episodes, or a decreasing factor by which SFRs are enhanced in starbursts. LIRGs at z ∼ 1 seem to mostly reflect the high SFR typical for massive galaxies at that epoch. The smooth MS may reflect that the same set of few physical processes governs SF prior to additional quenching processes. A gradual process like gas exhaustion may play a dominant role. © 2007. The American Astronomical Society. All rights reserved.
• Papovich, C., Cool, R., Eisenstein, D., Le Floc'h, E., Fan, X., Kennicutt, R. C., Smith, J. D., Rieke, G. H., & Vestergaard, M. (2007). An MMT hectospec redshift survey of 24 mu m sources in the Spitzer First Look Survey. ASTRONOMICAL JOURNAL, 132(1), 231-241.
  More info

  We present a spectroscopic survey using the MMT Hectospec fiber spectrograph of 24 mu m sources selected with the Spitzer Space Telescope in the Spitzer First Look Survey. We report 1296 new redshifts for 24 mu m sources, including 599 with f(v)(24 mu m) >= 1 mJy. Combined with 291 additional redshifts for sources from the Sloan Digital Sky Survey (SDSS), our observing program was highly efficient and is similar to 90% complete for i = 1 mJy and 35% complete for i
• Papovich, C., Rudnick, G., Floc'h, E. L., G., P., Rieke, G. H., Taylor, E. N., Armus, L., Gawiser, E., Huang, J., Marcillac, D., & Franx, M. (2007). Spitzer MID- to far-infrared flux densities of distant galaxies. Astrophysical Journal, 668(1 I), 45-61.
  More info

  Abstract: We study the infrared (IR) properties of high-redshift galaxies using deep Spitzer 24, 70, and 160 μm data. Our primary interest is to improve the constraints on the total IR luminosities, LIR, of these galaxies. We combine the Spitzer data in the southern Extended Chandra Deep Field with a Ks-band-selected galaxy sample and photometric redshifts from the Multiwavelength Survey by Yale-Chile. We used a stacking analysis to measure the average 70 and 160 μm flux densities of 1.5 < z < 2.5 galaxies as a function of 24 μm flux density, X-ray activity, and rest-frame near-IR color. Galaxies with 1.5 < z < 2.5 and S24 = 53-250 μJy have LIR derived from their average 24-160 μm flux densities within factors of 2-3 of those inferred from the 24 μm flux densities only. However, LIR derived from the average 24-160 μm flux densities for galaxies with S24 > 250 μJy and 1.5 < z < 2.5 are lower than those inferred using only the 24 μm flux density by factors of 2-10. Galaxies with S24 > 250 μJy have S70/S24 flux ratios comparable to sources with X-ray detections or red rest-frame IR colors, suggesting that warm dust possibly heated by AGNs may contribute to the high 24 μm emission. Based on the average 24-160 μm flux densities, nearly all 24 μm-selected galaxies at 1.5 < z < 2.5 have LIR < 6 × 1012 L⊙, which, if attributed to star formation, corresponds to ψ < 1000 M⊙ yr-1. This suggests that high-redshift galaxies may have star formation efficiencies and feedback processes similar to those of local analogs. Objects with L IR > 6 × 1012 L⊙ are quite rare, with a surface density ∼30 ±10 deg-2, corresponding to ∼2 ±1 × 10-6 Mpc-3 over 1.5 < z < 2.5. © 2007. The American Astronomical Society. All rights reserved.
• Rieke, G. H. (2007). Infrared detector arrays for astronomy. Annual Review of Astronomy and Astrophysics, 45, 77-115.
  More info

  Abstract: Use of infrared detector arrays in astronomy began roughly 20 years ago, and our detection capabilities in parts of this spectral range have doubled about every seven months since then. A variety of approaches are now used for detector arrays operating from 1 μm to 1 mm and beyond. They include direct hybrid arrays of InSb and HgCdTe photodiodes that operate from 0.6 μm to 5 μm, and of Si:As impurity band conduction detectors from 5 μm to 28 μm; a number of approaches to photoconductive detector arrays in the far-infrared; and bolometer arrays read out by transistors or superconducting devices in the far-infrared through millimeter-wave spectral range. The underlying principles behind these approaches are discussed. The application of these principles is illustrated through detailed discussion of a number of state-of-the-art detector arrays. Copyright © 2007 by Annual Reviews. All rights reserved.
• Rigby, J. R., Rieke, G. H., Donley, J. L., Alonso-Herrero, A., & Perez-Gonzalez, P. G. (2007). Why X-ray-selected active galactic nuclei appear optically dull. ASTROPHYSICAL JOURNAL, 645(1), 115-133.
  More info

  We investigate why half of X-ray-selected active galactic nuclei ( AGNs) in deep surveys lack signs of accretion in their optical spectra. The majority of these "optically dull'' AGNs are no more than similar to 6 times fainter than their host galaxies in rest-frame R band; as such, AGN lines are unlikely to be overwhelmed by stellar continuum in at least half the sample. We find that optically dull AGNs have the mid-infrared emission and LX/LIR ratios characteristic of local Seyfert galaxies, suggesting that the cause of optical dullness is not missing UV-optical continua. We compare the morphologies of 22 optically dull and 9 optically active AGNs at 0.5 < z < 0.8 and find that optically dull AGNs show a wide range of axis ratio, but optically active AGNs have only very round axis ratios. We conclude that hard X-rays select AGNs in host galaxies with a wide range of inclination angle, but only those AGNs in the most face-on or spheroidal host galaxies show optical emission lines. Thus, extranuclear dust in the host galaxy plays an important role in hiding the emission lines of optically dull AGNs.
• Seymour, N., Dwelly, T., Moss, D., McHardy, I., Zoghbi, A., Rieke, G., Page, M., Hopkins, A., & Loaring, N. (2007). The star formation history of the Universe as revealed by deep radio observations. MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, 386(3), 1695-1708.
  More info

  Discerning the exact nature of the sub-mJy radio population has been historically difficult due to the low luminosity of these sources at most wavelengths. Using deep ground based optical follow-up and observations from the Spitzer Space Telescope we are able to disentangle the radio-selected active galactic nuclei (AGN) and star-forming galaxy (SFG) populations for the first time in a deep multifrequency VLA/MERLIN Survey of the 13(H) XMM-Newton/Chandra Deep Field. The discrimination diagnostics include radio morphology, radio spectral index, radio/near-infrared (near-IR) and mid-IR/radio flux density ratios. We are now able to calculate the extragalactic Euclidean normalized source counts separately for AGN and SFGs. We find that while SFGs dominate at the faintest flux densities and account for the majority of the upturn in the counts, AGN still make up around one quarter of the counts at similar to 50 mu Jy (1.4 GHz). Using radio luminosity as an unobscured star formation rate (SFR) measure we are then able to examine the comoving SFR density of the Universe up to z = 3 which agrees well with measures at other wavelengths. We find a rough correlation of SFR with stellar mass for both the sample presented here and a sample of local radio-selected SFGs from the 6df-NVSS survey. This work also confirms the existence of, and provides alternative evidence for, the evolution of distribution of star formation by galaxy mass: 'downsizing'. As both these samples are SFR-selected, this result suggests that there is a maximum SFR for a given galaxy that depends linearly on its stellar mass. The low 'characteristic times' (inverse specific SFR) of the SFGs in our sample are similar to those of the 6dF-NVSS sample, implying that most of these sources are in a current phase of enhanced star formation.
• Shi, Y., Ogle, P., Rieke, G. H., Antonucci, R., Hines, D. C., Smith, P. S., Low, F. J., Bouwman, J., & Willmer, C. (2007). Aromatic features in AGNs: Star-forming infrared luminosity function of AGN host galaxies. Astrophysical Journal, 669(2), 841-861.
  More info

  Abstract: We describe observations of aromatic features at 7.7 and 11.3 μm in AGNs of three types, including PG, 2MASS, and 3CR objects. The feature has been demonstrated to originate predominantly from star formation. Based on the aromatic-derived star-forming luminosity, we find that the far-IR emission of AGNs can be dominated by either star formation or nuclear emission; the average contribution from star formation is around 25% at 70 and 160 μm. The starforming infrared luminosity functions of the three types of AGNs are flatter than those of field galaxies, implying that nuclear activity and star formation tend to be enhanced together. The star-forming luminosity function is also a function of the strength of nuclear activity from normal galaxies to the bright quasars, with luminosity functions becoming flatter for more intense nuclear activity. Different types of AGNs show different distributions in the level of star formation activity, with 2MASS > PG > 3CR star formation rates. © 2007. The American Astronomical Society. All rights reserved.
• Shi, Y., Rieke, G. H., Hines, D. C., Gordon, K. D., & Egami, E. (2007). Thermal and nonthermal infrared emission from M87. ASTROPHYSICAL JOURNAL, 655(2), 781-789.
  More info

  We discuss images of M87 from 3.6 to 160 mu m obtained with Spitzer. As found previously, there is an excess in the far-infrared over a simple power-law interpolation from the radio to the resolved nonthermal features in the mid-infrared and optical. We show that this excess is most likely due to warm dust in the galaxy itself and that the properties of this emission component are similar to the far-infrared emission of normal giant elliptical galaxies. The new observations allow us to determine the spectrum of the jet and surrounding lobes of nonthermal emission. We find that even in the lobes, the synchrotron break frequency is in the optical, probably requiring in situ particle acceleration not only in the jet but in the lobes as well.
• Shi, Y., Rieke, G. H., Hines, D. C., Gordon, K. D., & Egami, E. (2007). Thermal and nonthermal infrared emission from M87. Astrophysical Journal, 655(2 I), 781-789.
  More info

  Abstract: We discuss images of M87 from 3.6 to 160 μm obtained with Spitzer. As found previously, there is an excess in the far-infrared over a simple power-law interpolation from the radio to the resolved nonthermal features in the midinfrared and optical. We show that this excess is most likely due to warm dust in the galaxy itself and that the properties of this emission component are similar to the far-infrared emission of normal giant elliptical galaxies. The new observations allow us to determine the spectrum of the jet and surrounding lobes of nonthermal emission. We find that even in the lobes, the synchrotron break frequency is in the optical, probably requiring in situ particle acceleration not only in the jet but in the lobes as well. © 2007. The American Astronomical Society. All rights reserved.
• Shi, Y., Rieke, G. H., Hines, D. C., Gorjian, V., Werner, M. W., Cleary, K., Low, F. J., Smith, P. S., & Bouwman, J. (2007). 9.7 mu m Silicate features in active galactic nuclei: New insights into unification models. ASTROPHYSICAL JOURNAL, 653(1), 127-136.
  More info

  We describe observations of 9.7 mu m silicate features in 97 AGNs, exhibiting a wide range of AGN types and of X-ray extinction toward the central nuclei. We find that the strength of the silicate feature correlates with the H I column density estimated from fitting the X-ray data, such that low H I columns correspond to silicate emission, while high columns correspond to silicate absorption. The behavior is generally consistent with unification models in which the large diversity in AGN properties is caused by viewing-angle-dependent obscuration of the nucleus. Radio-loud AGNs and radio-quiet quasars follow roughly the correlation between H I columns and the strength of the silicate feature defined by Seyfert galaxies. The agreement among AGN types suggests a high-level unification with similar characteristics for the structure of the obscuring material. We demonstrate the implications for unification models qualitatively with a conceptual disk model. The model includes an inner accretion disk (< 0.1 pc in radius), a middle disk (0.1-10 pc in radius) with a dense diffuse component and with embedded denser clouds, and an outer clumpy disk (10-300 pc in radius).
• Siegler, N., Muzerolle, J., Young, E. T., Rieke, G. H., Mamajek, E. E., Trilling, D. E., Gorlova, N., & Y., K. (2007). Spitzer 24 μm observations of open cluster 1C 2391 and debris disk evolution of FGK stars. Astrophysical Journal, 654(1 I), 580-594.
  More info

  Abstract: We present 24 μm Spitzer MIPS photometric observations of the ∼50 Myr open cluster IC 2391. Thirty-four cluster members ranging in spectral type from B3 to M5 were observed in the central square degree of the cluster. Excesses indicative of debris disks were discovered around one A star, six FGK stars, and possibly one M dwarf. For the cluster members observed to their photospheric limit, we find a debris disk frequency of 107%-3 for B-A stars and 31+13%-9 for FGK stars using a 15% relative excess threshold. Relative to a model of decaying excess frequency, the frequency of debris disks around A-type stars appears marginally low for the cluster's age while that of FGK stars appears consistent. Scenarios that may qualitatively explain this result are examined. We conclude that planetesimal activity in the terrestrial region of FGK stars is common in the first ∼50 Myr and decays on timescales of ∼100 Myr. Despite luminosity differences, debris disk evolution does not appear to depend strongly on stellar mass. © 2007. The American Astronomical Society. All rights reserved.
• Stansberry, J. A., Gordon, K. D., Bhattacharya, B., Engelbracht, C. W., Rieke, G. H., Marleau, F. R., Fadda, D., Frayer, D. T., Noriega-Crespo, A., Wachter, S., Young, E. T., Müller, T., Kelly, D. M., Blaylock, M., Henderson, D., Neugebauer, G., Beeman, J. W., & Haller, E. E. (2007). Absolute calibration and characterization of the multiband imaging photometer for Spitzer. III. An asteroid-based calibration of MIPS at 160 μm. Publications of the Astronomical Society of the Pacific, 119(859), 1038-1051.
  More info

  Abstract: We describe the absolute calibration of the Multiband Imaging Photometer for Spitzer (MIPS) 160 μm channel. After the on-orbit discovery of a near-IR ghost image that dominates the signal for sources hotter than about 2000 K, we adopted a strategy utilizing asteroids to transfer the absolute calibrations of the MIPS 24 and 70 μm channels to the 160 μm channel. Near-simultaneous observations at all three wavelengths are taken, and photometry at the two shorter wavelengths is fit using the standard thermal model. The 160 μm flux density is predicted from those fits and compared with the observed 160 μm signal to derive the conversion from instrumental units to surface brightness. The calibration factor we derive is 41.7 MJy sr -1 MIPS160 -1 (MIPS 160 being the instrumental units). The scatter in the individual measurements of the calibration factor, as well as an assessment of the external uncertainties inherent in the calibration, lead us to adopt an uncertainty of 5.0 MJy sr -1 MIPS160 -1 (12%) for the absolute uncertainty on the 160 μm flux density of a particular source as determined from a single measurement. For sources brighter than about 2 Jy, nonlinearity in the response of the 160 μm detectors produces an underestimate of the flux density: for objects as bright as 4 Jy, measured flux densities are likely to be ≲ 20% too low. This calibration has been checked against that of the ISO (using ULIRGs) and IRAS (using IRAS-derived diameters), and is consistent with those at the 5% level. © 2007. The Astronomical Society of the Pacific. All rights reserved.
• Stauffer, J. R., Hartmann, L. W., Fazio, G. G., Allen, L. E., Patten, B. M., Lowrance, P. J., Hurt, R. L., Rebull, L. M., Cutri, R. M., Ramirez, S. V., Young, E. T., Rieke, G. H., Gorlova, N. I., Muzerolle, J. C., Slesnick, C. L., & Skrutskie, M. F. (2007). Near- and mid-infrared photometry of the pleiades and a new list of substellar candidate members. Astrophysical Journal, Supplement Series, 172(2), 663-685.
  More info

  Abstract: We make use of new near- and mid-IR photometry of the Pleiades cluster in order to help identify proposed cluster members. We also use the new photometry with previously published photometry to define the single-star main-sequence locus at the age of the Pleiades in a variety of color-magnitude planes. The new near- and mid-IR photometry extend effectively 2 mag deeper than the 2MASS All-Sky Point Source catalog, and hence allow us to select a new set of candidate very low-mass and sub stellar mass members of the Pleiades in the central square degree of the cluster. We identify 42 new candidate members fainter than K s = 14 (corresponding to 0.1 M⊙). These candidate members should eventually allow a better estimate of the cluster mass function to be made down to of order 0.04 M⊙. We also use new IRAC data, in particular the images obtained at 8 μm, in order to comment briefly on interstellar dust in and near the Pleiades. We confirm, as expected, that - with one exception - a sample of low-mass stars recently identified as having 24 μm excesses due to debris disks do not have significant excesses at IRAC wavelengths. However, evidence is also presented that several of the Pleiades high-mass stars are found to be impacting with local condensations of the molecular cloud that is passing through the Pleiades at the current epoch. © 2007. The American Astronomical Society. All rights reserved.
• Stutz, A. M., Bieging, J. H., Rieke, G. H., Shirley, Y. L., Balog, Z., Gordon, K. D., Green, E. M., Keene, J., Kelly, B. C., Rubin, M., & Werner, M. W. (2007). Spitzer observations of a 24 μm shadow: Bok globule CB 190. Astrophysical Journal, 665(1 PART 1), 466-477.
  More info

  Abstract: We present Spitzer observations of the dark globule CB 190 (LDN 771). We observe a roughly circular 24 μm shadow with a 70″ radius. The extinction profile of this shadow matches the profile derived from 2MASS photometry at the outer edges of the globule and reaches a maximum of ∼32 visual magnitudes at the center. The corresponding mass of CB 190 is ∼ 10 A⊙. Our 12CO and 13CO J = 2 - 1 data over a 10′ × 10″ region centered on the shadow show a temperature ∼10 K. The thermal continuum indicates a similar temperature for the dust. The molecular data also show evidence of freezeout onto dust grains. We estimate a distance to CB 190 of 400 pc using the spectroscopic parallax of a star associated with the globule. Bonnor-Ebert fits to the density profile, in conjunction with this distance, yield ξmax = 7.2, indicating that CB 190 may be unstable. The high temperature (56 K) of the best-fit Bonnor-Ebert model is in contradiction with the CO and thermal continuum data, leading to the conclusion that the thermal pressure is not enough to prevent free-fall collapse. We also find that the turbulence in the cloud is inadequate to support it. However, the cloud may be supported by the magnetic field, if this field is at the average level for dark globules. Since the magnetic field will eventually leak out through ambipolar diffusion, it is likely that CB 190 is collapsing or in a late precollapse stage. © 2007. The American Astronomical Society. All rights reserved.
• Su, K. Y., Chu, Y. -., Rieke, G. H., Huggins, P. J., Gruendl, R., Napiwotzki, R., Rauch, T., Latter, W. B., & Volk, K. (2007). A debris disk around the central star of the Helix Nebula?. Astrophysical Journal, 657(1 II), L41-L45.
  More info

  Abstract: Excess emission from a pointlike source coincident with the central star of the Helix Nebula is detected with Spitzer at 8, 24, and 70 μm. At 24 μm, the central source is superposed on an extended diffuse emission region. While the [O IV] 25.89 μm line contributes to the diffuse emission, a 10-35 μm spectrum of the central source shows a strong thermal continuum. The excess emission from the star most likely originates from a dust disk with blackbody temperatures of 90-130 K. Assuming a simple optically thin debris disk model, the dust is distributed in a ring between ∼35 and ∼150 AU from the central star, possibly arising from collisions of Kuiper Belt-like objects or the breakup of comets from an Oort-like cloud that have survived from the post-main-sequence evolution of the central star. © 2007. The American Astronomical Society. All rights reserved.
• Su, K. Y., Chu, Y., Rieke, G. H., Huggins, P. J., Gruendl, R., Napiwotzki, R., Rauch, T., Latter, W. B., & Volk, K. (2007). A debris disk around the central star of the Helix Nebula?. ASTROPHYSICAL JOURNAL, 657(1), L41-L45.
  More info

  Excess emission from a pointlike source coincident with the central star of the Helix Nebula is detected with Spitzer at 8, 24, and 70 mu m. At 24 mu m, the central source is superposed on an extended diffuse emission region. While the [O IV] 25.89 mu m line contributes to the diffuse emission, a 10-35 mu m spectrum of the central source shows a strong thermal continuum. The excess emission from the star most likely originates from a dust disk with blackbody temperatures of 90-130 K. Assuming a simple optically thin debris disk model, the dust is distributed in a ring between similar to 35 and similar to 150 AU from the central star, possibly arising from collisions of Kuiper Belt-like objects or the breakup of comets from an Oort-like cloud that have survived from the post-mainsequence evolution of the central star.
• Su, K. Y., Rieke, G. H., Stapelfeldt, K. R., Malhotra, R., Bryden, G., Smith, P. S., Misselt, K. A., Moro-Martin, A., & Williams, J. P. (2007). THE DEBRIS DISK AROUND HR 8799. ASTROPHYSICAL JOURNAL, 705(1), 314-327.
  More info

  We have obtained a full suite of Spitzer observations to characterize the debris disk around HR 8799 and to explore how its properties are related to the recently discovered set of three massive planets orbiting the star. We distinguish three components to the debris system: (1) warm dust (T similar to 150 K) orbiting within the innermost planet; (2) a broad zone of cold dust (T similar to 45 K) with a sharp inner edge orbiting just outside the outermost planet and presumably sculpted by it; and (3) a dramatic halo of small grains originating in the cold dust component. The high level of dynamical activity implied by this halo may arise due to enhanced gravitational stirring by the massive planets. The relatively young age of HR 8799 places it in an important early stage of development and may provide some help in understanding the interaction of planets and planetary debris, an important process in the evolution of our own solar system.
• Su, K. Y., Rieke, G. H., Stapelfeldt, K. R., Smith, P. S., Bryden, G., Chen, C. H., & Trilling, D. E. (2007). The exceptionally large debris disk around gamma Ophiuchi. ASTROPHYSICAL JOURNAL LETTERS, 679(2), L125-L129.
  More info

  Spitzer images resolve the debris disk around gamma Ophiuchi at both 24 and 70 mu m. The resolved images suggest a disk radius of similar to 520 AU at 70 mu m and greater than or similar to 260 AU at 24 mu m. The images, along with a consistent fit to the spectral energy distribution of the disk from 20 to 350 mu m, show that the primary disk structure is inclined by similar to 50 degrees from the plane of the sky at a position angle of 55 +/- 2 degrees. Among a group of 12 debris disks that have similar host star spectral types, ages, and infrared fractional luminosities, the observed sizes in the infrared and color temperatures indicate that evolution of the debris disks is influenced by multiple parameters in addition to the protoplanetary disk initial mass.
• Symeonidis, M., Rigopoulou, D., Huang, J. -., Davis, M., Ashby, M. L., Barmby, P., Egami, E., Fazio, G. G., Floc'h, E. L., Rieke, G., Willner, S. P., & Wilson, G. (2007). AEGIS: Infrared spectral energy distributions of MIPS 70 μm-selected sources. Astrophysical Journal, 660(1 II), L73-L76.
  More info

  Abstract: We present 0.5-160 μm spectral energy distributions (SEDs) of galaxies, detected at 70 μm with the Multiband Imaging Photometer for Spitzer (MIPS), using broadband imaging data from Spitzer and ground-based telescopes. Spectroscopic redshifts, in the range 0.2 ≤ z ≤ 1.5, have been measured as part of the Deep Extragalactic Evolutionary Probe 2 (DEEP2) project. On the basis of the SEDs, we explore the nature and physical properties of the sources. Using the optical spectra, we derive Hβ and [O II]-based star formation rates (SFRs) that are 10-100 times lower than SFR estimates based on IR and radio. The median offset in SFR between optical and IR is reduced by a factor of ∼3 when we apply a typical extinction correction. We investigate mid- to far-infrared correlations for low-redshift (>0.5) and high-redshift (0.5 < z < 1.2) bins. Using this unique "far-infrared"-selected sample, we derive an empirical mid- to far-infrared relationship that can be used to estimate the infrared energy budget of galaxies in the high-redshift universe. Our sample can be used as a template to translate far-infrared luminosities into bolometric luminosities for high-redshift objects. © 2007. The American Astronomical Society. All rights reserved.
• Tabatabaei, F. S., Beck, R., Krause, M., Berkhuijsen, E. M., Gehrz, R., Gordon, K. D., Hinz, J. L., Humphreys, R., McQuinn, K., Polomski, E., Rieke, G. H., & Woodward, C. E. (2007). A multi-scale study of infrared and radio emission from Scd galaxy M 33. Astronomy and Astrophysics, 466(2), 509-519.
  More info

  Abstract: Aims. We investigate the energy sources of the infrared (IR) emission and their relation to the radio continuum emission at various spatial scales within the Scd galaxy M 33. Methods. We use the data at the Spitzer wavelengths of 24, 70, and 160μm, as well as recent radio continuum maps at 3.6cm and 20 cm observed with the 100-m Effelsberg telescope and VLA, respectively. We use the wavelet transform of these maps to a) separate the diffuse emission components from compact sources, b) compare the emission at different wavelengths, and c) study the radio-IR correlation at various spatial scales. An Ha map serves as a tracer of the star forming regions and as an indicator of the thermal radio emission. Results. The bright HII regions affect the wavelet spectra causing dominant small scales or decreasing trends towards the larger scales. The dominant scale of the 70μm emission is larger than that of the 24μm emission, while the 160μm emission shows a smooth wavelet spectrum. The radio and Hα maps are well correlated with all 3 MIPS maps, although their correlations with the 160μm map are weaker. After subtracting the bright HII regions, the 24 and 70μm maps show weaker correlations with the 20cm map than with the 3.6cm map at most scales. We also find a strong correlation between the 3.6cm and Hα emission at all scales. Conclusions. Comparing the results with and without the bright HII regions, we conclude that the IR emission is influenced by young, massive stars increasingly with decreasing wavelength from 160 to 24μm. The radio-IR correlations indicate that the warm dust-thermal radio correlation is stronger than the cold dust-nonthermal radio correlation at scales smaller than 4 kpc. A perfect 3.6 cm-Hα correlation implies that extinction has no significant effect on Hα emitting structures. © ESO 2007.
• Trilling, D. E., Stansberry, J. A., Stapelfeldt, K. R., Rieke, G. H., Su, K. Y., Gray, R. O., Corbally, C. J., Bryden, G., Chen, C. H., Boden, A., & Beichman, C. A. (2007). Debris disks in main-sequence binary systems. Astrophysical Journal, 658(2 I), 1289-1311.
  More info

  Abstract: We observed 69 A3-F8 main-sequence binary star systems using the Muitiband imaging Photometer for spitzer on board the Spitzer Space Telescope. We find emission significantly in excess of predicted photospheric flux levels for 9-3+4% and 40-6-7 % of these systems at 24 and 70 μm, respectively. Twenty-two systems total have excess emission, including four systems that show excess emission at both wavelengths. A very large fraction (nearly 60%) of observed binary systems with small (
• Walter, F., Cannon, J. M., Roussel, H., Bendo, G. J., Calzetti, D., Dale, D. A., Draine, B. T., Helou, G., Kennicutt Jr., R. C., Moustakas, J., Rieke, G. H., Armus, L., Engelbracht, C. W., Gordon, K., Hollenbach, D. J., Lee, J., Aigen, L. i., Meyer, M. J., Murphy, E. J., , Regan, M. W., et al. (2007). Dust and atomic gas in dwarf irregular galaxies of the M81 group: The SINGS and things view. Astrophysical Journal, 661(1 I), 102-114.
  More info

  Abstract: We present observations of the dust and atomic gas phase in seven dwarf irregular galaxies of the M81 group from the Spitzer SINGS and VLA THINGS surveys. The Spitzer observations provide a first glimpse of the nature of the nonatomic ISM in these metal-poor (Z ∼ 0.1 Z⊙), quiescent (SFR ∼ 0.001-0.1 M⊙ yr-1) dwarf galaxies. Most detected dust emission is restricted to H I column densities >1 × 1021 cm-2, and almost all regions of high H I column density (>2.5 × 1021 cm-2) have associated dust emission. Spitzer spectroscopy of two regions in the brightest galaxies (IC 2574 and Holmberg II) show distinctly different spectral shapes and aromatic features, although the galaxies have comparable gas-phase metallicities. This result emphasizes that the strength of the aromatic features is not a simple linear function of metallicity. We estimate dust masses of ∼10 4-106 M⊙ for the M81 dwarf galaxies, resulting in an average dust-to-gas ratio (Mdust/MH I) of ∼3 × 10-4 (1.5 × 10-3 if only the H I that is associated with dust emission is considered); this is an order of magnitude lower than the typical value derived for the SINGS spirals. The dwarf galaxies are underluminous per unit star formation rate at 70 p,m as compared to the more massive galaxies in SINGS by a factor of ∼2. However, the average 70/160 μm ratio in the sample dwarf galaxies is higher than what is found in the other galaxies of the SINGS sample. This can be explained by a combination of a lower dust content in conjunction with a higher dust temperature in the dwarfs. © 2007. The American Astronomical Society. All rights reserved.
• Wyatt, M. C., Kennedy, G., Sibthorpe, B., Moro-Martin, A., Lestrade, J. -., Ivison, R. J., Matthews, B., Udry, S., Greaves, J. S., Kalas, P., Lawler, S., Su, K. Y., Rieke, G. H., Booth, M., Bryden, G., Horner, J., Kavelaars, J. J., & Wilner, D. (2007). Herschel imaging of 61 Vir: implications for the prevalence of debris in low-mass planetary systems. MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, 424(2), 1206-1223.
  More info

  This paper describes Herschel observations of the nearby (8.5 pc) G5V multi-exoplanet host star 61 Vir at 70, 100, 160, 250, 350 and 500 m carried out as part of the DEBRIS survey. These observations reveal emission that is significantly extended out to a distance of >15 arcsec with a morphology that can be fitted by a nearly edge-on (77 degrees inclination) radially broad (from 30 au out to at least 100 au) debris disc of fractional luminosity 2.7 x 10(-5), with two additional (presumably unrelated) sources nearby that become more prominent at longer wavelengths. Chance alignment with a background object seen at 1.4 GHz provides potential for confusion, however, the stars 1.4 arcsec yr-1 proper motion allows archival Spitzer 70 m images to confirm that what we are interpreting as disc emission really is circumstellar. Although the exact shape of the discs inner edge is not well constrained, the region inside 30 au must be significantly depleted in planetesimals. This is readily explained if there are additional planets outside those already known (i.e. in the 0.530 au region), but is also consistent with collisional erosion. We also find tentative evidence that the presence of detectable debris around nearby stars correlates with the presence of the lowest mass planets that are detectable in current radial velocity surveys. Out of an unbiased sample of the nearest 60 G stars, 11 are known to have planets, of which six (including 61 Vir) have planets that are all less massive than Saturn, and four of these have evidence for debris. The debris towards one of these planet hosts (HD 20794) is reported here for the first time. This fraction (4/6) is higher than that expected for nearby field stars (15 per cent), and implies that systems that form low-mass planets are also able to retain bright debris discs. We suggest that this correlation could arise because such planetary systems are dynamically stable and include regions that are populated with planetesimals in the formation process where the planetesimals can remain unperturbed over Gyr time-scales.
• Wyatt, M. C., Smith, R., Su, K. Y., Rieke, G. H., Greaves, J. S., Beichman, C. A., & Bryden, G. (2007). Steady state evolution of debris disks around a stars. ASTROPHYSICAL JOURNAL, 663(1), 365-382.
  More info

  This paper confronts a simple analytical model for the steady state evolution of debris disks due to collisions with Spitzer observations of dust around main-sequence A stars. It is assumed that every star has a planetesimal belt, the initial mass and radius of which are drawn from distributions. In the model disk mass is constant until the largest planetesimals reach collisional equilibrium, whereupon mass falls alpha t(age)(-1). We find that the detection statistics and trends seen at 24 and 70 mu m can be fitted well by the model. While there is no need to invoke stochastic evolution or delayed stirring to explain the statistics, a moderate rate of stochastic events is not ruled out. Potentially anomalous systems are identified by a high dust luminosity compared with the maximum permissible in the model (HD 3003, HD 38678, HD 115892, HD 172555); their planetesimals may have unusual properties (high strength or low eccentricity), or this dust could be transient. The overall success of our model, which assumes planetesimals in all belts have the same strength, eccentricity, and maximum size, suggests the outcome of planet formation is reasonably uniform. The distribution of planetesimal belt radii, once corrected for detection bias, follows N(r) alpha r(-0.8 +/- 0.3) for 3-120 AU. Since belt boundaries may be attributed to unseen planets, this provides a unique constraint on A star planetary systems. It is also shown that P-R drag may sculpt the inner edges of A star disks close to the Spitzer detection threshold (HD 2262, HD 19356, HD106591, HD115892). This model can be readily applied to the interpretation of future surveys, and predictions for the upcoming SCUBA-2 survey include that 17% of A star disks should be detectable at 850 mu m.
• Wyatt, M. C., Smith, R., Su, K. Y., Rieke, G. H., Greaves, J. S., Beichman, C. A., & Bryden, G. (2007). Steady state evolution of debris disks around a stars. Astrophysical Journal, 663(1 I), 365-382.
  More info

  Abstract: This paper confronts a simple analytical model for the steady state evolution of debris disks due to collisions with Spitzer observations of dust around main-sequence A stars. It is assumed that every star has a planetesimal belt, the initial mass and radius of which are drawn from distributions. In the model disk mass is constant until the largest plan-etesimals reach collisional equilibrium, whereupon mass falls ∝tage-1. We find that the detection statistics and trends seen at 24 and 70 μm can be fitted well by the model. While there is no need to invoke stochastic evolution or delayed stirring to explain the statistics, a moderate rate of stochastic events is not ruled out. Potentially anomalous systems are identified by a high dust luminosity compared with the maximum permissible in the model (HD 3003, HD 38678, HD 115892, HD 172555); their planetesimals may have unusual properties (high strength or low eccentricity), or this dust could be transient. The overall success of our model, which assumes planetesimals in all belts have the same strength, eccentricity, and maximum size, suggests the outcome of planet formation is reasonably uniform. The distribution of planetesimal belt radii, once corrected for detection bias, follows N(r) ∝ r -0.8±0.3 for 3-120 AU. Since belt boundaries may be attributed to unseen planets, this provides a unique constraint on A star planetary systems. It is also shown that P-R drag may sculpt the inner edges of A star disks close to the Spitzer detection threshold (HD 2262, HD 19356, HD 106591, HD 115892). This model can be readily applied to the interpretation of future surveys, and predictions for the upcoming SCUBA-2 survey include that 17% of A star disks should be detectable at 850 μm. © 2007, The American Astronomical Society. All rights reserved.
• Yusef-Zadeh, F., Arendt, R. G., Heinke, C. O., Hinz, J. L., Hewitt, J. W., Pratap, P., Ramirez, S. V., Rieke, G. H., Roberts, D. A., Stolovy, S. R., Wardle, M., & Whitney, B. A. (2007). Masers as probes of massive star formation in the nuclear disk. Proceedings of the International Astronomical Union, 3(S242), 366-373.
  More info

  Abstract: OH(1720 MHz) and methanol masers are now recognized to be excellent probes of the interactions of supernova remnants with molecular clouds and tracers of massive star formation, respectively. To better understand the nature of star formation activity in the central region of the Galaxy, we have used these two classes of masers combined with the IRAC and MIPS data to study prominent sites of ongoing star formation in the nuclear disk. The nuclear disk is characterized by massive GMCs with elevated gas temperatures, compared to their dust temperatures. We note an association between methanol masers and a class of mid-infrared "green sources". These highly embedded YSOs show enhanced 4.5m emission due to excited molecular lines.The distribution of methanol masers and supernova remnants suggest a low efficiency of star formation (with the exception of Sgr B2), which we believe is due to an enhanced flux of cosmic ray electrons impacting molecular clouds in the nuclear disk. We also highlight the importance of cosmic rays in their ability to heat molecular clouds, and thus increase the gas temperature. © 2008 International Astronomical Union.
• Zheng, X. Z., Bell, E. F., Papovich, C., Wolf, C., Meisenheimer, K., Rix, H., Rieke, G. H., & Somerville, R. (2007). The dependence of star formation on galaxy stellar mass. Astrophysical Journal, 661(1 II), L41-L44.
  More info

  Abstract: We combine Spitzer 24 μm observations with data from the COMBO-17 survey for ∼15,000 0.2 < z ≤ 1 galaxies to determine how the average star formation rates (SFRs) have evolved for galaxy subpopulations of different stellar masses. In the determination of 〈SFR〉, we consider both the ultraviolet (UV) and the infrared (IR) luminosities, and account for the contributions of galaxies that are individually undetected at 24 μm through image stacking. For all redshifts, we find that higher mass galaxies have a substantially lower specific SFR, 〈SFR〉/〈M〉, than lower mass ones. However, we find the striking result that the rate of decline in cosmic SFR with redshift is nearly the same for massive and low mass galaxies, i.e., not a strong function of stellar mass. This analysis confirms one version of what has been referred to as "downsizing," namely, that the epoch of major mass buildup in massive galaxies is substantially earlier than the epoch of mass buildup in low-mass galaxies. Yet it shows that star formation activity is not becoming increasingly limited to low-mass galaxies toward the present epoch. We argue that this suggests that heating by AGN-powered radio jets is not the dominant mechanism responsible for the decline in cosmic SFR since z ∼ 1, which is borne out by comparison with semianalytic models that include this effect. © 2007. The American Astronomical Society. All rights reserved.
• Zheng, X. Z., Dole, H., Bell, E. F., Floc'h, E. L., Rieke, G. H., Rix, H., & Schiminovich, D. (2007). Infrared spectral energy distributions of z ∼ 0.7 star-forming galaxies. Astrophysical Journal, 670(1), 301-312.
  More info

  Abstract: We analyze the infrared (IR) spectral energy distributions (SEDs) for 10 μm < λrest < 100 μm for ∼600 galaxies at z ∼ 0.7 in the extended Chandra Deep Field South by stacking their Spitzer 24, 70, and 160 μm images. We place interesting constraints on the average IR SED shape in two bins: the brightest 25% of z ∼ 0.7 galaxies detected at 24 μm, and the remaining 75% of individually detected galaxies. Galaxies without individual detections at 24 μm were not well detected at 70 and 160 μm even through stacking. We find that the average IR SEDs of z ∼ 0.7 star-forming galaxies fall within the diversity of z ∼ 0 templates. While dust obscuration LIR/LUV seems to be only a function of star formation rate (SFR; ∼LIR + LUV), not of redshift, the dust temperature of star-forming galaxies (with SFR ∼ 10 M⊙ yr-1) at a given IR luminosity was lower at z ∼ 0.7 than today. We suggest an interpretation of this phenomenology in terms of dust geometry: intensely star-forming galaxies at z ∼ 0 are typically interacting, and host dense centrally concentrated bursts of star formation and warm dust temperatures. At z ∼ 0.7, the bulk of intensely star-forming galaxies are relatively undisturbed spirals and irregulars, and we postulate that they have large amounts of widespread lower density star formation, yielding lower dust temperatures for a given IR luminosity. We recommend which IR SEDs are most suitable for modeling intermediate-redshift galaxies with different SFRs. © 2007. The American Astronomical Society. All rights reserved.
• Alonso-Herrero, A., Colina, L., Packham, C., Díaz-Santos, T., Rieke, G. H., Radomski, J. T., & Telesco, C. M. (2006). High spatial resolution T-ReCS mid-infrared imaging of luminous infrared galaxies. Astrophysical Journal, 652(2 II), L83-L87.
  More info

  Abstract: We present diffraction-limited (FWHM ∼ 0″.3) Gemini/T-ReCS mid-infrared (MIR; W-band or narrowband at 8.7 μm) imaging of four luminous infrared galaxies (LIRGs) drawn from a representative local sample. The MIR emission in the central few kiloparsecs is strikingly similar to that traced by Paα and generally consists of bright nuclear emission and several compact circumnuclear and/or extranuclear H II regions. The central MIR emission is dominated by these powerful H II regions, consistent with the majority of active galactic nuclei in this local sample of LIRGs contributing a minor part of the MIR emission. The luminous circumnuclear H II regions detected in LIRGs follow the extrapolation of the 8 μm versus Paα relation found for M51 H II knots. The integrated central 3-7 kpc of galaxies, however, present elevated 8 μm/Paα ratios with respect to individual H II regions, similar to the integrated values for star-forming galaxies. Our results show that the diffuse 8 μm emission, not directly related to the ionizing stellar population, can be as luminous as that from the resolved H II regions. Therefore, calibrations of the star formation rate for distant galaxies should be based on the integrated 8 μm emission of nearby galaxies, not that of the H II regions alone. © 2006. The American Astronomical Society. All rights reserved.
• Alonso-Herrero, A., Pérez-González, P., Alexander, D. M., Rieke, G. H., Rigopoulou, D., Floc'h, E. L., Barmby, P., Papovich, C., Rigby, J. R., Bauer, F. E., Brandt, W. N., Egami, E., Willner, S. P., Dole, H., & Huang, J. -. (2006). Infrared power-law galaxies in the chandra deep field-south: Active galactic nuclei and ultraluminous infrared galaxies. Astrophysical Journal Letters, 640(1 I), 167-184.
  More info

  Abstract: We investigate the nature of a sample of 92 Spitzer MIPS 24 μm-selected galaxies in the CDF-S, showing power-law-like emission in the Spitzer IRAC 3.6-8 μm bands. The main goal is to determine whether the galaxies not detected in X-rays (47% of the sample) are part of the hypothetical population of obscured AGNs not detected even in deep X-ray surveys. The majority of the IR power-law galaxies are ULIRGs at z > 1, and those with LIRG-like IR luminosities are usually detected in X-rays. The optical-to-IR SEDs of the X-ray-detected galaxies are almost equally divided between a BLAGN SED class (similar to an optically selected QSO) and an NLAGN SED (similar to the BLAGN SED but with an obscured UV/optical continuum). A small fraction of SEDs resemble warm ULIRGs (e.g., Mrk 231). Most galaxies not detected in X-rays have SEDs in the NLAGN+ULIRG class as they tend to be optically fainter and possibly more obscured. Moreover, the IR power-law galaxies have SEDs significantly different from those of high-z (zsp > 1) IR (24 μm) selected and optically bright (WDS IAB ≤ 24) star-forming galaxies whose SEDs show a very prominent stellar bump at 1.6 μm. The galaxies detected in X-rays have 2-8 keV rest-frame luminosities typical of AGNs. The galaxies not detected in X-rays have global X-ray-to-mid-IR SED properties that make them good candidates to contain IR-bright X-ray-absorbed AGNs. If all these sources are actually obscured AGNs, we would observe a ratio of obscured to unobscured 24 μm-detected AGNs of 2:1, whereas models predict a ratio of up to 3:1. Additional studies using Spitzer to detect X-ray-quiet AGNs are likely to find more such obscured sources. © 2006. The American Astronomical Society. All rights reserved.
• Alonso-Herrero, A., Rieke, G. H., Rieke, M. J., Colina, L., Perez-Gonzalez, P. G., & Ryder, S. D. (2006). Near-infrared and star-forming properties of local luminous infrared galaxies. ASTROPHYSICAL JOURNAL, 650(2), 835-849.
  More info

  We use Hubble Space Telescope (HST) NICMOS continuum and Pa alpha observations to study the near-infrared and star formation properties of a representative sample of 30 local (d similar to 35-75 Mpc) luminous infrared galaxies (LIRGs, infrared [8 - 1000 mu m] luminosities of log L-IR 11-11.9 L-circle dot). The data provide spatial resolutions of 25 - 50 pc and cover the central similar to 3.3 - 7.1 kpc regions of these galaxies. About half of the LIRGs show compact (similar to 1 - 2 kpc) Pa alpha emission with a high surface brightness in the form of nuclear emission, rings, and minispirals. The rest of the sample show Pa alpha emission along the disk and the spiral arms extending over scales of 3 - 7 kpc and larger. About half of the sample contains H (II) regions with H alpha luminosities significantly higher than those observed in normal galaxies. There is a linear empirical relationship between the mid-IR 24 mu m and hydrogen recombination (extinction-corrected Pa alpha) luminosity for these LIRGs, and the H (II) regions in the central part of M51. This relation holds over more than four decades in luminosity, suggesting that the mid-IR emission is a good tracer of the star formation rate (SFR). Analogous to the widely used relation between the SFR and total IR luminosity of R. Kennicutt, we derive an empirical calibration of the SFR in terms of the monochromatic 24 mu m luminosity that can be used for luminous, dusty galaxies.
• Alonso-Herrero, A., Rieke, G. H., Rieke, M. J., Colina, L., Pérez-González, P. G., & Ryder, S. D. (2006). Near-infrared and star-forming properties of local luminous infrared galaxies. Astrophysical Journal Letters, 650(2 I), 835-849.
  More info

  Abstract: We use Hubble Space Telescope (HST) NICMOS continuum and Paα observations to study the near-infrared and star formation properties of a representative sample of 30 local (d ∼ 35-75 Mpc) luminous infrared galaxies (LIRGs, infrared [8-1000 μm] luminosities of log LIR = 11-11.9 L⊙). The data provide spatial resolutions of 25-50 pc and cover the central ∼3.3-7.1 kpc regions of these galaxies. About half of the LIRGs show compact (∼1-2 kpc) Paα emission with a high surface brightness in the form of nuclear emission, rings, and minispirals. The rest of the sample show Paα emission along the disk and the spiral arms extending over scales of 3-7 kpc and larger. About half of the sample contains H II regions with Ha luminosities significantly higher than those observed in normal galaxies. There is a linear empirical relationship between the mid-IR 24 μm and hydrogen recombination (extinction-corrected Paα) luminosity for these LIRGs, and the H II regions in the central part of M51. This relation holds over more than four decades in luminosity, suggesting that the mid-IR emission is a good tracer of the star formation rate (SFR). Analogous to the widely used relation between the SFR and total IR luminosity of R. Kennicutt, we derive an empirical calibration of the SFR in terms of the monochromatic 24 μm luminosity that can be used for luminous, dusty galaxies. © 2006. The American Astronomical Society. All rights reserved.
• Bai, L., Rieke, G. H., Rieke, M. J., Hinz, J. L., Kelly, D. M., & Blaylock, M. (2006). Infrared luminosity function of the Coma Cluster. Astrophysical Journal Letters, 639(2 I), 827-837.
  More info

  Abstract: Using mid-IR and optical data, we deduce the total infrared (IR) luminosities of galaxies in the Coma Cluster and present their IR luminosity function (LF). The shape of the overall Coma IR LF does not show significant differences from the IR LFs of the general field, which indicates the general independence of global galaxy star formation from environment up to densities ∼40 times greater than in the field (we cannot test such independence above LIR ≈1044 ergs s-1). However, a shallower faint-end slope and a smaller LIR* are found in the core region (where the densities are still higher) compared to the outskirt region of the cluster, and most of the brightest IR galaxies are found outside the core region. The IR LF in the NGC 4839 group region does not show any unique characteristics. By integrating the IR LF, we find a total star formation rate in the cluster of about 97.0 M⊙ yr-1. We also studied the contributions of early- and late-type galaxies to the IR LF. The late-type galaxies dominate the bright end of the LF, and the early-type galaxies, although only making up a small portion (≈15%) of the total IR emission of the cluster, contribute greatly to the number counts of the LF at LIR < 1043 ergs s -1. © 2006. The American Astronomical Society. All rights reserved.
• Ballantyne, D. R., Shi, Y., Rieke, G. H., Donley, J. L., Papovich, C., & Rigby, J. R. (2006). Does the AGN unified model evolve with redshift? Using the X-ray background to predict the mid-infrared emission of AGNs. Astrophysical Journal, 653(2 I), 1070-1088.
  More info

  Abstract: Deep X-ray surveys by Chandra and XMM-Newton have resolved about 80% of the 2-10 keV cosmic extragalactic X-ray background (CXRB) into point sources, the majority of which are obscured AGNs. The obscuration might be connected to processes within the host galaxy, possibly the star formation rate. Here we use the results of CXRB synthesis calculations as input to detailed CLOUDY simulations in order to predict the evolution of AGN properties at several mid-IR wavelengths. Computations were performed for three different evolutions of the AGN type 2/type 1 ratio betweenz = 0 and 1, where the ratio increased as (1 + z)0.9, as (1 + z)0.3, and with one model having no redshift evolution. Models were calculated with the inner radius of the absorbing gas and dust at 1 or at 10 pc. Comparing the results of the calculations to combined X-ray and Spitzer data of AGNs show that the predicted spectral energy distributions are a good description of average AGNs found in the deep surveys. The existing data indicate that the mid-IR emission from an average AGN is best described by models in which the attenuating material is ∼ 10 pc from the central engine. We present the expected Spitzer cumulative number count distributions and the evolution of the total AGN (type 1+type 2) luminosity function (LF) between z = 0 and 1 at rest frame 8 and 30 μm for the three evolutionary scenarios. The mid-IR AGN LF will be an excellent tool to measure the evolution of the covering factor of the gas and dust from z ∼ 0 to 1. © 2006. The American Astronomical Society. All righls reserved.
• Balog, Z., Rieke, G. H., Su, K. Y., Muzerolle, J., & Young, E. T. (2006). Spitzer MIPS 24 μm detection of photoevaporating protoplanetary disks. Astrophysical Journal Letters, 650(1 II), L83-L86.
  More info

  Abstract: We present 24 μm images of three protoplanetary disks being photoevaporated around high-mass O-type stars. These objects have "cometary" structure where the dust pulled away from the disk by the photoevaporating flow is forced away from the O star by photon pressure on the dust and heating and ionization of the gas. Models of the 24 and 8 μm brightness profiles agree with this hypothesis. These models show that the mass-loss rate needed to sustain such a configuration is in agreement with or somewhat less than the theoretical predictions for the photoevaporation process. © 2006. The American Astronomical Society. All rights reserved.
• Barmby, P., Alonso-Herrero, A., Donley, J. L., Egami, E., Fazio, G. G., Georgakakis, A., Huang, J. -., Laird, E. S., Miyazaki, S., Nandra, K., Park, S. Q., Pérez-González, P., Rieke, G. H., Rigby, J. R., & Willner, S. P. (2006). Mid-infrared properties of X-ray sources in the extended groth strip. Astrophysical Journal Letters, 642(1 I), 126-139.
  More info

  Abstract: Mid-infrared observations of active galactic nuclei (AGNs) are important for understanding the physical conditions around the central accretion engines. Chandra and XMM-Newton X-ray observations of a 300 arcmin2 region in the extended Groth strip are used to select a sample of ∼150 AGNs. The Spitzer instruments IRAC and MIPS detect 68%-80% of these sources, which show a wide range of mid-infrared properties. About 40% of the sources have red power-law spectral energy distributions (fv ∝ v α, α < 0) in the 3.6-8 μm IRAC bands. In these sources the central engine dominates the emission at both X-ray and IR wavelengths. Another 40% of the sources have blue midIR spectral energy distributions (α > 0) with their infrared emission dominated by the host galaxy; the remaining 20% are not well fit by a power law. Published IRAC color criteria for AGNs select most of the red sources, but only some of the blue sources. As with all other known methods, selecting AGNs with mid-IR colors will not produce a sample that is simultaneously complete and reliable. The IRAC SED type does not directly correspond to X-ray spectral type (hard/soft). The mid-IR properties of X-ray-detected Lyman break, radio, submillimeter, and optically faint sources vary widely, and for the most part are not distinct from those of the general X-ray/infrared source population. X-ray sources emit 6%-11% of the integrated mid-IR light, making them significant contributors to the cosmic infrared background. © 2006. The American Astronomical Society. All rights reserved.
• Barmby, P., Ashby, M. L., Bianchi, L., Engelbracht, C. W., Gehrz, R. D., Gordon, K. D., Hinz, J. L., Huchra, J. P., Humphreys, R. M., Pahre, M. A., Pérez-González, P., Polomski, E. F., Rieke, G. H., Thilker, D. A., Willner, S. P., & Woodward, C. E. (2006). Dusty waves on a starry sea: The mid-infrared view of M31. Astrophysical Journal Letters, 650(1 II), L45-L49.
  More info

  Abstract: Mid-infrared observations of the Andromeda galaxy, M31, obtained with the Infrared Array Camera on board the Spitzer Space Telescope are presented. The image mosaics cover areas of approximately 3.°7 × 1.°6 and include the satellite galaxies M32 and NGC 205. The appearance of M31 varies dramatically in the different mid-infrared bands, from the smooth bulge and disk of the old stellar population seen at 3.6 μm to the well-known "10 kpc ring" dominating the 8 μm image. The similarity of the 3.6 μm and optical isophotes and the nearly constant optical-mid-infrared color over the inner 400'' confirm that there is no significant extinction at optical wavelengths in M31's bulge. The nuclear colors indicate the presence of dust but not an infrared-bright active galactic nucleus. The integrated 8 μm nonstellar luminosity implies a star formation rate of 0.4 Modot; yr-1, consistent with other indicators that show M31 to be a quiescent galaxy. © 2006. The American Astronomical Society. All rights reserved.
• Beichman, C. A., Bryden, G., Stapelfeldt, K. R., Gautier, T. N., Grogan, K., Shao, M., Velusamy, T., Lawler, S. M., Blaylock, M., Rieke, G. H., Lunine, J. I., Fischer, D. A., Marcy, G. W., Greaves, J. S., Wyatt, M. C., Holland, W. S., & Dent, W. R. (2006). New debris disks around nearby main-sequence stars: Impact on the direct detection of planets. Astrophysical Journal, 652(2 I), 1674-1693.
  More info

  Abstract: Using the MIPS instrument on Spitzer, we have searched for infrared excesses around a sample of 82 stars, mostly F, G, and K main-sequence field stars, along with a small number of nearby M stars. These stars were selected for their suitability for future observations by a variety of planet-finding techniques. These observations provide information on the asteroidal and cometary material orbiting these stars, data that can be correlated with any planets that may eventually be found. We have found significant excess 70 μm emission toward 12 stars. Combined with an earlier study, we find an overall 70 μm excess detection rate of 13% ± 3% for mature cool stars. Unlike the trend for planets to be found preferentially toward stars with high metallicity, the incidence of debris disks is uncorrelated with metallicity. By newly identifying four of these stars as having weak 24 μm excesses (fluxes ∼ 10% above the stellar photosphere), we confirm a trend found in earlier studies wherein a weak 24 μm excess is associated with a strong 70 μm excess. Interestingly, we find no evidence for debris disks around 23 stars cooler than K1, a result that is bolstered by a lack of excess around any of the 38 K1-M6 stars in two companion surveys. One motivation for this study is the fact that strong zodiacal emission can make it hard or impossible to detect planets directly with future observatories such as the Terrestrial Planet Finder (TPF). The observations reported here exclude a few stars with very high levels of emission, > 1000 times the emission of our zodiacal cloud, from direct planet searches. For the remainder of the sample, we set relatively high limits on dust emission from asteroid belt counterparts. © 2006. The Americani Astronomical Society. All rights reserved.
• Beichman, C. A., Tanner, A., Bryden, G., Stapelfeldt, K. R., Werner, M. W., Rieke, G. H., Trilling, D. E., Lawler, S., & Gautier, T. N. (2006). IRS spectra of solar-type stars: A search for asteroid belt analogs. Astrophysical Journal Letters, 639(2 I), 1166-1176.
  More info

  Abstract: We report the results of a spectroscopic search for debris disks surrounding 41 nearby solar-type stars, including eight planet-bearing stars, using the Infrared Spectrometer (IRS) on the Spitzer Space Telescope. With the accurate relative photometry of the IRS between 7 and 34 μm we are able to look for excesses as small as ∼2% of photospheric levels, with particular sensitivity to weak spectral features. For stars with no excess, the 3 σ upper limit in a band at 30-34 μm corresponds to ∼75 times the brightness of our zodiacal dust cloud. Comparable limits at 8.5-13 μm correspond to ∼1400 times the brightness of our zodiacal dust cloud. These limits correspond to material located within the < 1 to ∼5 AU region that, in our solar system, originates predominantly from debris associated with the asteroid belt. We find excess emission longward of ∼25 μm from five stars, of which four also show excess emission at 70 μm. This emitting dust must be located in a region starting around 5-10 AU. One star has 70 μm emission but no IRS excess. In this case, the emitting region must begin outside 10 AU; this star has a known radial velocity planet. Only two stars of the five show emission shortward of 25 μm, where spectral features reveal the presence of a population of small, hot dust grains emitting in the 7-20 μm band. One of these stars, HD 72905, is quite young (300 Myr), while the other, HD 69830, is older than 2 Gyr. The data presented here strengthen the results of previous studies to show that excesses at 25 μm and shorter are rare: only 1 out of 40 stars older than 1 Gyr or ∼2.5% shows an excess. Asteroid belts 10-30 times more massive than our own appear are rare among mature, solar-type stars. © 2006. The American Astronomical Society. All rights reserved.
• Beichman, C., Bryden, G., Rieke, G., Stansberry, J., Trilling, D., Stapelfeldt, K., Werner, M., Engelbracht, C., Blaylock, M., Gordon, K., Chen, C., Su, K., & Hines, D. (2006). Planets and infrared excesses: Preliminary results from a Spitzer MIPS survey of solar-type stars. ASTROPHYSICAL JOURNAL, 622(2), 1160-1170.
  More info

  As part of a large Spitzer MIPS Guaranteed Time Observation program, we have searched for infrared excesses due to debris disks toward 26 FGK field stars known from radial velocity (RV) studies to have one or more planets. While none of these stars show excesses at 24 mu m, we have detected 70 mu m excesses around six stars at the 3 sigma confidence level. The excesses are produced by cool material (
• Bryden, G., Beichman, C. A., Rieke, G. H., Stansberry, J. A., & Stapelfeldt, K. R. (2006). Spitzer MIPS limits on asteroidal dust in the pulsar planetary system PSR B1257+12. ASTROPHYSICAL JOURNAL, 646(2), 1038-1042.
  More info

  With the MIPS camera on Spitzer, we have searched for far-infrared emission from dust in the planetary system orbiting pulsar PSR B1257+12. With accuracies of 0.05 mJy at 24 mu m and 1.5 mJy at 70 mu m, photometric measurements find no evidence for emission at these wavelengths. These observations place new upper limits on the luminosity of dust with temperatures between 20 and 1000 K. They are particularly sensitive to dust temperatures of 100-200 K, for which they limit the dust luminosity to below 3 x 10(-5) of the pulsar's spin-down luminosity, 3 orders of magnitude better than previous limits. Despite these improved constraints on dust emission, an asteroid belt similar to the solar system's cannot be ruled out.
• Bryden, G., Beichman, C. A., Rieke, G. H., Stansberry, J. A., Stapelfeldt, K. R., Trilling, D. E., Turner, N. J., & Wolszczan, A. (2006). Spitzer MIPS limits on asteroidal dust in the pulsar planetary system PSR B1257+12. Astrophysical Journal Letters, 646(2 I), 1038-1042.
  More info

  Abstract: With the MIPS camera on Spitzer, we have searched for far-infrared emission from dust in the planetary system orbiting pulsar PSR B1257+12. With accuracies of 0.05 mJy at 24 μm and 1.5 mJy at 70 μm, photometric measurements find no evidence for emission at these wavelengths. These observations place new upper limits on the luminosity of dust with temperatures between 20 and 1000 K. They are particularly sensitive to dust temperatures of 100-200 K, for which they limit the dust luminosity to below 3 × 105 of the pulsar's spin-down luminosity, 3 orders of magnitude better than previous limits. Despite these improved constraints on dust emission, an asteroid belt similar to the solar system's cannot be ruled out. © 2006. The American Astronomical Society. All rights reserved.
• Bryden, G., Beichman, C. A., Trilling, D. E., Rieke, G. H., Holmes, E. K., Lawler, S. M., Stapelfeldt, K. R., Werner, M. W., Gautier, T. N., Blaylock, M., Gordon, K. D., Stansberry, J. A., & Su, K. Y. (2006). Frequency of debris disks around solar-type stars: First results from a spitzer mips survey. Astrophysical Journal Letters, 636(2 I), 1098-1113.
  More info

  Abstract: We have searched for infrared excesses around a well-defined sample of 69 FGK main-sequence field stars. These stars were selected without regard to their age, metallicity, or any previous detection of IR excess; they have a median age of ∼4 Gyr. We have detected 70 μm excesses around seven stars at the 3 σ confidence level. This extra emission is produced by cool material (< 100 K) located beyond 10 AU, well outside the "habitable zones" of these systems and consistent with the presence of Kuiper Belt analogs with ∼100 times more emitting surface area than in our own planetary system. Only one star, HD 69830, shows excess emission at 24 μm, corresponding to dust with temperatures ≳300 K located inside of 1 AU. While debris disks with Ldust/L* ≥ 10-3 are rare around old FGK stars, we find that the disk frequency increases from 2% ± 2% for L dust/L* ≥ 10-4 to 12% ± 5% for L dust/L* ≥ 10-5. This trend in the disk luminosity distribution is consistent with the estimated dust in our solar system being within an order of magnitude greater or less than the typical level around similar nearby stars. Although there is no correlation of IR excess with metallicity or spectral type, there is a weak correlation with stellar age, with stars younger than a gigayear more likely to have excess emission. © 2006. The American Astronomical Society. All rights reserved.
• Buckalew, B. A., Kobulnicky, H. A., Darnel, J. M., Polomski, E., Gehrz, R. D., Humphreys, R. M., Woodward, C. E., Hinz, J. L., Engelbracht, C. W., Gordon, K. D., Misselt, K., Pérez-González, P., Rieke, G. H., Willner, S. P., Ashby, M. L., Barmby, P., Pahre, M. A., Roellig, T. L., Devereux, N., , Loon, J. T., et al. (2006). Understanding radio-selected thermal sources in M33: Ultraviolet, optical, near-infrared, Spitzer mid-infrared, and radio observations. Astrophysical Journal, Supplement Series, 162(2), 329-345.
  More info

  Abstract: We present ultraviolet, optical, near-infrared, Spitzer mid-infrared, and radio images of 14 radio-selected objects in M33. These objects are thought to represent the youngest phase of star cluster formation. We have detected the majority of cluster candidates in M33 at all wavelengths. From the near-IR images, we derived ages 2-10 Myr, K s-band extinctions (A Ks) of 0-1 mag, and stellar masses of 10 3-10 4 M odot;. We have generated spectral energy distributions (SEDs) of each cluster from 0.1 to 160 μm. From these SEDs, we have modeled the dust emission around these star clusters to determine the dust masses (1-10 3 M ⊙) and temperatures (40-90 K) of the clusters' local interstellar medium. Extinctions derived from the JHK s, Hα, and UV images are similar to within a factor of 2 or 3. These results suggest that 11 of the 14 radio-selected objects are optically visible young star clusters with a surrounding H II region, that 2 are background objects, possibly active galactic nuclei (AGNs), and that 1 is a Wolf-Rayet star with a surrounding H II region. © 2006. The American Astronomical Society, All rights reserved.
• Burgarella, D., Pérez-González, P., Tyler, K. D., Rieke, G. H., Buat, V., Takeuchi, T. T., Lauger, S., Arnouts, S., Ilbert, O., Barlow, T. A., Bianchi, L., Lee, Y. -., Madore, B. F., Malina, R. F., Szalay, A. S., & Yi, S. K. (2006). Ultraviolet-to-far infrared properties of Lyman break galaxies and luminous infrared galaxies at z ∼ 1. Astronomy and Astrophysics, 450(1), 69-76.
  More info

  Abstract: Aims. We present the first large, unbiased sample of Lyman Break Galaxies (LBGs) at z ∼ 1. Far ultraviolet-dropout (1530 Å) galaxies in the Chandra Deep Field South have been selected using GALEX data. This first large sample in the z ∼ 1 universe provides us with a high quality reference sample of LBGs. Methods. We analyzed the sample from the UV to the IR using GALEX, SPITZER, ES O and HS T data. Results. The morphology (obtained from GOODS data) of 75% of our LBGs is consistent with a disk. The vast majority of LBGs with an IR detection are also Luminous Infrared Galaxies (LIRGs). As a class, the galaxies not detected at 24 μm are an order of magnitude fainter relative to the UV compared with those detected individually, suggesting that there may be two types of behavior within the sample. For the IR-bright galaxies, there is an apparent upper limit for the UV dust attenuation and this upper limit is anti-correlated with the observed UV luminosity. Previous estimates of dust attenuations based on the ultraviolet slope are compared to new ones based on the FIR/UV ratio (for LBGs detected at 24 μm), which is usually a more reliable estimator. Depending on the calibration we use to estimate the total IR luminosity, β-based attenuations AFUV are larger by 0.2 to 0.6 mag. than the ones estimated from FIR/UV ratio. Finally, for IR-bright LBGs, median estimated β-based SFRs are 2-3 times larger than the total SFRs estimated as SFRTOT = SFRUV + SFRIR while IR-based SFRs provide values below SFRTOT by 15-20%. We use a stacking method to statistically constrain the 24 μm flux of LBGs non individually detected. The results suggest that these LBGs do not contain large amounts of dust. © ESO 2006.
• Cannon, J. M., Smith, J. T., Walter, F., Bendo, G. J., Calzeti, D., Dale, D. A., Draine, B. T., Engelbracht, C. W., Gordon, K. D., Helou, G., Kennicutt Jr., R. C., Leitherer, C., Armus, L., Buckalew, B. A., Hollenbach, D. J., Jarrett, T. H., Aigen, L. i., Meyer, M. J., Murfhy, E. J., , Regan, M. W., et al. (2006). Warm dust and spatially variable polycyclic aromatic hydrocarbon emission in the dwarf starburst galaxy NGC 1705. Astrophysical Journal Letters, 647(1 I), 293-302.
  More info

  Abstract: We present Spitzer observations of the nearby dwarf starburst galaxy NGC 1705 obtained as part of the Spitzer Infrared Nearby Galaxies Survey. The galaxy morphology is very different shortward and longward of ∼5 μm: optical and short-wavelength IRAC imaging shows an underlying red stellar population, with the central super star cluster (SSC) dominating the luminosity; longer wavelength IRAC and MIPS imaging reveals warm dust emission arising from two off-nuclear regions that are offset by ∼250 pc from the SSC and that dominate the far-IR flux of the system. These regions show little extinction at optical wavelengths. The galaxy has a relatively low global dust mass (∼2 × 105 A⊙, implying a global dust-to-gas mass ratio ∼2-4 times lower than the Milky Way average, roughly consistent with the metallicity decrease). The off-nuclear dust emission appears to be powered by photons from the same stellar population responsible for the excitation of the observed Ha emission; these photons are unassociated with the SSC (although a contribution from embedded sources to the IR luminosity of the off-nuclear regions cannot be ruled out). Low-resolution IRS spectroscopy shows moderate-strength PAH emission in the 11.3 μm band in the more luminous eastern peak; no PAH emission is detected in the SSC or the western dust emission complex. There is significant diffuse emission in the IRAC 8 μm band after starlight has been removed by scaling shorter wavelength data; the fact that IRS spectroscopy shows spatially variable PAH emission strengths compared to the local continuum within this diffuse gas suggests caution in the interpretation of IRAC diffuse 8 μm emission as arising from PAH carriers alone. The nebular metallicity of NGC 1705 falls at the transition level of ∼0.35 Z⊙ found by Engelbracht and collaborators, below which PAH emission is difficult to detect; the fact that a system at this metallicity shows spatially variable PAH emission demonstrates the complexity of interpreting diffuse 8 mu;m emission in galaxies. NGC 1705 deviates significantly from the canonical far-infrared versus radio correlation, having significant far-infrared emission but no detected radio continuum. © 2006. The American Astronomical Society. All rights reserved.
• Caputi, K. I., Dole, H., Lagache, G., McLure, R. J., Puget, J. -., Rieke, G. H., Dunlop, J. S., Floc'h, E. L., Papovich, C., & Pérez-González, P. (2006). Linking stellar mass and star formation in Spitzer MIPS 24 μm galaxies. Astrophysical Journal Letters, 637(2 I), 727-740.
  More info

  Abstract: We present deep Ks < 21.5 (Vega) identifications, redshifts, and stellar masses for most of the sources composing the bulk of the 24 μm background in the GOODS/CDFS. Our identified sample consists of 747 Spitzer MIPS 24 μm objects and includes ∼94% of all the 24 μm sources in the GOODS-South field that have fluxes Sν(24 μm) > 83 μJy (the ∼80% completeness limit of the Spitzer/GTO 24 μm catalog); 36% of our galaxies have spectroscopic redshifts (mostly at z < 1.5), and the remaining ones have photometric redshifts of very good quality, with a median of |dz| = |zspec - zphot|/(1 + zspec) = 0.02. We find that MIPS 24 μm galaxies span the redshift range z ∼ 0-4 and that a substantial fraction (28%) lie at high redshifts z ≳ 1.5. We determine the existence of a bump in the redshift distribution at z ∼ 1.9, indicating the presence of a significant population of galaxies with PAH emission at these redshifts. The 24 μm galaxy population ranges from sources with intermediate luminosities (1010 L⊙ < LIR < 1011 L⊙) and low-to-intermediate assembled stellar masses (109 M⊙ ≲ M ≲ 1011 M ⊙) at z ≲ 0.8, to massive (M ≳ 1011 M ⊙) hyperluminous galaxies (LIR > 1012 L⊙) at redshifts z ∼ 2-3. Massive star-forming galaxies at redshifts 2 ≲ z ≲ 3 are characterized by very high star formation rates (SFR > 500 M⊙ yr-1), and some of them are able to construct a mass of ≈ 1010-1011 M ⊙ in a single burst lifetime (∼0.01-0.1 Gyr). At lower redshifts z ≲ 2, massive star-forming galaxies are also present but appear to be building their stars on long timescales, either quiescently or in multiple modest burstlike episodes. At redshifts z ∼ 1-2, the ability of the burstlike mode to produce entire galaxies in a single event is limited to some lower (M ≲ 7 × 1010 M⊙) mass systems, and it is basically negligible at z ≲ 1. Our results support a scenario in which star formation activity is differential with assembled stellar mass and redshift, and where the relative importance of the burstlike mode proceeds in a downsizing way from high to low redshifts. © 2006. The American Astronomical Society. All rights reserved.
• Chen, C. H., Li, A., Bohac, C., Kim, K. H., Watson, D. M., van Cleve, J., Houck, J., Stapelfeldt, K., Werner, M. W., Rieke, G., Su, K., Marengo, M., Backman, D., Beichman, C., & Fazio, G. (2006). The dust and gas around beta Pictoris. ASTROPHYSICAL JOURNAL, 666(1), 466-474.
  More info

  We have obtained Spitzer IRS 5.5-35 mu m spectroscopy of the debris disk around beta Pictoris. In addition to the 10 mu m silicate emission feature originally observed from the ground, we also detect the crystalline silicate emission bands at 28 and 33.5 mu m. This is the first time that the silicate bands at wavelengths longer than 10 mu m have ever been seen in the beta Pictoris disk. The observed dust emission is well reproduced by a dust model consisting of fluffy cometary and crystalline olivine aggregates. We searched for line emission from molecular hydrogen and atomic [S I], Fe II, and Si II gas but detected none. We place a 3 sigma upper limit of < 17M(circle plus) on the H-2 S(1) gas mass, assuming an excitation temperature of T-ex 100 K. This suggests that there is less gas in this system than is required to form the envelope of Jupiter. We hypothesize that some of the atomic Na I gas observed in Keplerian rotation around beta Pictoris may be produced by photon-stimulated desorption from circumstellar dust grains.
• Churcher, L. J., Wyatt, M. C., Duchene, G., Sibthorpe, B., Kennedy, G., Matthews, B. C., Kalas, P., Greaves, J., Su, K., & Rieke, G. (2006). Multiwavelength modelling of the beta Leo debris disc: one, two or three planetesimal populations?. MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, 417(3), 1715-1734.
  More info

  In this paper we present a model of the beta Leo debris disc, with an emphasis on modelling the resolved Photodetector Array Camera and Spectrometer (PACS) images obtained as a part of the Herschel key programme DEBRIS. We also present new Spectral and Photometric Imaging REceiver (SPIRE) images of the disc at 250 mu m, as well as new constraints on the disc from SCUBA-2, mid-infrared (mid-IR) and scattered light imaging. Combining all the available observational constraints, we find three possible models for the beta Leo (HD 102647) debris disc: (i) a two-component model, comprised of a hot component at 2 au and a cold component from 15 to 70 au; (ii) a three-component model with hot dust at 2 au, warm dust at 9 au and a cold component from 30 to 70 au, is equally valid since the cold emission is not resolved within 30 au; (iii) a somewhat less likely possibility is that the system consists of a single very eccentric planetesimal population, with pericentres at 2 au and apocentres at 65 au. Thus, despite the wealth of observational constraints significant ambiguities remain; deep mid-IR and scattered light imaging of the dust distribution within 30 au seems to be the most promising method to resolve the degeneracy. We discuss the implications for the possible planetary system architecture, e. g. the two-component model suggests that planets may exist at 2-15 au, while the three-component model suggests planets between 2 and 30 au with a stable region containing the dust belt at 9 au, and there should be no planets between 2 and 65 au in the eccentric planetesimal model. We suggest that the hot dust may originate in the disintegration of comets scattered in the cold disc, and examine all A stars known to harbour both hot and cold dust to consider the possibility that the ratio of hot and cold dust luminosities is indicative of the intervening planetary system architecture.
• Cortese, L., Marcillac, D., Richard, J., Bravo-Alfaro, H., Kneib, J. -., Rieke, G., Covone, G., Egami, E., Rigby, J., Czoske, O., & Davies, J. (2006). The strong transformation of spiral galaxies infalling into massive clusters at z∼ 0.2. Proceedings of the International Astronomical Union, 2(S235), 198-.
  More info

  Abstract: We report the discovery of two peculiar galaxies infalling into the lensing clusters of galaxies Abell 1689 (z∼ 0.18) and 2667 (z∼ 0.23). Hubble Space Telescope images show extraordinary trails composed by blue bright knots and stellar streams associated with both these systems, an ∼L* and ∼0.1L* galaxy. Under the combined action of tidal interaction with the cluster potential and of ram pressure by the intra-cluster medium the morphologies and star formation histories of these two galaxies are strongly perturbed. While in the massive system tidal interactions are the dominant effect and are able to produce a sinking of gas towards the galaxy center triggering a strong burst of star formation and changing galaxy's morphology, in the smaller galaxy the effects of gravitation are reduced by ram pressure stripping which blows away the neutral hydrogen from the galactic disk, quenching the star formation activity and transforming a gas rich late type spiral into quiescent disk dominated early type system. This result is a new additional evidence that galaxy mass represents the main driver of galaxy evolution, even during their dive into the harsh cluster environment and can give additional insights on the origin of S0s and dwarf cluster galaxies. © 2007 International Astronomical Union.
• Currie, T., Kenyon, S. J., Rieke, G., Balog, Z., & Bromley, B. C. (2006). Terrestrial zone debris disk candidates in h and x Persei. ASTROPHYSICAL JOURNAL, 663(2), L105-L108.
  More info

  We analyze eight sources with strong mid-infrared excesses in the 13 Myr old double cluster h and x Persei. New optical spectra and broadband spectral energy distributions (SEDs; 0.36-8 mu m) are consistent with cluster membership. We show that the material with Tau similar to 300-400 K and L-d/L-* similar to 10(-4) to 10-(3) produces the excesses in these sources. Optically thick blackbody disk models, including those with large inner holes, do not match the observed SEDs. The SEDs of optically thin debris disks produced from terrestrial planet formation calculations match the observations well. Thus, some h and x Persei stars may have debris from terrestrial zone planet formation.
• Davis, M., Guhathakurta, P., Konidaris, N. P., Newman, J. A., Ashby, M. L., Biggs, A. D., Barmby, P., Bundy, K., Chapman, S. C., Coil, A. L., Conselice, C. J., Cooper, M. C., Croton, D. J., Eisenhardt, P. R., Ellis, R. S., Faber, S. M., Fang, T., Fazio, G. G., Georgakakis, A., , Gerke, B. F., et al. (2006). The All-Wavelength Extended Groth Strip International Survey (AEGIS) data sets. ASTROPHYSICAL JOURNAL, 660(1), L1-L6.
  More info

  In this the first of a series of Letters, we present a panchromatic data set in the Extended Groth Strip region of the sky. Our survey, the All-Wavelength Extended Groth Strip International Survey (AEGIS), aims to study the physical properties and evolutionary processes of galaxies at. It includes the following deep, wide-field imaging data sets: z similar to 1 Chandra/ACIS X-ray, GALEX ultraviolet, CFHT/MegaCam Legacy Survey optical, CFHT/CFH12K optical, Hubble Space Telescope/ACS optical and NICMOS near-infrared, Palomar/WIRC near-infrared, Spitzer/IRAC mid-infrared, Spitzer/MIPS far-infrared, and VLA radio continuum. In addition, this region of the sky has been targeted for extensive spectroscopy using the Deep Imaging Multi-Object Spectrograph (DEIMOS) on the Keck II 10 m telescope. Our survey is compared to other large multiwavelength surveys in terms of depth and sky coverage.
• Dole, H., Lagache, G., Puget, J. -., Caputi, K. I., Fernández-Conde, N., Floc'h, E. L., Papovich, C., Pérez-González, P., Rieke, G. H., & Blaylock, M. (2006). The cosmic infrared background resolved by Spitzer Contributions of mid-infrared galaxies to the far-infrared background. Astronomy and Astrophysics, 451(2), 417-429.
  More info

  Abstract: Aims. We quantify the contributions of 24 μm galaxies to the Far-Infrared (FIR) Background at 70 and 160 μm. We provide new estimates of the Cosmic Infrared Background (CIB), and compare it with the Cosmic Optical Background (COB). Methods. Using Spitzer data at 24, 70 and 160 μm in three deep fields, we stacked more than 19000 MIPS 24 μm sources with S 24 ≥ 60μJy at 70 and 160 μm, and measured the resulting FIR flux densities. Results. This method allows a gain up to one order of magnitude in depth in the FIR. We find that the Mid-Infrared (MIR) 24 μm selected sources contribute to more than 70% of the Cosmic Infrared Background (CIB) at 70 and 160 μm. This is the first direct measurement of the contribution of MIR-selected galaxies to the FIR CIB. Galaxies contributing the most to the total CIB are thus z ∼ 1 luminous infrared galaxies, which have intermediate stellar masses. We estimate that the CIB will be resolved at 0.9 mJy at 70 and 3 mJy at 160 μm. By combining the extrapolation of the 24 pm source counts below analysis, we obtain lower limits of 7.1 ±1.0 and 13.4 ±1.7 nW m-27000 sr-1 for the CIB at 70 and 160 μm, respectively. Conclusions. The MIPS surveys have resolved more than three quarters of the MIR and FIR CIB. By carefully integrating the Extragalactic Background Light (EBL) SED, we also find that the CIB has the same brightness as the COB, around 24 nW m-2 sr-1. The EBL is produced on average by 115 infrared photons for one visible photon. Finally, the galaxy formation and evolution processes emitted a brightness equivalent to 5% of the primordial electromagnetic background (CMB). © ESO 2006.
• Donley, J. L., Rieke, G. H., Perez-Gonzalez, P. G., & Barro, G. (2006). SPITZER'S CONTRIBUTION TO THE AGN POPULATION. ASTROPHYSICAL JOURNAL, 687(1), 111-132.
  More info

  Infrared selection is a potentially powerful way to identify heavily obscured AGNs missed in even the deepest X-ray surveys. Using a 24 mu m-selected sample in GOODS-S, we test the reliability and completeness of three infrared AGN selection methods: (1) IRAC color-color selection, (2) IRAC power-law selection, and (3) IR-excess selection; we also evaluate a number of IR-excess approaches. We find that the vast majority of non-power-law IRAC color-selected AGN candidates in GOODS-S have colors consistent with those of star-forming galaxies. Contamination by star-forming galaxies is most prevalent at low 24 mu m flux densities (similar to 100 mu Jy) and high redshifts (z similar to 2), but the fraction of potential contaminants is still high (similar to 50%) at 500 mu Jy, the highest flux density probed reliably by our survey. AGN candidates selected via a simple, physically motivated power-law criterion ("power-law galaxies," or PLGs), however, appear to be reliable. We confirm that the IR-excess methods successfully identify a number of AGNs, but we also find that such samples may be significantly contaminated by star-forming galaxies. Adding only the secure Spitzer-selected PLG, color-selected, IR-excess, and radio/IR-selected AGN candidates to the deepest X-ray-selected AGN samples directly increases the number of known X-ray AGNs (84) by 54%-77%, and implies an increase to the number of 24 mu m-detected AGNs of 71%-94%. Finally, we show that the fraction of MIR sources dominated by an AGN decreases with decreasing MIR flux density, but only down to f(24 mu m) = 300 mu Jy. Below this limit, the AGN fraction levels out, indicating that a nonnegligible fraction (similar to 10%) of faint 24 mu m sources (the majority of which are missed in the X-ray) are powered not by star formation, but by the central engine. The fraction of all AGNs ( regardless of their MIR properties) exceeds 15% at all 24 mu m flux densities.
• Egami, E., Misselt, K. A., Rieke, G. H., Wise, M. W., Neugebauer, G., Kneib, J. -., Floc'h, E., Smith, G. P., Blaylock, M., Dole, H., Frayer, D. T., Huang, J. -., Krause, O., Papovich, C., Pérez-González, P., & Rigby, J. R. (2006). Spitzer observations of the brightest galaxies in x-ray-luminous clusters. Astrophysical Journal Letters, 647(2 I), 922-931.
  More info

  Abstract: We have studied the infrared properties of the brightest cluster galaxies (BCGs) located in the cores of X-ray-luminous clusters at 0.15 < z < 0.35. The majority of the BCGs are not particularly infrared-luminous compared with other massive early-type galaxies, suggesting that the cluster environment has little influence on the infrared luminosities of the BCGs. The exceptions, however, are the BCGs in the three X-ray-brightest clusters in the sample, A1835, Z3146, and A2390. These BCGs have a prominent far-infrared peak in their spectral energy distributions (SEDs), and two of them (those in A1835 and Z3146) can be classified as luminous infrared galaxies (LIRGs: LIR > 10 11 L⊙). Although radio AGNs (active galactic nuclei) are found to be prevalent among the BCGs, the infrared luminosities of these three BCGs, judged from the infrared SED signatures, are likely to be powered by star formation. Considering the overall trend that clusters with shorter radiative gas cooling times harbor more infraredluminous BCGs, the enhanced star formation may be caused by the cooling cluster gas accreting onto the BCGs. © 2006. The American Astronomical Society. All rights reserved.
• Egami, E., Misselt, K. A., Rieke, G. H., Wise, M. W., Neugebauer, G., Kneib, J. -., Le Floc'h, E., Smith, G. P., Blaylock, M., Dole, H., Frayer, D. T., Huang, J. -., Krause, O., Papovich, C., Perez-Gonzalez, P. G., & Rigby, J. R. (2006). Spitzer observations of the brightest galaxies in X-ray-luminous clusters. ASTROPHYSICAL JOURNAL, 647(2), 922-933.
  More info

  We have studied the infrared properties of the brightest cluster galaxies (BCGs) located in the cores of X-ray-luminous clusters at 0: 15 < z < 0: 35. The majority of the BCGs are not particularly infrared-luminous compared with other massive early-type galaxies, suggesting that the cluster environment has little influence on the infrared luminosities of the BCGs. The exceptions, however, are the BCGs in the three X-ray-brightest clusters in the sample, A1835, Z3146, and A2390. These BCGs have a prominent far-infrared peak in their spectral energy distributions (SEDs), and two of them ( those in A1835 and Z3146) can be classified as luminous infrared galaxies (LIRGs: L-IR > 10(11) L-circle dot). Although radio AGNs ( active galactic nuclei) are found to be prevalent among the BCGs, the infrared luminosities of these three BCGs, judged from the infrared SED signatures, are likely to be powered by star formation. Considering the overall trend that clusters with shorter radiative gas cooling times harbor more infrared-luminous BCGs, the enhanced star formation may be caused by the cooling cluster gas accreting onto the BCGs.
• Egami, E., Rieke, G. H., Fadda, D., & Hines, D. C. (2006). A large mass of H₂ in the brightest cluster galaxy in Zwicky 3146. Astrophysical Journal Letters, 652(1 II), L21-L24.
  More info

  Abstract: We present the Spitzer/IRS mid-infrared spectrum of the infrared-luminous (LIR = 4 × 1011 L⊙ brightest cluster galaxy (BCG) in the X-ray-luminous cluster Zwicky 3146 (Z3146; z = 0.29). The spectrum shows strong aromatic emission features, indicating that the dominant source of the infrared luminosity is star formation. The most striking feature of the spectrum, however, is the exceptionally strong molecular hydrogen (H 2) emission lines, which seem to be shock-excited. The line luminosities and inferred warm H2 gas mass (∼10 M⊙) are 6 times larger than those of NGC 6240, the most H 2-luminous galaxy at z =s 0.05. Together with the large amount of cold H2 detected previously (∼1011 M⊙), this indicates that the Z3146 BCG contains disproportionately large amounts of both warm and cold H2 gas for its infrared luminosity, which may be related to the intracluster gas cooling process in the cluster core. © 2006. The American Astronomical Society. All rights reserved.
• Engelbracht, C. W., Kundurthy, P., Gordon, K. D., Rieke, G. H., Kennicutt, R. C., Smith, J. -., Regan, M. W., Makovoz, D., Sosey, M., Draine, B. T., Helou, G., Armus, L., Calzetti, D., Meyer, M., Bendo, G. J., Walter, F., Hollenbach, D., Cannon, J. M., Murphy, E. J., , Dale, D. A., et al. (2006). Extended mid-infrared aromatic feature emission in M82. Astrophysical Journal Letters, 642(2 II), L127-L132.
  More info

  Abstract: We present new images (ground-based optical and mid-infrared [MIR] from the Spitzer Space Telescope) and spectra (from Spitzer) of the archetypal starburst galaxy M82. The Spitzer data show that the MIR emission extends at least 6 kpc along the minor axis of the galaxy. We use the optical and infrared data to demonstrate that the extended emission is dominated by emission from dust. The colors of the MIR emission and the spectra indicate that there is a strong component of aromatic feature emission (the MIR features commonly attributed to poly cyclic aromatic hydrocarbons). The dust continuum and aromatic feature emission are both strong in the well-known superwind region of this galaxy; clearly, the carrier of the aromatic features can survive in close proximity to the wind, far from the plane of the galaxy. We also see significant emission by dust well outside the superwind region, providing the clearest picture to date of the dust distribution in the halo of this galaxy. © 2006. The American Astronomical Society. All rights reserved.
• Gardner, J. P., Mather, J. C., Clampin, M., Doyon, R., Greenhouse, M. A., Hammel, H. B., Hutchings, J. B., Jakobsen, P., Lilly, S. J., Long, K. S., Lunine, J. I., McCaughrean, M. J., Mountain, M., Nella, J., Rieke, G. H., Rieke, M. J., Rix, H., Smith, E. P., Sonneborn, G., , Stiavelli, M., et al. (2006). Science with the James Webb Space Telescope. Proceedings of SPIE - The International Society for Optical Engineering, 6265 I.
  More info

  Abstract: The scientific capabilities of the James Webb Space Telescope (JWST) fall into four themes. The End of the Dark Ages: First Light and Reionization theme seeks to identify the first luminous sources to form and to determine the ionization history of the universe. The Assembly of Galaxies theme seeks to determine how galaxies and the dark matter, gas, stars, metals, morphological structures, and active nuclei within them evolved from the epoch of reionization to the present. The Birth of Stars and Protoplanetary Systems theme seeks to unravel the birth and early evolution of stars, from infall onto dust-enshrouded protostars, to the genesis of planetary systems. Planetary Systems and the Origins of Life theme seeks to determine the physical and chemical properties of planetary systems around nearby stars and of our own, and investigate the potential for life in those systems. To enable these for science themes, JWST will be a large (6.5m) cold (50K) telescope with four instruments, capable of imaging and spectroscopy from 0.6 to 29 microns wavelength.
• Gardner, J. P., Mather, J. C., Clampin, M., Doyon, R., Greenhouse, M. A., Hammel, H. B., Hutchings, J. B., Jakobsen, P., Lilly, S. J., Long, K. S., Lunine, J. I., McCaughrean, M. J., Mountain, M., Nella, J., Rieke, G. H., Rieke, M. J., Rix, H., Smith, E. P., Sonneborn, G., , Stiavelli, M., et al. (2006). The James Webb space telescope. Space Science Reviews, 123(4), 485-606.
  More info

  Abstract: The James Webb Space Telescope (JWST) is a large (6.6 m), cold (
• Gaspar, A., Su, K. Y., Rieke, G. H., Balog, Z., Kamp, I., Martinez-Galarza, J. R., & Stapelfeldt, K. (2006). Modeling the infrared bow shock at delta Velorum: Implications for studies of debris disks and lambda Bootis stars. ASTROPHYSICAL JOURNAL, 672(2), 974-983.
  More info

  We have discovered a bow shock shaped mid-infrared excess region in front of delta Velorum using 24 mu m observations obtained with the Multiband Imaging Photometer for Spitzer (MIPS). Although the bow shock morphology was only detected in the 24 mu m observations, its excess was also resolved at 70 mu m. We show that the stellar heating of an ambient interstellar medium (ISM) cloud can produce the measured flux. Since delta Velorum was classified as a debris disk star previously, our discovery may call into question the same classification of other stars. We model the interaction of the star and ISM, producing images that show the same geometry and surface brightness as is observed. The modeled ISM is similar to 15 times overdense relative to the average Local Bubble value, which is surprising considering the close proximity (24 pc) of delta Velorum. The abundance anomalies of lambda Bootis stars have been previously explained as arising from the same type of interaction of stars with the ISM. Low-resolution optical spectra of delta Velorum show that it does not belong to this stellar class. The star therefore is an interesting testbed for the ISM accretion theory of the lambda Bootis phenomenon.
• Gordon, K. D., Bailin, J., Engelbracht, C. W., Rieke, G. H., Misselt, K. A., Latter, W. B., Young, E. T., Ashby, M. L., Barmby, P., Gibson, B. K., Hines, D. C., Hinz, J., Krause, O., Levine, D. A., Marleau, F. R., Noriega-Crespo, A., Stolovy, S., Thilker, D. A., & Werner, M. W. (2006). Spitzer mips infrared imaging of M31: Further evidence for a spiral-ring composite structure. Astrophysical Journal Letters, 638(2 II), L87-L92.
  More info

  Abstract: New images of M31 at 24, 70, and 160 μm taken with the Multiband Imaging Photometer for Spitzer (MIPS) reveal the morphology of the dust in this galaxy. This morphology is well represented by a composite of two logarithmic spiral arms and a circular ring (radius ∼10 kpc) of star formation offset from the nucleus. The two spiral arms appear to start at the ends of a bar in the nuclear region and extend beyond the star-forming ring. As has been found in previous work, the spiral arms are not continuous, but composed of spiral segments. The star-forming ring is very circular except for a region near M32 where it splits. The lack of well-defined spiral arms and the prominence of the nearly circular ring suggest that M31 has been distorted by interactions with its satellite galaxies. Using new dynamical simulations of M31 interacting with M32 and NGC 205, we find that, qualitatively, such interactions can produce an offset, split ring like that seen in the MIPS images. © 2006. The American Astronomical Society. All rights reserved.
• Gorlova, N., Lobel, A., Burgasser, A. J., Rieke, G. H., Ilyin, I., & Stauffer, J. R. (2006). On the CO near-infrared band and the line-splitting phenomenon in the yellow hypergiant ρ cassiopeiae. Astrophysical Journal Letters, 651(2 I), 1130-1150.
  More info

  Abstract: We report on multiepoch optical and near-infrared spectroscopy around the first-overtone rovibrational band of CO in the pulsating yellow hypergiant ρ Cas, one of the most massive stars in the Galaxy and a candidate SN II progenitor. We argue that the double cores of the CO absorption lines, which have previously been attributed to separate circumstellar shells expelled during its recurrent outbursts, result in fact from a superposition of a wide absorption line and a narrow central emission line. The CO line doubling returns over subsequent pulsation cycles, where the superposed line emission assumes its largest intensity near phases of maximum light. We find that the morphology and behavior of the CO band closely resemble the remarkable "line-splitting phenomenon" also observed in optical low-excitation atomic lines. Based on radiative transport calculations, we present a simplified model of the near-infrared CO emission emerging from cooler atmospheric layers in the immediate vicinity of the photosphere. We speculate that the kinetic temperature minimum in our model results from a periodic pulsation-driven shock wave. We further discuss a number of alternative explanations for the origin of the ubiquitous emission-line spectrum, possibly due to a quasi-chromosphere or a steady shock wave at the interface of a fast expanding wind and the interstellar medium. We present a number of interesting spectroscopic similarities between ρ Cas and other types of cool variable supergiants, such as the RV Tau and R CrB stars. We further propose a possibly common mechanism for the enigmatic outburst behavior of these luminous pulsating cool stars. © 2006. The American Astronomical Society. All rights reserved.
• Gorlova, N., Rieke, G. H., Muzerolle, J., Stauffer, J. R., Siegler, N., Young, E. T., & Stansberry, J. H. (2006). Spitzer 24 μm survey of debris disks in the pleiades. Astrophysical Journal Letters, 649(2 I), 1028-1042.
  More info

  Abstract: We performed a 24 μm 2° × 1° survey of the Pleiades cluster, using the MIPS instrument on Spitzer. Fifty-four members ranging in spectral type from B8 to K6 show 24 μm fluxes consistent with bare photospheres. All Be stars show excesses attributed to free-free emission in their gaseous envelopes. Five early-type stars and four solar-type stars show excesses indicative of debris disks. We find a debris disk fraction of 25% for B-A members and 10% for F-K3 ones. These fractions appear intermediate between those for younger clusters and for the older field stars. They indicate a decay with age of the frequency of the dust production events inside the planetary zone, with similar timescales for solar-mass stars as have been found previously for A stars. © 2006. The American Astronomical Society. All rights reserved.
• Hines, D. C., Krause, O., Rieke, G. H., Fan, X., Blaylock, M., & Neugebauer, G. (2006). Spitzer observations of high-redshift QSOs. Astrophysical Journal Letters, 641(2 II), L85-L88.
  More info

  Abstract: We have observed 13 z ≥ 4.5 QSOs using the Multiband Imaging Photometer for Spitzer, nine of which were also observed with the Infrared Array Camera. The observations probe rest wavelengths ∼0.6-4.3 μm, bracketing the local minimum in QSO spectral energy distributions (SEDs) between strong optical emission associated directly with accretion processes and thermal emission from hot dust heated by the central engine. The new Spitzer photometry combined with existing measurements at other wavelengths shows that the SEDs of high-redshift QSOs (z ≥ 4.5) do not differ significantly from typical QSOs of similar luminosity at lower redshifts (z ≲ 2). This behavior supports other indications that all the emission components and physical structures that characterize QSO activity can be established by z = 6.4. The similarity also suggests that some QSOs at high redshift will be very difficult to identify because they are viewed along dust-obscured sight lines. © 2006. The American Astronomical Society. All rights reserved.
• Hinz, J. L., & Rieke, G. H. (2006). Dynamical masses in luminous infrared galaxies. Astrophysical Journal Letters, 646(2 I), 872-880.
  More info

  Abstract: We have studied the dynamics and masses of a sample of 10 nearby luminous and ultraluminous infrared galaxies (LIRGs and ULIRGs, respectively) using 2.3 μm 12CO-absorption line spectroscopy and near-infrared H- and Ks-band imaging. By combining velocity dispersions derived from the spectroscopy, disk scale lengths obtained from the imaging, and a set of likely model density profiles, we calculate dynamical masses for each LIRG. For the majority of the sample, it is difficult to reconcile our mass estimates with the large amounts of gas derived from millimeter observations and from a standard conversion between 12CO emission and H2 mass. Our results imply that LIRGs do not have huge amounts of molecular gas (10 10-1011 M⊙) at their centers and support previous indications that the standard conversion of 12CO to H 2 probably overestimates the gas masses and cannot be used in these environments. This in turn suggests much more modest levels of extinction in the near-infrared for LIRGs than previously predicted (Av ∼ 10-20 vs. Av ∼ 100-1000). The lower gas mass estimates indicated by our observations imply that the star formation efficiency in these systems is very high and is triggered by cloud-cloud collisions, shocks, and winds rather than by gravitational instabilities in circumnuclear gas disks. © 2006. The American Astronomical Society. All rights reserved.
• Hinz, J. L., Misselt, K., Rieke, M. J., Rieke, G. H., Smith, P. S., Blaylock, M., & Gordon, K. D. (2006). Extended emission by dust in the dwarf galaxy UGC 10445. ASTROPHYSICAL JOURNAL, 651(2), 874-881.
  More info

  We present Spitzer Space Telescope images of the isolated dwarf galaxy UGC 10445. The galaxy is detected at all photometric bands (3.6-160 mu m), as well as in the Multiband Imaging Photometer for Spitzer (MIPS) spectral energy distribution mode (55-95 mu m). We derive a star formation rate of 0.25 M(circle dot)yr(-1), based on H alpha and infrared flux densities. There is over 10(6) M-circle dot of cold dust (T similar to 18 K) in the galaxy, represented by 160 mu m emission, which extends to a larger radius than the ultraviolet (UV), optical, and near-infrared light. Such extended emission has been seen previously only in dwarf galaxies in cluster environments. We suggest that the source of heating for this dust is UV light, originating in star-forming complexes. To produce the large quantity of dust requires a higher rate of star formation in the past than is currently observed.
• Hinz, J. L., Misselt, K., Rieke, M. J., Rieke, G. H., Smith, P. S., Blaylock, M., & Gordon, K. D. (2006). Extended emission by dust in the dwarf galaxy UGC 10445. Astrophysical Journal Letters, 651(2 I), 874-881.
  More info

  Abstract: We present Spitzer Space Telescope images of the isolated dwarf galaxy UGC 10445. The galaxy is detected at all photometric bands (3.6-160 μm), as well as in the Multiband Imaging Photometer for Spitzer (MIPS) spectral energy distribution mode (55-95 μm). We derive a star formation rate of 0.25 M ⊙ yr-1, based on Hα and infrared flux densities. There is over 106M⊙ of cold dust (T ∼ 18 K) in the galaxy, represented by 160 μm emission, which extends to a larger radius than the ultraviolet (UV), optical, and near-infrared light. Such extended emission has been seen previously only in dwarf galaxies in cluster environments. We suggest that the source of heating for this dust is UV light, originating in star-forming complexes. To produce the large quantity of dust requires a higher rate of star formation in the past than is currently observed. © 2006. The American Astronomical Society. All rights reserved.
• Hinz, J. L., Rieke, M. J., Rieke, G. H., Willmer, C. N., Misselt, K., Engelbracht, C. W., & Blaylock, M. (2006). Spitzer observations of low-luminosity isolated and low surface brightness galaxies. ASTROPHYSICAL JOURNAL, 663(2), 895-907.
  More info

  We examine the infrared properties offive low surface brightness galaxies ( LSBGs) and compare them with related but higher surface brightness galaxies, using Spitzer Space Telescope images and spectra. All the LSBGs are detected in the 3.6 and 4.5 mu m bands, representing the stellar population. All but one are detected at 5.8 and 8.0 mu m, revealing emission from hot dust and aromatic molecules, although many are faint or pointlike at these wavelengths. Detections of LSBGs at the far- infrared wavelengths of 24, 70, and 160 mu m are varied in morphology and brightness, with only two detections at 160 mu m, resulting in highly varied spectral energy distributions. Consistent with previous expectations for these galaxies, we find that detectable dust components exist for only some LSBGs, with the strength of dust emission dependent on the existence of bright star- forming regions. However, the far- infrared emission may be relatively weak compared with normal star- forming galaxies.
• Ivison, R. J., Greve, T. R., Dunlop, J. S., Peacock, J. A., Egami, E., Smail, I., Ibar, E., van Kampen, E., Aretxaga, I., Babbedge, T., Biggs, A. D., Blain, A. W., Chapman, S. C., Clements, D. L., Coppin, K., Farrah, D., Halpern, M., Hughes, D. H., Jarvis, M. J., , Jenness, T., et al. (2006). The SCUBA HAlf degree extragalactic survey - III. Identification of radio and mid-infrared counterparts to submillimetre galaxies. MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, 380(1), 199-228.
  More info

  Determining an accurate position for a submillimetre (submm) galaxy (SMG) is the crucial step that enables us to move from the basic properties of an SMG sample - source counts and 2D clustering - to an assessment of their detailed, multiwavelength properties, their contribution to the history of cosmic star formation and their links with present-day galaxy populations. In this paper, we identify robust radio and/or infrared (IR) counterparts, and hence accurate positions, for over two-thirds of the SCUBA HAlf-Degree Extragalactic Survey (SHADES) Source Catalogue, presenting optical, 24-mu m and radio images of each SMG. Observed trends in identification rate have given no strong rationale for pruning the sample. Uncertainties in submm position are found to be consistent with theoretical expectations, with no evidence for significant additional sources of error. Employing the submm/radio redshift indicator, via a parametrization appropriate for radio-identified SMGs with spectroscopic redshifts, yields a median redshift of 2.8 for the radio-identified subset of SHADES, somewhat higher than the median spectroscopic redshift. We present a diagnostic colour-colour plot, exploiting Spitzer photometry, in which we identify regions commensurate with SMGs at very high redshift. Finally, we find that significantly more SMGs have multiple robust counterparts than would be expected by chance, indicative of physical associations. These multiple systems are most common amongst the brightest SMGs and are typically separated by 2-6 arcsec, similar to 15-20/sin i kpc at z similar to 2, consistent with early bursts seen in merger simulations.
• Jiang, L., Fan, X., Hines, D. C., Shi, Y., Vestergaard, M., Bertoldi, F., Brandt, W. N., Carilli, C. L., Cox, P., Floc'h, E. L., Pentericci, L., Richards, G. T., Rieke, G. H., Schneider, D. P., Strauss, M. A., Walter, F., & Brinkmann, J. (2006). Probing the evolution of infrared properties of z ∼ 6 quasars: Spitzer observations. Astronomical Journal, 132(5), 2127-2134.
  More info

  Abstract: We present Spitzer observations of 13 z ∼ 6 quasars using the Infrared Array Camera (IRAC) and Multiband Imaging Photometer for Spitzer (MIPS). All the quasars except SDSS J000552.34-000655.8 (SDSS J0005-0006) were detected with high signal-to-noise ratio in the four IRAC channels and the MIPS 24 μm band, while SDSS J0005-0006 was marginally detected in the IRAC 8.0 μm band and not detected in the MIPS 24 μm band. We find that most of these quasars have prominent emission from hot dust, as evidenced by the observed 24 μm fluxes. Their spectral energy distributions (SEDs) are similar to those of low-redshift quasars at rest frame 0.15-3.5 μm, suggesting that accretion disks and hot-dust structures for these sources have already reached maturity. However, SDSS J0005-0006 has an unusual SED that lies significantly below low-redshift SED templates at rest frame 1 and 3.5 μm and thus shows a strong near-IR (NIR) deficit and no hot-dust emission. Type I quasars with extremely small NIR-to-optical flux ratios such as SDSS J0005-0006 are not found in low-redshift quasar samples, indicating that SDSS J0005-0006 has different dust properties at high redshift. We combine the Spitzer observations with X-ray, UV/optical, millimeter/submillimeter, and radio observations to determine bolometric luminosities for all the quasars. We find that the four quasars with central black hole mass measurements have Eddington ratios of order unity. © 2006. The American Astronomical Society. All rights reserved.
• Kenworthy, M., Hofmann, K., Close, L., Hinz, P., Mamajek, E., Schertl, D., Weigelt, G., Angel, R., Balega, Y., Hinz, J., & Rieke, G. (2006). Gliese 569B: A young multiple brown dwarf system?. ASTROPHYSICAL JOURNAL, 554(1), L67-L70.
  More info

  The nearby late M star Gliese 569B was recently found by adaptive optics imaging to be a double with separation similar to1 AU. To explore the orbital motion and masses, we have undertaken a high-resolution (similar to0"05) astrometric study. Images were obtained over 1.5 yr with bispectrum speckle interferometry at the 6.5 m Multiple Mirror Telescope (MMT) and 6 m Special Astrophysical Observatory telescope. Our data show motion corresponding to more than half the orbital period and constrain the total mass to be greater than 0.115 M-circle dot, with a most probable value of 0.145 M-circle dot. Higher masses cannot be excluded without more extended observations, but from statistical analysis we find an 80% probability that the total mass is less than 0.21 M-circle dot.
• Lada, C. J., Muench, A. A., Luhman, K. L., Allen, L., Hartmann, L., Megeath, T., Myers, P., Fazio, G., Wood, K., Muzerolle, J., Rieke, G., Siegler, N., & Young, E. (2006). Spitzer observations of IC 348: The disk population at 2-3 million years. Astronomical Journal, 131(3), 1574-1607.
  More info

  Abstract: We present near- and mid-infrared photometry obtained with the Spitzer Space Telescope of ~300 known members of the IC 348 cluster. We merge this photometry with existing ground-based optical and near-infrared photometry in order to construct optical-infrared spectral energy distributions (SEDs) for all the cluster members and present a complete atlas of these SEDs. We employ these observations to investigate both the frequency and nature of the circumstellar disk population in the cluster. The Spitzer observations span a wavelength range between 3.6 and 24 μm, corresponding to disk radii of ∼0.1 -5 AU from the central star. The observations are sufficiently sensitive to enable the first detailed measurement of the disk frequency for very low mass stars at the peak of the stellar initial mass function. Using measurements of infrared excess between 3.6 and 8.0 μm, we find the total frequency of disk-bearing stars in the cluster to be 50% ± 6%. However, only 30% ± 4% of the member stars are surrounded by optically thick, primordial disks, while the remaining disk-bearing stars are surrounded by what appear to be optically thin, anemic disks. Both these values are below previous estimates for this cluster. The disk fraction appears to be a function of spectral type and stellar mass. The fraction of stars with optically thick disks ranges from 11% ± 8% for stars earlier than K6 to 47% ± 12% for K6-M2 stars to 28% ± 5% for M2-M6 stars. The disk longevity and thus conditions for planet formation appear to be most favorable for the K6-M2 stars, which are objects of comparable mass to the Sun for the age of this cluster. The optically thick disks around later type (>M4) stars appear to be less flared than the disks around earlier type stars. This may indicate a greater degree of dust settling and a more advanced evolutionary state for the late M disk population. Finally, we find that the presence of an optically thick dust disk is correlated with gaseous accretion, as measured by the strength of Hα emission. A large fraction of stars classified as classical T Tauri stars possess robust, optically thick disks, and very few such stars are found to be diskless. The majority (64%) of stars classified as weak-lined T Tauri stars are found to be diskless. However, a significant fraction (12%) of these stars are found to be surrounded by thick, primordial disks. These results suggest that it is more likely for dust disks to persist in the absence of active gaseous accretion than for active accretion to persist in the absence of dusty disks. © 2006. The American Astronomical Society. All rights reserved.
• Lada, C., Muench, A., Luhman, K., Allen, L., Hartmann, L., Megeath, T., Myers, P., Fazio, G., Wood, K., Muzerolle, J., Rieke, G., Siegler, N., & Young, E. (2006). Spitzer observations of IC 348: The disk population at 2-3 million years. ASTRONOMICAL JOURNAL, 131(3), 1574-1607.
  More info

  We present near- and mid- infrared photometry obtained with the Spitzer Space Telescope of similar to 300 known members of the IC 348 cluster. We merge this photometry with existing ground- based optical and near- infrared photometry in order to construct optical- infrared spectral energy distributions ( SEDs) for all the cluster members and present a complete atlas of these SEDs. We employ these observations to investigate both the frequency and nature of the circumstellar disk population in the cluster. The Spitzer observations span a wavelength range between 3.6 and 24 mu m, corresponding to disk radii of similar to 0.1 - 5 AU from the central star. The observations are sufficiently sensitive to enable the first detailed measurement of the disk frequency for very low mass stars at the peak of the stellar initial mass function. Using measurements of infrared excess between 3.6 and 8.0 mu m, we find the total frequency of disk-bearing stars in the cluster to be 50% +/- 6%. However, only 30% +/- 4% of the member stars are surrounded by optically thick, primordial disks, while the remaining disk- bearing stars are surrounded by what appear to be optically thin, anemic disks. Both these values are below previous estimates for this cluster. The disk fraction appears to be a function of spectral type and stellar mass. The fraction of stars with optically thick disks ranges from 11% +/- 8% for stars earlier than K6 to 47% +/- 12% for K6 - M2 stars to 28% +/- 5% for M2 - M6 stars. The disk longevity and thus conditions for planet formation appear to be most favorable for the K6 - M2 stars, which are objects of comparable mass to the Sun for the age of this cluster. The optically thick disks around later type (> M4) stars appear to be less flared than the disks around earlier type stars. This may indicate a greater degree of dust settling and a more advanced evolutionary state for the late M disk population. Finally, we find that the presence of an optically thick dust disk is correlated with gaseous accretion, as measured by the strength of H alpha emission. A large fraction of stars classified as classical T Tauri stars possess robust, optically thick disks, and very few such stars are found to be diskless. The majority ( 64%) of stars classified as weak- lined T Tauri stars are found to be diskless. However, a significant fraction ( 12%) of these stars are found to be surrounded by thick, primordial disks. These results suggest that it is more likely for dust disks to persist in the absence of active gaseous accretion than for active accretion to persist in the absence of dusty disks.
• Laurent, G. T., Glenn, J., Egami, E., Rieke, G. H., Ivison, R. J., Yun, M. S., Aguirre, J. E., Maloney, P. R., & Haig, D. (2006). The bolocam 1.1 mm lockman hole galaxy survey: Sharc II 350 μm photometry and implications for spectral models, dust temperatures, and redshift estimation. Astrophysical Journal Letters, 643(1 I), 38-58.
  More info

  Abstract: We present 350 μm photometry of all 17 galaxy candidates in the Lockman Hole detected in a 1.1 mm Bolocam survey. Several of the galaxies were previously detected at 850 μm, at 1.2 mm, in the infrared by Spitzer, and in the radio. Nine of the Bolocam galaxy candidates were detected at 350 μm, and two new candidates were serendipitously detected at 350 μm (bringing the total in the literature detected in this way to three). Five of the galaxies have published spectroscopic redshifts, enabling investigation of the implied temperature ranges and a comparison of photometric redshift techniques. For z ≈ 2.5 thermally emitting galaxies, λ = 350 μm lies near the spectral energy distribution peak. Thus, luminosities can be measured without extrapolating to the peak from detection wavelengths of λ ≥ 850 μm. Characteristically, the galaxy luminosities lie in the range 1.0-1.2 × 1013 L⊙, with dust temperatures in the range 40-70 K, depending on the choice of spectral index and wavelength of unit optical depth. The implied dust masses are (3-5) × 108 M⊙ We find that the far-infrared to radio relation for star-forming ULIRGs systematically overpredicts the radio luminosities and overestimates redshifts on the order of Δz ≈ s 1, whereas redshifts based on either submillimeter data alone or the 1.6 μm stellar bump and PAH features are more accurate. © 2006. The American Astronomical Society. All rights reserved.
• Luhman, K., Rieke, G., Lada, C., & Lada, E. (2006). Low-mass star formation and the initial mass function in IC 348. ASTROPHYSICAL JOURNAL, 508(1), 347-369.
  More info

  We have performed deep infrared and optical spectroscopy of virtually the entire stellar population within the 5' x 5' core of IC 348, measuring K (2.2 mu m) band and optical spectral types that are in good agreement. We have also identified several sources that may be substellar depending on the choice of temperature scales and evolutionary tracks, with three particularly late-type objects (M7.5-M8) that are likely bonafide brown dwarfs. In conjunction with the theoretical evolutionary tracks of D'Antona & Mazzitelli, the H-R diagram indicates a spread in ages from 0.5 to 10 Myr, with most of the core star formation occurring in the last 3 Myr. Using K-band imaging to provide a completeness correction to the spectroscopic sample, we arrive at an initial mass function (IMF) that matches that of Miller & Scale from 0.25 to 3 M.. The IMF appears to fall slowly from 0.25 M. to the hydrogen burning limit, slightly below the IMF of Miller & Scale, which is flat in logarithmic units (as compared to slopes of similar to 1.35 and -2.6 for Salpeter and Scalo). Correction for unresolved binary systems could steepen the slope of the low-mass IMF by about 0.5, which implies a single-star IMF that is roughly flat below 0.25 M,. The low-mass IMF in IC 348 is similar to that derived in studies of most other young clusters, implying that the IMF does not vary dramatically among clusters of differing environments; however, the derived IMF is dependent on the evolutionary tracks and the detailed shape of the IMF should be viewed with caution until these models are tested against observations, particularly at low masses (1 Angstrom) emission or K-band continuum veiling (r(K) greater than or equal to 0.5). Since no sources older than 3 Myr show evidence for massive disks, disk lifetimes in the core of IC 348 appear to be shorter than those observed in Taurus or in the outer regions of IC 348.
• Marleau, F. R., Noriega-Crespo, A., Misselt, K. A., Gordon, K. D., Engelbracht, C. W., Rieke, G. H., Barmby, P., Willner, S. P., Mould, J., Gehrz, R. D., & Woodward, C. E. (2006). Mapping and mass measurement of the cold dust in NGC 205 with Spitzer. Astrophysical Journal Letters, 646(2 I), 929-938.
  More info

  Abstract: We present observations at 3.6, 4.5, 5.8, 8, 24, 70, and 160 μm of NGC 205, the dwarf elliptical companion of M31, obtained with the Spitzer Space Telescope. The point-source-subtracted images at 8 and 24 μm display a complex and fragmented infrared emission coming from both very small dust particles and larger grains. The extended dust emission is spatially concentrated in three main emission regions, seen at all wavelengths from 8 to 160 μm. These regions lie approximately along NGC 205's semimajor axis and range from ∼100 to 300 pc in size. On the basis of our mid-/far-infrared flux density measurements alone, we derive a total dust mass estimate on the order of 3.2 × 104 M⊙, mainly at a temperature of ∼20 K. The gas mass associated with this component matches the predicted mass returned by the dying stars from the last burst of star formation in NGC 205 (∼0.5 Gyr ago). Analysis of the Spitzer data combined with previous 1.1 mm observations over a small central or "Core" region (18″ diameter) suggests the presence of very cold (T ∼ 12 K) dust and a dust mass about 16 times higher than is estimated from the Spitzer measurements alone. Assuming a gas-to-dust mass ratio of 100, these two data sets, i.e., with and without the millimeter observations, suggest a total gas mass in the range from 3.2 × 106 to 5 × 107 M⊙. © 2006. The American Astronomical Society. All rights reserved.
• Murphy, E. J., Braun, R., Helou, G., Armus, L., Kenney, J. D., Gordon, K. D., Bendo, G. J., Dale, D. A., Walter, F., Oosterloo, T. A., Kennicutt Jr., R. C., Calzetti, D., Cannon, J. M., Draine, B. T., Engelbracht, C. W., Hollenbach, D. J., Jarrett, T. H., Kewley, L. J., Leitherer, C., , Li, A., et al. (2006). An initial look at the far-infrared-radio correlation within nearby star-forming galaxies using the spitzer space telescope. Astrophysical Journal Letters, 638(1 I), 157-175.
  More info

  Abstract: We present an initial look at the far-infrared-radio correlation within the star-forming disks of four nearby, nearly face-on galaxies (NGC 2403, NGC 3031, NGC 5194, and NGC 6946). Using Spitzer MIPS imaging, observed as part of the Spitzer Infrared Nearby Galaxies Survey (SINGS), and Westerbork Synthesis Radio Telescope (WSRT) radio continuum data, taken for the WSRT SINGS radio continuum survey, we are able to probe variations in the logarithmic 24 μm/22 cm (q24) and 70 μm/22 cm (q70) surface brightness ratios across each disk at subkiloparsec scales. We find general trends of decreasing q24 and q70 with declining surface brightness and with increasing radius. The residual dispersion around the trend of q24 and q70 versus surface brightness is smaller than the residual dispersion around the trend of q24 and q70 versus radius, on average by ∼0.1 dex, indicating that the distribution of star formation sites is more important in determining the infrared/radio disk appearance than the exponential profiles of disks. We have also performed preliminary phenomenological modeling of cosmic-ray electron (CR electron) diffusion using an image-smearing technique and find that smoothing the infrared maps improves their correlation with the radio maps. We find that exponential smoothing kernels work marginally better than Gaussian kernels, independent of projection for these nearly face-on galaxies. This result suggests that additional processes besides simple random walk diffusion in three dimensions must affect the evolution of CR electrons. The best-fit smoothing kernels for the two less active star-forming galaxies (NGC 2403 and NGC 3031) have much larger scale lengths than those of the more active star-forming galaxies (NGC 5194 and NGC 6946). This difference may be due to the relative deficit of recent CR electron injection into the interstellar medium for the galaxies that have largely quiescent disks. © The American Astronomical Society. All rights reserved.
• Muzerolle, J., Adame, L., D'Alessio, P., Calvet, N., Luhman, K. L., Muench, A. A., Lada, C. J., Rieke, G. H., Siegler, N., Trilling, D. E., Young, E. T., Allen, L., Hartmann, L., & Megeath, S. T. (2006). 24 μm Detections of circum(sub)stellar disks in IC 348: Grain growth and inner holes?. Astrophysical Journal Letters, 643(2 I), 1003-1010.
  More info

  Abstract: We present observations of six late-type members of the young cluster IC 348 detected at 24 μm with the Multiband Imaging Photometer for Spitzer (MIPS). At least four of the objects are probably substellar. Combining these data with ground-based optical and near-infrared photometry and complementary observations with the Infrared Array Camera (IRAC), we have modeled the spectral energy distributions using detailed models of irradiated accretion disks. We are able to fit the observations with models using a range of maximum grain sizes from ISM-type dust to grains as large as 1 mm. Two objects show a lack of excess emission at wavelengths shortward of 5.8-8 μm but significant excess at longer wavelengths, indicative of large optically thin or evacuated inner holes. Our models indicate an inner hole of radius ∼0.5-0.9 AU for the brown dwarf L316; this is the first brown dwarf with evidence for an AU-scale inner disk hole. We examine several possible mechanisms for the inner disk clearing in this case, including photoevaporation and planet formation. © 2006. The American Astronomical Society. All rights reserved.
• Papovich, C., Cool, R., Eisenstein, D., Floc'h, E. L., Xiaohui, F. A., Kennicutt Jr., R. C., Smith, J. D., Rieke, G. H., & Vestergaard, M. (2006). An MMT hectospec redshift survey of 24 μm sources in the SPITZER First Look Survey. Astronomical Journal, 132(1), 231-241.
  More info

  Abstract: We present a spectroscopic survey using the MMT Hectospec fiber spectrograph of 24 μm sources selected with the Spitzer Space Telescope in the Spitzer First Look Survey. We report 1296 new redshifts for 24 μm sources, including 599 with fν(24 μm) ≥ 1 mJy. Combined with 291 additional redshifts for sources from the Sloan Digital Sky Survey (SDSS), our observing program was highly efficient and is ∼90% complete for i ≤ 21 mag and fν(24 μm) ≥ 1 mJy and 35% complete for i ≤ 20.5 mag and 0.3 mJy ≤ fν(24 μm) < 1.0 mJy. Our Hectospec survey includes 1078 and 168 objects spectroscopically classified as galaxies and QSOs, respectively. Combining the Hectospec and SDSS samples, we find 24 μm-selected galaxies to z gal ≤ 0.98 and QSOs to Z QSO ≤ 3.6, with mean redshifts of 〈z gal〉 = 0.27 and (Z QSO) = 1.1. As part of this publication, we include the redshift catalogs and the reduced spectra; these are also available through the NASA/IPAC Infrared Science Archive. © 2006. The American Astronomical Society. All rights reserved.
• Papovich, C., Moustakas, L. A., Dickinson, M., Floc'h, E. L., Rieke, G. H., Daddi, E., Alexander, D. M., Bauer, F., Brandt, W. N., Dahlen, T., Egami, E., Eisenhardt, P., Elbaz, D., Ferguson, H. C., Giavalisco, M., Lucas, R. A., Mobasher, B., Pérez-González, P., Stutz, A., , Rieke, M. J., et al. (2006). Spitzer observations of massive, red galaxies at high redshift. Astrophysical Journal Letters, 640(1 I), 92-113.
  More info

  Abstract: We study massive galaxies at z ∼ 1-3.5 using HST optical imaging, ground-based near-IR imaging, and Spitzer observations at 3-24 μm. From Ks-selected galaxies in the ≃130 arcmin2 GOODS-S field, we identify 153 distant red galaxies (DRGs) with (J - Ks) Vega ≥ 2.3. This sample is approximately complete in stellar mass for passively evolving galaxies above 1011 M⊙ and z ≤ 3. Roughly half of the DRGs are objects whose optical and near-IR rest-frame light is dominated by evolved stars combined with ongoing star formation (at zmed ∼ 2.5), and the others are galaxies whose light is dominated by heavily reddened (A1600 ≳ 4-6 mag) starbursts (at zmed ∼ 1.7). Very few DRGs (≲ 10%) have no indication of current star formation. DRGs at z ∼ 1.5-3 with stellar masses ≥ 1011 M⊙ have specific star formation rates (SFRs per unit mass) including the reradiated far-IR emission that range from 0.2 to 10 Gyr-1. Based on the X-ray luminosities and rest-frame near-IR colors, roughly one-quarter of the DRGs contain AGNs, implying that the growth of supermassive black holes coincides with the formation of massive galaxies. At 1.5 ≤ z ≤ 3, the DRGs with M ≥ 1011 M⊙ have an integrated specific SFR comparable to the global value of all galaxies. In contrast, galaxies at z ∼ 0.3-0.75 with M ≥ 1011 M ⊙have an integrated specific SFR less than the global value and more than an order of magnitude lower than that for massive DRGs. At z ≲ 1, lower mass galaxies dominate the overall cosmic mass assembly. This suggests that the bulk of star formation in massive galaxies occurs at early cosmic epochs and is largely complete by z ∼ 1.5. Further mass assembly in these galaxies takes place with low specific SFRs. © 2006. The American Astronomical Society. All rights reserved.
• Pérez-González, P. G., Kennicutt Jr., R. C., Gordon, K. D., Misselt, K. A., Gil, A., Engelbracht, C. W., Rieke, G. H., Bendo, G. J., Bianchi, L., Boissier, S., Calzetti, D., Dale, D. A., Draine, B. T., Jarrett, T. H., Hollenbach, D., & Prescott, M. K. (2006). Erratum: Ultraviolet through far-infrared spatially resolved analysis of the recent star formation in M81 (NGC 3031) (The Astrophysical Journal (2006) 648 (987)). Astrophysical Journal, 653(1 I), 812-814.
• Pérez-González, P. G., Kennicutt Jr., R. C., Gordon, K. D., Misselt, K. A., Gil, A., Engelbracht, C. W., Rieke, G. H., Bendo, G. J., Bianchi, L., Boissier, S., Calzetti, D., Dale, D. A., Draine, B. T., Jarrett, T. H., Hollenbach, D., & Prescott, M. K. (2006). Ultraviolet through far-infrared spatially resolved analysis of the recent star formation in M81 (NGC 3031). Astrophysical Journal Letters, 648(2 I), 987-1006.
  More info

  Abstract: The recent star formation (SF) in the early-type spiral galaxy M81 is characterized using imaging observations from the far-ultraviolet to the far-infrared. We compare these data with models of the stellar, gas, and dust emission for subgalactic regions. Our results suggest the existence of a diffuse dust emission not directly linked to the recent star formation. We find a radial decrease of the dust temperature and dust mass density, and in the attenuation of the stellar light. The IR emission in M81 can be modeled with three components: (1) cold dust with a temperature 〈Tc〉 = 18 ± 2 K, concentrated near the H II regions but also presenting a diffuse distribution; (2) warm dust with 〈Tw〉 = 53 ± 7 K, directly linked with the H II regions; and (3) aromatic molecules, with diffuse morphology peaking around the H II regions. We derive several relationships to obtain total IR luminosities from IR monochromatic fluxes, and we compare five different star formation rate (SFR) estimators for H II regions in M81 and M51: the UV, Hα, and three estimators based on Spitzer data. We find that the Hα luminosity absorbed by dust correlates tightly with the 24 μm emission. The correlation with the total IR luminosity is not as good. Important variations from galaxy to galaxy are found when estimating the total SFR with the 24 μm or the total IR emission alone. The most reliable estimations of the total SFRs are obtained by combining the Hα emission (or the UV) and an IR luminosity (especially the 24 μm emission), which probe the unobscured and obscured SF, respectively. For the entire M81 galaxy, about 50% of the total SF is obscured by dust. The percentage of obscured SF ranges from 60% in the inner regions of the galaxy to 30% in the outer zones. © 2006. The American Astronomical Society. All rights reserved.
• RIEKE, G. (2006). INFRARED-EMISSION OF SEYFERT-GALAXIES. ASTROPHYSICAL JOURNAL, 226(2), 550-558.
• RIEKE, G., COYNE, G., & LEE, T. (2006). PHOTOMETRY AND POLARIMETRY OF V 1057 CYGNI. PUBLICATIONS OF THE ASTRONOMICAL SOCIETY OF THE PACIFIC, 84(497), 37-&.
• Regan, M. W., Thornley, M. D., Vogel, S. N., Sheth, K., Draine, B. T., Hollenbach, D. J., Meyer, M., Dale, D. A., Engelbracht, C. W., Kennicutt, R. C., Lee, A., Buckalew, B., Calzetti, D., Gordon, K. D., Helou, G., Leitherer, C., Malhotra, S., Murphy, E., Rieke, G. H., , Rieke, M. J., et al. (2006). The radial distribution of the interstellar medium in disk galaxies: Evidence for secular evolution. Astrophysical Journal, 652(2 I), 1112-1121.
  More info

  Abstract: One possible way for spiral galaxies to internally evolve would be for gas to flow to the center and form stars in a central disk (pseudo-bulge). If the inflow rate is faster than the rate of star formation, a central concentration of gas will form. In this paper we present radial profiles of stellar and 8 μm emission from polycyclic aromatic hydrocarbons (PAHs) for 11 spiral galaxies to investigate whether the interstellar medium in these galaxies contains a central concentration above that expected from the exponential disk. In general, we find that the two-dimensional CO and PAH emission morphologies are similar, and that they exhibit similar radial profiles. We find that in 6 of the 11 galaxies there is a central excess in the 8 μm and CO emission above the inward extrapolation of an exponential disk. In particular, all four barred galaxies in the sample have strong central excesses in both 8 μm and CO emission. These correlations suggest that the excess seen in the CO profiles is, in general, not simply due to a radial increase in the CO emissivity. In the inner disk, the ratio of the stellar to the 8 μm radial surface brightness is similar for 9 of the 11 galaxies, suggesting a physical connection between the average stellar surface brightness and the average gas surface brightness at a given radius. We also find that the ratio of the CO to 8 μm PAH surface brightness is consistent over the sample, implying that the 8 μm PAH surface brightness can be used as an approximate tracer of the interstellar medium. © 2006. The American Astronomical Society. All rights reserved.
• Rieke, G. H. (2006). Learning about other planetary systems from space. Proceedings of SPIE - The International Society for Optical Engineering, 6265 I.
  More info

  Abstract: We only began to detect other planetary systems with the discovery of debris disks in 1983 with IRAS, followed by the great success of gravitational recoil measurements starting in 1995. We now know of many hundreds of them. Despite the phenomenal growth of this new field of study, our knowledge of each system is meager, strongly conditioned by observational limitations. In addition, our grasp of the ensemble properties is weak because of strong selection effects in the known samples. A series of new capabilities - Herschel, Kepler, WISE, SIM Planetquest, and JWST - will provide a systematic understanding by 2018, marking the 35th anniversary of the first IRAS detections. Specifically, we should have a good census of solar-type stars in habitable zones, a far better understanding of the evolution of terrestrial planets, and direct detections of a number of gas giants as well as new insights to their frequent migration into orbits very close to their stars and the consequences of this process for planetary systems in general.
• Rieke, G. H. (2006). Learning about other planetary systems from space. Proceedings of SPIE - The International Society for Optical Engineering, 6266 I.
  More info

  Abstract: We only began to detect other planetary systems with the discovery of debris disks in 1983 with IRAS, followed by the great success of gravitational recoil measurements starting in 1995. We now know of many hundreds of them. Despite the phenomenal growth of this new field of study, our knowledge of each system is meager, strongly conditioned by observational limitations. In addition, our grasp of the ensemble properties is weak because of strong selection effects in the known samples. A series of new capabilities - Herschel, Kepler, WISE, SIM Planetquest, and JWST - will provide a systematic understanding by 2018, marking the 35th anniversary of the first IRAS detections. Specifically, we should have a good census of solar-type stars in habitable zones, a far better understanding of the evolution of terrestrial planets, and direct detections of a number of gas giants as well as new insights to their frequent migration into orbits very close to their stars and the consequences of this process for planetary systems in general.
• Rieke, G. H. (2006). Learning about other planetary systems from space. Proceedings of SPIE - The International Society for Optical Engineering, 6269 I.
  More info

  Abstract: We only began to detect other planetary systems with the discovery of debris disks in 1983 with IRAS, followed by the great success of gravitational recoil measurements starting in 1995. We now know of many hundreds of them. Despite the phenomenal growth of this new field of study, our knowledge of each system is meager, strongly conditioned by observational limitations. In addition, our grasp of the ensemble properties is weak because of strong selection effects in the known samples. A series of new capabilities - Herschel, Kepler, WISE, SIM Planetquest, and JWST - will provide a systematic understanding by 2018, marking the 35th anniversary of the first IRAS detections. Specifically, we should have a good census of solar-type stars in habitable zones, a far better understanding of the evolution of terrestrial planets, and direct detections of a number of gas giants as well as new insights to their frequent migration into orbits very close to their stars and the consequences of this process for planetary systems in general.
• Rieke, G. H. (2006). Learning about other planetary systems from space. Proceedings of SPIE - The International Society for Optical Engineering, 6272 I, xxxi-xxxix.
  More info

  Abstract: We only began to detect other planetary systems with the discovery of debris disks in 1983 with IRAS, followed by the great success of gravitational recoil measurements starting in 1995. We now know of many hundreds of them. Despite the phenomenal growth of this new field of study, our knowledge of each system is meager, strongly conditioned by observational limitations. In addition, our grasp of the ensemble properties is weak because of strong selection effects in the known samples. A series of new capabilities - Herschel, Kepler, WISE, SIM Planetquest, and JWST - will provide a systematic understanding by 2018, marking the 35th anniversary of the first IRAS detections. Specifically, we should have a good census of solar-type stars in habitable zones, a far better understanding of the evolution of terrestrial planets, and direct detections of a number of gas giants as well as new insights to their frequent migration into orbits very close to their stars and the consequences of this process for planetary systems in general.
• Rigby, J. R., Rieke, G. H., Donley, J. L., Alonso-Herrero, A., & Pérez-González, P. (2006). Why X-ray-selected active galactic nuclei appear optically dull. Astrophysical Journal Letters, 645(1 I), 115-133.
  More info

  Abstract: We investigate why half of X-ray-selected active galactic nuclei (AGNs) in deep surveys lack signs of accretion in their optical spectra. The majority of these "optically dull" AGNs are no more than ×6 times fainter than their host galaxies in rest-frame R band; as such, AGN lines are unlikely to be overwhelmed by stellar continuum in at least half the sample. We find that optically dull AGNs have the mid-infrared emission and LX/L IR ratios characteristic of local Seyfert galaxies, suggesting that the cause of optical dullness is not missing UV-optical continua. We compare the morphologies of 22 optically dull and 9 optically active AGNs at 0.5 < z < 0.8 and find that optically dull AGNs show a wide range of axis ratio, but optically active AGNs have only very round axis ratios. We conclude that hard X-rays select AGNs in host galaxies with a wide range of inclination angle, but only those AGNs in the most face-on or spheroidal host galaxies show optical emission lines. Thus, extranuclear dust in the host galaxy plays an important role in hiding the emission lines of optically dull AGNs. © 2006. The American Astronomical Society. All rights reserved.
• Roussel, H., Helou, G., Smith, J. D., Draine, B. T., Hollenbach, D. J., Moustakas, J., Spoon, H. W., Kennicutt, R. C., Rieke, G. H., Walter, F., Armus, L., Dale, D. A., Sheth, K., Bendo, G. J., Engelbracht, C. W., Gordon, K. D., Meyer, M. J., Regan, M. W., & Murphy, E. J. (2006). The opaque nascent starburst in NGC 1377: Spitzer sings observations. Astrophysical Journal Letters, 646(2 I), 841-857.
  More info

  Abstract: We analyze extensive data on NGC 1377 from the Spitzer Infrared Nearby Galaxies Survey (SINGS). Within the category of nascent starbursts that we previously selected as having infrared-to-radio continuum ratios in large excess of the average and containing hot dust, NGC 1377 has the largest infrared excess yet measured. Optical imaging reveals a morphological distortion suggestive of a recent accretion event. Infrared spectroscopy reveals a compact and opaque source dominated by a hot, self-absorbed continuum (τ ∼ 20 in the 10 μm silicate band). We provide physical evidence against nonstellar activity being the heating source. H II regions are detected through the single [Ne II] line, probing < 1% of the ionizing radiation. Not only is the optical depth in different gas and dust phases very high, but >85% of ionizing photons are suppressed by dust. The only other detected emission features are molecular hydrogen lines, arguably excited mainly by shocks, besides photodissociation regions, and weak aromatic bands. The new observations support our interpretation in terms of an extremely young starburst (
• Shi, Y., Rieke, G. H., Hines, D. C., Gorjian, V., Werner, M. W., Cleary, K., Low, F. J., Smith, P. S., & Bouman, J. (2006). 9.7 μm silicate features in active galactic nuclei: New insights into unification models. Astrophysical Journal, 653(1 I), 127-136.
  More info

  Abstract: We describe observations of 9.7 μm silicate features in 97 AGNs, exhibiting a wide range of AGN types and of X-ray extinction toward the central nuclei. We find that the strength of the silicate feature correlates with the H i column density estimated from fitting the X-ray data, such that low H I columns correspond to silicate emission, while high columns correspond to silicate absorption. The behavior is generally consistent with unification models in which the large diversity in AGN properties is caused by viewing-angle-dependent obscuration of the nucleus. Radio-loud AGNs and radio-quiet quasars follow roughly the correlation between H I columns and the strength of the silicate feature defined by Seyfert galaxies. The agreement among AGN types suggests a high-level unification with similar characteristics for the structure of the obscuring material. We demonstrate the implications for unification models qualitatively with a conceptual disk model. The model includes an inner accretion disk (
• Shi, Y., Rieke, G. H., Papovich, C., Pérez-González, P., & Floc'h, E. (2006). Morphology of spitzer 24 μm detected galaxies in the UDF: The links between star formation and galaxy morphology. Astrophysical Journal Letters, 645(1 I), 199-208.
  More info

  Abstract: We have studied the morphologies of infrared-luminous galaxies at 0.3 ≤ z < 1.4 in the HST Ultra Deep Field (UDF) by calculating concentration and asymmetry indices and comparing the results with similar calculations for: (1) galaxies at similar redshift that are less infrared-active, and (2) local luminous infrared galaxies [LIRGs; LIR(8-1000 μm)> 10 11 L⊙]. We find that the high-redshift samples are dominated by galaxies with concentrations similar to local late-type disk galaxies; however, they are significantly more asymmetric than most local galaxies but are similar in both regards to local LIRGs. On average, the high-redshift infrared-active galaxies are slightly more asymmetric than the less active ones, although they do include a significantly higher portion of highly asymmetric (merging?) systems and a lower portion of more concentrated, symmetric ones. The morphological similarity of infrared-active and typical infrared-inactive galaxies at high redshift suggests that they may be from the same parent population, but are in different stages of an episodic star formation process. The similarity between high redshift and local LIRGs suggests that a certain level of asymmetry is generally associated with LIRG-level activity. © 2006. The American Astronomical Society. All rights reserved.
• Stansberry, J. A., Grundy, W. M., Margot, J. L., Cruikshank, D. P., Emery, J. P., Rieke, G. H., & Trilling, D. E. (2006). The albedo, size, and density of binary Kuiper Belt object (47171) 1999 TC₃₆. Astrophysical Journal Letters, 643(1 I), 556-566.
  More info

  Abstract: We measured the system-integrated thermal emission of the binary Kuiper Belt object (47171 ) 1999 TC36, at wavelengths near 24 and 70 μm using the Spitzer Space Telescope. We fit these data and the visual magnitude using both the standard thermal model and thermophysical models. We find that the effective diameter of the binary is 405 km, with a range of 350-470 km, and the effective visible geometric albedo for the system is 0.079, with a range of 0.055-0.11. The binary orbit, magnitude contrast between the components, and system mass have been determined from HSTdata studied by Margot et al. Our effective diameter, combined with that system mass, indicates an average density for the objects of 0.5 g cm-3, with a range 0.3-0.8 g cm -3. This density is low compared to that of materials expected to be abundant in solid bodies in the trans-Neptunian region, requiring 50%-75% of the interior of (47171 ) 1999 TC36 be taken up by void space. This conclusion is not greatly affected if (47171)1999 TC36 is "differentiated" (in the sense of having either a rocky or just a nonporous core). If the primary is itself a binary, the average density of that (hypothetical) triple system would be in the range 0.4-1.l g cm -3, with a porosity in the range 15%-70%. © 2006. The American Astronomical Society. All rights reserved.
• Stapelfeldt, K., Holmes, E., Chen, C., Rieke, G., Su, K., Hines, D., Werner, M., Beichman, C., Jura, M., Padgett, D., Stansberry, J., Bendo, G., Cadien, J., Marengo, M., Thompson, T., Velusamy, T., Backus, C., Blaylock, M., Egami, E., , Engelbracht, C., et al. (2006). First look at the Fomalhaut debris disk with the Spitzer Space Telescope. ASTROPHYSICAL JOURNAL SUPPLEMENT SERIES, 154(1), 458-462.
  More info

  We present Spitzer Space Telescope early release observations of Fomalhaut, a nearby A-type star with dusty circumstellar debris. The disk is spatially resolved at 24, 70, and 160 mum using the Multiband Imaging Photometer for Spitzer (MIPS). While the disk orientation and outer radius are comparable to values measured in the submillimeter, the disk inner radius cannot be precisely defined: the central hole in the submillimeter ring is at least partially filled with emission from warm dust, seen in Spitzer Infrared Spectrograph (IRS) 17.5-34 mum spectra and MIPS 24 mum images. The disk surface brightness becomes increasingly asymmetric toward shorter wavelengths, with the south-southeast ansa always brighter than the north-northwest one. This asymmetry may reflect perturbations on the disk by an unseen interior planet.
• Stocke, J. T., Rieke, G. H., & Lebofsky, M. J. (2006). New observational constraints on the M87 jet. NATURE, 294(5839), 319-322.
  More info

  New observations at 1.6-3.45 mu m confirm the presence of a dramatic (Delta alpha similar to 1) break between radio-IR wavelengths and 6,000 angstrom, in the spectrum of the M87 jet. These data, in combination with data taken in other spectral regions, show that the individual knots in the M87 jet have nearly the same spectral indices and nearly the same large (Delta alpha similar to 1) spectral break. This large spectral break and the constancy of spectral properties between the knots pose serious constraints for models of the M87 jet.
• Su, K. Y., Rieke, G. H., Stansberry, J. A., Bryden, G., Stapelfeldt, K. R., Trilling, D. E., Muzerolle, J., Beichman, C. A., Moro-Martin, A., Hlnes, D. C., & Werner, M. W. (2006). Debris disk evolution around a stars. Astrophysical Journal, 653(1 I), 675-689.
  More info

  Abstract: We report 24 and/or 70 μm measurements of ∼ 160 A-type main-sequence stars using the Multiband Imaging Photometer for Spitzer (MIPS). Their ages range from 5 to 850 Myr, based on estimates from the literature (cluster or moving group associations) or from the H-R diagram and isochrones. The thermal infrared excess is identified by comparing the deviation (∼3% and ∼15% at the 1 σ level at 24 and 70 μm, respectively) between the measurements and the synthetic Kurucz photospheric predictions. Stars showing excess infrared emission due to strong emission lines or extended nebulosity seen at 24 μm are excluded from our sample; therefore, the remaining infrared excesses are likely to arise from circumstellar debris disks. At the 3 σ confidence level, the excess rate at 24 and 70 μm is 32% and ≥33% (with an uncertainty of 5%), considerably higher than what has been found for old solar analogs and M dwarfs. Our measurements place constraints on the fractional dust luminosities and temperatures in the disks. We find that older stars tend to have lower fractional dust luminosity than younger ones. While the fractional luminosity from the excess infrared emission follows a general 1/t relationship, the values at a given stellar age vary by at least 2 orders of magnitude. We also find that (1) older stars possess a narrow range of temperature distribution peaking at colder temperatures, and (2) the disk emission at 70 μm persists longer than that at 24 μm. Both results suggest that the debris disk clearing process is more effective in the inner regions. © 2006. The American Astronomical Society. All rights reserved.
• Tabatabaei, F. S., Beck, R., Krause, M., Berkhuijsen, E. M., Gehrz, R., Gordon, K. D., Hinz, J. L., Humphreys, R., McQuinn, K., Polomski, E., Rieke, G. H., & Woodward, C. E. (2006). A multi-scale study of infrared and radio emission from Scd galaxy M 33. ASTRONOMY & ASTROPHYSICS, 466(2), 509-519.
  More info

  Aims. We investigate the energy sources of the infrared (IR) emission and their relation to the radio continuum emission at various spatial scales within the Scd galaxy M 33.
• Teixeira, P. S., Lada, C. J., Young, E. T., Marengo, M., Muench, A., Muzerolle, J., Siegler, N., Rieke, G., Hartmann, L., Megeath, S. T., & Fazio, G. (2006). Identifying primordial substructure in NGC 2264. Astrophysical Journal Letters, 636(1 II), L45-L48.
  More info

  Abstract: We present new Spitzer Space Telescope observations of the young cluster NGC 2264. Observations at 24 μm with the Multiband Imaging Photometer have enabled us to identify the most highly embedded and youngest objects in NGC 2264. This Letter reports on one particular region of NGC 2264 where bright 24 μm sources are spatially configured in curious linear structures with quasi-uniform separations. The majority of these sources (∼60%) are found to be protostellar in nature, with Class I spectral energy distributions. Comparison of their spatial distribution with submillimeter data from Wolf-Chase et al. and millimeter data from Peretto et al. shows a close correlation between the dust filaments and the linear spatial configurations of the protostars, indicating that star formation is occurring primarily within dense, dusty filaments. Finally, the quasi-uniform separations of the protostars are found to be comparable in magnitude to the expected Jeans length, suggesting thermal fragmentation of the dense filamentary material. © 2006. The American Astronomical Society. All rights reserved.
• Werner, M., Fazio, G., Rieke, G., Roellig, T. L., & Watson, D. M. (2006). First fruits of the Spitzer Space Telescope: Galactic and solar system studies. ANNUAL REVIEW OF ASTRONOMY AND ASTROPHYSICS, 44, 269-321.
  More info

  The Spitzer Space Telescope, launched in August 2003, is the infrared member of NASAs Great Observatory family. Spitzer combines the intrinsic sensitivity of a cryogenic telescope in space with the imaging and spectroscopic power of modern infrared detector arrays. This review covers early results from Spitzer that have produced major advances in our understanding of our own solar system and phenomena within the Galaxy. Spitzer has made the first detection of light from extrasolar planets, characterized planet-forming and planetary debris disks around solar-type stars, showed that substellar objects with masses smaller than 10 M(Jup) form through the same processes as do solar-mass stars, and studied in detail the composition of cometary ejecta in our Solar System. Spitzer major technical advances will pave the way for yet more powerful future instruments. Spitzer should operate with full capabilities well into 2009, enabling several additional cycles of discovery and follow-up.
• Werner, M., Fazio, G., Rieke, G., Roellig, T. L., & Watson, D. M. (2006). First fruits of the spitzer space telescope: Galactic and solar system studies. Annual Review of Astronomy and Astrophysics, 44, 269-321.
  More info

  Abstract: The Spitzer Space Telescope, launched in August 2003, is the infrared member of NASA's Great Observatory family. Spitzer combines the intrinsic sensitivity of a cryogenic telescope in space with the imaging and spectroscopic power of modern infrared detector arrays. This review covers early results from Spitzer that have produced major advances in our understanding of our own solar system and phenomena within the Galaxy. Spitzer has made the first detection of light from extrasolar planets, characterized planet-forming and planetary debris disks around solar-type stars, showed that substellar objects with masses smaller than 10 M Jup form through the same processes as do solar-mass stars, and studied in detail the composition of cometary ejecta in our Solar System. Spitzer's major technical advances will pave the way for yet more powerful future instruments. Spitzer should operate with full capabilities well into 2009, enabling several additional cycles of discovery and follow-up. Copyright © 2006 by Annual Reviews. All rights reserved.
• Werner, M., Roellig, T., Low, F., Rieke, G., Rieke, M., Hoffmann, W., Young, E., Houck, ., Brandl, B., Fazio, G., Hora, J., Gehrz, R., Helou, G., Soifer, B., Stauffer, J., Keene, J., Eisenhardt, P., Gallagher, D., Gautier, T., , Irace, W., et al. (2006). The Spitzer Space Telescope mission. ASTROPHYSICAL JOURNAL SUPPLEMENT SERIES, 154(1), 1-9.
  More info

  The Spitzer Space Telescope, NASA's Great Observatory for infrared astronomy, was launched 2003 August 25 and is returning excellent scientific data from its Earth-trailing solar orbit. Spitzer combines the intrinsic sensitivity achievable with a cryogenic telescope in space with the great imaging and spectroscopic power of modern detector arrays to provide the user community with huge gains in capability for exploration of the cosmos in the infrared. The observatory systems are largely performing as expected, and the projected cryogenic lifetime is in excess of 5 years. This paper summarizes the on-orbit scientific, technical, and operational performance of Spitzer. Subsequent papers in this special issue describe the Spitzer instruments in detail and highlight many of the exciting scientific results obtained during the first 6 months of the Spitzer mission.
• Zemcov, M., Rex, M., Rawle, T. D., Bock, J. J., Egami, E., Altieri, B., Blain, A. W., Boone, F., Bridge, C. R., Clement, B., Combes, F., Dowell, C. D., Dessauges-Zavadsky, M., Fadda, D., Ilbert, O., Ivison, R. J., Jauzac, M., Kneib, J. -., Lutz, D., , Pello, R., et al. (2006). First detection of the Sunyaev Zel'dovich effect increment at lambda < 650 mu m. ASTRONOMY & ASTROPHYSICS, 518.
  More info

  The Sunyaev-Zel'dovich (SZ) effect is a spectral distortion of the cosmic microwave background as observed through the hot plasma in galaxy clusters. This distortion is a decrement in the CMB intensity for lambda > 1.3 mm, an increment at shorter wavelengths, and small again by lambda similar to 250 mu m. As part of the Herschel Lensing Survey (HLS) we have mapped 1E0657-56 (the Bullet cluster) with SPIRE with bands centered at 250, 350 and 500 mu m and have detected the SZ effect at the two longest wavelengths. The measured SZ effect increment central intensities are Delta I(0) = 0.097 +/- 0.019 MJy sr(-1) at 350 mu m and Delta I(0) = 0.268 +/- 0.031 MJy sr(-1) at 500 mu m, consistent with the SZ effect spectrum derived from previous measurements at 2 mm. No other diffuse emission is detected. The presence of the finite temperature SZ effect correction is preferred by the SPIRE data at a significance of 2.1 sigma, opening the possibility that the relativistic SZ effect correction can be constrained by SPIRE in a sample of clusters. The results presented here have important ramifications for both sub-mm measurements of galaxy clusters and blank field surveys with SPIRE.
• Zheng, X. Z., Bell, E. F., Rix, H., Papovich, C., Floc'h, E. L., Rieke, G. H., & Pérez-González, P. (2006). Detecting faint galaxies by stacking at 24 μm. Astrophysical Journal Letters, 640(2 I), 784-800.
  More info

  Abstract: We stack Spitzer 24 μm images for ∼7000 galaxies with 0.1 ≤ z < 1 in the Chandra Deep Field South to probe the thermal dust emission in low-luminosity galaxies over this redshift range. Through stacking, we can detect mean 24 μm fluxes that are more than an order of magnitude below the individual detection limit. We find that the correlations for low- and moderate-luminosity galaxies between the average LIR/LUV and rest-frame B-band luminosity, and between the star formation rate (SFR) and LIR/LUV, are similar to those in the local universe. This verifies that oft-used assumption in deep UV/optical surveys that the dust obscuration - SFR relation for galaxies with SFR ≤ 20 M⊙ yr-1 varies little with epoch. We have used this relation to derive the cosmic IR luminosity density from z = 1 to z = 0.1. The results also demonstrate directly that little of the bolometric luminosity of the galaxy population arises from the faint end of the luminosity function, indicating a relatively flat faint-end slope of the IR luminosity function with a power-law index of 1.2 ± 0.3. © 2006. The American Astronomical Society. All rights reserved.
• Beichman, C. A., Bryden, G., Gautier, T. N., Stapelfeldt, K. R., Werner, M. W., Misselt, K., Rieke, G., Stansberry, J., & Trilling, D. (2005). An excess due to small grains around the nearby K0 v star HD 69830: Asteroid or cometary debris?. Astrophysical Journal Letters, 626(2 I), 1061-1069.
  More info

  Abstract: Spitzer photometry and spectroscopy of the star HD 69830 reveal an excess of emission relative to the stellar photosphere between 8 and 35 μm dominated by strong features attributable to crystalline silicates with an emitting surface area more than 1000 times that of our zodiacal cloud. The spectrum closely resembles that of the comet C/1995 O1 (Hale-Bopp). Since no excess is detected at 70 μm, the emitting material must be quite warm, be confined within a few AU of the star, and originate in grains with low, long-wavelength emissivity, i.e., grains much smaller than 70 μm/2π ∼ 10 μm. The strong mineralogical features are evidence for even smaller, possibly submicron-sized grains. This small grain size is in direct contrast to the 10-100 μm grains that dominate the relatively featureless spectra of our zodiacal dust cloud and most other main-sequence stars with excesses. The upper limit at 70 μm also implies that any Kuiper Belt analog must be either very cold or less massive than ∼5 times our own Kuiper Belt. With collisional and Poynting-Robertson drag times of less than 1000 yr for small grains, the emitting material must either (1) be created through continual grinding down of material in a dense asteroid belt, or (2) originate in cometary debris arising from either a single "supercomet" or a very large number of individual comets arriving from a distant reservoir. In the case of a cometary origin for the emission, the mass requirements for continuous generation by many individual comets are unreasonable, and we favor the capture of a single super comet into a 0.5-1 AU orbit, where it can evolve a large number of small grains over a 2 Myr period. © 2005. The American Astronomical Society. All rights reserved.
• Beichman, C. A., Bryden, G., Rieke, G. H., Stansberry, J. A., Trilling, D. E., Stapelfeldt, K. R., Werner, M. W., Engelbracht, C. W., Blaylock, M., Gordon, K. D., Chen, C. H., Su, K. Y., & Hines, D. C. (2005). Planets and infrared excesses: Preliminary results from a spitzer MIPS survey of solar-type stars. Astrophysical Journal Letters, 622(2 I), 1160-1170.
  More info

  Abstract: As part of a large Spitzer MIPS Guaranteed Time Observation program, we have searched for infrared excesses due to debris disks toward 26 FGK field stars known from radial velocity (RV) studies to have one or more planets. While none of these stars show excesses at 24 μm, we have detected 70 μm excesses around six stars at the 3 σ confidence level. The excesses are produced by cool material (
• Bell, E. F., Papovich, C., Wolf, C., Floc'h, E. L., Caldwell, J. A., Barden, M., Egami, E., McIntosh, D. H., Meisenheimer, K., Pérez-González, P. G., Rieke, G. H., Rieke, M. J., Rigby, J. R., & Rix, H. (2005). Toward an understanding of the rapid decline of the cosmic star formation rate. Astrophysical Journal Letters, 625(1 I), 23-36.
  More info

  Abstract: We present a first analysis of deep 24 μm observations with the Spitzer Space Telescope of a sample of nearly 1500 galaxies in a thin redshift slice, 0.65 ≤ z < 0.75. We combine the infrared data with redshifts, rest-frame luminosities, and colors from COMBO-17 and with morphologies from Hubble Space Telescope images collected by the Galaxy Evolution from Morphology and SEDs (GEMS) and Great Observatories Origins Deep Survey (GOODS) projects. To characterize the decline in star formation rate (SFR) since z ∼ 0.7, we estimate the total thermal IR luminosities, SFRs, and stellar masses for the galaxies in this sample. At z ∼ 0.7, nearly 40% of intermediate- and high-mass galaxies (with stellar masses ≥2 × 1010 M⊙) are undergoing a period of intense star formation above their past-averaged SFR. In contrast, less than 1 % of equally massive galaxies in the local universe have similarly intense star formation activity. Morphologically undisturbed galaxies dominate the total infrared luminosity density and SFR density: at z ∼ 0.7, more than half of the intensely star-forming galaxies have spiral morphologies, whereas less than ∼30% are strongly interacting. Thus, a decline in major merger rate is not the underlying cause of the rapid decline in cosmic SFR since z ∼ 0.7. Physical properties that do not strongly affect galaxy morphology - for example, gas consumption and weak interactions with small satellite galaxies - appear to be responsible. © 2005. The American Astronomical Society. All rights reserved.
• Calzett, D., Kennicutt Jr., R. C., Bianchi, L., Thilker, D. A., Dale, D. A., Engelbracht, C. W., Leitherer, C., Meyer, M. J., Sosey, M. L., Mutchler, M., Regan, M. W., Thornley, M. D., Armus, L., Bendo, G. J., Boissier, S., Boselli, A., Draine, B. T., Gordon, K. D., Helou, G., , Hollenbach, D. J., et al. (2005). Star formation in NGC 5194 (M51a): The panchromatic view from Galex to Spitzer. Astrophysical Journal Letters, 633(2 I), 871-893.
  More info

  Abstract: Far-ultraviolet to far-infrared images of the nearby galaxy NGC 5194 (M51a), from a combination of space-based (Spitzer, GALEX, and Hubble Space Telescope) and ground-based data, are used to investigate local and global star formation and the impact of dust extinction. The Spitzer data provide unprecedented spatial detail in the infrared, down to sizes ∼500 pc at the distance of NGC 5194. The multiwavelength set is used to trace the relatively young stellar populations, the ionized gas, and the dust absorption and emission in H II-emitting knots, over 3 orders of magnitude in wavelength range. As is common in spiral galaxies, dust extinction is high in the center of the galaxy (Av ∼ 3.5 mag), but its mean value decreases steadily as a function of galactocentric distance, as derived from both gas emission and stellar continuum properties. In the IR/UV-UV color plane, the NGC 5194 H II knots show the same trend observed for normal star-forming galaxies, having a much larger dispersion (∼ 1 dex peak to peak) than starburst galaxies. We identify the dispersion as due to the UV emission predominantly tracing the evolved, nonionizing stellar population, up to ages ∼50-100 Myr. While in starbursts the UV light traces the current star formation rate (SFR), in NGC 5194 it traces a combination of current and recent past SFRs. Possibly, mechanical feedback from supernovae is less effective at removing dust and gas from the star formation volume in normal star-forming galaxies than in starbursts because of the typically lower SFR densities in the former. The application of the starburst opacity curve for recovering the intrinsic UV emission (and deriving SFRs) in local and distant galaxies appears therefore appropriate only for SFR densities ≳1 M⊙ yr-1 kpc-2. Unlike the UV emission, the monochromatic 24 μm luminosity is an accurate local SFR tracer for the 24 μm knots in NGC 5194, with a peak-to-peak dispersion of less than a factor of 3 relative to hydrogen emission line tracers; this suggests that the 24 μm emission carriers are mainly heated by the young, ionizing stars. However, preliminary results show that the ratio of the 24 μm emission to the SFR varies by a factor of a few from galaxy to galaxy; this variation needs to be understood and carefully quantified before the 24 μm luminosity can be used as an SFR tracer for galaxy populations. While also correlated with star formation, the 8 μm emission is not directly proportional to the number of ionizing photons; it is overluminous, by up to a factor of ∼2, relative to the galaxy's average in weakly ionized regions and is underluminous, by up to a factor of ∼3, in strongly ionized regions. This confirms earlier suggestions that the carriers of the 8 μm emission are heated by more than one mechanism. © 2005. The American Astronomical Society. All rights reserved.
• Cruikshank, D. P., Stansberry, J. A., Emery, J. P., Fernández, Y. R., Werner, M. W., Trilling, D. E., & Rieke, G. H. (2005). The high-albedo kuiper belt object (55565) 2002 AW₁₉₇. Astrophysical Journal Letters, 624(1 II), L53-L56.
  More info

  Abstract: We detected thermal emission from the Kuiper Belt object 2002 AW 197 in 2003 December and again in 2004 April using the Multiband Imaging Photometer on the Spitzer Space Telescope. In combination with the absolute visual magnitude, the thermal measurements indicate a geometric albedo of 0.17 ± 0.03 and a diameter of 700 ± 50 km. The albedo of 2002 AW197 is significantly higher than the 0.04 value typically assumed for trans-Neptunian objects, and consequently the object is smaller than previously thought based on that assumption. Our thermal measurements at two wavelengths (24 and 70 μm) allow us to constrain the surface temperature and thereby place constraints on the thermal inertia. We find that the standard thermal model (STM) is inconsistent with the 24/70 μm color unless we set the beaming parameter η > 0.95, indicating that the object has a significant thermal inertia and, therefore, that the STM is inappropriate. The other end-member thermal inertia model is the fast-rotator, or isothermal-latitude, model (ILM). The data are well represented by an ILM with the pole of rotation inclined to the Sun by 45° ± 10°. The high albedo is consistent with a surface containing significant amounts of weakly absorbing materials, with ices and/or fine-grained silicates as likely candidates. © 2005. The American Astronomical Society. All rights reserved.
• Dale, D. A., Bendo, G. J., Engelbracht, C. W., Gordon, K. D., Regan, M. W., Armus, L., Cannon, J. M., Calzetti, D., Draine, B. T., Helou, G., Joseph, R. D., Kennicutt, R. C., Li, A., Murphy, E. J., Roussel, H., Walter, F., Hanson, H. M., Hollenbach, D. J., Jarrett, T. H., , Kewley, L. J., et al. (2005). Infrared spectral energy distributions of nearby galaxies. Astrophysical Journal Letters, 633(2 I), 857-870.
  More info

  Abstract: The Spitzer Infrared Nearby Galaxies Survey (SINGS) is carrying out a comprehensive multiwavelength survey on a sample of 75 nearby galaxies. The 1-850 μm spectral energy distributions (SEDs) are presented using broadband imaging data from Spitzer, 2MASS, ISO, IRAS, and SCUBA. The infrared colors derived from the globally integrated Spitzer data are generally consistent with the previous generation of models that were developed using global data for normal star-forming galaxies, although significant deviations are observed. Spitzer's excellent sensitivity and resolution also allow a detailed investigation of the infrared SEDs for various locations within the three large, nearby galaxies NGC 3031 (M81), NGC 5194 (M51), and NGC 7331. A wide variety of spectral shapes is found within each galaxy, especially for NGC 3031, the closest of the three targets and thus the galaxy for which the smallest spatial scales can be explored. Strong correlations exist between the local star formation rate and the infrared colors fv(70 μm)/fv(160 μm) and fv(24 μm)/fv(160 μm), suggesting that the 24 and 70 μm emission are useful tracers of the local star formation activity level. Preliminary evidence indicates that variations in the 24 μm emission, and not variations in the emission from polycyclic aromatic hydrocarbons at 8 μm, drive the variations in thefv8.0 μm)/fv(24 μm) colors within NGC 3031, NGC 5194, and NGC 7331. If the galaxy-to-galaxy variations in SEDs seen in our sample are representative of the range present at high redshift, then extrapolations of total infrared luminosities and star formation rates from the observed 24 μm flux will be uncertain at the factor of 5 level (total range). The corresponding uncertainties using the redshifted 8.0 μm flux (e.g., observed 24 μm flux for a z = 2 source) are factors of 10-20. Considerable caution should be used when interpreting such extrapolated infrared luminosities. © 2005. The American Astronomical Society. All rights reserved.
• Dale, D., Bendo, G., Engelbracht, C., Gordon, K., Regan, M., Armus, L., Cannon, J., Calzetti, D., Draine, B., Helou, G., Joseph, R., Kennicutt, R., Li, A., Murphy, E., Roussel, H., Walter, F., Hanson, H., Hollenbach, D., Jarrett, T., , Kewley, L., et al. (2005). Infrared spectral energy distributions of nearby galaxies. ASTROPHYSICAL JOURNAL, 633(2), 857-870.
  More info

  The Spitzer Infrared Nearby Galaxies Survey (SINGS) is carrying out a comprehensive multiwavelength survey on a sample of 75 nearby galaxies. The 1 - 850 mu m spectral energy distributions (SEDs) are presented using broadband imaging data from Spitzer, 2MASS, ISO, IRAS, and SCUBA. The infrared colors derived from the globally integrated Spitzer data are generally consistent with the previous generation of models that were developed using global data for normal star-forming galaxies, although significant deviations are observed. Spitzer's excellent sensitivity and resolution also allow a detailed investigation of the infrared SEDs for various locations within the three large, nearby galaxies NGC 3031 (M81), NGC 5194 (M51), and NGC 7331. A wide variety of spectral shapes is found within each galaxy, especially for NGC 3031, the closest of the three targets and thus the galaxy for which the smallest spatial scales can be explored. Strong correlations exist between the local star formation rate and the infrared colors f(nu)(70 mu m)/ f(nu)(160 mu m) and f(nu)(24 mu m)/ f(nu)(160 mu m), suggesting that the 24 and 70 mu m emission are useful tracers of the local star formation activity level. Preliminary evidence indicates that variations in the 24 mu m emission, and not variations in the emission from polycyclic aromatic hydrocarbons at 8 mu m, drive the variations in the f(nu)(8.0 mu m)/ f(nu)(24 mu m) colors within NGC 3031, NGC 5194, and NGC 7331. If the galaxy-to-galaxy variations in SEDs seen in our sample are representative of the range present at high redshift, then extrapolations of total infrared luminosities and star formation rates from the observed 24 mu m flux will be uncertain at the factor of 5 level ( total range). The corresponding uncertainties using the redshifted 8.0 mu m flux (e.g., observed 24 mu m flux for a z = 2 source) are factors of 10 - 20. Considerable caution should be used when interpreting such extrapolated infrared luminosities.
• Donley, J. L., Rieke, G. H., Rigby, J. R., & Pérez-González, P. (2005). Unveiling a population of agns not detected in x-rays. Astrophysical Journal Letters, 634(1 I), 169-182.
  More info

  Abstract: We define a sample of 27 radio-excess AGNs in the Chandra Deep Field-North by selecting galaxies that do not obey the radio/infrared correlation for radio-quiet AGNs and star-forming galaxies. Approximately 60% of these radio-excess AGNs are undetected in X-rays in the 2 Ms Chandra catalog, even at exposures of ≥1 Ms; 25% lack even 2 σ X-ray detections. The absorbing columns to the faint objects detected in X-rays are 1022 cm -2 < NH < 1024 cm-2; i.e., they are obscured but unlikely to be Compton-thick. Using a local sample of radio-selected AGNs, we show that a low ratio of X-ray to radio emission, as seen in the samples of AGNs weakly detected and undetected in X-rays, is correlated with the viewing angle of the central engine and therefore with obscuration. Our technique can explore the proportion of obscured AGNs in the distant universe; the results reported here for radio-excess objects are consistent with, but at the low end of, the overall theoretical predictions for Compton-thick objects. © 2005. The American Astronomical Society. All rights reserved.
• Egami, E., Dole, H., Huang, J., Perez-Gonzalez, P., Le Floc'h, E., Papovich, C., Barmby, P., Ivison, R., Serjeant, S., Mortier, A., Frayer, D., Rigopoulou, D., Lagache, G., Rieke, G., Willner, S., Alonso-Herrero, A., Bai, L., Engelbracht, C., Fazio, G., , Gordon, K., et al. (2005). Spitzer observations of the SCUBA/VLA sources in the Lockman Hole: Star formation history of infrared-luminous galaxies. ASTROPHYSICAL JOURNAL SUPPLEMENT SERIES, 154(1), 130-136.
  More info

  We present Spitzer Space Telescope imaging observations at 3.6, 4.5, 5.8, 8.0, and 24 mum of the SCUBA submillimeter sources and muJy VLA radio sources in a 5' x 5' area in the Lockman Hole East region. Out of the similar to 40 SCUBA/VLA sources in the field, Spitzer counterparts were detected for nearly all except for the few low-weight SCUBA detections. We show that the majority (80% - 90%) of the detected sources are cold (i.e., starburst-like) infrared-luminous galaxies (L-IR > 10(11) L-.) at redshift 0.5 < z < 3.5, whose star-formation rate density (SFRD) is comparable to that of the optically selected star-forming galaxies.
• Eisenstein, D. J., Weinberg, D. H., Agol, E., Aihara, H., Allende Prieto, C., Anderson, S. F., Arns, J. A., Aubourg, E., Bailey, S., Balbinot, E., Barkhouser, R., Beers, T. C., Berlind, A. A., Bickerton, S. J., Bizyaev, D., Blanton, M. R., Bochanski, J. J., Bolton, A. S., Bosman, C. T., , Bovy, J., et al. (2005). SDSS-III: MASSIVE SPECTROSCOPIC SURVEYS OF THE DISTANT UNIVERSE, THE MILKY WAY, AND EXTRA-SOLAR PLANETARY SYSTEMS. ASTRONOMICAL JOURNAL, 142(3).
  More info

  Building on the legacy of the Sloan Digital Sky Survey (SDSS-I and II), SDSS-III is a program of four spectroscopic surveys on three scientific themes: dark energy and cosmological parameters, the history and structure of the Milky Way, and the population of giant planets around other stars. In keeping with SDSS tradition, SDSS-III will provide regular public releases of all its data, beginning with SDSS Data Release 8 (DR8), which was made public in 2011 January and includes SDSS-I and SDSS-II images and spectra reprocessed with the latest pipelines and calibrations produced for the SDSS-III investigations. This paper presents an overview of the four surveys that comprise SDSS-III. The Baryon Oscillation Spectroscopic Survey will measure redshifts of 1.5 million massive galaxies and Ly alpha forest spectra of 150,000 quasars, using the baryon acoustic oscillation feature of large-scale structure to obtain percent-level determinations of the distance scale and Hubble expansion rate at z < 0.7 and at z approximate to 2.5. SEGUE-2, an already completed SDSS-III survey that is the continuation of the SDSS-II Sloan Extension for Galactic Understanding and Exploration (SEGUE), measured medium-resolution (R = lambda/lambda Delta approximate to 1800) optical spectra of 118,000 stars in a variety of target categories, probing chemical evolution, stellar kinematics and substructure, and the mass profile of the dark matter halo from the solar neighborhood to distances of 100 kpc. APOGEE, the Apache Point Observatory Galactic Evolution Experiment, will obtain high-resolution (R approximate to 30,000), high signal-to-noise ratio (S/N >= 100 per resolution element), H-band (1.51 mu m < lambda < 1.70 mu m) spectra of 105 evolved, late-type stars, measuring separate abundances for similar to 15 elements per star and creating the first high-precision spectroscopic survey of all Galactic stellar populations (bulge, bar, disks, halo) with a uniform set of stellar tracers and spectral diagnostics. The Multi-object APO Radial Velocity Exoplanet Large-area Survey (MARVELS) will monitor radial velocities of more than 8000 FGK stars with the sensitivity and cadence (10-40 ms(-1), similar to 24 visits per star) needed to detect giant planets with periods up to two years, providing an unprecedented data set for understanding the formation and dynamical evolution of giant planet systems. As of 2011 January, SDSS-III has obtained spectra of more than 240,000 galaxies, 29,000 z >= 2.2 quasars, and 140,000 stars, including 74,000 velocity measurements of 2580 stars for MARVELS.
• Engelbracht, C. W., Gordon, K. D., Rieke, G. H., Werner, M. W., Dale, D. A., & Latter, W. B. (2005). Metallicity effects on mid-infrared colors and the 8 μm PAH emission in galaxies. Astrophysical Journal Letters, 628(1 II), L29-L32.
  More info

  Abstract: We examine colors from 3.6 to 24 μm as a function of metallicity (O/H) for a sample of 34 galaxies. The galaxies range over 2 orders of magnitude in metallicity. They display an abrupt shift in the 8 μm-to-24 μm color for metallicities between one-third and one-fifth of the solar value. The mean 8-to-24 μm flux density ratio below and above 12 + log (O/H) = 8.2 is 0.08 ± 0.04 and 0.70 ± 0.53, respectively. We use mid-IR colors and spectroscopy to demonstrate that the shift is primarily due to a decrease in the 8 μm flux density, as opposed to an increase in the 24 μm flux density. This result is most simply interpreted as being due to a weakening at low metallicity of the mid-IR emission bands usually attributed to PAHs (polycyclic aromatic hydrocarbons) relative to the small-grain dust emission. However, existing empirical spectral energy distribution models cannot account for the observed short-wavelength (below 8 μm) colors of the low-metallicity galaxies merely by reducing the strength of the PAH features; some other emission source (e.g., hot dust) is required. © 2005. The American Astronomical Society. All rights reserved.
• Floc'h, E. L., Papovich, C., Dole, H., Bell, E. F., Lagache, G., Rieke, G. H., Egami, E., Pérez-González, P. G., Alonso-Herrero, A., Rieke, M. J., Blaylock, M., Engelbracht, C. W., Gordon, K. D., Hines, D. C., Misselt, K. A., Morrison, J. E., & Mould, J. (2005). Infrared luminosity functions from the chandra deep field-south: The Spitzer view on the history of dusty star formation at 0 ≲ z ≲ 1 ¹. Astrophysical Journal Letters, 632(1 I), 169-190.
  More info

  Abstract: We analyze a sample of ∼2600 Spitzer MIPS 24 μm sources brighter than ∼80μJy and located in the Chandra Deep Field-South to characterize the evolution of the comoving infrared (IR) energy density of the universe up to z ∼ 1. Using published ancillary optical data, we first obtain a nearly complete redshift determination for the 24 μm objects associated with R ≲ 24 mag counterparts at z ≲ 1. These sources represent ∼55%-60% of the total MIPS 24 μm population with f24 μm ≳ 80 μJy, the rest of the sample likely lying at higher redshifts. We then determine an estimate of their total IR luminosities using various libraries of IR spectral energy distributions. We find that the 24μm population at 0.5 ≲ z ≲ 1 is dominated by "luminous infrared galaxies" (i.e., 1011 L⊙ ≤ LIR ≤ 1012 L⊙), the counterparts of which appear to be also luminous at optical wavelengths and tend to be more massive than the majority of optically selected galaxies. A significant number of fainter sources (5 × 10 10 L⊙ ≤ LIR ≤ 1012 L ⊙) are also detected at similar distances. We finally derive 15 μm and total IR luminosity functions (LFs) up to z ∼ 1. In agreement with the previous results from the Infrared Space Observatory (ISO) and SCUBA and as expected from the MIPS source number counts, we find very strong evolution of the contribution of the IR-selected population with look-back time. Pure evolution in density is firmly excluded by the data, but we find considerable degeneracy between strict evolution in luminosity and a combination of increases in both density and luminosity [ZLIR* ∝ (1 + z) 3.2_0.7 -0.2, φIR*IR ∝ (1 + z)0.7 +0.2 -0.6]. A significant steepening of the faint-end slope of the IR luminosity function is also unlikely, as it would overproduce the faint 24 μm source number counts. Our results imply that the comoving IR energy density of the universe evolves as (1 + z)3.9±0.4 up to z ∼ 1 and that galaxies luminous in the infrared (i.e., LIR ≥ 1011 L⊙) are responsible for 70% ± 15% of this energy density at z ∼ 1. Taking into account the contribution of the UV luminosity evolving as (1 + z)∼2.5, we infer that these IR-luminous sources dominate the star-forming activity beyond z ∼ 0.7. The uncertainties affecting these conclusions are largely dominated by the errors in the k-corrections used to convert 24 μm fluxes into luminosities.
• Gordon, K. D., Rieke, G. H., Engelbracht, C. W., Muzerolle, J., Stansberry, J. A., Misselt, K. A., Morrison, J. E., Cadien, J., Young, E. T., Dole, H., Kelly, D. M., Alonso-Herrero, A., Egami, E., Su, K. Y., Papovich, C., Smith, P. S., Hines, D. C., Rieke, M. J., Blaylock, M., , Pérez-González, P. G., et al. (2005). Reduction algorithms for the multiband imaging photometer for Spitzer. Publications of the Astronomical Society of the Pacific, 117(831), 503-525.
  More info

  Abstract: We describe the data reduction algorithms for the Multiband Imaging Photometer for Spitzer (MIPS). These algorithms were based on extensive preflight testing and modeling of the Si:As (24 μm) and Ge:Ga (70 and 160 μm) arrays in MIPS and have been refined based on initial flight data. The behaviors we describe are typical of state-of-the-art infrared focal planes operated in the low backgrounds of space. The Ge arrays are bulk photoconductors and therefore show a variety of artifacts that must be removed to calibrate the data. The Si array, while better behaved than the Ge arrays, does show a handful of artifacts that must also be removed to calibrate the data. The data reduction to remove these effects is divided into three parts. The first part converts the nondestructively read data ramps into slopes while removing artifacts with time constants of the order of the exposure time. The second part calibrates the slope measurements while removing artifacts with time constants longer than the exposure time. The third part uses the redundancy inherent in the MIPS observing modes to improve the artifact removal iteratively. For each of these steps, we illustrate the relevant laboratory experiments or theoretical arguments, along with the mathematical approaches taken to calibrate the data. Finally, we describe how these preflight algorithms have performed on actual flight data. © 2005. The Astronomical Society of the Pacific. All rights reserved.
• Krause, O., Rieke, G. H., Birkmann, S. M., Floc'h, E. L., Gordon, K. D., Egami, E., Bieging, J., Hughes, J. P., Young, E. T., Hinz, J. L., Quanz, S. P., & Hines, D. C. (2005). Astronomy: Infrared echoes near the supernova remnant Cassiopeia A. Science, 308(5728), 1604-1606.
  More info

  Abstract: Two images of Cassiopeia A obtained at 24 micrometers with the Spitzer Space Telescope over a 1-year time interval show moving structures outside the shell of the supernova remnant to a distance of more than 20 arc minutes. Individual features exhibit apparent motions of 10 to 20 arc seconds per year, independently confirmed by near-infrared observations. The observed tangential velocities are at roughly the speed of light. It is likely that the moving structures are infrared echoes, in which interstellar dust is heated by the explosion and by flares from the compact object near the center of the remnant.
• Moro-Martín, A., Wolf, S., Malhotra, R., & Rieke, G. H. (2005). Signatures of planets in debris disks. European Space Agency, (Special Publication) ESA SP, 163-166.
  More info

  Abstract: In a planetary system with a belt of planetesimals and interior giant planets, the trapping of dust in mean motion resonances (MMRs) with the planet, and the ejection of particles due to gravitational scattering, create structure in the dust disk. In anticipation of Spitzer Space Telescope observations, we study how this affects the shape of the disk's spectral energy distribution (SED), and discuss its use to infer the presence of planets in spatially unresolved debris disks. In some cases, there are degeneracies that can only be resolved through high spatial resolution observations, like those by the Atacama Large Millimeter Array (ALMA). Debris disk structure is sensitive to long period planets, complementing a parameter space not covered by other methods, and therefore it is a valuable tool to help us understand the diversity of planetary systems.
• Muzerolle, J., Megeath, S. T., Flaherty, K. M., Gordon, K. D., Rieke, G. H., Young, E. T., & Lada, C. J. (2005). The outburst of V1647 orionis revealed by spitzer. Astrophysical Journal Letters, 620(2 II), L107-L110.
  More info

  Abstract: We present Spitzer Space Telescope observations of V1647 Ori, the outbursting source lighting McNeil's Nebula, taken near the optical peak of the outburst in early March 2004. The source is easily detected in all Spitzer imaging bands from 3.6 to 70 μm. The fluxes at all wavelengths are roughly a factor of 15 brighter than pre-outburst levels; we measure a bolometric luminosity of 44 L⊙. We posit that this event is due to an increase in the accretion luminosity of the source. Simple models of an accretion disk plus a tenuous envelope can qualitatively explain the observed pre- and post-outburst spectral energy distributions. The accretion activity implied by our results indicates that the outburst may be intermediate between FUor- and EXor-type events. We also report the discovery of a previously unknown mid-infrared counterpart to the nearby Herbig-Haro object HH 22. © 2005 The American Astronomical Society. All rights reserved.
• Noriega-Crespo, A., Marston, A. P., Reach, W. T., Rho, J., Carey, S., Latter, W. B., Rebull, L., Smith, H. A., Melnick, G., Fazio, G., Rieke, G., Muzerolle, J., Egami, E., Watson, D. M., Pipher, J. L., & Stapelfeldt, K. (2005). Spitzer's new view of the DR 21 star forming region. European Space Agency, (Special Publication) ESA SP, 399-400.
  More info

  Abstract: New observations of the DR 21 star forming region obtained with IRAC and MIPS, the IR camera and photometer onboard the Spitzer Space Telescope are presented. The unprecedented high sensitivity and resolution of the images, over an area of more than 0.5 , display a richness of detail in the complex structure of the ISM and reveal the presence of several new self-obscured (protostars) sources.
• Pérez-GonzáLez, P. G., Rieke, G. H., Egami, E., Alonso-Herrero, A., Dole, H., Papovich, C., Blaylock, M., Jones, J., Rieke, M., Rigby, J., Barmby, P., Fazio, G. G., Huang, J., & Martin, C. (2005). Spitzer view on the evolution of star-forming galaxies from z = 0 to z ∼ 3. Astrophysical Journal Letters, 630(1 I), 82-107.
  More info

  Abstract: We use a 24 μm-selected sample containing more than 8000 sources to study the evolution of star-forming galaxies in the redshift range from z = 0 to z ∼ 3. We obtain photometric redshifts for most of the sources in our survey using a method based on empirically built templates spanning from ultraviolet to mid-infrared wavelengths. The accuracy of these redshifts is better than 10% for 80% of the sample. The derived redshift distribution of the sources detected by our survey peaks at around z = 0.6-1.0 (the location of the peak being affected by cosmic variance) and decays monotonically from z ∼ 1 to z ∼ 3. We have fitted infrared luminosity functions in several redshift bins in the range 0 < z ≲ 3. Our results constrain the density and/or luminosity evolution of infrared-bright star-forming galaxies. The typical infrared luminosity (L*) decreases by an order of magnitude from z ∼ 2 to the present. The cosmic star formation rate (SFR) density goes as (1 + z)4.0±0.2 from z = 0 to 0.8. From z = 0.8 to z ∼ 1.2, the SFR density continues rising with a smaller slope. At 1.2 < z ≲ the cosmic SFR density remains roughly constant. The SFR density is dominated at low redshift (z ≲ 0.5) by galaxies that are not very luminous in the infrared (LTIR < 1011 L⊙, where LTIR is the total infrared luminosity, integrated from 8 to 1000 μm). The contribution from luminous and ultraluminous infrared galaxies (LTIR > 1011 L⊙) to the total SFR density increases steadily from z ∼ 0 up to z ∼ 2.5, forming at least half of the newly born stars by z ∼ 1.5. Ultraluminous infrared galaxies (LTIR > 1012 L⊙) play a rapidly increasing role for z ≳1.3. © 2005. The American Astronomical Society. All rights reserved.
• Pérez-González, P., Rieke, G. H., Floch, E. L., Papovich, C., Huang, J. S., Barmby, P., Dole, H., Egami, E., Alonso-Herrero, A., Rigby, J. R., Bei, L., Blaylock, M., Engelbracht, C. W., Fazio, G. G., Gordon, K. D., Misselt, K. A., Morrison, J. E., Muzerolle, J., Rieke, M. J., , Willner, S. P., et al. (2005). Cosmological surveys with the Spitzer space telescope. Revista Mexicana de Astronomia y Astrofisica: Serie de Conferencias, 24, 205-209.
  More info

  Abstract: NASA's Spitzer Space Telescope (formerly known as the Space Infrared Telescope Facility SIRTF) is now on normal science operation and open to the international community. One of the Guaranteed Time Observer programs consists in a series of surveys using the two imaging instruments on Spitzer: MIPS (observing at 24, 70, and 160 microns) and IRAC (3.6, 4.5, 5.6 and 8 microns). The program includes observations to various depths, from wide field shallow, to very deep confusion limited surveys. We are also conducting a series of supporting programs (including also data from the spectrograph on Spitzer, IRS) to help interpret what we see in the deep surveys, e.g., the characterization of the spectral energy distributions of about 150 QSOs, and an extensive study of low-metallicity nearby star-forming galaxies. GTC first light is scheduled when the first well-established results from our Cosmological Surveys program will be released, offering us an incomparable facility to perform spectroscopic and photometric follow-ups of mid- and far-infrared selected sources. Moreover, the combination of the GTC, Spitzer and the Large Millimeter Telescope (LMT) facilities will allow us to study the galaxy populations in the Universe with a sensitivity and a coverage of the electromagnetic spectrum that have no precedents until today. © 2005: Instituto de Astronomía.
• RIEKE, G., & LEBOFSKY, M. (2005). THE INTERSTELLAR EXTINCTION LAW FROM 1 TO 13 MICRONS. ASTROPHYSICAL JOURNAL, 288(2), 618-621.
• RIEKE, G., & LOW, F. (2005). INFRARED PHOTOMETRY OF EXTRAGALACTIC SOURCES. ASTROPHYSICAL JOURNAL, 176(3), L95-&.
• RIEKE, G., & RIEKE, M. (2005). STELLAR VELOCITIES AND THE MASS-DISTRIBUTION IN THE GALACTIC-CENTER. ASTROPHYSICAL JOURNAL, 330(1), L33-L37.
• RIEKE, G., LEBOFSKY, M., & WALKER, C. (2005). NGC-253 AND A PROPOSED SEQUENCE FOR NUCLEAR STARBURSTS. ASTROPHYSICAL JOURNAL, 325(2), 679-686.
• RIEKE, G., RIEKE, M., & PAUL, A. (2005). ORIGIN OF THE EXCITATION OF THE GALACTIC-CENTER. ASTROPHYSICAL JOURNAL, 336(2), 752-761.
• Rieke, G. H., Gordon, K. D., Hinz, J. L., Engelbracht, C. W., Peréz-González, P., Misselt, K. A., & Morrison, J. (2005). Galaxy spectral energy distributions: Results from spitzer. AIP Conference Proceedings, 761, 364-379.
  More info

  Abstract: Spitzer provides substantial advances for studies of external galaxies: 1.) it has the very high sensitivity toward extended, low-surface-brightness sources made possible by a cryogenic telescope in space; 2.) the use of large format arrays and projected pixel scales that sample the telescope image well provide substantial improvements in angular resolution compared with previous space infrared telescopes; and 3.) its spectrograph has wavelength resolution well-suited to extragalactic studies, as well as high performance arrays that provide a major advance in sensitivity. We show how these capabilities are already leading to new possibilities in studying the structure of nearby galaxies. Combined with recent breakthroughs in high quality imaging at other wavelengths, we can anticipate a substantial improvement in our understanding of how different components of a galaxy relate to each other and how their interactions influence galaxy evolution. In addition, Spitzer is advancing our understanding of the behavior of the polyaromatic hydrocarbon (PAH) emission features, as a function of environment and metallicity. New features are also being discovered due to the high-sensitivity mapping capabilities of the spectrograph. An additional direction for research with Spitzer arises from its deep survey capabilities and the possibility of testing how the spectral energy distributions of galaxies evolve at large look-back times. © 2005 American Institute of Physics.
• Rieke, G. H., Su, K. Y., Stansberry, J. A., Trilling, D., Bryden, G., Muzerolle, J., White, B., Gorlova, N., Young, E. T., Beichman, C. A., Stapelfeldt, K. R., & Hines, D. C. (2005). Decay of planetary debris disks. Astrophysical Journal Letters, 620(2 I), 1010-1026.
  More info

  Abstract: We report new Spitzer 24 μm photometry of 76 main-sequence A-type stars. We combine these results with previously reported Spitzer 24 μm data and 24 and 25 μm photometry from the Infrared Space Observatory and the Infrared Astronomy Satellite. The result is a sample of 266 stars with mass close to 2.5 M⊙ all detected to at least the ∼7 σ level relative to their photospheric emission. We culled ages for the entire sample from the literature and/or estimated them using the H-R diagram and isochrones; they range from 5 to 850 Myr. We identified excess thermal emission using an internally derived K - 24 (or 25) μm photospheric color and then compared all stars in the sample to that color. Because we have excluded stars with strong emission lines or extended emission (associated with nearby interstellar gas), these excesses are likely to be generated by debris disks. Younger stars in the sample exhibit excess thermal emission more frequently and with higher fractional excess than do the older stars. However, as many as 50% of the younger stars do not show excess emission. The decline in the magnitude of excess emission, for those stars that show it, has a roughly t0/time dependence, with to ∼150 Myr. If anything, stars in binary systems (including Algol-type stars) and λ Boo stars show less excess emission than the other members of the sample. Our results indicate that (1) there is substantial variety among debris disks, including that a significant number of stars emerge from the protoplanetary stage of evolution with little remaining disk in the 10-60 AU region and (2) in addition, it is likely that much of the dust we detect is generated episodically by collisions of large planetesimals during the planet accretion end game, and that individual events often dominate the radiometric properties of a debris system. This latter behavior agrees generally with what we know about the evolution of the solar system, and also with theoretical models of planetary system formation. © 2005, The American Astronomical Society. All rights reserved.
• Rigby, J. R., Rieke, G. H., Pérez-González, P., Donley, J. L., Alonso-Herrero, A., Huang, J. -., Barmby, P., & Fazio, G. G. (2005). Why optically faint AGNs are optically faint: The spitzer perspective. Astrophysical Journal Letters, 627(1 I), 134-139.
  More info

  Abstract: Optically faint X-ray sources (those fX/fR > 10) constitute about 20% of X-ray sources in deep surveys and are potentially highly obscured and/or at high redshift. Their faint optical fluxes are generally beyond the reach of spectroscopy. For a sample of 20 optically faint sources in CDFS, we compile 0.4-24 μm photometry, relying heavily on the Spitzer Space Telescope. We estimate photometric redshifts for 17 of these 20 sources. We find that these AGNs are optically faint, both because they lie at significantly higher redshifts (median z ∼ 1.6) than most X-ray-selected AGNs, and because their spectra are much redder than standard AGNs. They have 2-8 keV X-ray luminosities in the Seyfert range, unlike the QSO luminosities of optically faint AGNs found in shallow wide-field surveys. Their contribution to the X-ray Seyfert luminosity function is comparable to that of z > 1 optically bright AGNs. © 2005. The American Astronomical Society. All rights reserved.
• Shi, Y., Rieke, G. H., Hines, D. C., Neugebauer, G., Blaylock, M., Rigby, J., Egami, E., Gordon, K. D., & Alonso-Herrero, A. (2005). Far-infrared observations of radio quasars and FR II radio galaxies. Astrophysical Journal Letters, 629(1 I), 88-99.
  More info

  Abstract: We report MIPS photometry of 20 radio-loud quasars and galaxies at 24 and 70 μm (and of five at 160 μm). We combine this sample with additional sources detected in the far-infrared by IRAS and ISO for a total of 47 objects, including 23 steep-spectrum type I AGNs: radio-loud quasars and broad-line radio galaxies; and 24 type II AGNs: narrow-line and weak-line FR II radio galaxies. Of this sample, the far-infrared emission of all but 3C 380 appears to be dominated by emission by dust heated by the AGN and by star formation. The AGN appears to contribute more than 50% of the far-infrared luminosity in most of the sources. It is also expected that the material around the nucleus is optically thin in the far-infrared. Thus, the measurements at these wavelengths can be used to test the orientation-dependent unification model. As predicted by the model, the behavior of the sources is consistent with the presence of an obscuring circumnuclear torus; in fact, we find that it may still have significant optical depth at 24 μm. In addition, as expected for the radio-loud quasars, there is a significant correlation between the low-frequency radio (178 MHz) and the 70 μm emission, two presumably isotropic indicators of nuclear activity. This result is consistent with the simple unified scheme. However, there is a population of radio galaxies that are underluminous at 70 μm compared with the radio-loud quasars and hence are a challenge to the simple unified model. © 2005. The American Astronomical Society. All rights reserved.
• Su, K. Y., Rieke, G. H., Misselt, K. A., Stansberry, J. A., Moro-Martin, A., Stapelfeldt, K. R., Werner, M. W., Trilling, D. E., Bendo, G. J., Gordon, K. D., Hines, D. C., Wyatt, M. C., Holland, W. S., Marengo, M., Megeath, S. T., & Fazio, G. G. (2005). The Vega debris disk: A surprise from spitzer. Astrophysical Journal Letters, 628(1 I), 487-500.
  More info

  Abstract: We present high spatial resolution mid- and far-infrared images of the Vega debris disk obtained with the Multiband Imaging Photometer for Spitzer (MIPS). The disk is well resolved, and its angular size is much larger than found previously. The radius of the disk is at least 43″ (330 AU), 70″ (543 AU), and 105″ (815 AU) in extent at 24, 70, and 160 μm, respectively. The disk images are circular, smooth, and without dumpiness at all three wavelengths. The radial surface brightness profiles follow radial power laws of r-3 or r-4 and imply an inner boundary at a radius of 11″ ± 2″ (86 AU). Assuming an amalgam of amorphous silicate and carbonaceous grains, the disk can be modeled as an axially symmetric and geometrically thin disk, viewed face-on, with the surface particle number density following an inverse radial power law. The disk radiometric properties are consistent with a range of models using grains of sizes ∼1 to ∼50 μm. The exact minimum and maximum grain size limits depend on the adopted grain composition. However, all of these models require an r-1 surface number density profile and a total mass of (3 ± 1.5) × 10-3 M⊕ in grains. We find that a ring, containing grains larger than 180 μm and at radii of 86-200 AU from the star, can reproduce the observed 850 μm flux, while its emission does not violate the observed MIPS profiles. This ring could be associated with a population of larger asteroidal bodies analogous to our own Kuiper Belt. Cascades of collisions starting with encounters among these large bodies in the ring produce the small debris that is blown outward by radiation pressure to much larger distances, where we detect its thermal emission. The relatively short lifetime (
• Young, E. T., Rieke, G. H., Blaylock, M., Cadien, J., Engelbracht, C. W., Gordon, K. D., Kelly, D., Misselt, K., Morrison, J., Muzerolle, J., Stansberry, J., Su, K. Y., Fadda, D., Frayer, D., Noriega-Crespo, A., & Rho, J. (2005). On-orbit experience with the Spitzer far infrared detectors. Proceedings of SPIE - The International Society for Optical Engineering, 5883, 1-8.
  More info

  Abstract: The far-infrared detectors on the Multiband Imaging Photometer for Spitzer (MIPS) represent a significant advancement in both format and sensitivity. We describe some of the operational experience since launch in August 2003. MIPS has three infrared detector arrays, a 128×128 format Si:As impurity band conduction detector operating at 24 μm, a 32×32 format Ge:Ga array operating at 70 μm and a 2×20 format stressed Ge:Ga array operating at 160 μm. Since both germanium detectors utilize conventional bulk photoconductors, they are subject to a number of non-ideal behaviors that are inherent in these types of devices when operated in ultra-low backgrounds. The principal problems are nonlinear time response, changing responsivity in a radiation environment, and flux non-linearities. We describe observing strategies that are used on MIPS to minimize the impact of these effects.
• Zheng, X. Z., Bell, E. F., Papovich, C., Wolf, C., Meisenheimer, K., Rix, H., Rieke, G. H., & Somerville, R. (2005). The dependence of star formation on galaxy stellar mass. ASTROPHYSICAL JOURNAL, 661(1), L41-L44.
  More info

  We combine Spitzer 24 mm observations with data from the COMBO-17 survey for similar to 15,000 galaxies 0.2 < z , we consider both the ultraviolet ( UV) and the infrared ( IR) luminosities, and account for the contributions of galaxies that are individually undetected at 24 mu m through image stacking. For all redshifts, we find that higher mass galaxies have a substantially lower specific SFR, < SFR >/< M-*>, than lower mass ones. However, we find the striking result that the rate of decline in cosmic SFR with redshift is nearly the same for massive and low mass galaxies, i.e., not a strong function of stellar mass. This analysis confirms one version of what has been referred to as "downsizing," namely, that the epoch of major mass buildup in massive galaxies is substantially earlier than the epoch of mass buildup in low-mass galaxies. Yet it shows that star formation activity is not becoming increasingly limited to low-mass galaxies toward the present epoch. We argue that this suggests that heating by AGN-powered radio jets is not the dominant mechanism responsible for the decline in cosmic SFR since, which is z similar to 1 borne out by comparison with semianalytic models that include this effect.
• Alonso-Herrero, A., Pérez-González, P., Rigby, J., Rieke, G. H., Floc'h, E. L., Barmby, P., Page, M. J., Papovich, C., Dole, H., Egami, E., Huang, J. -., Rigopoulou, D., Cristóbal-Hornillos, D., Eliche-Moral, C., Balcells, M., Prieto, M., Erwin, P., Engelbracht, C. W., Gordon, K. D., , Werner, M., et al. (2004). The nature of luminous X-ray sources with mid-infrared counterparts. Astrophysical Journal, Supplement Series, 154(1), 155-159.
  More info

  Abstract: We investigate the luminous X-ray sources in the Lockman Hole (LH) and the extended Groth strip (EGS) detected at 24 μm using the Multiband Imaging Photometer (MIPS) and also with the Infrared Array Camera (IRAC) on board the Spitzer Space Telescope. We assemble optical/infrared spectral energy distributions (SEDs) for 45 X-ray/24 μm sources in the EGS and LH. Only about one-quarter of the hard X-ray/24 μm sources show pure type 1 active galactic nucleus (AGN) SEDs. More than half of the X-ray/24 μm sources have stellar emission-dominated or obscured SEDs, similar to those of local type 2 AGN and spiral/starburst galaxies. One-third of the sources detected in hard X-rays do not have a 24 μm counterpart. Two such sources in the LH have SEDs resembling those of S0/elliptical galaxies. The broad variety of SEDs in the optical-to-Spitzer bands of X-ray-selected AGNs means that AGNs selected according to the behavior in the optical/infrared will have to be supplemented by other kinds of data (e.g., X-ray) to produce unbiased samples of AGNs.
• Alonso-Herrero, A., Takagi, T., Baker, A. J., Rieke, G. H., Rieke, M. J., Imanishi, M., & Scoville, N. Z. (2004). Obscured star formation in the central region of the dwarf galaxy NGC 5253. Astrophysical Journal Letters, 612(1 I), 222-237.
  More info

  Abstract: We present Hubble Space Telescope (HST) NICMOS observations (1.1-2.2 μm) and 1.9-4.1 μm spectroscopy of the central region of the dwarf galaxy NGC 5253. The HST NICMOS observations reveal the presence of a nuclear double star cluster separated by ≃0″.3-0″.4, or 6-8 pc (for a distance d = 4.1 Mpc). The double star cluster, also a bright double source of Paα emission, appears to be coincident with the double radio nebula detected at 1.3 cm. The eastern near-infrared star cluster (C1) is identified with the youngest optical cluster, whereas the western star cluster (C2), although it is almost completely obscured in the optical, becomes the brightest star cluster in the central region of NGC 5253 at wavelengths longer than 2 μm. Both clusters are extremely young, with ages of approximately 3.5 Myr. C2 is more massive than C1 by a factor of 6-20 (MC2 = 7.7 × 105 - 2.6 × 106 M⊙, for a Salpeter initial mass function [IMF] in the mass range 0.1-100 M⊙). Analysis of the circumnuclear spectrum excluding C1 and C2, as well as of a number of other near-infrared-selected clusters with a range of (young) ages, suggests that the star formation was triggered across the central regions of the galaxy. We have also modeled the nuclear UV to mid-infrared spectral energy distribution (SED) of NGC 5253 and found that the infrared part is well modeled by a highly obscured (AV = 17 mag) young starburst with a stellar mass consistent with our photometric estimates for C1 and C2. The SED model predicts a moderately bright polycyclic aromatic hydrocarbon (PAH) feature at 3.3 μm that is not detected in our nuclear L-band spectrum. NGC 5253's low metallicity and a top-heavy IMF likely combine to suppress the 3.3 μm PAH emission that is commonly seen in more massive starburst systems.
• Bell, E., Papovich, C., Wolf, C., Le Floc'h, E., Caldwell, J., Barden, M., Egami, E., McIntosh, D., Meisenheimer, K., Perez-Gonzalez, P., Rieke, G., Rieke, M., Rigby, ., & Rix, H. (2004). Toward an understanding of the rapid decline of the cosmic star formation rate. ASTROPHYSICAL JOURNAL, 625(1), 23-36.
  More info

  We present a first analysis of deep 24 μ m observations with the Spitzer Space Telescope of a sample of nearly 1500 galaxies in a thin redshift slice, 0: 65 &LE; z &LE; 0: 75. We combine the infrared data with redshifts, rest- frame luminosities, and colors from COMBO- 17 and with morphologies from Hubble Space Telescope images collected by the Galaxy Evolution from Morphology and SEDs ( GEMS) and Great Observatories OriginsDeep Survey ( GOODS) projects. To characterize the decline in star formation rate ( SFR) since z &SIM; 0: 7, we estimate the total thermal IR luminosities, SFRs, and stellar masses for the galaxies in this sample. At z &SIM; 0: 7, nearly 40% of intermediate- and high- mass galaxies ( with stellarmasses &GE; 2; 10(10) M-&ODOT;) are undergoing a period of intense star formation above their past- averaged SFR. In contrast, less than 1% of equally massive galaxies in the local universe have similarly intense star formation activity. Morphologically undisturbed galaxies dominate the total infrared luminosity density and SFR density: at z &SIM; 0: 7, more than half of the intensely star- forming galaxies have spiral morphologies, whereas less than &SIM; 30% are strongly interacting. Thus, a decline in major merger rate is not the underlying cause of the rapid decline in cosmic SFR since z &SIM; 0: 7. Physical properties that do not strongly affect galaxy morphology - for example, gas consumption and weak interactions with small satellite galaxies - appear to be responsible.
• Dole, H., Floc'h, E. L., Pérez-González, P., Papovich, C., Egami, E., Lagache, G., Alonso-Herrero, A., Engelbracht, C. W., Gordon, K. D., Hines, D. C., Krause, O., Misselt, K. A., Morrison, J. E., Rieke, G. H., Rieke, M. J., Rigby, J. R., Young, E. T., Bai, L., Blaylock, M., , Neugebauer, G., et al. (2004). Far-infrared source counts at 70 and 160 microns in Spitzer deep surveys. Astrophysical Journal, Supplement Series, 154(1), 87-92.
  More info

  Abstract: We derive galaxy source counts at 70 and 160 μm using the Multiband Imaging Photometer for Spitzer (MIPS) to map the Chandra Deep Field-South (CDF-S) and other fields. At 70 μm, our observations extend upward about 2 orders of magnitude in flux density from a threshold of 15 mJy, and at 160 μm they extend about an order of magnitude upward from 50 mJy. The counts are consistent with previous observations on the bright end. Significant evolution is detected at the faint end of the counts in both bands, by factors of 2-3 over no-evolution models. This evolution agrees well with models that indicate that most of the faint galaxies lie at redshifts between 0.7 and 0.9. The new Spitzer data already resolve about 23% of the cosmic far-infrared background at 70 μm and about 7% at 160 μm.
• Dole, H., Rieke, G. H., Lagache, G., Puget, J. -., Alonso-Herrero, A., Bai, L., Blaylock, M., Egami, E., Engelbracht, C. W., Gordon, K. D., Hines, D. C., Kelly, D. M., Floc'h, E. L., Misselt, K. A., Morrison, J. E., Muzerolle, J., Papovich, C., Pérez-González, P., Rieke, M. J., , Rigby, J. R., et al. (2004). Confusion of extragalactic sources in the mid- and far-infrared: Spitzer and beyond. Astrophysical Journal, Supplement Series, 154(1), 93-96.
  More info

  Abstract: We use the source counts measured with the Multiband Imaging Photometer for Spitzer at 24, 70, and 160 μm to determine the 5 σ confusion limits due to extragalactic sources: 56 μJy, 3.2 mJy, and 40 mJy at 24, 70, and 160 μm, respectively. We also make predictions for confusion limits for a number of proposed far-infrared missions of larger aperture (3.5-10 m diameter).
• EDELSON, R., MALKAN, M., & RIEKE, G. (2004). BROAD-BAND PROPERTIES OF THE CFA SEYFERT-GALAXIES .2. INFRARED TO MILLIMETER PROPERTIES. ASTROPHYSICAL JOURNAL, 321(1), 233-250.
• Egami, E., Dole, H., Huang, J. -., Pérez-Gonzalez, P., Floc'h, E. L., Papovich, C., Barmby, P., Ivison, R. J., Serjeant, S., Mortier, A., Frayer, D. T., Rigopoulou, D., Lagache, G., Rieke, G. H., Willner, S. P., Alonso-Herrero, A., Bai, L., Engelbracht, C. W., Fazio, G. G., , Gordon, K. D., et al. (2004). Spitzer observations of the SCUBA/VLA sources in the Lockman Hole: Star formation history of infrared-luminous galaxies. Astrophysical Journal, Supplement Series, 154(1), 130-136.
  More info

  Abstract: We present Spitzer Space Telescope imaging observations at 3.6, 4.5, 5.8, 8.0, and 24 μm of the SCUBA submillimeter sources and μJy VLA radio sources in a 5′ x 5′ area in the Lockman Hole East region. Out of the ∼40 SCUBA/VLA sources in the field, Spitzer counterparts were detected for nearly all except for the few low-weight SCUBA detections. We show that the majority (80%-90%) of the detected sources are cold (i.e., starburst-like) infrared-luminous galaxies (L IR > 10 11 L ⊙) at redshift 0.5 < z < 3.5, whose star-formation rate density (SFRD) is comparable to that of the optically selected star-forming galaxies.
• Engelbracht, C. W., Gordon, K. D., Bendo, G. J., Pérez-González, P., Misselt, K. A., Rieke, G. H., Young, E. T., Hines, D. C., Kelly, D. M., Stansberry, J. A., Papovich, C., Morrison, J. E., Egami, E., Su, K. Y., Muzerolle, J., Dole, H., Alonso-Herrero, A., Hinz, J. L., Smith, P. S., , Latter, W. B., et al. (2004). Far-infrared imaging of NGC 55. Astrophysical Journal, Supplement Series, 154(1), 248-252.
  More info

  Abstract: We present images of the galaxy NGC 55 at 24, 70, and 160 μm obtained with the Multiband Imaging Photometer for Spitzer (MIPS) instrument on board the Spitzer Space Telescope. The new images display the far infrared emission in unprecedented detail and demonstrate that the infrared morphology differs dramatically from that at shorter wavelengths. The most luminous emission region in the galaxy is marginally resolved at 24 μm and has a projected separation of nearly 520 pc from the peak emission in the optical and near-infrared. This region is responsible for ∼9% of the total emission at 24 μm and is likely a young star formation region. We show that this and other compact sources account for more than one-third of the total 24 μm emission. We compute a total infrared luminosity for NGC 55 of 1.2 × 109 L⊙. The star formation rate implied by our measurements is 0.22 M⊙ yr-1. We demonstrate that the cold dust is more extended than the warm dust in NGC 55 - the minor-axis scale heights are 0.32, 0.43, and 0.49 kpc at 24, 70, and 160 μm, respectively. The dust temperature map shows a range of temperatures that are well correlated with the 24 μm surface brightness, from 20 K in low surface brightness regions to 26 K in high surface brightness regions.
• Engelbracht, C., Gordon, K., Rieke, G., Werner, M., Dale, D., & Latter, W. (2004). Metallicity effects on mid-infrared colors and the 8 mu m PAH emission in galaxies. ASTROPHYSICAL JOURNAL, 628(1), L29-L32.
  More info

  We examine colors from 3.6 to 24 mm as a function of metallicity (O/H) for a sample of 34 galaxies. The galaxies range over 2 orders of magnitude in metallicity. They display an abrupt shift in the 8 mu m-to-24 mu m color for metallicities between one-third and one-fifth of the solar value. The mean 8-to-24 mu m flux density ratio below and above 12 + log (O/H) p 8.2 is 0.08 +/- 0.04 and 0.70 +/- 0.53, respectively. We use mid-IR colors and spectroscopy to demonstrate that the shift is primarily due to a decrease in the 8 mm flux density, as opposed to an increase in the 24 mm flux density. This result is most simply interpreted as being due to a weakening at low metallicity of the mid-IR emission bands usually attributed to PAHs (polycyclic aromatic hydrocarbons) relative to the small-grain dust emission. However, existing empirical spectral energy distribution models cannot account for the observed short-wavelength (below 8 mm) colors of the low-metallicity galaxies merely by reducing the strength of the PAH features; some other emission source (e. g., hot dust) is required.
• Floc'h, E. L., Pérez-González, P., Rieke, G. H., Papovich, C., Huang, J. -., Barmby, P., Dole, H., Egami, E., Alonso-Herrero, A., Wilson, G., Miyazaki, S., Rigby, J. R., Bei, L., Blaylock, M., Engelbracht, C. W., Fazio, G. G., Frayer, D. T., Gordon, K. D., Hines, D. C., , Misselt, K. A., et al. (2004). Identification of luminous infrared galaxies at 1 ≲ z ≲ 2.5. Astrophysical Journal, Supplement Series, 154(1), 170-173.
  More info

  Abstract: We present preliminary results on 24 μm detections of luminous infrared galaxies at z ≳ 1 with the Multiband Imaging Photometer for Spitzer (MIPS). Observations were performed in the Lockman Hole and the Extended Groth Strip (EGS) and were supplemented by data obtained with the Infrared Array Camera (IRAC) between 3 and 9 μm. The positional accuracy of ≲2″ for most MIPS/IRAC detections provides unambiguous identifications of their optical counterparts. Using spectroscopic redshifts from the Deep Extragalactic Evolutionary Probe survey, we identify 24 μm sources at z ≳ 1 in the EGS, while the combination of the MIPS/IRAC observations with BVRIJHK ancillary data in the Lockman Hole also shows very clear cases of galaxies with photometric redshifts at 1 ≲ z ≲ 2.5. The observed 24 μm fluxes indicate infrared luminosities greater than 1011 L⊙, while the data at shorter wavelengths reveal rather red and probably massive (M ≳ M*) galaxy counterparts. It is the first time that this population of luminous objects is detected up to z ∼ 2.5 in the infrared. Our work demonstrates the ability of the MIPS instrument to probe the dusty universe at very high red shift and illustrates how the forthcoming Spitzer deep surveys will offer a unique opportunity to illuminate a dark side of cosmic history not explored by previous infrared experiments.
• Gardner, J. P., Mather, J. C., Clampin, M., Greenhouse, M. A., Hammel, H. B., Hutchings, J. B., Jakobsen, P., Lilly, S. J., Lunine, J. I., McCaughrean, M. J., Mountain, M., Rieke, G. H., Rieke, M. J., Smith, E. P., Stiavelli, M., Stockman, H. S., Windhorst, R. A., & Wright, G. S. (2004). The science requirements of the James Webb space telescope. Proceedings of SPIE - The International Society for Optical Engineering, 5487(PART 2), 564-575.
  More info

  Abstract: The scientific requirements of the James Webb Space Telescope fall into four themes. The End of the Dark Ages: First Light and Reionization seeks to identify the first luminous sources to form and to determine the ionization history of the Universe. The Assembly of Galaxies seeks to determine how galaxies and the dark matter, gas, stars, metals, morphological structures, and active nuclei within them evolved from the epoch of reionization to the present. The Birth of Stars and Protoplanetary Systems seeks to unravel the birth and early evolution of stars, from infall onto dust-enshrouded protostars, to the genesis of planetary systems. Planetary Systems and the Origins of Life seeks to determine the physical and chemical properties of planetary systems including our own, and investigate the potential for life in those systems. These themes will guide the design and construction of the observatory.
• Gordon, K. D., Engelbracht, C. W., Muzerolle, J., Stansberry, J. A., Misselt, K. A., Morrison, J. E., Rieke, G., Cadien, J., Young, E. T., Dole, H., Kelly, D. M., Alonso-Herrero, A., Egami, E., Su, K. Y., Papovich, C., Smith, P. S., Hines, D. C., Rieke, M. J., Blaylock, M., , Pérez-González, P., et al. (2004). Reduction algorithms for the multiband imaging photometer for spitzer: 6 months of flight data. Proceedings of SPIE - The International Society for Optical Engineering, 5487(PART 1), 177-185.
  More info

  Abstract: The first six months of flight data from the Multiband Imaging Photometer for Spitzer (MIPS) were used to test MIPS reduction algorithms based on extensive preflight laboratory data and modeling. The underlying approach for the preflight algorithms has been found to be sound, but some modifications have improved the performance. The main changes are scan mirror dependent flat fields at 24 μm, hand processing to remove the time dependent stim flash latents and fast/slow response variations at 70 μm, and the use of asteroids and other sources instead of stars for flux calibration at 160 μm due to a blue "leak." The photometric accuracy of flux measurements is currently 5%, 10%, and 20% at 24, 70, and 160 μm, respectively. These numbers are expected to improve as more flight data are analyzed and data reduction algorithms refined.
• Gordon, K. D., Pérez-González, P., Misselt, K. A., Murphy, E. J., Bendo, G. J., Walter, F., Thornley, M. D., Kennicutt Jr., R. C., Rieke, G. H., Engelbracht, C. W., Smith, J. -., Alonso-Herrero, A., Appleton, P. N., Calzetti, D., Dale, D. A., Draine, B. T., Frayer, D. T., Helou, G., Hinz, J. L., , Hines, D. C., et al. (2004). Spatially resolved ultraviolet, Hα, infrared, and radio star formation in M81. Astrophysical Journal, Supplement Series, 154(1), 215-221.
  More info

  Abstract: We present Multiband Imaging Photometer for Spitzer (MIPS) observations of M81 at 24, 70, and 160 μm. The grand design nature of M81 is clearly seen, showing two well-resolved spiral arms containing numerous bright star-forming regions. The MIPS images reveal a significant amount of cold dust associated with the spiral arms. We investigate the variation of the ultraviolet (UV), Hα, and infrared (IR) luminosities and star formation rate (SFR) indicators across the face of M81 using the MIPS images and archival UV and Hα images. For regions in M81, we find that UV and Hα SFRs (uncorrected for dust attenuation) are always lower than the IR SFR. The cause of this behavior is dust attenuation and/or using SFR calibrations appropriate for entire galaxies, not regions in galaxies. The characteristics of the dust attenuation for the regions indicate the dust grains and/or geometry are different from those in starburst galaxies. The behavior of the infrared-radio correlation in M81 is seen to vary from the global average, with variations correlated with the morphology of M81.
• Gorlova, N., Padgett, D. L., Rieke, G. H., Muzerolle, J., Morrison, J. E., Gordon, K. D., Engelbracht, C. W., Hines, D. C., Hinz, J. C., Noriega-Crespo, A., Rebull, L., Stansberry, J. A., Stapelfeldt, K. R., Y., K., & Young, E. T. (2004). New debris-disk candidates: 24 Micron stellar excesses at 100 million years. Astrophysical Journal, Supplement Series, 154(1), 448-452.
  More info

  Abstract: Sixty-three members of the 100 Myr old open cluster M47 (NGC 2422) have been detected at 24 μm with the Spitzer Space Telescope. The Be star V 378 Pup shows an excess both in the near-infrared and at 24 μm (K - [24] = 2.4 mag), probably due to free-free emission from the gaseous envelope. Seven other early-type stars show smaller excesses, K - [24] = 0.6-0.9. Among late-type stars, two show large excesses: P922, a K1 V star with K - [24] = 1.08 ± 0.11, and P1121, an F9 V star with K - [24] = 3.72 ± 0.02. P1121 is the first known main-sequence star showing an excess comparable to that of β Pic, which may indicate the presence of an exceptionally massive debris disk. It is possible that a major planetesimal collision has occurred in this system, consistent with the few hundred Myr timescales estimated for the clearing of the solar system.
• Helou, G., Roussel, H., Appleton, P., Frayer, D., Stolovy, S., Storrie-Lombardi, L., Hurt, R., Lowrance, P., Makovoz, D., Maso, F., Surace, J., Gordon, K. D., Alonso-Herrero, A., Engelbracht, C. W., Misselt, K., Rieke, G., Rieke, M., Willner, S. P., Pahre, M., , Ashby, M. L., et al. (2004). The anatomy of star formation in NGC 300. Astrophysical Journal, Supplement Series, 154(1), 253-258.
  More info

  Abstract: The Spitzer Space Telescope was used to study the mid- to far-infrared properties of NGC 300 and to compare dust emission to Hα to elucidate the heating of the interstellar medium (ISM) and the star formation cycle at scales smaller than 100 pc. The new data allow us to discern clear differences in the spatial distribution of 8 μm dust emission with respect to 24 μm dust and to H II regions traced by Hα light. The 8 μm emission highlights the rims of H II regions, and the 24 μm emission is more strongly peaked in star-forming regions than 8 μm. We confirm the existence and approximate amplitude of interstellar dust emission at 4.5 μm, detected statistically in Infrared Space Observatory (ISO) data, and conclude it arises in star-forming regions. When averaging over regions larger than ∼1 kpc, the ratio of Hα to aromatic feature emission in NGC 300 is consistent with the values observed in disks of spiral galaxies. The mid- to far-infrared spectral energy distribution of dust emission is generally consistent with pre-Spitzer models.
• Hines, D. C., Rieke, G. H., Gordon, K. D., Rho, J., Misselt, K. A., Woodward, C. E., Werner, M. W., Krause, O., Latter, W. B., Engelbracht, C. W., Egami, E., Kelly, D. M., Muzerolle, J., Stansberry, J. A., Su, K. Y., Morrison, J. E., Young, E. T., Noriega-Crespo, A., Padgett, D. L., , Gehrz, R. D., et al. (2004). Imaging of the supernova remnant cassiopeia a with the Multiband Imaging Photometer For Spitzer (MIPS). Astrophysical Journal, Supplement Series, 154(1), 290-295.
  More info

  Abstract: We present new images of the supernova remnant (SNR) Cas A observed in the 24 and 70 μm bands of the Spitzer Space Telescope (Spitzer). The IR emission correlates well with the Si X-ray and optical [S II] emission but poorly with either the synchrotron-dominated radio structure or the continuum X-ray emission. The IR is therefore dominated by thermal emission from dust within the SNR and associated with emission-line gas inside the reverse shock region, confirming earlier IRAS and Infrared Space Observatory results. Supplemented by new photometric measurements from archived Midcourse Space Experiment images, we suggest stochastic heating to model the overall mid- to far-IR spectral energy distribution. The 24 and 70 μm images also reveal a counterjet to the well-known northeast jet feature imaged previously at X-ray, optical, and radio wavelengths. This IR counterjet corresponds well with (optical) fast-moving knots confirming its outflow nature. The opposing jetlike features define a symmetry axis that bisects the SNR and suggest that the supernova explosion was axisymmetric. The IR images also show a region in which the SNR forward shock appears to be propagating into a ∼650 M⊙ molecular cloud. The new images also show other details of the surrounding ISM structure, including two groups of knots extending ∼6′-12′ on either side of the SNR.
• Hinz, J. L., Rieke, G. H., Gordon, K. D., Pérez-González, P., Engelbracht, C. W., Alonso-Herrero, A., Morrison, J. E., Misselt, K., Hines, D. C., Gehrz, R. D., Polomski, E., Woodward, C. E., Humphreys, R. M., Regan, M. W., Rho, J., Beeman, J. W., & Haller, E. E. (2004). Energy sources of the far-infrared emission of M33. Astrophysical Journal, Supplement Series, 154(1), 259-265.
  More info

  Abstract: We present observations of the spiral galaxy M33 with Spitzer at 24, 70, and 160 μm. The excellent resolution and mapping capabilities of Spitzer combined with the proximity of M33 result in observations that enable a detailed study of the distribution of star formation (SF) and dust in the galaxy. We compare the morphology of M33 at far-infrared wavelengths with other standard SF indicators such as Hα and radio continuum using a Fourier filtering technique to separate the diffuse emission components from compact sources. We find that the infrared emission at 24 and 70 μm follows closely the structure of the ionized gas, indicating that it is heated largely by hot, ionizing stars. At 160 μm a diffuse cold dust component matches only approximately the structure of the old red stellar population or the distribution of blue light. It is, however, very similar to the structure of the diffuse nonthermal radio emission.
• Huang, J. -., Barmby, P., Fazio, G. G., Willner, S. P., Wilson, G., Rigopoulou, D., Alonso-Herrero, A., Dole, H., Egami, E., Floc'h, E. L., Papovich, C., Pérez-González, P., Rigby, J., Engelbracht, C. W., Gordon, K., Hines, D., Rieke, M., Rieke, G. H., Meisenheimer, K., & Miyazaki, S. (2004). Infrared array camera (IRAC) imaging of the Lockman Hole. Astrophysical Journal, Supplement Series, 154(1), 44-47.
  More info

  Abstract: IRAC imaging of a 4′.7 x 4′.7 area in the Lockman Hole detected over 400 galaxies in the IRAC 3.6 and 4.5 μm bands, 120 in the 5.8 μm band, and 80 in the 8.0 μm band in 30 minutes of observing time. Color-color diagrams suggest that about half of these galaxies are at redshifts 0.6 < z < 1.3 with about a quarter at higher redshifts (z > 1.3). We also detect IRAC counterparts for six of the seven SCUBA sources and all nine XMM-Newton sources in this area. The detection of the counterparts of the SCUBA sources and galaxies at z > 1.3 demonstrates the ability of IRAC to probe the universe at very high redshifts.
• Ivanov, V. D., Rieke, M. J., Engelbracht, C. W., Alonso-Herrero, A., Rieke, G. H., & Luhman, K. L. (2004). A medium-resolution near-infrared spectral library of late-type stars. I. Astrophysical Journal, Supplement Series, 151(2), 387-397.
  More info

  Abstract: We present an empirical infrared spectral library of medium-resolution (R ≈ 2000-3000) H (1.6 μm) and K (2.2 μm) band spectra of 218 red stars, spanning a range of [Fe/H] from ∼-2.2 to ∼+0.3. The sample includes Galactic disk stars, bulge stars from Baade's window, and red giants from Galactic globular clusters. We report the values of 19 indices covering 12 spectral features measured from the spectra in the library. Finally, we derive calibrations to estimate the effective temperature, and diagnostic relationships to determine the luminosity classes of individual stars from near-infrared spectra. This paper is part of a larger effort aimed at building a near-IR spectral library to be incorporated in population synthesis models, as well as at testing synthetic stellar spectra.
• Ivison, R. J., Greve, T. R., Serjeant, S., Bertoldi, F., Egami, E., Mortier, A. M., Alonso-Herrero, A., Barmby, P., Bei, L., Dole, H., Engelbracht, C. W., Fazio, G. G., Frayer, D. T., Gordon, K. D., Hines, D. C., Huang, J. -., Floc'h, E. L., Misselt, K. A., Miyazaki, S., , Morrison, J. E., et al. (2004). Spitzer observations of MAMBO galaxies: Weeding out active nuclei in starbursting protoellipticals. Astrophysical Journal, Supplement Series, 154(1), 124-129.
  More info

  Abstract: We present 3.6-24 μm Spitzer observations of an unbiased sample of nine luminous, dusty galaxies selected at 1200 μm by MAMBO on the IRAM 30 m telescope, a population akin to the well-known submillimeter or SCUBA galaxies (hereafter SMGs). Owing to the coarse resolution of submillimeter/millimeter cameras, SMGs have traditionally been difficult to identify at other wavelengths. We compare our multiwavelength catalogs to show that the overlap between 24 and 1200 μm must be close to complete at these flux levels. We find that all (4/4) of the most secure ≥ 4 σ SMGs have ≥4 σ counterparts at 1.4 GHz, while the fraction drops to 7/9 using all ≥3 σ SMGs. We show that combining mid-infrared (MIR) and marginal (≥3 σ) radio detections provides plausible identifications in the remaining cases, enabling us to identify the complete sample. Accretion onto an obscured central engine is betrayed by the shape of the MIR continuum emission for several sources, confirming Spitzer's potential to weed out active galaxies. We demonstrate the power of an S 24 μm/S 8 μm versus S 8 μm/S 4.5 μm color-color plot as a diagnostic for this purpose. However, we conclude that the majority (∼75%) of SMGs have rest-frame mid/far-IR spectral energy distributions commensurate with obscured starbursts. Sensitive 24 μm observations are clearly a useful route to identify and characterize reliable counterparts to high-redshift far-IR-bright galaxies. complementing what is possible via deep radio imaging.
• Krause, O., Birkmann, S. M., Rieke, G. H., Lentke, D., Klaas, U., Hines, D. C., & Gordon, K. D. (2004). No cold dust within the supernova remnant Cassiopeia A. Nature, 432(7017), 596-598.
  More info

  PMID: 15577902;Abstract: A large amount (about three solar masses) of cold (18 K) dust in the prototypical type II supernova remnant Cassiopeia A was recently reported. It was concluded that dust production in type II supernovae can explain how the large quantities (∼108 solar masses) of dust observed in the most distant quasars could have been produced within only 700 million years after the Big Bang. Foreground clouds of interstellar material, however, complicate the interpretation of the earlier submillimetre observations of Cas A. Here we report far-infrared and molecular line observations that demonstrate that most of the detected submillimetre emission originates from interstellar dust in a molecular cloud complex located in the line of sight between the Earth and Cas A, and is therefore not associated with the remnant. The argument that type II supernovae produce copious amounts of dust is not supported by the case of Cas A, which previously appeared to provide the best evidence for this possibility.
• LEBOFSKY, M., & RIEKE, G. (2004). EXTINCTION IN INFRARED-EMITTING GALACTIC NUCLEI. ASTROPHYSICAL JOURNAL, 229(1), 111-117.
• Lagache, G., Dole, H., Puget, J. -., Pérez-Gonzalez, P., Floc'h, E. L., Rieke, G. H., Papovich, C., Egami, E., Alonso-Herrero, A., Engelbracht, C. W., Gordon, K. D., Misselt, K. A., & Morrison, J. E. (2004). Polycyclic aromatic hydrocarbon contribution to the infrared output energy of the universe at z ≃ 2. Astrophysical Journal, Supplement Series, 154(1), 112-117.
  More info

  Abstract: We present an updated phenomenological galaxy evolution model to fit the Spitzer 24, 70, and 160 μm number counts, as well as all the previous mid- and far-infrared observations. Only a minor change of the comoving luminosity density distribution in the previous model (Lagache, Dole, & Puget), combined with a slight modification of the starburst template spectra mainly between 12 and 30 μm, are required to fit all the data available. We show that the peak in the Spitzer Multiband Imaging Photometer 24 μm counts is dominated by galaxies with redshift between 1 and 2, with a nonnegligible contribution from the z ≥ 2 galaxies (∼30% at S = 0.2 mJy). The very close agreement between the model and number counts at 15 and 24 μm strikingly implies that (1) the polycyclic aromatic hydrocarbon features remain prominent in the redshift band 0.5-2.5 and (2) the IR energy output has to be dominated by ∼ 3 × 1011 L⊙ to ∼3 × 1012 L⊙ galaxies from redshift 0.5 to 2.5. Combining Spitzer with Infrared Space Observatory deep cosmological surveys gives for the first time an unbiased view of the infrared universe from z = 0 to 2.5.
• Lester, D., Benford, D., Blain, A., Bradford, C. M., Dragovan, M., Langer, W., Lawrence, C., Leisawitz, D., Mather, J., Moseley, S. H., Lee, M., Rieke, G., Stacey, G., Yorke, H., & Young, E. (2004). The science case and mission concept for the single aperture far-infrared (SAFIR) observatory. Proceedings of SPIE - The International Society for Optical Engineering, 5487(PART 3), 1507-1521.
  More info

  Abstract: SAFIR is a large (10 m-class), cold (4-10 K) space telescope for wavelengths between 20 microns and 1 mm. It will provide sensitivity a factor of a hundred or more greater than that of Spitzer and Herschel, leveraging their capabilities and building on their scientific legacies. Covering this scientifically critical wavelength regime, it will complement the expected wavelength performance of the future flagship endeavors JWST and ALMA. This vision mission will probe the origin of stars and galaxies in the early universe, and explore the formation of solar systems around nearby young stars. Endorsed as a priority by the Decadal Study and successive OSS roadmaps, SAFIR represents a huge science need that is matched by promising and innovative technologies that will allow us to satisfy it. In exercising those technologies it will create the path for future infrared missions. This paper reviews the scientific goals of the mission and promising approaches for its architecture, and considers remaining technological hurdles. We review how SAFIR responds to the scientific challenges in the OSS Strategic Plan, and how the observatory can be brought within technological reach.
• Lotz, J. M., Davis, M., Faber, S. M., Guhathakurta, P., Gwyn, S., Huang, J., Koo, D. C., Le Floc'h, E., Lin, L., Newman, J., Noeske, K., Papovich, C., Willmer, C. N., Coil, A., Conselice, C. J., Cooper, M., Hopkins, A. M., Metevier, A., Primack, J., , Rieke, G., et al. (2004). The evolution of galaxy mergers and morphology at z < 1.2 in the Extended Groth Strip. ASTROPHYSICAL JOURNAL, 672(1), 177-197.
  More info

  We present the quantitative rest-frame B morphological evolution and galaxy merger fraction at 0.2 < z < 1.2 as observed by the All-Wavelength Extended Groth Strip International Survey (AEGIS). We use the Gini coefficient and M(20) to identify major mergers and classify galaxy morphology for a volume-limited sample of 3009 galaxies brighter than 0.4L(B)*, assuming pure luminosity evolution. We find that the merger fraction remains roughly constant at 10% +/- 2% for 0.2 < z < 1.2. The fraction of E/S0/Sa galaxies increases from 21% +/- 3% at z similar to 1.1 to 44% +/- 9% at z similar to 0.3, while the fraction of Sb-Ir galaxies decreases from 64% +/- 6% at z similar to 1.1 to 47% +/- 9% at z similar to 0.3. The majority of z 1.2 Spitzer MIPS 24 mu m sources with L(IR) > 10(11) L(circle dot) are disk galaxies, and only similar to 15% are classified as major merger candidates. Edge-on and dusty disk galaxies (Sb-Ir) are almost a third of the red sequence at z similar to 1.1, while E/S0/Sa make up over 90% of the red sequence at z similar to 0.3. Approximately 2% of our full sample are red mergers. We conclude (1) the merger rate does not evolve strongly between 0.2 < z < 1.2; (2) the decrease in the volume-averaged star formation rate density since z similar to 1 is a result of declining star formation in disk galaxies rather than a disappearing population of major mergers; (3) the build-up of the red sequence at z < 1 can be explained by a doubling in the number of spheroidal galaxies since z similar to 1.2.
• Marston, A. P., Reach, W. T., Noriega-Crespo, A., Rho, J., Smith, H. A., Melnick, G., Fazio, G., Rieke, G., Carey, S., Rebull, L., Muzerolle, J., Egami, E., Watson, D. M., Pipher, J. L., Latter, W. B., & Stapelfeldt, K. (2004). DR 21: A major star formation site revealed by Spitzer. Astrophysical Journal, Supplement Series, 154(1), 333-338.
  More info

  Abstract: We have obtained images of the obscured massive star-forming region DR 21 using both the Infrared Array Camera (IRAC) and Multiband Imaging Photometer for Spitzer (MIPS) instruments aboard the Spitzer Space Telescope. Our images cover an area of more than half a square degree. The unprecedented high sensitivity and resolution of both IRAC and MIPS allow us to reveal the complexity of this region for the first time. Our images show extended outflows from a dense disk of material. Previously observed molecular outflows from the center of DR 21 are clearly visible in our images and are embedded in a much larger region of diffuse filaments apparently flowing out from DR 21. Many of the point sources in the region seen by Spitzer at 8 and 24 μm are both very obscured and intrinsically red. We discuss the properties of some of these extremely red objects and indicate that they are likely to be Class I or earlier protostars. Other features observed include mid-infrared dark clouds that occasionally appear as swept up features from extremely red objects, including a 15 pc long north-south filament to the south of DR 21 itself.
• Muzerolle, J., Megeath, S. T., Gutermuth, R. A., Allen, L. E., Pipher, J. L., Hartmann, L., Gordon, K. D., Padgett, D. L., Noriega-Crespo, A., Myers, P. C., Fazio, G. G., Rieke, G. H., Young, E. T., Morrison, J. E., Hines, D. C., Su, K. Y., Engelbracht, C. W., & Misselt, K. A. (2004). The 24 micron view of embedded star formation in NGC 7129. Astrophysical Journal, Supplement Series, 154(1), 379-384.
  More info

  Abstract: We present observations of the star formation region NGC 7129 taken with the Multiband Imaging Photometer for Spitzer (MIPS). A significant population of sources, likely pre-main-sequence members of the young stellar cluster, are revealed outside the central photoionization region. Combining Infrared Array Camera (IRAC) and ground-based near-infrared images, we have obtained colors and spectral energy distributions for some 60 objects. The [3.6]-[4.5] versus [8]-[24] color-color plane shows sources clustered at several different loci, which roughly correspond to the archetypal evolutionary sequence Class 0, I, II, and III. We obtain preliminary classifications for 36 objects and find significant numbers of both Class I and II objects. Most of the pre-main-sequence candidates are associated with the densest part of the molecular cloud surrounding the photoionization region, indicating active star formation over a broad area outside the central cluster. We discuss three Class II candidates that exhibit evidence of inner disk clearing, which would be some of the youngest known examples of a transition from accretion to optically thin quiescent disks.
• Papovich, C., Dole, H., Egami, E., Floc'h, E. L., Pérez-González, P., Alonso-Herrero, A., Bai, L., Beichman, C. A., Blaylock, M., Engelbracht, C. W., Gordon, K. D., Hines, D. C., Misselt, K. A., Morrison, J. E., Mould, J., Muzerolle, J., Neugebauer, G., Richards, P. L., Rieke, G. H., , Rieke, M. J., et al. (2004). The 24 micron source counts in deep Spitzer Space Telescope surveys. Astrophysical Journal, Supplement Series, 154(1), 70-74.
  More info

  Abstract: Galaxy source counts in the infrared provide strong constraints on the evolution of the bolometric energy output from distant galaxy populations. We present the results from deep 24 μm imaging from Spitzer surveys, which include ≈5 × 104 sources to an 80% completeness of ≈60 μJy. The 24 μm counts rapidly rise at near-Euclidean rates down to 5 mJy, increase with a super-Euclidean rate between 0.4 and 4 mJy, and converge below ∼0.3 mJy. The 24 μm counts exceed expectations from nonevolving models by a factor of ≳10 at Sv ∼0.1 mJy. The peak in the differential number counts corresponds to a population of faint sources that is not expected from predictions based on 15 μm counts from the Infrared Space Observatory. We argue that this implies the existence of a previously undetected population of infrared-luminous galaxies at z ∼ 1-3. Integrating the counts to 60 μJy, we derive a lower limit on the 24 μm background intensity of 1.9 ± 0.6 nW m-2 sr-1 of which the majority (∼60%) stems from sources fainter than 0.4 mJy. Extrapolating to fainter flux densities, sources below 60 μJy contribute 0.8-0.4+0.9 n W m-2 sr-1 to the background, which provides an estimate of the total 24 μm background of 2.7-0.7+1.1 m-2 sr-1.
• RIEKE, G., LEBOFSKY, M., THOMPSON, R., LOW, F., & TOKUNAGA, A. (2004). THE NATURE OF THE NUCLEAR SOURCES IN M82 AND NGC-253. ASTROPHYSICAL JOURNAL, 238(1), 24-40.
• Regan, M. W., Thornley, M. D., Bendo, G. J., Draine, B. T., Aigen, L. i., Dale, D. A., Engelbracht, C. W., Kennicutt Jr., R. C., Armus, L., Calzetti, D., Gordon, K. D., Helou, G., Hollenbach, D. J., Jarrett, T. H., Kewley, L. J., Leitherer, C., Malhotra, S., Meyer, M., Misselt, K. A., , Morrison, J. E., et al. (2004). Spitzer Infrared Nearby Galaxies Survey (SINGS) imaging of NGC 7331: A panchromatic view of a ringed galaxy. Astrophysical Journal, Supplement Series, 154(1), 204-210.
  More info

  Abstract: Well-resolved infrared observations of nearby galaxies are of fundamental importance to the study of the processes that affect galactic evolution. In this paper we report on the first imaging results from the Spitzer Infrared Nearby Galaxies Survey (SINGS) using observations of the Sb galaxy NGC 7331. We present images of NGC 7331 over a large range of wavelengths that allow us to compare the distributions of gas, stars, and dust in unprecedented detail. As an example of the types of information that the full SINGS will provide, we use three methods to determine that the interstellar medium mass in the ring of NGC 7331 is ∼5 × 109 M⊙. We also present the first images showing emission from small hot (∼1000 K) dust grains, but we show that these dust grains contribute only a small fraction of the integrated 4.5 μm emission from NGC 7331.
• Rieke, G. H., Young, E. T., Cadien, J., Engelbracht, C. W., Gordon, K. D., Kelly, D. M., Low, F. J., Misselt, K. A., Morrison, J. E., Muzerolle, J., Rivlis, G., Stansberry, J. A., Beeman, J. W., Haller, E. E., Frayer, D. T., Latter, W. B., Noriega-Crespo, A., Padgett, D. L., Hines, D. C., , Bean, D., et al. (2004). On orbit performance of the MIPS instrument. Proceedings of SPIE - The International Society for Optical Engineering, 5487(PART 1), 50-61.
  More info

  Abstract: The Multiband Imaging Photometer for Spitzer (MIPS) provides long wavelength capability for the mission, in imaging bands at 24, 70, and 160μm and measurements of spectral energy distributions between 52 and 100μ,m at a spectral resolution of about 7%. By using true detector arrays in each band, it provides both critical sampling of the Spitzer point spread function and relatively large imaging fields of view, allowing for substantial advances in sensitivity, angular resolution, and efficiency of areal coverage compared with previous space far-infrared capabilities. The Si:As BIB 24μm array has excellent photometric properties, and measurements with rms relative errors of 1% or better can be obtained. The two longer wavelength arrays use Ge:Ga detectors with poor photometric stability. However, the use of 1.) a scan mirror to modulate the signals rapidly on these arrays, 2.) a system of on-board stimulators used for a relative calibration approximately every two minutes, and 3.) specialized reduction software result in good photometry with these arrays also, with rms relative errors of less than 10%.
• Rieke, G. H., Young, E. T., Engelbracht, C. W., Keely, D. M., Low, F. J., Haller, E. E., Beeman, J. W., Gordon, K. D., Stansberry, J. A., Misselt, K. A., Cadien, J., Morrison, J. E., Rivlis, G., Latter, W. B., Noriega-Crespo, A., Padgett, D. L., Stapelfeldt, K. R., Hines, D. C., Egami, E., , Muzerolle, J., et al. (2004). The Multiband Imaging Photometer for Spitzer (MIPS). Astrophysical Journal, Supplement Series, 154(1), 25-29.
  More info

  Abstract: The Multiband Imaging Photometer for Spitzer (MIPS) provides long-wavelength capability for the mission in imaging bands at 24, 70, and 160 μm and measurements of spectral energy distributions between 52 and 100 μm at a spectral resolution of about 7%. By using true detector arrays in each band, it provides both critical sampling of the Spitzer point-spread function and relatively large imaging fields of view, allowing for substantial advances in sensitivity, angular resolution, and efficiency of areal coverage compared with previous space far-infrared capabilities. The 24 μm array has excellent photometric properties, and measurements with rms relative errors of about 1% can be obtained. The two longer-wavelength arrays use detectors with poor photometric stability, but a system of onboard stimulators used for relative calibration, combined with a unique data pipeline, produce good photometry with rms relative errors of less than 10%.
• Rigby, J. R., & Rieke, G. H. (2004). Missing massive stars in starbursts: Stellar temperature diagnostics and the initial mass function. Astrophysical Journal Letters, 606(1 I), 237-257.
  More info

  Abstract: Determining the properties of starbursts requires spectral diagnostics of their ultraviolet radiation fields, to test whether very massive stars are present. We test several such diagnostics, using new models of line ratio behavior combining CLOUDY, Starburst99, and up-to-date spectral atlases. For six galaxies we obtain new measurements of He I 1.7 μm/Br10, a difficult to measure but physically simple (and therefore reliable) diagnostic. We obtain new measurements of He I 2.06 μm/Brγ in five galaxies. We find that He I 2.06 μm/Brγ and [O III]/H/β are generally unreliable diagnostics in starbursts. The heteronuclear and homonuclear mid-infrared line ratios (notably [Ne III] 15.6 μm/[Ne II] 12.8 μm) consistently agree with each other and with He I 1.7 μm/Br10; this argues that the mid-infrared line ratios are reliable diagnostics of spectral hardness. In a sample of 27 starbursts, [Ne III]/[Ne II] is significantly lower than model predictions for a Salpeter initial mass function (IMF) extending to 100 M⊙. Plausible model alterations strengthen this conclusion. By contrast, the low-mass and low-metallicity galaxies II Zw 40 and NGC 5253 show relatively high neon line ratios, compatible with a Salpeter slope extending to at least ∼40-60 M⊙. One solution for the low neon line ratios in the high-metallicity starbursts would be that they are deficient in ≥40 M ⊙ stars compared to a Salpeter IMF. An alternative explanation, which we prefer, is that massive stars in high-metallicity starbursts spend much of their lives embedded within ultra-compact H II regions that prevent the near- and mid-infrared nebular lines from forming and escaping. This hypothesis has important consequences for starburst modeling and interpretation.
• Rigby, J. R., Marcillac, D., Egami, E., Rieke, G. H., Richard, J., Kneib, J. -., Fadda, D., Willmer, C. N., Borys, C., van der Werf, P. P., Perez-Gonzalez, P. G., Knudsen, K. K., & Papovich, C. (2004). Mid-infrared spectroscopy of lensed galaxies at 1 < z < 3: The nature of sources near the MIPS confusion limit. ASTROPHYSICAL JOURNAL, 675(1), 262-280.
  More info

  We present Spitzer IRS mid-infrared spectra for 15 gravitationally lensed, 24 mu m-selected galaxies, and combine the results with four additional very faint galaxies with IRS spectra in the literature. The median intrinsic 24 mu m flux density of the sample is 130 mu Jy, enabling a systematic survey of the spectral properties of the very faint 24 mu m sources that dominate the number counts of Spitzer cosmological surveys. Six of the 19 galaxy spectra (32%) show the strong mid-IR continuua expected of AGNs; X-ray detections confirm the presence of AGNs in three of these cases, and reveal AGNs in two other galaxies. These results suggest that nuclear accretion may contribute more flux to faint 24 mu m-selected samples than previously assumed. Almost all the spectra show some aromatic (PAH) emission features; the measured aromatic flux ratios do not show evolution from z = 0. In particular, the high signal-to-noise mid-IR spectrum of SMMJ163554.2+ 661225 agrees remarkably well with low-redshift,lower luminosity templates. We compare the rest-frame 8 mu m and total infrared luminosities of star-forming galaxies, and find that the behavior of this ratio with total IR luminosity has evolved modestly from z = 2 to z = 0. Since the high aromatic-to-continuum flux ratios in these galaxies rule out a dominant contribution by AGNs, this finding implies systematic evolution in the structure and/or metallicity of infrared sources with redshift. It also has implications for the estimates of star-forming rates inferred from 24 mu m measurements, in the sense that at z similar to 2, a given observed frame 24 mu m luminosity corresponds to a lower bolometric luminosity than would be inferred from low-redshift templates of similar luminosity at the corresponding rest wavelength.
• Rigby, J. R., Rieke, G. H., Maiolino, R., Gilli, R., Papovich, C., Pérez-Gonzàlez, P., Alonso-Herrero, A., Floc'h, E. L., Engelbracht, C. W., Gordon, K., Hines, D. C., Hinz, J. L., Morrison, J. E., Muzerolle, J., Rieke, M. J., & Su, K. Y. (2004). 24 Micron properties of X-ray-selected active galactic nuclei. Astrophysical Journal, Supplement Series, 154(1), 160-165.
  More info

  Abstract: We examine the 24 μm to X-ray color of 157 X-ray-selected active galactic nuclei (AGNs) as a function of X-ray obscuration and optical classification in the Chandra Deep Field-South. The sample consists of the Chandra hard-band detections with 2-8 keV flux above 10-15 ergs s-1 cm-2. A deep 24 μm mosaic obtained with Spitzer provides mid-infrared fluxes for the sample. Since obscured AGNs locally have higher 24 μm/2-8 keV flux ratios than unobscured AGNs, and since X-ray background models predict a large population of obscured AGNs, we expect to find many X-ray-hard, IR-bright AGNs. Instead, we find that the 24 μm to X-ray flux ratio does not depend on X-ray hardness in the full sample, nor does it differ between narrow- and broad-line AGNs. We identify five nearly Compton-thick AGNs and find they have similar 24 μm to X-ray flux ratios compared to the full sample. We consider AGNs in the narrow redshift spikes at z ∼ 0.7; for these AGNs, there is some evidence that the flux ratio increases with X-ray hardness. The redshift slice also shows an odd trend that is also prominent in the full sample: a group of X-ray-hard AGNs with very low 24 μm to X-ray flux ratios.
• Roellig, T., Werner, M., Gallagher, D., Irace, W., Fazio, G., James, H., Rieke, G., Wilson, R., & Soifer, T. (2004). On-orbit performance of the spitzer space telescope. Proceedings of SPIE - The International Society for Optical Engineering, 5487(PART 1), 38-49.
  More info

  Abstract: The Spitzer Space Telescope (formally known as SIRTF) was successfully launched on August 25, 2003, and has completed its initial in-orbit checkout and science validation and calibration period. The measured performance of the observatory has met or exceeded all of its high-level requirements, it entered normal operations in January 2004, and is returning high-quality science data. A superfluid-helium cooled 85 cm diameter telescope provides extremely low infrared backgrounds and feeds three science instruments covering wavelengths ranging from 3.6 to 160 microns. The telescope optical quality is excellent, providing diffraction-limited performance down to wavelengths below 6.5 microns. Based on the first helium mass and boil-off rate measurements, a cryogenic lifetime in excess of 5 years is expected. This presentation will provide a summary of the overall performance of the observatory, with an emphasis on those performance parameters that have the greatest impact on its ultimate science return.
• Serjeant, S., Mortier, A. M., Ivison, R. J., Egami, E., Rieke, G. H., Willner, S. P., Rigopoulou, D., Alonso-Herrero, A., Barmby, P., Bei, L., Dole, H., Engelbracht, C. W., Fazio, G. G., Floc'h, E. L., Gordon, K. D., Greve, T. R., Hines, D. C., Huang, J. -., Misselt, K. A., , Miyazaki, S., et al. (2004). Submillimeter detections of Spitzer Space Telescope galaxy populations. Astrophysical Journal, Supplement Series, 154(1), 118-123.
  More info

  Abstract: We present submillimeter statistical detections of galaxies discovered in the 5′ x 5′ Spitzer Early Release Observations (to ∼4-15 μJy 5 σ at 3.6-8 μm, 170 μJy at 24 μm) through a stacking analysis of our reanalyzed SCUBA 8 mJy survey maps and a Spitzer identification of a new submillimeter point source in the 8 mJy survey region. For sources detected at 5.8 or 8 μm (154 and 111 sources, respectively), we detect positive skews in the submillimeter flux distributions at 99.2%-99.8% confidence using Kolmogorov-Smirnov tests, at both 850 and 450 μm. We also marginally detect the Spitzer 24 μm galaxies at 850 μm at 97% confidence and place limits on the mean submillimeter fluxes of the 3.6 and 4.5 μm sources. Integrating the submillimeter fluxes of the Spitzer populations, we find the 5.8 μm galaxies contribute 0.12 ± 0.05 nW m -2 sr -1 to the 850 μm background and 2.4 ± 0.7 nW m -2 sr -1 to the 450 μm background; similar contributions are made by the 8 μm-selected sample. We infer that the populations dominating the 5.8 and 8 μm extragalactic background light also contribute around a quarter of the 850 μm background and the majority of the 450 μm background.
• Smith, J. D., Dale, D. A., Armus, L., Draine, B. T., Hollenbach, D. J., Roussel, H., Helou, G., Kennicutt Jr., R. C., Li, A., Bendo, G. J., Calzetti, D., Engelbracht, C. W., Gordon, K. D., Jarrett, T. H., Kewley, L., Leitherer, C., Malhotra, S., Meyer, M. J., Murphy, E. J., , Regan, M. W., et al. (2004). Mid-infrared IRS spectroscopy of NGC 7331: A first look at the Spitzer Infrared Nearby Galaxies Survey (SINGS) legacy. Astrophysical Journal, Supplement Series, 154(1), 199-203.
  More info

  Abstract: The nearby spiral galaxy NGC 7331 was spectrally mapped from 5 to 38 μm using all modules of Spitzer's Infrared Spectrograph (IRS). A strong new dust emission feature, presumed due to polycyclic aromatic hydrocarbons, was discovered at 17.1 μm. The feature's intensity is nearly half that of the ubiquitous 11.3 μm band. The 7-14 μm spectral maps revealed significant variation in the 7.7 and 11.3 μm PAH features between the stellar ring and nucleus. Weak [O IV] 25.9 μm line emission was found to be centrally concentrated in the nucleus, with an observed strength of over 10% of the combined neon line flux, indicating an AGN or unusually active massive star photoionization. Two [S III] lines fix the characteristic electron density in the H II regions at ne ≲ 200 cm-3. Three detected H2 rotational lines, tracing warm molecular gas, together with the observed IR continuum, are difficult to match with standard photodissociation region (PDR) models. Either additional PDR heating or shocks are required to simultaneously match lines and continuum.
• Stansberry, J. A., Cleve, J. V., Reach, W. T., Cruikshank, D. P., Emery, J. P., Fernandez, Y. R., Meadows, V. S., Su, K. Y., Misselt, K., Rieke, G. H., Young, E. T., Werner, M. W., Engelbracht, C. W., Gordon, K. D., Hines, D. C., Kelly, D. M., Morrison, J. E., & Muzerolle, J. (2004). Spitzer observations of the dust coma and nucleus of 29P/Schwassmann- Wachmann. Astrophysical Journal, Supplement Series, 154(1), 463-468.
  More info

  Abstract: We obtained thermal images and spectra of comet and Centaur object 29P/Schwassmann-Wachmann 1 in late 2003 November. Images at 8, 24, and 70 μm reveal an extensive coma. At 24 μm the coma extends at least 8′ from the nucleus and exhibits a single jet. The dust production rate is estimated as ≲50 kg s-1. The 24 to 70 μm color temperature of the coma is 160 K. The debris trail is also detected at 24 μm and has an optical depth of ∼(7 ± 3) × 10-9. Thermal models fitted to photometry at 8, 24, and 70 μm indicate a nuclear radius of 27 ± 5 km, larger than all previous size estimates, and a geometric albedo of 0.025 ± 0.01, lower than any other Centaur object, but consistent with other comets. Analysis of the jet morphology indicates a rotation period in excess of 60 days. The spectra reveal features at 11.3 and 34 μm, which are tentatively identified as emission from olivine, including forsterite. This is the first identification of the mineralogy of the dust emitted by a Centaur object.
• Stapelfeldt, K. R., Holmes, E. K., Chen, C., Rieke, G. H., Su, K. Y., Hines, D. C., Werner, M. W., Beichman, C. A., Jura, M., Padgett, D. L., Stansberry, J. A., Bendo, G., Cadien, J., Marengo, M., Thompson, T., Velusamy, T., Backus, C., Blaylock, M., Egami, E., , Engelbracht, C. W., et al. (2004). First look at the Fomalhaut debris disk with the Spitzer Space Telescope. Astrophysical Journal, Supplement Series, 154(1), 458-462.
  More info

  Abstract: We present Spitzer Space Telescope early release observations of Fomalhaut, a nearby A-type star with dusty circumstellar debris. The disk is spatially resolved at 24, 70, and 160 μm using the Multiband Imaging Photometer for Spitzer (MIPS). While the disk orientation and outer radius are comparable to values measured in the submillimeter, the disk inner radius cannot be precisely defined: the central hole in the submillimeter ring is at least partially filled with emission from warm dust, seen in Spitzer Infrared Spectrograph (IRS) 17.5-34 μm spectra and MIPS 24 μm images. The disk surface brightness becomes increasingly asymmetric toward shorter wavelengths, with the south-southeast ansa always brighter than the north-northwest one. This asymmetry may reflect perturbations on the disk by an unseen interior planet.
• Su, K. Y., Kelly, D. M., Latter, W. B., Misselt, K. A., Frank, A., Volk, K., Engelbracht, C. W., Gordon, K. D., Hines, D. C., Morrison, J. E., Muzerolle, J., Rieke, G. H., Stansberry, J. A., & Young, E. (2004). High spatial resolution mid- and far-infrared imaging study of NGC 2346. Astrophysical Journal, Supplement Series, 154(1), 302-308.
  More info

  Abstract: We present the first high spatial resolution mid-IR and far-IR images of the planetary nebula NGC 2346 using the Multiband Imaging Photometer for Spitzer (MIPS) on board the Spitzer Space Telescope. The morphology at 24 μm is strikingly similar to that seen in the optical image, with an additional unresolved hot dust component at the center. The 70 μm image reveals a torus-like structure near the narrow waist of the bipolar nebula, while the 160 μm image shows a very extended cold dust envelope around the nebula. Our new MIPS data provide direct evidence that the mass loss in the end of the asymptotic giant branch (AGB) phase diverts from spherical symmetry to axisymmetry and that the binary central star has played an important role in the bipolar nebular evolution.
• Swinyard, B. M., Rieke, G., Ressler, M., Glasse, A., Wright, G., Ferlet, M., & Wells, M. (2004). Sensitivity estimates for the mid-infrared instrument (MIRI) on the JWST. Proceedings of SPIE - The International Society for Optical Engineering, 5487(PART 2), 785-793.
  More info

  Abstract: Modelling the scientific performance of infrared instruments during the design and definition phase of a project is an essential part of the system design optimisation for both the instrument and the observatory. This is particularly so in the case of space observatories where the opportunities for correcting design errors or omissions following launch are limited. We describe the approach taken to the estimation of the sensitivity of the Mid Infrared Instrument (MIRI) operating from 5 to 28 microns on the NASA/ESA James Webb Space Telescope (JWST) due for launch in 2011. We show how the sensitivity is estimated both for the photometric imager and the integral field spectrometer using a model that includes the effects of background radiation from the telescope and its surroundings; diffraction effects and detector performance and operations.
• Tyler, K., Quillen, A. C., LaPage, A., & Rieke, G. H. (2004). Diffuse X-ray emission in spiral galaxies. Astrophysical Journal Letters, 610(1 I), 213-225.
  More info

  Abstract: We compare the soft diffuse X-ray emission from Chandra images of 12 nearby intermediate-inclination spiral galaxies to the morphology seen in Hα, molecular gas, and mid-infrared emission. We find that diffuse X-ray emission is often located along spiral arms in the outer parts of spiral galaxies but tends to be distributed in a more nearly radially symmetric morphology in the center. The X-ray morphology in the spiral arms matches that seen in the mid-infrared or H α and thus implies that the X-ray emission is associated with recent active star formation. In the spiral arms there is a good correlation between the level of diffuse X-ray emission and that in the mid-infrared in different regions. The correlation between X-ray and mid-IR flux in the galaxy centers is less strong. We also find that the central X-ray emission tends to be more luminous in galaxies with brighter bulges, suggesting that more than one process is contributing to the level of central diffuse X-ray emission. We see no strong evidence for X-ray emission trailing the location of high-mass star formation in spiral arms. However, population synthesis models predict a high mechanical energy output rate from supernovae for a time period that is about 10 times longer than the lifetime of massive ionizing stars, conflicting with the narrow appearance of the arms in X-rays. The fraction of supernova energy that goes into heating the interstellar medium must depend on environment and is probably higher near sites of active star formation. The X-ray estimated emission measures suggest that the volume filling factors and scale heights are low in the outer parts of these galaxies but higher in the galaxy centers. The differences between the X-ray properties and morphology in the centers and outer parts of these galaxies suggest that galactic fountains operate in outer galaxy disks but that winds are primarily driven from galaxy centers.
• WILKING, B., LEBOFSKY, M., & RIEKE, G. (2004). THE WAVELENGTH DEPENDENCE OF INTER-STELLAR LINEAR-POLARIZATION - STARS WITH EXTREME VALUES OF LAMBDA-MAX. ASTRONOMICAL JOURNAL, 87(4), 695-697.
• WILKING, B., LEBOFSKY, M., MARTIN, P., RIEKE, G., & KEMP, J. (2004). WAVELENGTH DEPENDENCE OF INTER-STELLAR LINEAR-POLARIZATION. ASTROPHYSICAL JOURNAL, 235(3), 905-910.
• Werner, M. W., Roellig, T. L., Low, F. J., Rieke, G. H., Rieke, M., Hoffmann, W. F., Young, E., Houck, J. R., Brandl, B., Fazio, G. G., Hora, J. L., Gehrz, R. D., Helou, G., Soifer, B. T., Stauffer, J., Keene, J., Eisenhardt, P., Gallagher, D., Gautier, T. N., , Irace, W., et al. (2004). The Spitzer Space Telescope mission. Astrophysical Journal, Supplement Series, 154(1), 1-9.
  More info

  Abstract: The Spitzer Space Telescope, NASA's Great Observatory for infrared astronomy, was launched 2003 August 25 and is returning excellent scientific data from its Earth-trailing solar orbit. Spitzer combines the intrinsic sensitivity achievable with a cryogenic telescope in space with the great imaging and spectroscopic power of modern detector arrays to provide the user community with huge gains in capability for exploration of the cosmos in the infrared. The observatory systems are largely performing as expected, and the projected cryogenic lifetime is in excess of 5 years. This paper summarizes the on-orbit scientific, technical, and operational performance of Spitzer. Subsequent papers in this special issue describe the Spitzer instruments in detail and highlight many of the exciting scientific results obtained during the first 6 months of the Spitzer mission.
• Wilson, G., Huang, J. -., Pérez-González, P., Egami, E., Ivison, R. J., Rigby, J. R., Alonso-Herrero, A., Barmby, P., Dole, H., Fazio, G. G., Floc'h, E. L., Papovich, C., Rigopoulou, D., Bai, L., Engelbracht, C. W., Frayer, D., Gordon, K. D., Hines, D. C., Misselt, K. A., , Miyazaki, S., et al. (2004). Extremely red objects in the Lockman hole. Astrophysical Journal, Supplement Series, 154(1), 107-111.
  More info

  Abstract: We investigate extremely red objects (EROs) using near- and mid-infrared observations in five passbands (3.6 to 24 μm) obtained from the Spitzer Space Telescope, and deep ground-based R and K imaging. The great sensitivity of the Infrared Array Camera (IRAC) camera allows us to detect 64 EROs (a surface density of 2.90 ± 0.36 arcmin-2; [3.6]AB < 23.7) in only 12 minutes of IRAC exposure time, by means of an R - [3.6] color cut (analogous to the traditional red R - K cut). A pure infrared K - [3.6] red cut detects a somewhat different population and may be more effective at selecting z > 1.3 EROs. We find ∼17% of all galaxies detected by IRAC at 3.6 or 4.5 μm to be EROs. These percentages rise to about 40% at 5.8 μm, and about 60% at 8.0 μm. We utilize the spectral bump at 1.6 μm to divide the EROs into broad redshift slices using only near-infrared colors (2.2/3.6/4.5 μm). We conclude that two-thirds of all EROs lie at redshift z > 1.3. Detections at 24 μm imply that at least 11% of 0.6 < z < 1.3 EROs and at least 22% of z > 1.3 EROs are dusty star-forming galaxies.
• Young, E. T., Lada, C. J., Teixeira, P., Muzerolle, J., Muench, A., Stauffer, J., Beichman, C. A., Rieke, G. H., Hines, D. C., Su, K. Y., Engelbracht, C. W., Gordon, K. D., Misselt, K., Morrison, J., Stansberry, J., & Kelly, D. (2004). Spitzer observations of NGC 2547: The disk population at 25 million years. Astrophysical Journal, Supplement Series, 154(1), 428-432.
  More info

  Abstract: We present Spitzer observations of the young cluster NGC 2547, obtaining photometry at 3.6, 4.5, 5.8, 8.0, and 24 μm, reaching significantly fainter infrared sensitivities than previous studies. With these observations, we investigate the disk frequency in this cluster. A total of 3770, 2408, 1988, 1238, and 1123 sources were detected in the common region of the five respective bands. The detection limits were 14.9, 14.0, 13.5, 13.3, and 12.0 mag, respectively. The large majority of sources are associated with 2MASS objects. From this large ensemble, we utilize the criteria of Naylor et al. to identify 184 likely members of the cluster. The analyses in this paper are focused on these likely members. Of the 184 candidates, 162 were detected in at least one Infrared Array Camera (IRAC) band. These objects form a well-defined family in the J - K,K -[3.6] color-color diagram. There is no evidence for excess emission at 3.6 μm for cluster candidates with J - K < 0.8, corresponding to spectral types earlier than late K. For later type stars, only 12 have evidence for a 3.6 μm excess. Hence, we derive a 3.6 μm emitting disk fraction of less than 7%. The lack of excess for the more massive stars may indicate a difference in the disk dissipation timescales for different mass stars. At 24 μm, 32 of the sources are detected. Most of them have photospheric K -[3.6] and K -[24] colors, but approximately a quarter show an excess at 24 μm. This observation may be evidence for cool disks with central holes.
• Alonso-Herrero, A., Quillen, A. C., Rieke, G. H., Ivanov, V. D., & Efstathiou, A. (2003). Spectral energy distributions of Seyfert nuclei. Astronomical Journal, 126(1 1771), 81-100.
  More info

  Abstract: We present nuclear spectral energy distributions (SEDs) in the range 0. 4-16 μm for an expanded CfA sample of Seyfert galaxies. The spectral indexes (fν α ν-αIR) from 1 to 16 μm range from αIR ∼ 0.9 to 3.8. The shapes of the spectra are correlated with Seyfert type in the sense that steeper nuclear SEDs (νf ν increasing with increasing wavelength) tend to be found in Seyfert 2's, and flatter SEDs (νfν is constant) in Seyfert 1-1.5's. The galaxies optically classified as Seyferts 1.8's and 1.9's display values of αIR as in type 1 objects, or values intermediate between those of Seyfert 1's and Seyfert 2's. The intermediate SEDs of many Seyfert 1.81.9's may be consistent with the presence of a pure Seyfert 1 viewed through a moderate amount (AV ≲ 5 mag) of foreground galaxy extinction. We find, however, that between 10% and 20% of galaxies with broad optical line components have steep infrared SEDs. Torus models usually adopt high equatorial opacities to reproduce the infrared properties of Seyfert 1's and 2's, resulting in a dichotomy of infrared SEDs (flat for type 1's, and steep for type 2's). Such a dichotomy, however, is not observed in our sample. The wide range of spectral indexes observed in the type 2 objects, the lack of extremely steep SEDs, and the large numbers of objects with intermediate spectral indexes cannot be reconciled with predictions from existing optically thick torus models. We discuss possible modifications to improve torus models, including low optical depth tori, clumpy dusty tori, and high optical depth tori with an extended optically thin component.
• Alonso-Herrero, A., Rieke, G. H., Dole, H., Hines, D., Rieke, M. J., Egami, E., Papovich, C., Gordon, K., Misselt, K., & Engelbracht, C. (2003). Follow-up science of the SIRTF GTO Cosmological Survey Program with the GTC. Revista Mexicana de Astronomia y Astrofisica: Serie de Conferencias, 16, 257-258.
  More info

  Abstract: In this paper we describe the SIRTF/MIPS Cosmological Survey and the AGN Spectral Energy Distribution Programs. These programs are aimed at understanding the csmological evolution of star formation rate traced by the far infrared (IR) emission, to estimate the fraction of far-IR light from AGN, to resolve the far-IR background into galaxies, and to look for possible new classes of galaxies. The SIRTF photometric data alone will not be able to distinguish between AGN and powerful starbursts, based on experience from the ultraluminous IR galaxies (ULIRGs) discovered by IRAS. In addition, we will need spectroscopic confirmation of the photometric redshifts of the sources detected. In this paper we describe a few examples of possible follow-up observations with the GTC of sources detected by the SIRTF Cosmological Survey Program.
• Alonso-Herrero, A., Rieke, G. H., Rieke, M. J., & Kelly, D. M. (2003). The [Fe II] 1.644 micron emission in M82 and NGC 253: Is it a measure of the supernova rate?. Astronomical Journal, 125(3 1767), 1210-1225.
  More info

  Abstract: We present Hubble Space Telescope NICMOS [Fe II] 1.644 μm, Paα (1.87 μm), and continuum images of the starburst galaxies M82 and NGC 253 at an unprecedented spatial resolution, In both galaxies we detect [Fe II] compact sources superposed on a diffuse background in the disk of the galaxies, together with a component above and below the plane of the galaxy. The radio and [Fe II] emissions perpendicular to the disk of M82 show a remarkable similarity to each other, suggesting that both emissions originate in shocks from supernova explosions. We find a spatial correspondence between bright compact [Fe II]-emitting regions and the location of radio supernova remnants (SNRs) for approximately 30%-50% of radio SNRs in M82 and NGC 253. This lack of a one-to-one correspondence, more than being indicative of a different origin for the radio and [Fe II] emission in starbursts, suggests two populations of SNRs: an older population (≤, 104 yr), traced by the [Fe II] emission, and a younger population (a few hundred years old), traced by the radio SNRs. We therefore conclude that the [Fe II] emission in starburst galaxies provides a good estimate of the supernova activity. Using our newly determined [Fe II] luminosities (corrected for extinction) of M82 and NGC 253, we reevaluate the calibration of the supernova rate in terms of the [Fe II] luminosity for starburst galaxies.
• Gorlova, N. I., Meyer, M. R., Rieke, G. H., & Liebert, J. (2003). Gravity indicators in the near-infrared spectra of brown dwarfs. Astrophysical Journal Letters, 593(2 I), 1074-1092.
  More info

  Abstract: We investigate the sensitivity to temperature and gravity of the strong absorption features in the J- and K-band spectra of substellar objects. We compare the spectra of giants and young M dwarfs (of low gravity) to field M and L dwarfs (of high gravity) and to model spectra from the Lyon group. We find that low-resolution spectra of M4-M9 stars and young brown dwarfs at R ∼ 350 and signal-to-noise ratios greater than 70 can determine the spectral type to a precision of ±1 subtype using the H2O and CO bands and can measure the surface gravity to ±0.5 dex using the atomic lines of K I and Na I. This result points toward the development of photometric spectral indices to separate low-mass members from foreground and background objects in young clusters and associations. We also emphasize the complexity of the interpretation of the empirical quantities (e.g., spectral types) in terms of the physical variables (e.g., temperature, opacities) in the cool atmospheres of young brown dwarfs.
• Hinz, J. L., Rieke, G. H., & Caldwell, N. (2003). The Tully-Fisher relation in Coma and Virgo Cluster s0 galaxies. Astronomical Journal, 126(6 1776), 2622-2634.
  More info

  Abstract: We use the Tully-Fisher relation (TFR) to compare the behavior of S0 and late-type spiral galaxies. We determine circular velocities based on stellar kinematics derived from stellar absorption line spectroscopy for 10 S0's in the Coma Cluster and eight S0's in the Virgo Cluster. We combine these results with similar measurements of 13 Coma S0 galaxies obtained previously. We find that there is only a small offset, Δm H ∼ 0.2, in the H-band luminosity at a given circular velocity, v c ∼ 200 km s -1, between S0 and late-type spirals. This result implies a similar total H-band mass-to-light ratio (within an effective radius) among disk galaxies of different Hubble types. As the older stellar population in S0's is dimmer, this suggests a somewhat larger fraction of stellar mass in these S0's than in late-type spirals. We also find that the relation between (I- and H-band) luminosity and v c for the S0 galaxies is at best poorly defined and has a scatter of ∼1 mag, significantly larger than the TFR for late-type spirals, where the observed I- and H-band scatter is σ ∼ 0.3-0.5 mag. This substantial scatter confirms the original findings of Dressler & Sandage and is similar to that found in a study by Neistein and coworkers of 18 nearby S0 galaxies in the field where σ I ∼ 0.7 mag, but differs from the small scatter found by Mathieu and coworkers, σ I ∼ 0.3 mag, for six nearby S0's. Our results suggest that differing formation histories can lead to S0's with diverse properties and that S0's are more likely to be the outcomes of minor mergers or some "preprocessing" in groups of galaxies falling into clusters, rather than simply late-type spirals that have been stripped of their gas but are kinematically preserved. We suggest that it is likely that many mechanisms, such as slow encounters, tidal interactions, and gas stripping, may have occurred in the lifetimes of the galaxies and produced the heterogeneous class of S0's that are observed today.
• Kennicutt Jr., R. C., Armus, L., Bendo, G., Calzett, D., Dale, D. A., Draine, B. T., Engelbracht, C. W., Gordon, K. D., Grauer, A. D., Helou, G., Hollenbach, D. J., Jarrett, T. H., Kewley, L. J., Leitherer, C., Aigen, L. i., Malhotra, S., Regan, M. W., Rieke, G. H., Rieke, M. J., , Roussel, H., et al. (2003). SINGS: The SIRTF Nearby Galaxies Survey. Publications of the Astronomical Society of the Pacific, 115(810), 928-952.
  More info

  Abstract: The SIRTF Nearby Galaxy Survey is a comprehensive infrared imaging and spectroscopic survey of 75 nearby galaxies. Its primary goal is to characterize the infrared emission of galaxies and their principal infrared-emitting components, across a broad range of galaxy properties and star formation environments. SINGS will provide new insights into the physical processes connecting star formation to the interstellar medium properties of galaxies and provide a vital foundation for understanding infrared observations of the distant universe and ultraluminous and active galaxies. The galaxy sample and observing strategy have been designed to maximize the scientific and archival value of the data set for the SIRTF user community at large. The SIRTF images and spectra will be supplemented by a comprehensive multiwavelength library of ancillary and complementary observations, including radio continuum, H I, CO, submillimeter, BVRIJHK, Hα, Paα, ultraviolet, and X-ray data. This paper describes the main astrophysical issues to be addressed by SINGS, the galaxy sample and the observing strategy, and the SIRTF and other ancillary data products.
• Luhman, K. L., Stauffer, J. R., Muench, A. A., Rieke, G. H., Lada, E. A., Bouvier, J., & Lada, C. J. (2003). A census of the young cluster IC 348. Astrophysical Journal Letters, 593(2 I), 1093-1115.
  More info

  Abstract: We present a new census of the stellar and substellar members of the young cluster IC 348. We have obtained images at I and Z for a 42′ × 28′ field encompassing the cluster and have combined these measurements with previous optical and near-infrared photometry. From spectroscopy of candidate cluster members appearing in these data, we have identified 122 new members, 15 of which have spectral types of M6.5-M9, corresponding to masses of ∼0.08-0.015 M⊙ by recent evolutionary models. The latest census for IC 348 now contains a total of 288 members, 23 of which are later than M6 and thus are likely to be brown dwarfs. From an extinction-limited sample of members (AV ≤ 4) for a 16′ × 14′ field centered on the cluster, we construct an initial mass function (IMF) that is unbiased in mass and nearly complete for M/M⊙ ≥ 0.03 (≲M8). In logarithmic units where the Salpeter slope is 1.35, the mass function for IC 348 rises from high masses down to a solar mass, rises more slowly down to a maximum at 0.1-0.2 M⊙, and then declines into the substellar regime. In comparison, the similarly derived IMF for Taurus from Briceño et al. and Luhman et al. rises quickly to a peak near 0.8 M ⊙ and steadily declines to lower masses. The distinctive shapes of the IMFs in IC 348 and Taurus are reflected in the distributions of spectral types, which peak at M5 and K7, respectively. These data provide compelling, model-independent evidence for a significant variation of the IMF with star-forming conditions.
• MCLEOD, K., & RIEKE, G. (2003). NEAR-INFRARED IMAGING OF LOW-REDSHIFT QUASAR HOST GALAXIES .2. HIGH-LUMINOSITY QUASARS. ASTROPHYSICAL JOURNAL, 431(1), 137-146.
  More info

  We present H-band images of a complete sample of 26 high-luminosity quasars selected from the Bright Quasar Survey. We detect the quasar host galaxy in at least 23 of these objects. We compare these galaxies with host galaxies from a complementary sample of low-luminosity quasars and find the hosts of the high-luminosity quasars to be significantly brighter at H and possibly more massive. The average galaxy magnitude corresponds to a luminosity (and approximate mass) twice that of an L* galaxy. The high-luminosity quasars are possibly more likely to have brighter interacting companions than their low-luminosity counterparts. These results are consistent with suggestions that the highest levels of activity in radio-quiet quasars require a large host galaxy or a close interaction with a massive galaxy and that some of these interactions result in mergers.
• Alonso-Herrero, A., Rieke, G. H., Rieke, M. J., & Scoville, N. Z. (2002). Massive star formation in luminous infrared galaxies: Giant H II regions and their relation to super-star clusters. Astronomical Journal, 124(1 1759), 166-182.
  More info

  Abstract: We have used Hubble Space Telescope Near-Infrared Camera and Multi-Object Spectrometer broadband (at 1.6 μm) and narrowband Paα (λ rest = 1.87 μm) images to identify, respectively, star clusters and H II regions in a sample of eight luminous infrared galaxies (LIRGs). These observations have revealed the presence of a large population of super-star clusters and bright H II regions. A significant fraction of the H II regions shows Hα luminosities above that of 30 Doradus, the prototypical giant H II region. The excess of extremely luminous H II regions in LIRGs has been confirmed by comparison with normal galaxies observed at similar spatial resolutions. Despite the large numbers of identified star clusters and H II regions in LIRGs, we find only a small fraction of coincidences, between 4% and 30% of the total number of detected sources. Using evolutionary synthesis models we have reproduced the relative fractions of young H II regions and intermediate and old star clusters observed in Arp 299 and the central region NGC 3256 by using a Salpeter initial mass function and instantaneous star formation. H II regions with no detected near-infrared cluster counterpart (25%-39% of the detected sources) represent the youngest sites of star formation, with ages up to approximately 5 Myr and mostly intermediate mass (≃105 M⊙) ionizing clusters. For these two galaxies, within the present detection threshold we can detect only coincidences (4%-10% of the detected sources) between an H II region and a near-infrared star cluster for the most massive star clusters (≃10 6 M⊙) during the first 7 Myr of their evolution. If there is significant extinction during the first million years, we may not detect the youngest star-forming regions, and hence the observed fractions of H II regions and coincidences will be lower limits. The identified near-infrared super-star clusters with no detectable Paα emission represent the "old" population (53%-66% of the detected sources), with ages between 7 and 20-40 Myr. Older clusters possibly created in this or previous episodes of star formation are likely to exist in these systems but cannot be identified with the present detection threshold. Our study demonstrates that Pa" narrowband imaging of LIRGs and interacting galaxies identifies the youngest sites of star formation that could be otherwise missed by near-infrared broadband continuum surveys.
• Bieging, J. H., Rieke, M. J., & Rieke, G. H. (2002). CO 1st overtone spectra of cool evolved stars: Diagnostics for hydrodynamic atmosphere models. Astronomy and Astrophysics, 384(3), 965-981.
  More info

  Abstract: We present spectra covering the wavelength range 2.28 to 2.36 μm at a resolution of Δλ = 0.0007 μm (or R = 3500) for a sample of 24 cool evolved stars. The sample comprises 8 M supergiants, 5 M giants, 3 S stars, 6 carbon stars, and 2 RV Tauri variables. The wavelengths covered include the main parts of the 12C16O v = 2-0 and 3-1 overtone bands, as well as the v = 4-2 and 13CO v = 2-0 bandhead regions. CO lines dominate the spectrum for all the stars observed, and at this resolution most of the observed features can be identified with individual CO R- or P-branch lines or blends. The observed transitions arise from a wide range of energy levels extending from the ground state to E/k > 20 000 K. We looked for correlations between the intensities of various CO absorption line features and other stellar properties, including IR colors and mass loss rates. Two useful CO line features are the v = 2-0 R14 line, and the CO v = 2-0 bandhead. The intensity of the 2-0 bandhead shows a trend with K-[12] color such that the reddest stars (K-[12] > 3 mag) exhibit a wide range in 2-0 bandhead depth, while the least reddened have the deepest 2-0 bandheads, with a small range of variation from star to star. Gas mass loss rates for both the AGB stars and the red supergiants in our sample correlate with the K-[12] color, consistent with other studies. The data imply that stars with Mgas < 5 × 10-7 M⊙ y-1 exhibit a much narrower range in the relative strengths of CO 2-0 band features than stars with higher mass loss rates. The range in observed spectral properties implies that there are significant differences in atmospheric structure among the stars in this sample.
• Hanson, M. M., Luhman, K. L., & Rieke, G. H. (2002). A near-infrared survey of radio-selected ultracompact H II regions. Astrophysical Journal, Supplement Series, 138(1), 35-61.
  More info

  Abstract: A near-infrared (NIR) survey of 63 radio-selected, ultracompact (UC) H II regions representing 47 different star-forming sites has been completed. The survey was obtained using H-band imaging and moderate-resolution, R = 1200, K-band spectroscopy, centered on the radio emission peak of the UC H II regions. The goal of this survey was to determine the fraction of radio-selected UC H II regions that can be studied with NIR observations and analysis. Approximately 50% of the 63 radio-selected UC H II regions appear to be detected at NIR wavelengths in Brγ emission (107 ergs s -1 cm-2 sr-1). Typical line-of-sight extinction toward the detected UC H II regions ranged from AV = 30 to 50, though one source was measured to have AV = 80. For a few of these UC H II regions, the central ionizing sources are detected through high signal-to-noise ratio NIR spectra of photospheric transitions. This preliminary survey suggests that perhaps 5%-10% of UC H II regions showing NIR counterparts will have directly detectable central ionizing sources. Using the ratio of He I 2.11 to Brγ, the effective temperatures of the central ionizing stars in 25 UC H II regions have been estimated. While He I is not always detected in UC H II regions, when it was found or a meaningful upper limit determined, the spectral type implied by the ratio of He I 2.11 to Brγ closely matched similar estimates of spectral type derived from radio. Model predictions based on mid-infrared measurements appear to underestimate the temperature of the central ionizing stars for which we have directly detected spectral types. The line ratios of H2 2-1 S(1) and 1-0 S(0) relative to the 1-0 S(1) line in our sample of UC H II regions are generally indicative of dense photodissociation regions rather than shocks, similar to what is seen in the Orion Bar. This was true even for UC H II regions showing very weak Brγ emission. While Brγ was generally found to be spatially correlated with the radio emission, H2 showed little correlation with the UC H II regions, typically lying ≳ 10″ from the central radio emission. A discussion of each UC H II region studied is included in an extensive appendix.
• Harvey, P. M., Rieke, G. H., Lester, D. F., & Benford, D. J. (2002). Single aperture far-infrared observatory (SAFIR). Proceedings of SPIE - The International Society for Optical Engineering, 4850(2), 1097-1108.
  More info

  Abstract: The study on the single aperture far-infrared telescopes (SAFIR) is presented. The two most critical requirements for SAFIR are aperture and operating temperature, assuming the emissivity is minimized to a level limited by optical coatings and reasonable stray light considerations. The aperture and telescope background emission determine its ultimate limiting sensitivity as well as the practical limit of the number of seconds of integration required to reach the confusion limit on the sky.
• Rieke, M., Baum, S., Beichman, C., Crampton, D., Doyon, R., Eisenstein, D., Greene, T., Hodapp, K., Horner, S., Johnstone, D., Lesyna, L., Lilly, S., Meyer, M., Martin, P., McCarthy, D., Rieke, G., Roellig, T., Stauffer, J., Trauger, J., & Young, E. (2002). NGST NIRCam scientific program and design concept. Proceedings of SPIE - The International Society for Optical Engineering, 4850(1), 478-485.
  More info

  Abstract: The science program for the Next Generation Space Telescope (NGST) relies heavily on a high performance near-infrared imager. A design which supports the observations outlined in the Design Reference Mission (DRM) and which also supports enhanced searches for "first light" objects and planets has been developed. Key features of the design include use of refractive optics to minimize the volume and mass required, tunable filters for spectroscopic imaging, and redundant imagers for fail-safe wavefront sensing.
• Young, E. T., Rieke, G. H., Cadien, J. D., Dole, H. A., Englebracht, C. W., Gordon, K. D., Heim, G. B., Kelly, D. M., & Stansberry, J. A. (2002). Ground test characterization of the Muliband Imaging Photometer for SIRTF (MIPS). Proceedings of SPIE - The International Society for Optical Engineering, 4850(1), 98-107.
  More info

  Abstract: We describe the ground testing and characterization of the Multiband Imaging Photometer for SIRTF (MIPS). This instrument is a camera with three focal plane arrays covering broad spectral bands centered at 24 μm, 70 μm, and 160 μm. The instrument features a variety of operation modes that permit accurate photometry, diffraction-limited imaging, efficient mapping, and low resolution spectral energy distribution determinations. The observational philosophy of MIPS relies heavily on the frequent use of internal relative calibration sources as well as a high level of redundancy in the data collection. We show that by using this approach, users of MIPS can expect very sensitive, highly repeatable observations of astronomical sources. The ground characterization program for MIPS involved a number of facilities including test dewars for focal-plane level testing, a specialized cryostat for instrument-level testing, and tests in the flight SIRTF Cryo-Telescope Assembly.
• Alonso-Herrero, A., Engelbracht, C. W., Rieke, M. J., Rieke, G. H., & Quillen, A. C. (2001). NGC 1614: A laboratory for starburst evolution. Astrophysical Journal Letters, 546(2 PART 1), 952-965.
  More info

  Abstract: The modest extinction and reasonably face-on viewing geometry make the luminous infrared galaxy NGC 1614 an ideal laboratory for the study of a powerful starburst. Hubble Space Telescope/near-infrared camera and multiobject spectrometer (NICMOS) observations show (1) deep CO stellar absorption, tracing a starburst nucleus about 45 pc in diameter (2) surrounded by a ∼600 pc diameter ring of supergiant H II regions revealed in Paα line emission (3) lying within a molecular ring indicated by its extinction shadow in H - K, (4) all at the center of a disturbed spiral galaxy. The luminosities of the giant H II regions in the ring are extremely high, an order of magnitude brighter than 30 Doradus; very luminous H II regions, comparable with 30 Dor, are also found in the spiral arms of the galaxy. Luminous stellar clusters surround the nucleus and lie in the spiral arms, similar to clusters observed in other infrared luminous and ultraluminous galaxies. The star-forming activity may have been initiated by a merger between a disk galaxy and a companion satellite whose nucleus appears in projection about 300 pc to the northeast of the nucleus of the primary galaxy. The relation of deep stellar CO bands to surrounding ionized gas rings to molecular gas indicates that the luminous starburst started in the nucleus and is propagating outward into the surrounding molecular ring. This hypothesis is supported by evolutionary starburst modeling that shows that the properties of NGC 1614 can be fitted with two short-lived bursts of star formation separated by 5 Myr (and by inference by a variety of models with a similar duration of star formation). The total dynamical mass of the starburst region of 1.3 x 109 M⊙ is mostly accounted for by the old prestarburst stellar population. Although our starburst models use a modified Salpeter initial mass function (IMF) (turning over near 1 M⊙), the tight mass budget suggests that the IMF may contain relatively more 10-30 M⊙ stars and fewer low-mass stars than the Salpeter function. The dynamical mass is nearly 4 times smaller than the mass of molecular gas estimated from the standard ratio of 12CO (1-0) to H2. A number of arguments place the mass of gas in the starburst region at ∼25% of the dynamical mass, nominally about 1/15 and with an upper limit of 1/10 of the amount estimated from 12CO and the standard ratio.
• Alonso-Herrero, A., Rieke, M. J., Rieke, G. H., & Kelly, D. M. (2001). HST/NICMOS observations of M82. Astrophysics and Space Science, 276(2-4), 1109-1120.
  More info

  Abstract: The irregular galaxy M82 is known as the archetypal starburst galaxy. Its proximity (3.5 Mpc) makes this galaxy an ideal laboratory for studying the properties of its starburst. The detailed morphology of the [FeII] 1.644 μm and emission Paα (at 1.87 μm) is revealed by the NICMOS images. The peak of the 2.2 μm continuum brightness (evolved population) lies very close to the dynamical centre. Most of the Paα emission (which traces the young population) is distributed in a ring of star formation (with a 'hole' lacking line emission at the centre of the galaxy). These observations support the scenario in which the starburst in M82 is propagating outwards. It has long been suggested that the [FeII] emission in starburst galaxies can be used as a measure of supernova (SN) activity. M82 shows a large number of radio supernova remnants (SNRs), approximately 50, lying in the plane of the galaxy. The comparison of the positions of the bright compact [FeII] emitting regions with the location of the radio SNRs shows that there is no one-to-one spatial correspondence between the two emissions, suggesting that the radio and [FeII] emissions trace two populations of SNRs with different ages. Young (a few hundred years) SNRs are best traced by their radio emission, whereas the [FeII] stage lasts for at least a few 104 yr. The compact [FeII] sources contribute only some 20 % of the total [FeII] emission observed in M82. However, much of the remaining unresolved [FeII] emission in the plane of the galaxy may arise from SNRs that expanded and merged into a general interstellar medium within a few 104 yr. Presumably, as much as 70% of the total extinction-corrected [FeII] 1.644 μm in M82 is associated with SNRs. The extended and diffuse [FeII] component in M82 seems to be related with the superwind above and below the disc of the galaxy.
• Kenworthy, M., Hofmann, K., Close, L., Hinz, P., Mamajek, E., Schertl, D., Weigelt, G., Angel, R., Balega, Y. Y., Hinz, J., & Rieke, G. (2001). Gliese 569B: A young multiple brown dwarf system?. Astrophysical Journal Letters, 554(1 PART 2), L67-L70.
  More info

  Abstract: The nearby late M star Gliese 569B was recently found by adaptive optics imaging to be a double with separation ∼1 AU. To explore the orbital motion and masses, we have undertaken a high-resolution (∼0″.05) astrometric study. Images were obtained over 1.5 yr with bispectrum speckle interferometry at the 6.5 m Multiple Mirror Telescope (MMT) and 6 m Special Astrophysical Observatory telescope. Our data show motion corresponding to more than half the orbital period and constrain the total mass to be greater than 0.115 M⊙, with a most probable value of 0.145 M⊙. Higher masses cannot be excluded without more extended observations, but from statistical analysis we find an 80% probability that the total mass is less than 0.21 M⊙. An infrared spectrum of the blended B double obtained with the MMT has been modeled as a blend of two different spectral types, chosen to be consistent with the measured J-and K-band brightness difference of a factor of ∼2. The blended fit is not nearly as good as that to a pure M8.5+ template. Therefore, we hypothesize that the brighter component likely has two unresolved components with near equal masses, each the same as the fainter component. If G1 569B is a triple, our dynamical limits suggest each component has a mass of 50+23-4 MJup. We infer an age for the system of 300 Myr from its kinematic motion, which places it as a member of the Ursa Major moving group. All the above parameters are consistent with the latest DUSTY evolution models for brown dwarfs.
• Quillen, A. C., McDonald, C., Alonso-Herrero, A., Lee, A., Shaked, S., Rieke, M. J., & Rieke, G. H. (2001). The multitude of unresolved continuum sources at 1.6 microns in Hubble Space Telescope images of Seyfert galaxies. Astrophysical Journal Letters, 547(1 PART 1), 129-139.
  More info

  Abstract: We examine 112 Seyfert galaxies observed by the Hubble Space Telescope at 1.6 μm. We find that ∼ 50% of the Seyfert 2.0 galaxies which are part of the Revised Shapely-Ames (RSA) Catalog or the CfA redshift sample contain unresolved continuum sources at 1.6 μm. All but a couple of the Seyfert 1.0-1.9 galaxies display unresolved continuum sources. The unresolved sources have fluxes of order 1 mJy, near infrared luminosities of order 1041 ergs s-1, and absolute magnitudes MH ∼ -16. Comparison non-Seyfert galaxies from the RSA Catalog display significantly fewer (∼20%), somewhat lower luminosity nuclear sources, which could be due to compact star clusters. We find that the luminosities of the unresolved Seyfert 1.0-1.9 sources at 1.6 μm are correlated with [O III] λ15007 and hard X-ray luminosities, implying that these sources are nonstellar. Assuming a spectral energy distribution similar to that of a Seyfert 2 galaxy, we estimate that a few percent of local spiral galaxies contain black holes emitting as Seyferts at a moderate fraction, ∼10-1-10-4, of their Eddington luminosities. We find no strong correlation between 1.6 μm fluxes and hard X-ray or [O III] λ5007 fluxes for the pure Seyfert 2.0 galaxies. These galaxies also tend to have lower 1.6 μm luminosities compared to the Seyfert 1.0-1.9 galaxies of similar [O III] luminosity. Either large extinctions (AV ∼ 20-40) are present toward their continuumemitting regions or some fraction of the unresolved sources at 1.6 μ are compact star clusters. With increasing Seyfert type the fraction of unresolved sources detected at 1.6 μm and the ratio of 1.6 μm to [O III] fluxes tend to decrease. These trends are consistent with the unification model for Seyfert 1 and 2 galaxies.
• Alonso-Herrero, A., Rieke, G. H., Rieke, M. J., & Scoville, N. Z. (2000). Extreme star formation in the interacting galaxy Arp 299 (IC 694 + NGC 3690). Astrophysical Journal Letters, 532(2 PART 1), 845-866.
  More info

  Abstract: We present a comprehensive study of the star formation properties of the infrared luminous galaxy Arp 299 (IC 694 + NGC 3690). The observations include Hubble Space Telescope (HST) NICMOS imaging and Multiple Mirror Telescope optical and near-infrared spectroscopy together with HST archival data. We correct the galaxy parameters for extinction and use the results as boundary conditions for evolutionary starburst models. These models and other arguments show that Arp 299 has been going through a broad variety of interaction-induced star formation for the last ∼15 Myr. In addition to nuclear starbursts in the two colliding galaxies, there are nearby luminous star-forming regions that may be the result of molecular clouds breaking up and starting to form massive stars as they approach the nuclear potential. Two regions near the interaction region have very recently formed massive stars ( ∼4 Myr old). One of these regions in particular appears to have undergone a starburst of very short duration, in contrast with the 5-10 Myr durations that are typical of nuclear events. These regions will probably form gravitationally bound new dwarf galaxies, although they are close enough to the more massive original galaxies that they will probably eventually be subsumed into them. In addition, we find 19 H II regions at least as energetic as 30 Doradus, and 21 older star clusters that likely are the products of similar H II regions formed in the past. This population of supergiant H II regions is unprecedented in normal galaxies and emphasizes that the effects of the interaction propagate through the entire pair of galaxies.
• Alonso-Herrero, A., Rieke, M. J., Rieke, G. H., & Shields, J. C. (2000). The nature of LINERs. Astrophysical Journal Letters, 530(2 PART 1), 688-703.
  More info

  Abstract: We present J-band (1.15-1.35 μm) spectroscopy of a sample of nine galaxies showing some degree of LINER activity (classical LINERs, weak-[O I] LINERs, and transition objects), together with H-band spectroscopy for some of them. A careful subtraction of the stellar continuum allows us to obtain reliable [Fe II] 1.2567 μm/Paβ line ratios. We conclude that different types of LINERs (i.e., photoionized by a stellar continuum or by an active galactic nucleus) cannot be easily distinguished based solely on the [Fe II] 1.2567 μm/Paβ line ratio. The emission-line properties of many LINERs can be explained in terms of an aging starburst. The optical line ratios of these LINERs are reproduced by a model with a metal-rich H II region component photoionized with a single stellar temperature T* = 38,000 K, plus a supernova remnant (SNR) component. The [Fe II] line is predominantly excited by shocks produced by SNRs in starbursts and starburst-dominated LINERs, while Paβ tracks H II regions ionized by massive young stars. The contribution from SNRs to the overall emission-line spectrum is constrained by the [Fe II] 1.2567 μm/Paβ line ratio. Although our models for aging starbursts are constrained only by these infrared lines, they consistently explain the optical spectra of the galaxies also. The LINER-starburst connection is tested by predicting the time dependence of the ratio of the ionizing luminosity (Lion) to the supernova rate (SNr), Lion/(SNr). We predict the relative number of starbursts to starburst-dominated LINERs (aging starbursts) and show that it is in approximate agreement with survey findings for nearby galaxies.
• Engelbracht, C. W., Young, E. T., Rieke, G. H., Rivlis, G., Beeman, J. W., & Haller, E. E. (2000). Observing and calibration strategies for fir imaging with SIRTF. Experimental Astronomy, 10(2-3), 403-413.
  More info

  Abstract: We present data from a 16×32 array of unstressed Ge:Ga detectors, showing the long time constant responses and hook effect characteristic of these devices. This array is half the size of the 70 μm imaging array planned for MIPS, the Multiband Imaging Photometer for SIRTF. We present simulations of the FIR (far infrared) sky as viewed by a MIPS array, including realistic noise effects and extraction of point sources with a standard photometry package, showing that the photometric goals of MIPS are attainable with the current array performance and using standard analysis techniques. Previous calculations by Heim et al. (1998) had determined that MIPS would achieve 5-σ detections of ≤1 mJy at 70 μm in 2000 s; the simulations presented here obtain results consistent with those calculations.
• Ivanov, V. D., Rieke, G. H., Groppi, C. E., Alonso-Herrero, A., Rieke, M. J., & Engelbracht, C. W. (2000). Testing the AGN-starburst connection in Seyfert galaxies. Astrophysical Journal Letters, 545(1 PART 1), 190-204.
  More info

  Abstract: We use the CO band at 2.3 μm to constrain the populations of young stars in the central regions of Seyfert galaxies. We report new CO band spectroscopy of 46 Seyfert galaxies. In most cases, the observed CO indices appear diluted by the presence of a nonstellar component (most likely, warm dust surrounding the active nucleus). We used JHKL aperture photometry to estimate the nonstellar contribution at 2.3 μm. We successfully corrected the CO band for the dilution for 16 galaxies which were not dominated by the nonstellar component. Comparing with CO indices measured in elliptical and purely starbursting galaxies, we find no evidence for strong starbursts in the majority of these galaxies.
• Luhman, K. L., Rieke, G. H., Young, E. T., Cotera, A. S., Chen, H., Rieke, M. J., Schneider, G., & Thompson, R. I. (2000). The initial mass function of low-mass stars and brown dwarfs in young clusters. Astrophysical Journal Letters, 540(2 PART 1), 1016-1040.
  More info

  Abstract: We have obtained images of the Trapezium Cluster (140″ × 140″; 0.3 pc × 0.3 pc) with the Hubble Space Telescope Near-Infrared Camera and Multi-Object Spectrometer (NICMOS). Combining these data with new ground-based K-band spectra (R = 800) and existing spectral types and photometry, we have constructed an H-R diagram and used it and other arguments to infer masses and ages. To allow comparison with the results of our previous studies of IC 348 and ρ Oph, we first use the models of D'Antona & Mazzitelli. With these models, the distributions of ages of comparable samples of stars in the Trapezium, ρ Oph, and IC 348 indicate median ages of ∼0.4 Myr for the first two regions and ∼1-2 Myr for the latter. The low-mass initial mass functions (IMFs) in these sites of clustered star formation are similar over a wide range of stellar densities (ρ Oph, n = 0.2-1 × 103 pc-3; IC 348, n = 1 × 103 pc-3; Trapezium, n = 1-5 × 104 pc-3) and other environmental conditions (e.g., presence or absence of OB stars). With current data, we cannot rule out modest variations in the substellar mass functions among these clusters. We then make the best estimate of the true form of the IMF in the Trapezium by using the evolutionary models of Baraffe et al. and an empirically adjusted temperature scale and compare this mass function to recent results for the Pleiades and the field. All of these data are consistent with an IMF that is flat or rises slowly from the substellar regime to about 0.6 M⊙ and then rolls over into a power law that continues from about 1 M⊙ to higher masses with a slope similar to or somewhat larger than the Salpeter value of 1.35. For the Trapezium, this behavior holds from our completeness limit of ∼0.02 M⊙ and probably, after a modest completeness correction, even from 0.01-0.02 M⊙. These data include ∼50 likely brown dwarfs. We test the predictions of theories of the IMF against (1) the shape of the IMF, which is not log-normal, in clusters and the field, (2) the similarity of the IMFs among young clusters, (3) the lowest mass observed for brown dwarfs, and (4) the suggested connection between the stellar IMF and the mass function of prestellar clumps. In particular, most models do not predict the formation of the moderately large numbers of isolated objects down to 0.01 M⊙ that we find in the Trapezium.
• Maiolino, R., Alonso-Herrero, A., Anders, S., Quillen, A., Rieke, M. J., Rieke, G. H., & Tacconi-Garman, L. (2000). Discovery of a nuclear gas bar feeding the active nucleus in Circinus. Astrophysical Journal Letters, 531(1 PART 1), 219-231.
  More info

  Abstract: We report the discovery of gas inflow motions toward the active nucleus of the Circinus galaxy caused by the nonaxisymmetric potential of a nuclear gas bar. Evidence for dust associated with the bar comes from the HST/NICMOS H-K color map, whereas the streaming motions along the gas bar are seen in the velocity field of the H2 S(1) (1-0) emission line. The gas bar is about 100 pc long with a visual extinction in excess of 10 mag. Indication for the gaseous nature of this bar comes from the lack of a stellar counterpart even in the K band, where the extinction is greatly reduced. We also use the NICMOS emission-line images (Paα, [Si VI], and [Fe II]) to study the innermost region of the ionization cones and the nuclear star-forming activity. We discuss the possible relationship of these components with the gaseous bar.
• Quillen, A. C., Shaked, S., Alonso-Herrero, A., McDonald, C., Lee, A., Rieke, M. J., & Rieke, G. H. (2000). The variability of Seyfert 1.8 and 1.9 galaxies at 1.6 microns. Astrophysical Journal Letters, 532(1 PART 2), L17-L20.
  More info

  Abstract: We present a study of Seyfert 1.5-2.0 galaxies observed at two epochs with the Rubble Space Telescope (HST) at 1.6 μm. We find that unresolved nuclear emission from nine of 14 nuclei varies at the level of 10%-40% on timescales of 0.7-14 months, depending upon the galaxy. A control sample of Seyfert galaxies lacking unresolved sources and galaxies lacking Seyfert nuclei show less than 3% instrumental variation in equivalent aperture measurements. This proves that the unresolved sources are nonstellar and associated with the central parsecs of active galactic nuclei. Unresolved sources in Seyfert 1.8 and 1.9 galaxies are not usually detected in HST optical surveys; however, high angular resolution infrared observations will provide a way to measure time delays in these galaxies.
• RIEKE, G., GRASDALEN, G., KINMAN, T., HINTZEN, P., WILLS, B., & WILLS, D. (2000). PHOTOMETRIC AND SPECTROSCOPIC OBSERVATIONS OF BL LACERTAE OBJECT AO 0235+164. NATURE, 260(5554), 754-759.
• Rieke, G. H., Young, E. T., Ade, P. A., Beeman, J. W., Burmester, W., Cadien, J., Ennico, K. A., Gordon, K. D., Hegge, M., Heim, G. B., Henderson, M. L., Horne, T., Kelly, D. M., McMahon, T. J., & Neitenbach, M. (2000). Performance of the multiband imaging photometer for SIRTF. Proceedings of SPIE - The International Society for Optical Engineering, 4131, 38-49.
  More info

  Abstract: We describe the test approaches and results for the Multiband Imaging Photometer for SIRTF (MIPS). To verify the performance within a `faster, better, cheaper' budget required innovations in the test plan, such as heavy reliance on measurements with optical photons to determine instrument alignment, and use of an integrating sphere rather than a telescope to feed the completed instrument at its operating temperature. The tests of the completed instrument were conducted in a cryostat of unique design that allowed us to achieve the ultra-low background levels the instrument will encounter in space. We controlled the instrument through simulators of the mission operations control system and the SIRTF spacecraft electronics, and used cabling virtually identical to that which will be used in SIRTF. This realistic environment led to confidence in the ultimate operability of the instrument. The test philosophy allowed complete verification of the instrument performance and showed it to be similar to pre-integration predictions and to meet the instrument requirements.
• Gordon, K. D., Hanson, M. M., Clayton, G. C., Rieke, G. H., & Misselt, K. A. (1999). The dusty starburst nucleus of M33. Astrophysical Journal Letters, 519(1 PART 1), 165-176.
  More info

  Abstract: We have thoroughly characterized the ultraviolet to near-infrared (0.15-2.2 μm) spectral energy distribution (SED) of the central parsec of the M33 nucleus through new infrared photometry and optical/ near-infrared spectroscopy, combined with ultraviolet/optical observations from the literature and the Hubble Space Telescope archive. The SED shows evidence for a significant level of attenuation, which we model through a Monte Carlo radiative transfer code as a shell of clumpy Milky Way-type dust (τV ∼ 2 ± 1). The discovery of Milky Way-type dust (with a strong 2175 Å bump) internal to the M33 nucleus is different from previous work, which has found SMC-like dust (no bump) near starburst regions. The amount by which dust can be processed may be related to the mass and age of the starburst as well as the extent to which the dust can shield itself. Our starburst models include the effects of this dust and can fit the SED if the nucleus was the site of a moderate (∼108 L⊙ at 10 Myr) episode of coeval star formation about 70 Myr ago. This result is quite different from previous studies, which resorted to multiple stellar populations (between two and seven) attenuated by either no or very little internal dust. The M33 nuclear starburst is remarkably similar to an older version (70 versus 10 Myr) of the ultracompact starburst in the center of the Milky Way.
• Kim, S. J., Ruiz, M., Rieke, G. H., Rieke, M. J., & Zahnle, K. (1999). High Temperatures in Returning Ejecta from the R Impact of Comet SL9. Icarus, 138(2), 164-172.
  More info

  Abstract: Observations from ground-based observatories and with the Galileo spacecraft suggest that the flares from the SL9 impacts resulted from ejecta falling back onto Jupiter in ballistic plumes. This explanation is supported by comparing the plume height as a function of time in HST images with the flare light curve. We show that the rotational temperature of CO in the shock from the R impact rose from less than 2000 K near the beginning of the main flare to about 5000 K at its end. This behavior agrees with a simple physical model of ballistic plumes with a mean molecular weight indicating they are 50% or more jovian air. Alternate models involving formation of molecules at the original impact site, or formation of dust grains to initiate the flare, are inconsistent with these measurements. The energy is emitted primarily as a hot continuum, supporting the possibility that finely divided dust grains are heated in the reentry shock and emit to create the flare. Scaling such models to the energy of the K/T event supports proposals that ballistic plumes were responsible for the global disaster associated with it. © 1999 Academic Press.
• Luhman, K. L., & Rieke, G. H. (1999). Low-mass star formation and the initial mass function in the ρ Ophiuchi cloud core. Astrophysical Journal Letters, 525(1 PART 1), 440-465.
  More info

  Abstract: We have obtained moderate-resolution (R = 800-1200) K-band spectra for ∼100 stars within and surrounding the cloud core of ρ Oph. We have measured spectral types and continuum veilings and have combined this information with results from new deep imaging. Using the latest evolutionary tracks of D'Antona & Mazzitelli to interpret the H-R diagram for ρ Oph, we infer ages ranging between 0.1 and 1 Myr for the class II and III sources (i.e., those that have emerged from their natal cocoons). A few stars may be slightly older. The initial mass function (IMF) peaks at about 0.4 M⊙ and slowly declines to the hydrogen-burning limit with a slope of ∼ -0.5 in logarithmic units (Salpeter is +1.35). Our lower limits on the numbers of substellar objects demonstrate that the IMF probably does not fall more steeply below the hydrogen-burning limit, at least down to ∼0.02 M⊙. The derived IMF is consistent with previous findings that the ρ Oph IMF is roughly flat from 0.05 to 1 M⊙. The exact shape of the mass function remains a function of the theoretical evolutionary tracks and, at the lowest masses, the conversion from spectral types to effective temperatures. We then make the first comparison of mass functions of stars and prestellar clumps measured in the same region. The similar behavior of the two mass functions in ρ Oph supports the suggestion of Motte et al. and Testi & Sargent that the stellar mass function in young clusters is a direct product of the process of cloud fragmentation. We have also studied the very young and often still embedded class I and flat-spectrum objects. After considering the effect of extinction on the SED classifications of the sample, we find that ∼17% of the ρ Oph stars are class I, implying ∼0.1 Myr for the lifetime of this stage. In spectra separated by 2 yr, we observe simultaneous variability in the Brγ emission and K-band continuum veiling for two stars, where the hydrogen emission is brighter in the more heavily veiled data. This behavior indicates that the disk may contribute significantly to continuous K-band emission, in contrast to the proposal that the infalling envelope always dominates. Our detection of strong 2 μm veiling (rK = 1-4) in several class II and III stars, which should have disks but little envelope material, further supports this proposition. We also detect absorption features in the spectra of ∼25% of class I and flat-spectrum sources, demonstrating the feasibility of studying the photospheres of extremely young protostars.
• MAIOLINO, R., RUIZ, M., RIEKE, G., & KELLER, L. (1999). NEW CONSTRAINTS ON THE UNIFIED MODEL OF SEYFERT-GALAXIES. ASTROPHYSICAL JOURNAL, 446(2), 561-573.
  More info

  We present new 10 mu m (N-band) photometry for 70 Seyfert galaxies, 43 of them previously unobserved. These observations, together with those collected from the literature, complete the 10 mu m photometry for the CfA Sy galaxies and cover 80% of the Sy found in the RSA and 70% of the Sy in the IRAS 12 mu m sample.
• Maiolino, R., Herrero, A., Anders, S., Quillen, A., Rieke, G. H., & Tacconi-Garman, L. (1999). Star formation and AGN fuelling. Advances in Space Research, 23(5-6), 875-880.
  More info

  Abstract: We present new observational data that tackle the issues of the star formation in Seyfert galaxies, the obscuration and fuelling mechanisms of active galactic nuclei, and the connection between these phenomena. New ISOCAM mid-IR images of nearby Seyfert 2 galaxies confirm that these systems are characterized by enhanced star forming activity. In barred systems the star forming activity occurs preferentially along the bar, indicating that these bars have formed recently and are still in the process of transporting gas towards the center. New X-ray data indicate that the gaseous column density absorbing Sy2 nuclei is a function of the bar strength, therefore indicating that stellar bars play an important role in obscuring AGNs. We speculate that non-axisymmetric disturbances (interaction/bars) both enhance the star forming activity in host galaxy and drive gas into the nuclear region to obscure the AGN, thus making the observed starburst-Sy2 connection. On smaller scales (10-100 pc), we report the discovery of a nuclear gaseous bar in the nearby Sy2 Circinus galaxy. The molecular gas kinematics indicates that this bar causes the gas to flow into the nuclear 10 pc. In the nuclear 10 pc we detect a young nuclear stellar cluster. We show that the post-main-sequence mass loss of this young nuclear stellar population could account for the fuelling of the active nucleus. © 1999 COSPAR. Published by Elsevier Science Ltd.
• McLeod, K. K., Rieke, G. H., & Storrie-Lombardi, L. (1999). Quasars and ultraluminous infrared galaxies: At the limit?. Astrophysical Journal Letters, 511(2 PART 2), L67-L70.
  More info

  Abstract: We have detected the host galaxies of 16 nearby, radio-quiet quasars using images obtained with the Near-Infrared Camera and MultiObject Spectrometer. We confirm that these luminous quasars tend to live in luminous, early-type host galaxies, and we use the host-galaxy magnitudes to refine the luminosity/host-mass limit inferred from ground-based studies. If quasars obey the relation Mblackhole/Mspheroid ∼ 0.006 found for massive dark objects in nonactive galaxies, then our analysis implies that they radiate at up to ∼20% of the Eddington rate. An analogous analysis for ultraluminous infrared galaxies shows them to accrete at up to similar Eddington fractions, consistent with the hypothesis that some of them are powered by embedded quasars.
• Quillen, A. C., Alonso-Herrero, A., Rieke, M. J., McDonald, C., Falcke, H., & Rieke, G. H. (1999). Dust lanes causing structure in the extended narrow-line region of early-type seyfert galaxies. Astrophysical Journal Letters, 525(2 PART 1), 685-690.
  More info

  Abstract: We construct near-infrared to visible broadband NICMOS/WFPC color maps for four early-type Seyfert galaxies with S-shaped or one-sided ionization cones. We find that dust lanes are near or connected to many of the features seen in the [O III] and Hα + [N II] line emission maps. This suggests that much of the structure of line emission in these ionization cones is determined by the distribution of ambient dense galactic gas. Spiral arms, dust lanes caused by bars, or gaseous warps provide dense gas, which when illuminated by a conical beam of ultraviolet photons can result in the complicated line emission morphologies observed.
• Quillen, A. C., Alonso-Herrero, A., Rieke, M. J., Rieke, G. H., Ruiz, M., & Kulkarni, V. (1999). NICMOS imaging of molecular hydrogen emission in seyfert galaxies. Astrophysical Journal Letters, 527(2 PART 1), 696-708.
  More info

  Abstract: We present near-infrared (NICMOS) imaging of broadband and molecular hydrogen emission in Seyfert galaxies. In six of 10 Seyfert galaxies we detect resolved or extended emission in the 1-0 S(1) 2.121 μm or 1-0 S(3) 1.9570 μm molecular hydrogen lines. We did not detect emission in the most distant galaxy or in two Seyfert 1 galaxies because of the luminosity of the nuclear point sources. In NGC 5643, NGC 2110, and Mrk 1066, molecular hydrogen emission is detected in the extended narrow-line region on scales of a few hundred parsecs from the nucleus. Emission is coincident with [O III] and Hα + [N II] line emission. This emission is also near dust lanes observed in the visible to near-infrared color maps, suggesting that a multiphase medium exists near the ionization cones and that the morphology of the line emission is dependent on the density of the ambient media. The high 1-0 S(1) or S(3) H2 to Hα flux ratio suggests that shock excitation of molecular hydrogen (rather than UV fluorescence) is the dominant excitation process in these extended features. In NGC 2992 and NGC 3227 the molecular hydrogen emission is from 800 and 100 pc diameter "disks" (respectively) that are not directly associated with [O III] emission and are near high levels of extinction (Av ≳ 10). The molecular hydrogen emission in NGC 4945 appears to be from the edge of a 100 pc superbubble. The molecular gas in these three galaxies could be excited by processes associated with local star formation. We confirm previous spectroscopic studies finding that no single mechanism is likely to be responsible for the molecular hydrogen excitation in Seyfert galaxies.
• Quillen, A. C., Rieke, G. H., Rieke, M. J., Caldwell, N., & Engelbracht, C. W. (1999). Mid-infrared emission from E+A galaxies in the coma cluster. Astrophysical Journal Letters, 518(2 PART 1), 632-640.
  More info

  Abstract: We have used ISO to observe at 12 μm seven E+A galaxies plus an additional emission-line galaxy, all in the Coma Cluster. E+A galaxies lacking narrow emission lines have 2.2-12 μmi flux density ratios or limits similar to old stellar populations (typical of early-type galaxies). Only galaxies with emission lines have enhanced 12 μm flux density. Excess 12 μm emission is therefore correlated with the presence of ongoing star formation or an active galactic nucleus (AGN). From the mid- and far-infrared colors of the brightest galaxy in our sample, which was detected at longer wavelengths with IRAS, we estimate the far-infrared luminosity of these galaxies. By comparing the current star formation rates with previous rates estimated from the Balmer absorption features, we divide the galaxies into two groups: those for which star formation has declined significantly following a dramatic peak ∼1 Gyr ago; and those with a significant level of ongoing star formation or/and an AGN. There is no strong difference in the spatial distribution on the sky between these two groups. However, the first group has systemic velocities above the mean cluster value and the second group has systemic velocities below that value. This suggests that the two groups differ kinematically. Based on surveys of the Coma Cluster in the radio, the IRAS sources, and galaxies detected in Hα emission, we sum the far-infrared luminosity function of galaxies in the cluster. We find that star formation in late-type galaxies is probably the dominant component of the Coma Cluster far-infrared luminosity. The presence of significant emission from intracluster dust is not yet firmly established. The member galaxies also account for most of the far-infrared output from nearby rich clusters in general. We update estimates of the far-infrared luminosities of nearby, rich clusters and show that such clusters are likely to undergo luminosity evolution from z = 0.4 at a rate similar to, or faster than, field galaxies.
• Alonso-Herrero, A., Rieke, M. J., & Rieke, G. H. (1998). The starburst properties of the interacting system ARP 299 (IC 694 + NGC 3690). Astrophysics and Space Science, 263(1-4), 131-134.
  More info

  Abstract: We present a detailed study of the starburst properties of the components of the interacting system Arp 299. The burst ages range from 1 to 8 million years, with effective SFR from 60 to 300M⊙ yr-1.
• Comerón, F., Rieke, G. H., Claes, P., Torra, J., & Laureijs, R. J. (1998). ISO observations of candidate young brown dwarfs. Astronomy and Astrophysics, 335(2), 522-532.
  More info

  Abstract: ISOCAM measurements or upper limits for low mass members of the ρ Ophiuchi embedded cluster extend the sampling of the spectral energy distributions already obtained from the ground towards longer wavelengths, where emission by circumstellar material is significant. Good fits to the combined (ground-based + ISOCAM) photometry are obtained with theoretical models of pre-main sequence evolution, complemented with models of the spectrum of circumstellar emission, synthetic spectra of cold atmospheres, and an extinction law. The most important physical parameters of the targets, such as mass and luminosity, can be estimated with more confidence than with ground-based data alone, thanks to the much more robust reconstruction of the intrinsic spectral energy distribution made possible by the new ISOCAM data. An object-by-object discussion, based on both published and new material, shows that estimates of the source temperatures from fitting of the photometry agree closely with spectroscopy for all seven sources where both techniques have been applied. The agreement between the new fits and those based on groundbased photometry alone is also reasonably good. Three of the sources are very likely to be young brown dwarfs, five are transitional, and three appear to be low mass stars.
• ELSTON, R., RIEKE, G., & RIEKE, M. (1998). DEEP 2-MICRON IMAGING OF THE SKY - EVIDENCE FOR A NEW EXTRAGALACTIC POPULATION. ASTROPHYSICAL JOURNAL, 331(2), L77-&.
• Egami, E., Rieke, G. H., Fadda, D., & Hines, D. C. (1998). A large mass of H(2) in the brightest cluster galaxy in Zwicky 3146. ASTROPHYSICAL JOURNAL, 652(1), L21-L24.
  More info

  We present the Spitzer/IRS mid-infrared spectrum of the infrared-luminous (L(IR) = 4 x 10(11) L(circle dot)) brightest cluster galaxy (BCG) in the X-ray-luminous cluster Zwicky 3146 (Z3146; z = 0.29). The spectrum shows strong aromatic emission features, indicating that the dominant source of the infrared luminosity is star formation. The most striking feature of the spectrum, however, is the exceptionally strong molecular hydrogen (H(2)) emission lines, which seem to be shock-excited. The line luminosities and inferred warm H(2) gas mass (similar to 10(10) M(circle dot)) are 6 times larger than those of NGC 6240, the most H(2)-luminous galaxy at z
• Engelbracht, C. W., Rieke, M. J., Rieke, G. H., Kelly, D. M., & Achtermann, J. M. (1998). The nuclear starburst in NGC 253. Astrophysical Journal Letters, 505(2 PART I), 639-658.
  More info

  Abstract: We have obtained long-slit spectra of NGC 253 in the J, H, K, and N bands, broadband images in the J, H, and Ks bands, narrowband images centered at the wavelengths of Brγ and H2(1, 0) S(1), and imaging spectroscopy centered on [Ne II] (12.8 μm). We have subtracted a composite stellar spectrum from the galaxy spectrum to measure faint emission lines that otherwise would be buried in the complicated continuum structure. We use these data and data from the literature in a comprehensive reassessment of the starburst in this galaxy. We confirm that the [Fe II] emission is predominantly excited by supernova explosions and show that the rate of these events can be derived from the strength of the infrared [Fe II] lines. Although the H2 emission superficially resembles a thermally excited spectrum, most of the H2 infrared luminosity is excited by fluorescence in low-density gas. We confirm the presence of a bar and also show that this galaxy has a circumnuclear ring. The relation of these features to the gaseous bar seen in CO is in agreement with the general theoretical picture of how gas can be concentrated into galaxy centers by bars. We derive a strong upper limit of ∼37,000 K for the stars exciting the emission lines. We use velocity-resolved infrared spectra to determine the mass in the starburst region. Most of this mass appears to be locked up in the old, preexisting stellar population. Using these constraints and others to build an evolutionary synthesis model, we find that the initial mass function (IMF) originally derived to fit the starburst in M82 also accounts for the properties of NGC 253; this IMF is similar to a modified Salpeter IMF. The models indicate that rapid massive star formation has been ongoing for 20-30 million yr in NGC 253; that is, it is in a late phase of its starburst. Its optical spectrum has characteristics of a transitional H II/weak-[O I] LINER. We model the emission-line spectrum expected from a late phase starburst and demonstrate that it reproduces these characteristics. © 1998. The American Astronomical Society. All rights reserved.
• Falcke, H., Rieke, M. J., Rieke, G. H., Simpson, C., & Wilson, A. S. (1998). Molecular hydrogen and Paα emission in cooling flow galaxies. Astrophysical Journal Letters, 494(2 PART II), L155-L158.
  More info

  Abstract: We present near-infrared spectra that were obtained in order to search for Paα and molecular hydrogen lines in edge-darkened (FR I-type) radio galaxies with bright Ha emission in the redshift range 0.0535 < z < 0.15. We find that all three galaxies in our sample (PKS 0745-191, PKS 1346+26, and PKS 2322-12) associated with strong cooling flows also have strong Paα and H2 1-0 5(1) through S(5) emission, while other radio galaxies do not. Together with earlier observations, this confirms the claims that cooling flow galaxies are copious emitters of molecular hydrogen with large H2 1-0 S(3)/Paα ratios in the range 0.5-2. The emission is centrally concentrated within the inner few kiloparsecs and could come from warm (T ≃ 1000-1500 K) molecular material that is being deposited by the cooling flow. We speculate that the H2 emission could be related to the interaction between the jets and this molecular gas. © 1998. The American Astronomical Society. All rights reserved.
• Fanson, J., Fazio, G., Houck, J., Kelly, T., Rieke, G., Tenerelli, D., & Whitten, M. (1998). Space Infrared Telescope Facility (SIRTF). Proceedings of SPIE - The International Society for Optical Engineering, 3356(1), 478-491.
  More info

  Abstract: This paper describes the design of the Space Infrared Telescope Facility (SIRTF) as the project enters the detailed design phase. SIRTF is the fourth of NASA's Great Observatories, and is scheduled for launch in December 2001. SIRTF provides background limited imaging and spectroscopy covering the spectral range from 3 to 180 μm, complementing the capabilities of the other Great Observatories - the Hubble Space Telescope (HST), the Advanced X-ray Astrophysics Facility (AXAF), and the Compton Gamma Ray Observatory (CGRO). SIRTF will be the first mission to be combine the high sensitivity achievable from a cryogenic space telescope with the imaging and spectroscopic power of the new generation of infrared detector arrays. The scientific capabilities of this combination are so great that SIRTF was designated the highest priority major mission for all of US astronomy in the 1990s.
• Hanson, M. M., Rieke, G. H., & Luhman, K. L. (1998). Near-infrared H-band features in late O and B stars. Astronomical Journal, 116(4), 1915-1921.
  More info

  Abstract: We examine the spectral characteristics of normal OB stars with high-signal-to-noise ratio (>120) H-band (1.6 μm) spectra at a resolution of 2000. We find that several atomic lines vary smoothly with stellar temperature, as first shown by Blum et al. However, we find a previously unreported, significant variation in the strength of some of these lines with stellar luminosity. B supergiant stars show stronger He I and weaker Br II as compared with low-luminosity B dwarf stars of the same spectral class. It is for this reason that luminosity class must also be determined to obtain an accurate spectral type for a given star using H-band spectra. We suggest a method for estimating the spectral type and luminosity of an OB star over the wavelength range from 1.66 to 1.72 μm using hydrogen Br 11 at 1.681 μm, He I at 1.700 μm, and He 11 at 1.693 μm. The use of the near-infrared spectral range for classification has obvious advantages over optical classification when applied to heavily reddened stars, such as in starforming regions or deeply embedded lines of sight within the plane of the Galaxy, such as the Galactic center. Furthermore, the H band is less likely to be contaminated by infrared excess emission, which is frequently seen around massive young stellar objects beyond 2 μm.
• Heim, G. B., Henderson, M. L., MacFeely, K., McMahon, T. J., Michika, D., Pearson, R. J., Rieke, G. H., Schwenker, J. P., Strecker, D. W., Thompson, C., Warden, R. M., Wilson, D. A., & Young, E. T. (1998). Multiband Imaging Photometer for SIRTF. Proceedings of SPIE - The International Society for Optical Engineering, 3356(2), 985-1000.
  More info

  Abstract: Multiband Imaging Photometer for SIRTF (MIPS) provides the Space Infrared Telescope Facility (SIRTF) with imaging, photometry, and total power measurement capability in broad spectral bands centered at 24, 70, and 160μm, and with low resolution spectroscopy between 50 and 95μm. The optical train directs the light from three zones in the telescope focal plane to three detector arrays: 128×128 Si:As BIB, 32×32 Ge:Ga, and 2×20 stressed Ge:Ga. A single axis scan mirror is placed at a pupil to allow rapid motion of the field of view as required to modulate above the 1/f noise in the germanium detectors. The scan mirror also directs the light into the different optical paths of the instrument and makes possible an efficient mapping mode in which the telescope line of sight is scanned continuously while the scan mirror freezes the image motion on the detector arrays. The instrument is designed with pixel sizes that oversample the telescope Airy pattern to operate at the diffraction limit and, through image processing, to allow superresolution beyond the traditional Rayleigh criterion. The instrument performance and interface requirements, the design concept, and the mechanical, optical, thermal, electrical, software, and radiometric aspects of MIPS are discussed in this paper. Solutions are shown to the challenge of operating the instrument below 3K, with focal plane cooling requirements down to 1.5K. The optical concept allows the versatile operations described above with only a single mechanism and includes extensive self-test and on-board calibration capabilities. In addition, we discuss the approach to cryogenic end-to-end testing and calibration prior to delivery of the instrument for integration into SIRTF.
• Luhman, K. L., & Rieke, G. H. (1998). The low-mass initial mass function in young clusters: L1495E. Astrophysical Journal Letters, 497(1 PART I), 354-369.
  More info

  Abstract: We have developed a technique of IR spectral classification in which we use K-band spectra (R ∼ 1000) to derive the spectral types and continuum veilings of young, late-type stars (∼1 Myr, >GO). We show close agreement between the spectral types derived in this manner and those obtained optically. We complement previous optical spectroscopy with IR spectra of the most heavily embedded members of the young, embedded cluster L1495E. We critically analyze the translation between observable (spectral type, photometry) and theoretical (Teff, Lbol) parameters and use these data to construct an H-R diagram. We find that the evolutionary tracks of D'Antona & Mazzitelli imply a coeval population of ≤1 Myr and a plausible initial mass function (IMF). However, these models may underestimate the masses of objects near and below the hydrogen burning limit. The models of Swenson produce implausibly old ages and the models of Baraffe et al. yield somewhat old ages and an implausible IMF. We use infrared imaging to show that the spectroscopic sample for this cluster may be seriously incomplete below ∼0.15 M⊙. After applying a completeness correction to the IMF derived with the tracks of D'Antona & Mazzitelli, we find no evidence for a turnover at low masses; the IMF appears roughly flat in logarithmic mass units. Compared to the results of photometric studies of ρ Oph and NGC 2024, the IMF appears roughly invariant among star-forming environments representing a 2 order of magnitude range in the density of young stars. However, the detailed behavior of the IMF from low stellar masses into the substellar regime will remain uncertain until (1) better evolutionary tracks are available and (2) the sources in the photometric completeness correction can be spectroscopically confirmed as low-mass cluster members. © 1998. The American Astronomical Society. All rights reserved.
• Luhman, K. L., Briceño, C., Rieke, G. H., & Hartmann, L. (1998). A young star near the hydrogen-burning limit. Astrophysical Journal Letters, 493(2 PART I), 909-913.
  More info

  Abstract: We show that V410 X-ray 3, toward the L1495E star-forming complex, is an object with a mass of 0.08-0.15 M⊙ and an age of ∼1 Myr. Nonetheless, it has emerged from its natal cloud and can be studied in detail throughout the optical and near-infrared, providing new insights into the character of very young and low-mass objects. It has spectral characteristics intermediate between those of late dwarfs and giants (e.g., first-overtone CO typical of an M6 dwarf, but K i, Na i, and TiO/VO typical of an M6 giant and CaH intermediate between the luminosity classes). Its optical and IR photometric colors are consistent with those of an M6 dwarf. If the latest theoretical evolutionary tracks are valid at young ages and low masses, it appears that the hydrogen-burning limit at an age of ∼1 Myr occurs at a spectral type of M6-M7. © 1993. The American Astronomical Society. All rights reserved.
• Luhman, K. L., Rieke, G. H., Lada, C. J., & Lada, E. A. (1998). Low-mass star formation and the initial mass function in IC 348. Astrophysical Journal Letters, 508(1 PART I), 347-369.
  More info

  Abstract: We have performed deep infrared and optical spectroscopy of virtually the entire stellar population within the 5′ × 5′ core of IC 348, measuring K (2.2 μm) band and optical spectral types that are in good agreement. We have also identified several sources that may be substellar depending on the choice of temperature scales and evolutionary tracks, with three particularly late-type objects (M7.5-M8) that are likely bonafide brown dwarfs. In conjunction with the theoretical evolutionary tracks of D'Antona & Mazzitelli, the H-R diagram indicates a spread in ages from 0.5 to 10 Myr, with most of the core star formation occurring in the last 3 Myr. Using K-band imaging to provide a completeness correction to the spectroscopic sample, we arrive at an initial mass function (IMF) that matches that of Miller & Scalo from 0.25 to 3 M⊙. The IMF appears to fall slowly from 0.25 M⊙ to the hydrogen burning limit, slightly below the IMF of Miller & Scalo, which is flat in logarithmic units (as compared to slopes of ∼1.35 and -2.6 for Salpeter and Scalo). Correction for unresolved binary systems could steepen the slope of the low-mass IMF by about 0.5, which implies a single-star IMF that is roughly flat below 0.25 M⊙. The low-mass IMF in IC 348 is similar to that derived in studies of most other young clusters, implying that the IMF does not vary dramatically among clusters of differing environments; however, the derived IMF is dependent on the evolutionary tracks and the detailed shape of the IMF should be viewed with caution until these models are tested against observations, particularly at low masses (1 Å) emission or X-band continuum veiling (rK ≥ 0.5). Since no sources older than 3 Myr show evidence for massive disks, disk lifetimes in the core of IC 348 appear to be shorter than those observed in Taurus or in the outer regions of IC 348. © 1998. The American Astronomical Society. All rights reserved.
• Luhman, K., & Rieke, G. (1998). Low-mass star formation and the initial mass function in the rho Ophiuchi cloud core. ASTROPHYSICAL JOURNAL, 525(1), 440-465.
  More info

  We have obtained moderate-resolution (R = 800-1200) K-band spectra for similar to 100 stars within and surrounding the cloud core of rho Oph. We have measured spectral types and continuum veilings and have combined this information with results from new deep imaging. Using the latest evolutionary tracks of D'Antona & Mazzitelli to interpret the M-R diagram for rho Oph, we infer ages ranging between 0.1 and 1 Myr for the class II and III sources (i.e., those that have emerged from their natal cocoons). A few stars may be slightly older. The initial mass function (IMF) peaks at about 0.4 M. and slowly declines to the hydrogen-burning limit with a slope of similar to-0.5 in logarithmic units (Salpeter is +1.35). Our lower limits on the numbers of substellar objects demonstrate that the IMF probably does not fall more steeply below the hydrogen-burning limit, at least down to similar to 0.02 M.. The derived IMF is consistent with previous findings that the rho Oph IMF is roughly flat from 0.05 tol M.. The exact shape of the mass function remains a function of the theoretical evolutionary tracks and, at the lowest masses, the conversion from spectral types to effective temperatures. We then make the first comparison of mass functions of stars and prestellar clumps measured in the same region. The similar behavior of the two mass functions in rho Oph supports the suggestion of Motte et al. and Testi & Sargent that the stellar mass function in young clusters is a direct product of the process of cloud fragmentation. We have also studied the very young and often still embedded class I and hat-spectrum objects. After considering the effect of extinction on the SED classifications of the sample, we find that similar to 17% of the rho Oph stars are class I, implying similar to 0.1 Myr for the lifetime of this stage. In spectra separated by 2 yr, we observe simultaneous variability in the Br gamma emission and K-band continuum veiling for two stars, where the hydrogen emission is brighter in the more heavily veiled data. This behavior indicates that the disk may contribute significantly to continuous K-band emission, in contrast to the proposal that the infalling envelope always dominates. Our detection of strong 2 mu m veiling (r(K) =1-4) in several class II and III stars, which should have disks but little envelope material, further supports this proposition. We also detect absorption features in the spectra of similar to 25% of class I and Bat-spectrum sources, demonstrating the feasibility of studying the photospheres of extremely young protostars.
• RIEKE, G., & LEBOFSKY, M. (1998). 10 MICRON OBSERVATIONS OF BRIGHT GALAXIES. ASTROPHYSICAL JOURNAL, 220(2), L37-L41.
• Schnurr, R., Thompson, C. L., Davis, J. T., Beeman, J. W., Cadien, J., Young, E. T., Haller, E. E., & Rieke, G. H. (1998). Design of the stressed Ge:Ga far-infrared array for SIRTF. Proceedings of SPIE - The International Society for Optical Engineering, 3354, 322-331.
  More info

  Abstract: Stressed Ge:Ga is currently the most suitable detector type for very low background operation in the 115 to 200 micrometers range. Nonetheless, substantial advances have been required to develop stressed Ge:Ga detectors that work at the background limit in SIRTF. Both dark current and read noise have been improved significantly for the SIRTF devices. The design also takes account of space flight requirements such as the necessity to anneal the focal plane thermally using a minimum of cryogenic power dissipation, and the desire that any failures not propagate through an entire focal plane. The SIRTF 2 X 20 pixel focal plane will have dark current of about 200 e/s, read noise of 100 e rms, and responsivity > 7 A/W. As a result, even in the darkest parts of the sky, it will reach the background limit in less than 4 seconds of integration. ©2003 Copyright SPIE - The International Society for Optical Engineering.
• Vanzi, L., Alonso-Herrero, A., & Rieke, G. H. (1998). Near-infrared spectroscopy of ARP interacting galaxies. Astrophysical Journal Letters, 504(1 PART I), 93-106.
  More info

  Abstract: We discuss near-infrared spectra of 20 interacting galaxies from the Arp Catalog and analyze the properties of similar galaxies for which only optical spectra are available. We find excellent agreement between the types of activity determined from the infrared and optical, demonstrating that obscuration does not seriously bias the optical results. None of the 20 galaxies show infrared spectral characteristics that differ from expectations for isolated galaxies; the very strong shock-excited lines seen in a few interacting systems must be uncommon. Most of the galaxies in our infrared sample are the sites of starbursts that appear to have had durations of 1 to 5 Myr and to be observed 3 to 10 Myr after the peak starforming episode. Four of the 20 galaxies have LINER or composite starburst/LINER spectra that are likely to arise from shocks due to supernovae in late phase starbursts. In the full interacting galaxy sample, there is a substantial excess of Seyfert 2 nuclei, supporting previous indications that this type of activity tends to occur in interacting host galaxies. © 1998. The American Astronomical Society. All rights reserved.
• Young, E. T., Davis, J. T., Thompson, C. L., Rieke, G. H., Rivlis, G., Schnurr, R., Cadien, J., Davidson, L., Winters, G. S., & Kormos, K. A. (1998). Far-infrared imaging array for SIRTF. Proceedings of SPIE - The International Society for Optical Engineering, 3354, 57-65.
  More info

  Abstract: We describe the design, construction, and performance of the 32 X 32 Ge:Ga imaging array being built at the University of Arizona for the Multiband Imaging Photometer for SIRTF (MIPS). The array will support a number of operational modes in the MIPS instrument including natural background-limited mapping at 70 micrometers , super-resolution observations at 70 micrometers , and spectral energy distribution measurements between 50 and 100 micrometers. The array is constructed in a modular manner using eight 4 X 32 pixel building blocks. To meet the sensitivity and stability requirements, the array must have excellent photometric repeatability, low noise, and robustness to the effects of the ionizing radiation environment in space. Key elements in attaining this level of performance are the Ge:Ga detectors materials and the cryogenic CRC-696 readout electronics. We present laboratory data for a 16 X 32 prototype of the array, and describe the plans for the construction of the qualification and flight units. ©2003 Copyright SPIE - The International Society for Optical Engineering.
• Alonso-Herrero, A., Rieke, M. J., Rieke, G. H., & Ruiz, M. (1997). Using near-infrared [Fe II] lines to identify active galaxies 1. Astrophysical Journal Letters, 482(2 PART I), 747-756.
  More info

  Abstract: The ([Fe II] 1.644 μ)/Brγ and ([Fe II] 1.2567 μm)/Paβ ratios provide good separation of starburst and Seyfert galaxies; we show that ([Fe II] 1.644 μm)/Brγ is nearly as good a discriminant as the commonly used ([O I] λ6300)/Hα ratio. The behavior of both the ([O I] λ6300)/Hα and the ([Fe II] 1.644 μm)/Brγ ratios is readily understood if there is a progression in the proportion of shock excitation going from H II region through starburst and Seyfert galaxies to supernova remnants. We use the CLOUDY program to show that the behavior is also explained if the dominant excitation mechanism is photoionization. As a test of this technique for identifying excitation mechanisms, we have obtained infrared spectra of two LINER galaxies. NGC 1052, which is thought to be excited by a nuclear power-law UV source, is the prototype of LINERs, and NGC 3504 is classified as a weak-[O I] λ6300 LINER, better understood in terms of photoionization by O stars than by a nonstellar source. The placement of these galaxies on the ([Fe II] 1.644 μm)/Brγ versus ([O I] λ6300)/Hα diagram is in agreement with these previously determined characteristics. The ([Fe II] 1.644 μm)/Brγ and ([Fe II] 1.2567 μm)/Paβ ratios should be useful in classifying heavily obscured galaxies because the ratios (1) are constructed at wavelengths where extinction is relatively small and (2) involve lines over narrow spectral ranges. © 1997. The American Astronomical Society. All rights reserved.
• Biscaya, A. M., Rieke, G. H., Narayanan, G., Luhman, K. L., & Young, E. T. (1997). First-overtone co variability in young stellar objects. Astrophysical Journal Letters, 491(1 PART I), 359-365.
  More info

  Abstract: We have monitored the 2.3 μm Δν = 2 CO bands toward young stellar objects that are predominantly of low luminosity (L < 10,000 L⊙) and show evidence of mass loss. The CO emission can be highly variable, on timescales as short as a few days. In DG Tau, the bands have been observed to disappear and reappear and may also have a periodic modulation. For the BN object, the equivalent width has varied by a factor of 3; and for VI331 Cyg, the equivalent width doubled in 9 days. Changes in equivalent width also occurred in SSV 13, AS 353A, and 1548C27, while WL 16 and S106 have not shown variations. Of the nine CO absorption sources reobserved, only the FU Ori-type star V1057 Cyg went through a significant change in equivalent width. It also presents an unusual and variable band profile. © 1997. The American Astronomical Society. All rights reserved.
• Hubbard, W. B., Porco, C. C., Hunten, D. M., Rieke, G. H., Rieke, M. J., McCarthy, D. W., Haemmerle, V., Haller, J., McLeod, B., Lebofsky, L. A., Marcialis, R., Holberg, J. B., Landau, R., Carrasco, L., Elias, J., Buie, M. W., Dunham, E. W., Persson, S. E., Boroson, T., , West, S., et al. (1997). Structure of Saturn's mesosphere from the 28 Sgr occultations. Icarus, 130(2), 404-425.
  More info

  Abstract: We analyze an extensive data set of immersion and emersion lightcurves of the occultation of 28 Sgr by Saturn's atmosphere on 3 July 1989. The data give profiles of number density as a function of altitude at a variety of latitudes, at pressures ranging from about 0.5 to about 20 μbar. The atmosphere is essentially isothermal in this range, with a temperature close to 140 K for an assumed mean molecular weight of 2.135. Owing to favorable ring geometry, an accurate radial scale is available for all observations, and we confirm the substantial equatorial bulge produced by zonal winds of ~450 m/s first observed in the Voyager radio-occultation experiments. The fact that the bulge is still present at microbar pressures suggests that the equatorial winds persist to high altitudes. According to our radial scale, the 2.4-μbar level, which corresponds to half-flux in the stellar occultations, is at an equatorial radius of 60,960 km. This radial scale is in good agreement with the Voyager radio-occultation data at mbar pressures and allows smooth interpolation of the isothermal structure between the stellar-occultation and radio-occultation regions. We do not have such a smooth interpolation between our data and Voyager ultraviolet occultation data, unless we discard the lowest 200 km of Voyager ultraviolet data. When this is done, we obtain a complete atmospheric model from an equatorial radius of 61,500 km down to an equatorial radius of 60,500 km. This model gives excellent agreement between all 28 Sgr, Voyager, and Pioneer 11 data. © 1997 Academic Press.
• Luhman, K. L., Liebert, J., & Rieke, G. H. (1997). Spectroscopy of a young brown dwarf in the ρ ophiuchi cluster. Astrophysical Journal Letters, 489(2 PART II), L165-L168.
  More info

  Abstract: We present observations of a young (∼3-10 Myr old) brown dwarf within the ρ Ophiuchi star-forming region. A low-resolution optical spectrum exhibits a spectral type of M8.5 ± 0.5 and strong Hα emission (Wλ ∼ 60 Å). After demonstrating the youth of this source through several additional lines of evidence, we place it on the H-R diagram and use the latest evolutionary tracks to derive a substellar mass of 0.01-0.06 M⊙. A more accurate mass estimate will require tests of the evolutionary tracks and temperature scales at such young ages and late types. © 1997. The American Astronomical Society. All rights reserved.
• Vanzi, L., & Rieke, G. H. (1997). Infrared spectroscopy of blue dwarf galaxies. Astrophysical Journal Letters, 479(2 PART I), 694-701.
  More info

  Abstract: We present a survey of the near-infrared emission lines of eight blue dwarf galaxies. These galaxies have advantages for study of the excitation of the interstellar medium by starbursts because the effects are relatively undiluted by the quiescent stellar population, the star formation episodes usually appear to be of short duration, and the effects of metallicity can be examined. Diagnostic tools for the interpretation of [Fe II](1.64) and H2(2.12) emission lines emitted by starburst galaxies are developed and the results are compared with a starburst model. We confirm that the [Fe II](1.64) line is mainly excited in supernova remnants, but the H2 emission appears to arise from a variety of different excitation mechanisms. Many of the galaxies show evidence for a fluorescently excited component of H2. The temperature of the hot stellar population is analyzed by means of the He I(1.70 μm) emission line and compared with estimates from the [O II]/Hβ ratio in the optical and from the mid-infrared fine structure lines. The agreement is reasonably good, although there appears to be a tendency for the temperature to be overestimated by use of the [O III]/Hβ ratio. © 1997. The American Astronomical Society. All rights reserved.
• CAMPINS, H., RIEKE, G., & LEBOFSKY, M. (1996). ABSOLUTE CALIBRATION OF PHOTOMETRY AT 1-MU-M THROUGH 5-MU-M. ASTRONOMICAL JOURNAL, 90(5), 896-899.
• Cleve, J. V., Rieke, G., & Cruikshank, D. (1996). Infrared inferences of planetary systems among the nearby stars. JBIS - Journal of the British Interplanetary Society, 49(1), 3-6.
  More info

  Abstract: The infrared excesses observed around nearby main-sequence stars such as α Lyr and β Pic are often taken as evidence that planetary system formation has occurred around them, in a process similar to the one which we believe produced our own Solar System. However, it is also possible that such disks are evidence that planetesimals have ground themselves to bits without forming large solid bodies. A critical missing piece of data is the infrared excess of the Solar System at 60 and 100 μm. It is not known whether the typical excess of the G stars observed by IRAS is comparable to the Solar System excess. While IRAS measurements of diffuse emission near the ecliptic are consistent with such a cold cloud, confusion with the foreground of zodiacal emission and the background of Galactic emission prevent a definitive answer. It is then necessary to examine the Solar System with sensitive infrared instruments from a vantage point beyond the orbit of Jupiter, and preferably well into the Kuiper Belt. We propose TRISOPS, a three-colour, regenerative H2 cooled, imaging telescope operated in an interstellar trajectory for 10 years. TRISOPS would map the diffuse emission of the Solar System (both zodiacal emission and the Cold Cloud) as a function of distance from the Sun beginning at 1AU in order to understand the fragmentation processes in the Solar System which may be related to the processes sustaining dust disks around stars like Vega. TRISOPS uses the improvements in detector and spacecraft technology developed by the SIRTF and WIRE projects.
• Comerón, F., Rieke, G. H., & Rieke, M. J. (1996). Properties of low-mass objects in NGC 2024. Astrophysical Journal Letters, 473(1 PART I), 294-303.
  More info

  Abstract: We have obtained deep JHK imaging of the central region of the NGC 2024 embedded cluster, allowing three-color measurements of 151 sources. We show that contamination by background sources is small, and we reject a small number of sources that are probably foreground. We use a Monte Carlo isochrone fitting technique to estimate the luminosities and masses of the low-mass members of the embedded cluster. We find that the IMF between ∼0.04 and ∼0.5 M⊙ can be fitted within the errors with a power law of slope -1.2 in linear mass units (or -0.2 in logarithmic units). There is no indication of a turnover of the IMF at the bottom of the main sequence; it appears to continue down to ∼0.04 Mg with no significant deviation (within our moderately large errors) from the power law. This estimate of the IMF includes only the primary members of binary (or multiple) systems. Of a subset of 35 sources, 24 (69%) appear to have infrared excesses indicating possible circumstellar disks, supporting arguments that disk formation is not inhibited in high-density clusters. © 1996. The American Astronomical Society. All rights reserved.
• Comerón, F., Torra, J., & Rieke, G. H. (1996). Clumpiness in molecular clouds and statistics of embedded sources. Astronomy and Astrophysics, 308(2), 565-572.
  More info

  Abstract: Statistical studies of stellar populations embedded in molecular clouds are affected by several potential biases. In this paper we use a simple model of a clumpy molecular cloud to evaluate how star counts, from which volume densities are derived, can be altered by background source contamination and by an incorrect evaluation of the sampled volume in a magnitude limited survey, due to the dumpiness of the embedding cloud.
• Engelbracht, C. W., Rieke, M. J., Rieke, G. H., & Latter, W. B. (1996). Observations and modeling of the nuclear starburst in NGC 69461. Astrophysical Journal Letters, 467(1 PART I), 227-240.
  More info

  Abstract: Near-infrared images in both broad and narrow bands, plus long-slit and aperture spectroscopy at moderate and high resolution have been obtained for NGC 6946. We have used these data and data from the literature to derive a set of observational constraints on the stellar population in the nucleus. We estimate an ultraviolet flux of 1052 ionizing photons s-1. A thorough examination of the gas and stellar motions puts a 2 a upper limit on the dynamical mass in the central 8″5 (which corresponds to 230 pc at an assumed distance of 5.5 Mpc) of ∼3 × 108 M⊙. A detailed study of broadband colors, emission-line ratios, and the 10 μm silicate absorption feature indicates that the extinction to the starburst is high, with Av = 10.4 mag. An estimate of the supernova rate from both nonthermal radio emission and [Fe II] 1.644 μm emission from gas excited in fast shocks agrees well with our models. The current rate of supernova explosions in the nucleus is ∼6 × 10-3 yr-1. The bolometric luminosity of the starburst region is greater than 2.2 × 109 L⊙. In addition to the diagnostic features we have used here, the infrared spectra show a wealth of stellar features and weaker emission lines, including atomic absorption lines and several H2 emission lines. We have measured the lines of H2 and compared the ratios to models to determine the excitation mechanism. The properties of NGC 6946 have been fitted with a starburst model. We find that the starburst probably had a duration of ∼20 million years and that the star formation is likely to be biased toward high-mass stars compared with those in the local neighborhood. © 1996. The American Astronomical Society. All rights reserved.
• Haller, J. W., Rieke, M. J., Rieke, G. H., Tamblyn, P., Close, L., & Melia, F. (1996). Stellar kinematics and the black hole in the galactic center. Astrophysical Journal Letters, 456(1 PART I), 194-205.
  More info

  Abstract: We estimate the amount and distribution of matter in the Galactic center, based on measurements of stellar velocities. In addition to published data, we consider new observations of the CO (v = 2 0) 2.3 μm absorption feature in the unresolved stellar emission at 41 positions within 20″ of Sgr A*. Because the CO band strength is greatly reduced within 6″-8″ of Sgr A*, we model the three-dimensional distribution of the stars with this feature. We find that the CO-bearing stars can provide a useful lower limit to the enclosed mass. We also analyze the velocities of the He I-emitting stars within 20″ of Sgr A*. We find a correlation between the He I line width and the radial velocity of these stars, indicating that the velocity dispersion derived from the He I stars is an upper limit to the intrinsic value, and hence the corresponding enclosed mass is an upper limit. Because this upper limit and the lower limits derived from the CO-bearing stars are virtually the same, at just under 2 × 106 M⊙, we conclude that the stellar dynamics require a concentrated central mass of this amount. This value is in close agreement with the mass deduced from gas velocities measured with the [Ne II] line. Although it is most likely that this central mass is in the form of a black hole, we cannot exclude the possibility of a tightly concentrated cluster of stellar remnants. In addition, we infer the possible existence of an extended component of dark matter, which might also be attributed to stellar remnants. © 1996. The American Astronomical Society. All rights reserved.
• Luhman, K. L., & Rieke, G. H. (1996). High-resolution near-infrared spectroscopy of Hubble. Astrophysical Journal Letters, 461(1 PART I), 298-306.
  More info

  Abstract: Spectra at H (1.6 μm) and K (2.2 μm) have been obtained of the young planetary nebula Hubble 12. The prominent features in these rich spectra include emission from the Brackett and Pfund series of hydrogen, [Fe II], [Fe III], Mg II, He I, and H2. Our high-resolution spectra (RH ∼ 2200, RK ∼ 3500) have revealed ∼50 H2 lines at both H and K. H2 emission in the H window and transitions from levels as high as v = 12 confirm the fluorescent excitation. The large number of detected H2 lines allows us to compare in detail the observed strengths to those predicted by models of fluorescent emission. We find good agreement with models that give gas densities in the outer regions of the nebula close to nH = 3.0 × 103 cm-3. The surface brightness of the 1-0 S(1) line is an order of magnitude higher than that predicted by models of steady state fluorescent emission, which is possibly due to the time dependence of the emission. The helium emission lines are found to agree well with theoretical predictions of helium recombination, although the blended lines at 2.11 μm imply a rather high Te ∼ 2 × 104 K. The line ratios of seven [Fe II] and three [Fe III] emission features in the H and K windows, respectively, are found to agree with the latest theoretical predictions for Te ∼ 104 K and ne ∼ 104 cm-3. This emission may originate in pockets of shocked material in the core of the nebula. The hydrogen emission in both the Brackett and Pfund series is found to differ significantly from case B recombination predictions, the cause of which is as yet unexplained. © 1996. The American Astronomical Society. All rights reserved.
• Maiolino, R., Rieke, G. H., & Rieke, M. J. (1996). Correction of the atmospheric transmission in infrared spectroscopy. Astronomical Journal, 111(1), 537-540.
  More info

  Abstract: High-resolution and sensitive near-infrared spectroscopy is often limited by the ability to correct the atmospheric transmission. The simple division of the object spectrum by the spectrum of a nearby star turns out to be unsatisfactory because of the stellar features in the latter. We show how to measure the atmospheric transmission with a nearby early GV or late FV star, and to correct for the stellar features by means of the (atmospheric-transmission-corrected) solar spectrum. © 1995 American Astronomical Society.
• Shier, L. M., Rieke, M. J., & Rieke, G. H. (1996). Obscured active galactic nuclei in luminous infrared galaxies. Astrophysical Journal Letters, 470(1 PART I), 222-236.
  More info

  Abstract: We examine the nature of the central power source in very luminous infrared galaxies. The infrared properties of the galaxies, including their far-infrared and 2.2 μm fluxes, CO indices, and Brackett line fluxes are compared to models of starburst stellar populations. Among seven galaxies we found two dominated by emission from young stars, two dominated by emission from an AGN, and three transition cases. Our results are consistent with evidence for active nuclei in the same galaxies at other wave-lengths. Nuclear mass measurements obtained for the galaxies indicate an initial mass function biased toward high-mass stars in two galaxies. After demonstrating our methods in well-studied galaxies, we define complete samples of high luminosity and ultraluminous galaxies. We find that the space density of embedded and unembedded quasars in the local universe is similar for objects of similar luminosity. If quasars evolve from embedded sources to optically prominent objects, it appears that the lifetime of a quasar is no more than about 108 yr. © 1996. The American Astronomical Society. All rights reserved.
• Stickel, M., Rieke, G. H., Kühr, H., & Rieke, M. J. (1996). Flat-spectrum radio sources with faint optical counterparts. Astrophysical Journal Letters, 468(2 PART I), 556-564.
  More info

  Abstract: For the last 15 years, we have monitored the infrared variability of 14 flat-spectrum radio sources with very faint optical-infrared counterparts and of the steep spectrum source 3C 422. We find that variability is a salient property of most of these objects, demonstrating that the near-infrared is sampling directly the output of the active galactic nuclei (AGNs). However, the infrared-to-optical continua tend to be so steep that these sources are frequently classified as flat-spectrum radio galaxies, and many of them have narrow, moderate-ionization emission-line spectra in support of this classification. We conclude that many radio galaxy identifications of flat-spectrum radio sources would have been classified as quasars with infrared observations. The red colors that cause these AGNs to drop from sight in the visible appear in many cases to arise from reddening within the QSO host galaxy or a foreground galaxy along the line of sight. However, the faint identifications are not all of this type, but they include traditional high-redshift galaxies, sources with intrinsically red continua, and objects that have anomalously faint optical outputs for their radio flux densities. For example, the steepest intrinsic nonthermal continua appear to have spectral indices ≥ -2.5 between the infrared and optical. One object in our sample, 0742 + 103, and a closely related object, 1413 + 349, have ratios of infrared-optical to radio luminosity far below the average for these sources and may represent a rare class of truly optically quiet quasar. © 1996. The American Astronomical Society. All rights reserved.
• Stickel, M., Rieke, M. J., Rieke, G. H., & Kühr, H. (1996). The optical cut-off source 0500+019: A background quasar seen through a foreground galaxy?. Astronomy and Astrophysics, 306(1), 49-54.
  More info

  Abstract: The optical spectrum of the extremely red (αR-B ≈ -7) optical counterpart of the radio source 0500+019 shows an unidentified emission line at 6543 Å in addition to absorption and emission lines of Ca H&K λλ 3933,3968, [O II] λ 3727, and [O III] λλ 4959,5007 at a redshift of z = 0.583. The optical (R-band) morphology of 0500+019 consists of an asymmetric galaxy with no obvious point source. In contrast, the infrared (Ks) morphology is dominated by a point source, while the galaxy component seen in the R-band is clearly visible only after image restoration. Since the emission line at 6543 Å cannot be identified within the z = 0.583 redshift system, it is interpreted as being due to a second system of currently unknown redshift. The optical and infrared morphologies then naturally lead to a picture, where a background source, likely a quasar seen in the infrared, is located behind a foreground galaxy, which is most clearly detected in the optical. In this case the steep optical spectral index may be the result of foreground absorption rather than being a source intrinsinc property.
• Tamblyn, P., Rieke, G. H., Hanson, M. M., Close, L. M., McCarthy Jr., D. W., & Rieke, M. J. (1996). The peculiar population of hot stars at the galactic center. Astrophysical Journal Letters, 456(1 PART I), 206-216.
  More info

  Abstract: Brγ and He I 2.058 μm images of the Galactic center reveal that most of the Brγ emission is associated with interstellar gas but that the He I is largely concentrated on individual, luminous stars that therefore must be hot. High-resolution spectra of these stars, emphasizing He I 2.058 μm through Brγ 2.166 μm, are compared with spectra of 98 hot, luminous stars from the literature and new spectra of 43 luminous galactic emission-line stars including late nitrogen sequence Wolf-Rayet, luminous blue variable (LBV), Oe, Of, and ON supergiant stars. Combining our data with other observations from the literature, the He I sources in the central parsec include approximately five Ofpe/WN stars and one late-WC star. The inferred luminosity and detection of Mg II emission lines in the spectrum of IRS 16NE make it a likely LBV candidate. However, we find six stars with line widths < 500 km s-1 which defy easy classification, even from the extensive library of comparison spectra we have compiled. Considering the ultraviolet constraints of Serabyn & Lacy and Shields & Ferland and the large number of peculiar hot stars, either we see this stellar population at a very distinctive moment in its evolution, or the conditions of formation or the evolution of the stars must be significantly altered by the environment in the central parsec. © 1996. The American Astronomical Society. All rights reserved.
• Williams, D. M., Boyle, R. P., Morgan, W. T., Rieke, G. H., Stauffer, J. R., & Rieke, M. J. (1996). Very low mass stars and substellar objects in the pleiades. Astrophysical Journal Letters, 464(1 PART I), 238-246.
  More info

  Abstract: We have identified a small number of faint, red stars in optical and infrared frames taken near the center of the Pleiades cluster. The sampled masses range from 0.25 to 0.04 M⊙. The Pleiades mass function in linear units is consistent with a M-1 power law or with a flat dependence in logarithmic mass units. This dependence is consistent with studies of other young open clusters and suggests that massive brown dwarfs and low-mass stars do not contribute significantly to the dark matter. © 1996. The American Astronomical Society. All rights reserved.
• Bloemhof, E. E., & Rieke, G. H. (1995). IRIS: a high-resolution midinfrared spectrometer for the upgraded 6.5-meter Multiple Mirror Telescope. Proceedings of SPIE - The International Society for Optical Engineering, 2540, 236-246.
  More info

  Abstract: In mid-1996, the Multiple Mirror Telescope (MMT) will be upgraded from its current configuration of six 1.8-meter primary mirrors to house a single 6.5-meter primary. To exploit the dramatic increase in collecting area and spatial resolution, as well as the high infrared quality of the observing site, we have designed a new spectrometer that will cover the thermal infrared (4 to 25 micrometer) at high spectral and spatial resolution. The design is based on the new generation of Si:As BIB detectors with 256 by 256 formats, which represent a substantial advance in array size at these wavelengths. The design consists entirely of reflecting optics, and is arranged to deliver diffraction-limited resolution longwards of 8 micrometers. A maximum spectral resolving power of R equals 15,000 is provided by an echelle grating. A lower resolution grating or a plane mirror for two-dimensional imaging may be substituted for the echelle.
• Campins, H., Osip, D. J., Rieke, G. H., & Rieke, M. J. (1995). Estimates of the radius and albedo of comet-asteroid transition object 4015 Wilson-Harrington based on infrared observations. Planetary and Space Science, 43(6), 733-736.
  More info

  Abstract: We present simultaneous near-infrared and thermal-infrared observations of 4015 1979 VA, also known as comet P/Wilson-Harrington, which permit an estimate of its albedo and radius. If the standard thermal model (STM, highest nuclear temperature) is assumed, a radius of 1.30±0.16 km and a geometric albedo in the J bandpass of 0.10±0.02 are obtained. Although our observations of P/WH do not rule out the applicability of the STM, we believe the isothermal latitude model (ILM, lowest temperature) better describes the thermal properties of this object because of its size and rotation period. The ILM case yields a radius of 1.95±0.25 km and an albedo in the J bandpass of 0.05±0.01. We compare the nuclear characteristics of comet P/Wilson-Harrington with those of four other periodic comets observed in sufficient detail. © 1995.
• Dole, H., Lagache, G., Puget, J., Caputi, K., Fernandez-Conde, N., Le Floc'h, E., Papovich, C., Perez-Gonzalez, P., Rieke, G., & Blaylock, M. (1995). The cosmic infrared background resolved by Spitzer - Contributions of mid-infrared galaxies to the far-infrared background. ASTRONOMY & ASTROPHYSICS, 451(2), 417-429.
  More info

  Aims. We quantify the contributions of 24 mu m galaxies to the Far-Infrared ( FIR) Background at 70 and 160 mu m. We provide new estimates of the Cosmic Infrared Background ( CIB), and compare it with the Cosmic Optical Background ( COB).
• Giannuzzo, E., Rieke, G. H., & Rieke, M. J. (1995). Infrared coronal line widths in type 1 Seyfert galaxies. Astrophysical Journal Letters, 446(1 PART 2), L5-L9.
  More info

  Abstract: We present high-resolution observations of six Seyfert 1 galaxies in the 2 μm region. We detected the [Si vi] 1.96 μm coronal line in all the galaxies and analyzed its profile, finding it to be variable in width from object to object, from very narrow profiles (FWHM ∼ 300 km s-1) to profiles approaching the width of the broad lines. The coronal region seems to be placed differently in different galaxies, and in some cases the infrared coronal lines are useful as a probe of the structure of the broad-line region.
• Hubbard, W. B., Haemmerle, V., Porco, C. C., Rieke, G. H., & Rieke, M. J. (1995). The Occultation of SAO 78505 by Jupiter. Icarus, 113(1), 103-109.
  More info

  Abstract: On 13 December 1989, Jupiter occulted a star with visual magnitude 8.7 and an estimated K magnitude of 7. We observed the event from Kitt Peak, Arizona, using a 64 × 64 infrared camera at a wavelength of 2.16 μm. The resulting data on refractive defocusing of the stellar signal give information on the temperature of the jovian atmosphere at pressures ∼2 to 10 μbar, at near-equatorial latitudes. These are the first new stellar-occultation data for the high jovian atmosphere since the widely observed occultation of β Sco A and C in 1971. Because of improvements in instrumental capability, our data are comparable to the best β Sco A data though the star is six magnitudes fainter. We derive a mean atmospheric temperature of 176 ± 12 K on a level surface corresponding to an equatorial radius of 71,880 km and a pressure of 1.8 μbar at a jovicentric latitude of 8°. This result complements the β Sco results by providing improved precision at low jovicentric latitudes where the fainter star β Sco C was used in 1971. © 1995 Academic Press. All rights reserved.
• Luhman, K., Rieke, G., Young, E., Cotera, A., Chen, H., Rieke, M., Schneider, G., & Thompson, R. (1995). The initial mass function of low-mass stars and brown dwarfs in young clusters. ASTROPHYSICAL JOURNAL, 540(2), 1016-1040.
  More info

  We have obtained images of the Trapezium Cluster (140 " x 140 "; 0.3 pc x 0.3 pc) with the Hubble Space Telescope Near-Infrared Camera and Multi-Object Spectrometer (NICMOS). Combining these data with new ground-based K-band spectra (R = 800) and existing spectral types and photometry, we have constructed an H-R diagram and used it and other arguments to infer masses and ages. To allow comparison with the results of our previous studies of IC 348 and rho Oph, we first use the models of D'Antona & Mazzitelli. With these models, the distributions of ages of comparable samples of stars in the Trapezium, rho Oph, and IC 348 indicate median ages of similar to 0.4 Myr for the first two regions and similar to 1-2 Myr for the latter. The low-mass initial mass functions (IMFs) in these sites of clustered star formation are similar over a wide range of stellar densities (rho Oph, n = 0.2-1 x 10(3) pc(-3); IC 348, n = 1 x 10(3) pc(-3); Trapezium, n = 1-5 x 10(4) pc(-3)) and other environmental conditions (e.g., presence or absence of OB stars). With current data, we cannot rule out modest variations in the substellar mass functions among these clusters. We then make the best estimate of the true form of the IMF in the Trapezium by using the evolutionary models of Baraffe et al, and an empirically adjusted temperature scale and compare this mass function to recent results for the Pleiades and the held. All of these data are consistent with an IMF that is flat or rises slowly from the substellar regime to about 0.6 M. and then rolls over into a power law that continues from about 1 M, to higher masses with a slope similar to or somewhat larger than the Salpeter value of 1.35. For the Trapezium, this behavior holds from our completeness limit of similar to 0.02 M. and probably, after a modest completeness correction, even from 0.01-0.02 M.. These data include similar to 50 likely brown dwarfs. We test the predictions of theories of the IMF against (1) the shape of the IMF, which is not log-normal, in clusters and the field, (2) the similarity of the IMFs among young clusters, (3) the lowest mass observed for brown dwarfs, and (4) the suggested connection between the stellar IMF and the mass function of prestellar clumps. In particular, most models do not predict the formation of the moderately large numbers of isolated objects down to 0.01 M. that we find in the Trapezium.
• Maiolino, R., & Rieke, G. H. (1995). Low-luminosity and obscured seyfert nuclei in nearby galaxies. Astrophysical Journal Letters, 454(1), 95-105.
  More info

  Abstract: We discuss the Seyfert galaxies in the Revised Shapley-Ames catalog (BT < 13.31) and in three extensions to it (BT < 13.4). The sample contains 91 relatively nearby Seyfert galaxies. The proximity of the objects reduces the dilution of their nuclear spectra by the host galaxy light. As a consequence, biases against low-luminosity nuclei (relative to the host) and against edge-on galaxies are reduced compared with other samples of Seyfert galaxies. From this sample, we set a lower limit of 5% to the portion of galaxies with Seyfert nuclei; completeness arguments could support a percentage as high as 16%. We find type 2 Seyfert nuclei (i.e., types 1.8 + 1.9 + 2) to be 4 times more numerous than type 1 ones (types 1 + 1.2 + 1.5). Seyfert nuclei of types 1 + 1.2 + 1.5 are mostly found in face-on galaxies, while intermediate nuclei of types 1.8 + 1.9 are mostly found in edge-on hosts. These results suggest that most of the intermediate type Seyfert nuclei are type 1 nuclei seen through a 100 pc-scale torus coplanar with the galactic disk and not type 1 nuclei partially obscured by an inner parsecscale torus.
• Maiolino, R., Ruiz, M., Rieke, G. H., & Keller, L. D. (1995). New constraints on the unified model of Seyfert galaxies. Astrophysical Journal Letters, 446(2), 561-573.
  More info

  Abstract: We present new 10 μm (N-band) photometry for 70 Seyfert galaxies, 43 of them previously unobserved. These observations, together with those collected from the literature, complete the 10 μm photometry for the CfA Sy galaxies and cover 80% of the Sy found in the RSA and 70% of the Sy in the IRAS 12 μm sample. From this data set, we find that Sy not showing any evidence for broad lines are systematically weaker in 10 μm nuclear emission than Sy nuclei having broad lines. This result may indicate the existence of a group of very low-luminosity Sy2 galaxies that do not have Sy1 counterparts in equal numbers, contrary to the strict unified theory. Alternately, the result can be reconciled with unified theories if a specific type of geometry is assumed for the circumnuclear obscuring material. By comparing the 10 μm ground-based observations with the IRAS 12 μm fluxes, we also study the properties of the extended mid-IR emission, i.e., the star forming activity of the host galaxy of the Sy nucleus. We find Sy2 to lie preferentially in galaxies experiencing enhanced star-forming activity, while Sy1 lie in normal or quiescent galaxies. This result appears to be inconsistent with the strict unified model, since the host galaxy properties should be independent of the orientation of a circumnuclear torus and therefore should be independent of nuclear type. Our finding could be explained by adding to the unified model a link between starforming activity and the amount of obscuring material collected in the circumnuclear region.
• McLeod, K. K., & Rieke, G. H. (1995). Luminous quasars in luminous early-type host galaxies. Astrophysical Journal Letters, 454(2 PART 2), L77-L80.
  More info

  Abstract: Some recent observations of nearby quasars with Hubble Space Telescope (HST) have apparently failed to detect host galaxies. We review the HST observations as well as near-infrared ground-based observations of the same objects. We find that the quasar hosts can be detected in the HST data if they are smoothed sufficiently to reveal low surface brightness. The smooth hosts are very difficult to detect with HST but are more easily visible in the deeper, ground-based IR images. The V - H colors obtained by combining the HST and IR data are compatible with normal galaxy colors at the redshifts of the quasars. This behavior can be explained if the hosts are massive early-type galaxies. All together, HST images have been reported for 15 luminous quasars, ∼13 of which have smooth early-type hosts. This kind of galaxy therefore appears to be the most common host for a luminous quasar.
• Mcleod, K. K., & Rieke, G. H. (1995). Near-infrared imaging of CfA Seyfert galaxies. Astrophysical Journal Letters, 441(1), 96-112.
  More info

  Abstract: We present near-IR images of 43 Seyfert galaxies from the CfA Seyfert sample. The near-IR luminosity is a good tracer of luminous mass in these galaxies. Most of the Seyfert nuclei are found in hosts of mass similar to that of L* galaxies and ranging in type from S0 to Sc. In addition, there is a population of low-mass host galaxies with very low luminosity Seyfert nuclei. We have examined our images for signs of perturbations that could drive fuel toward the galaxy nucleus, but there are none we can identify at a significant level. The critical element for fueling is evidently not reflected clearly in the large-scale distribution of luminous mass in the galaxy. The Seyfert hosts are compared with a sample of 50 low-redshift quasar host galaxies we have also imaged. The radio-quiet quasars and the Seyfert nuclei lie in similar kinds of galaxies spanning the same range of mass centered around L*. However, for the most luminous quasars, there is a correlation between the minimum host-galaxy mass and the luminosity of the active nucleus. Radio-loud quasars are generally found in hosts more massive than an L* galaxy. The low-luminosity quasars and the Seyfert nuclei both tend to lie in host galaxies seen preferentially face-on, which suggests that there is a substantial amount of obscuration coplanar with the galaxian disk. The obscuration must be geometrically thick (thickness-to-radius ratio ∼1) and must cover a significant fraction of the narrow-line region (r > 100 pc).
• Rieke, G. H., Young, E. T., & Gautier, T. N. (1995). Detection limits in the far infrared. Space Science Reviews, 74(1-2), 17-25.
  More info

  Abstract: The advent of far infrared arrays will change fundamentally the means of analyzing observations in this spectral region. Sources much fainter than traditional "confusion limits" will be extracted from images by using computer algorithms similar to CLEAN or DAOPHOT. We have conducted numerical experiments to evaluate these techniques and show that they will permit long integrations (∼10,000 sec at 60 μm, ∼200 sec at 100 μm) to achieve nearly photon-background-limited performance and hence very deep detection limits. The dominant noise sources-photon noise, confusion by distant galaxies, and confusion by IR cirrus - scale with nearly the same power of the telescope aperture. As a result, the integration times required to reach confusion limits are nearly aperture-independent. © 1995 Kluwer Academic Publishers.
• Stickel, M., Fried, J. W., Mcleod, K. K., & Rieke, G. H. (1995). The optical and IR morphology of the BAL quasar PG 1700+518. Astronomical Journal, 109(5), 1979-1982.
  More info

  Abstract: A deep R-band image of the low-redshift (z = 0.292) BAL quasar PG 1700+518 (with 0.5″ resolution after image restoration) reveals an unusual boomerang-like morphological feature only ≈2.5″ north of the quasar point source. A relatively faint and almost symmetric nebulosity is possibly hidden by the bright quasar point source, which might be interpreted as the host galaxy. From the suspected host galaxy component, an even fainter asymmetric extension is possibly detected towards the southwest. In contrast to the suspected host galaxy, the boomerang feature north and the asymmetric extension southwest of the quasar are also detected in an H-band image of PG 1700+518, which might be due to the fact that they are redder than any nebulosity underlying the bright quasar point source. The new data give a much clearer view of the unusual morphology of PG 1700+518, the components of which had been suggested by previous images of similar angular resolution.
• Thompson, C. L., Rieke, G. H., & Young, E. T. (1995). Compact and versatile far-infrared imager for SIRTF. Proceedings of SPIE - The International Society for Optical Engineering, 2475, 449-455.
  More info

  Abstract: We present the design for the multiband imaging photometer for SIRTF (MIPS). MIPS is a versatile instrument that provides diffraction-limited imaging at 30 μm, 70 μm, and 160 μm. MIPS also provides low resolution (5%) spectroscopy in the 50 - 100 μm wavelength range to allow the determination of far-infrared spectral energy distributions. The 70 μm array can also be used in a special high resolution mode that supports image reconstruction techniques for improved angular resolution. The one cryogenic mechanism on MIPS is a scanning mirror based on a space-qualified design used on the Infrared Space Observatory. We describe modifications to the scan mechanism to optimize it for use at very long wavelengths.
• Williams, D. M., Comerón, F., Rieke, G. H., & Rieke, M. J. (1995). The low-mass IMF in the ρ Ophiuchi cluster. Astrophysical Journal Letters, 454(1), 144-150.
  More info

  Abstract: We compare the methods for estimating the masses of young, embedded stars developed by Comerón et al. (1993) and by Strom et al. (1995) and show them to be in good agreement. Spectra in the 2 μm region of six low-mass objects are also in agreement with the mass estimates using these methods. The spectrum of a brown dwarf candidate can be used to place an upper limit on its mass of 60% of the minimum required for hydrogen burning. This limit is independent of the photometric analysis, which we update in this paper to make use of new calculations of brown dwarf evolution. This new analysis indicates a mass for this object of roughly 40% of the minimum hydrogen-burning mass, supporting the possibility that it is a young brown dwarf. The initial mass functions (IMFs) obtained for low-mass stars in the ρ Ophiuchi cloud cores by Comerón et al. (1993) and by Strom et al. (1995) also agree well. The data have been combined to increase the statistical weight of the determination of the IMF. The IMF between 0.03 and 1 M⊙ can be fitted satisfactorily by a power law with index in linear mass units of ∼ -1.1, or in logarithmic mass units of ∼ -0.1.
• Williams, D. M., Rieke, G. H., & Stauffer, J. R. (1995). The stellar mass function of Praesepe. Astrophysical Journal Letters, 445(1), 359-366.
  More info

  Abstract: We have obtained V, I, and K band photometry for 290 square arcminutes in the Praesepe open cluster. The photometry reliably reaches 0.08 M⊙. We find six probable cluster members in the range 0.40 M⊙> M > 0.08 M⊙. The mass function we derive for Praesepe is similar to the field star IMF. We conclude that dynamical processes that can lead to evaporation of low-mass members from stellar clusters have not occurred to a substantial extent in Praesepe.
• Young, E. T., Rieke, G. H., Dang, H., Barg, I., & Thompson, C. L. (1995). Test results for the SIRTF far-infrared array module. Proceedings of SPIE - The International Society for Optical Engineering, 2475, 435-440.
  More info

  Abstract: We present initial test results for far-infrared arrays built at the University of Arizona using Ge:Ga photoconductors and low temperature readouts operating at a temperature of 2 K. We also present separate test results for the Hughes CRC-696 multiplexer used in this program. The two array configurations considered are a 1 × 32 based on an older heated readout concept and a new 4 × 32 module that takes advantage of the benefits of having a true cryogenic readout. Based on these results, performance meeting the SIRTF goal of background-limited imaging can be expected for the 32 × 32 array under construction.
• Young, E. T., Scutero, M. J., Rieke, G. H., & Davis, J. T. (1995). Construction of the large-format far-infrared array for SIRTF. Proceedings of SPIE - The International Society for Optical Engineering, 2475, 441-448.
  More info

  Abstract: We report on the design, modeling, and construction of far-infrared focal plane array modules for the Space Infrared Telescope Facility (SIRTF). The modules consist of 4 × 32 detector elements, readout electronics, and interconnections. The modules, which are of Z- plane architecture, may be stacked to produce imaging arrays of at least 32 × 32 format. These arrays are the largest available operating in the wavelength range 50 - 120 μm. The design takes advantage of the Hughes CRC-696 readout which was specifically developed for use with far-infrared photoconductive detectors. Since the readouts have excellent performance at temperatures below 2 K, a simplified construction concept using the proven interconnection methods of wire boding and multilayer ceramic boards are used. We report on additional design considerations such as minimization of parasitic capacitance at the input node and accommodation of thermal annealing of the detectors.
• Alonso-Herrero, A., Perez-Gonzalez, P., Alexander, D., Rieke, G., Rigopoulou, D., Le Floc'h, E., Barmby, P., Papovich, C., Rigby, ., Bauer, F., Brandt, W., Egami, E., Willner, S., Dole, H., & Huang, J. (1994). Infrared power-law galaxies in the Chandra deep field-south: Active galactic nuclei and ultraluminous infrared galaxies. ASTROPHYSICAL JOURNAL, 640(1), 167-184.
  More info

  We investigate the nature of a sample of 92 Spitzer MIPS 24 mu m-selected galaxies in the CDF-S, showing power-law-like emission in the Spitzer IRAC 3.6-8 mu m bands. The main goal is to determine whether the galaxies not detected in X-rays (47% of the sample) are part of the hypothetical population of obscured AGNs not detected even in deep X-ray surveys. The majority of the IR power-law galaxies are ULIRGs at z > 1, and those with LIRG-like IR luminosities are usually detected in X-rays. The optical-to-IR SEDs of the X-ray-detected galaxies are almost equally divided between a BLAGN SED class (similar to an optically selected QSO) and an NLAGN SED ( similar to the BLAGN SED but with an obscured UV/optical continuum). A small fraction of SEDs resemble warm ULIRGs (e. g., Mrk 231). Most galaxies not detected in X-rays have SEDs in the NLAGN+ULIRG class as they tend to be optically fainter and possibly more obscured. Moreover, the IR power-law galaxies have SEDs significantly different from those of high-z (zsp > 1) IR (24 mu m) selected and optically bright (VVDS I-AB
• Campins, H., Telesco, C. M., Osip, D. J., Rieke, G. H., Rieke, M. J., & Schulz, B. (1994). The color temperature of (2060) Chiron: A warm and small nucleus. Astronomical Journal, 108(6), 2318-2322.
  More info

  Abstract: We present three sets of thermal-infrared observations of (2060) Chiron, obtained in 1991, 1993, and 1994. These observations allow the first estimates of the color temperature of Chiron as well as refined estimates of the radius and albedo of its nucleus. 10/20 μm color temperatures of 126-6+11 and 137-9+14 K are obtained from the 1993 and 1994 observations, respectively. These temperatures are consistent with the Standard Thermal Model [STM; Lebofsky & Spencer, 1989, Asteroids II, p. 128 (University of Arizona, Tucson)] but significantly higher than those predicted by the Isothermal Latitude Model. Our estimates of Chiron's radius based on the STM are in agreement with each other, with the observations of Lebofsky et al. [Icarus, 60, 532 (1984)], and with recent occultation results [Buie et al, IAU Cire. 5898 (1993)]. We obtained values for the radius of 74±11 km in 1991, 88±10 and 104±10 km in 1993, and, 94±6 and 91±13 km in 1994.
• Kelly, D. M., Rieke, G. H., & Campbell, B. (1994). Near-infrared spectroscopy of young stellar objects. Astrophysical Journal Letters, 425(1), 231-242.
  More info

  Abstract: We present spectra between 0.9 and 1.35 μm for MWC 349, LkHα 101, R Mon, V645 Cyg, GL 490, T Tau, and HH 1. The spectra are rich in emission lines. We find evidence for many different emission regions, including virtually all those previously deduced from shorter wavelength spectra. A number of objects have optically thick regions in which O I emission is excited by UV and Lyβ fluorescence. We discuss the physical implications of the observed lines and the role spectroscopy between 0.9 and 1.35 μm can play in future investigations of the evolution of young stars.
• Kirby, D. J., Rieke, G. H., & Lebofsky, L. A. (1994). Stellar-based calibration in the far infrared with application to iras band 4. Astronomical Journal, 107(6), 2226-2232.
  More info

  Abstract: Because stars emit very small portions of their outputs in the far infrared, using them as calibrators requires precise measurement and correction for filter leaks at shorter wavelengths. Therefore, it is common to base far infrared calibrations on planetary objects such as asteroids. However, asteroids are complex geological bodies whose thermal properties depend on their evolutionary histories as well as on their gross parameters such as mass and composition, making them difficult to model as calibrators. We propose a new method for measuring filter leaks that can be carried out using the end-to-end detector system and therefore allows reliable use of stellar calibrators. We illustrate this method by showing that the IRAS 100 μm (Band 4) filters had a short wavelength leak of 14.3%±3.6% on stars similar to α Boo, but that there is no detectable leak in the 60 μm (Band 3) filters. We derive a calibration for Band 4 from stellar colors in a way that is closely analogous to the calibrations of Bands 1, 2, and 3. With correction for the leak, the stellar-based calibration is virtually identical to the original calibration based on asteroids; this result requires that the spectra of the asteroids used for the original calibration differ from greybody behavior between 60 and 100 μm by about 10%.
• McLeod, K. K., & Rieke, G. H. (1994). Near-infrared imaging of low-redshift quasar host galaxies. Astrophysical Journal Letters, 420(1), 58-67.
  More info

  Abstract: We present H-band images of a complete sample of 24 low-luminosity quasars selected from the Bright Quasar Survey. We detect the quasar host galaxy in at least 22 of these objects. We use a one-dimensional radial profile analysis to remove the contribution of the nucleus to the H-band light and to investigate the properties of the underlying galaxy. In most cases, the galaxy profiles are fitted better by exponential disk models than by de Vaucouleurs models. The average galaxy magnitude is 〈MH〈; = -23.9 mag, which is approximately the H magnitude of an L* galaxy. This result argues against the quasar activity being triggered by the merger of two large galaxies. No quasar host galaxies have inclinations greater than 60°, suggesting that obscuration near the active nucleus hides many of these objects from our view; their space density could be underestimated by a factor of ∼2. We combine our results with previously published results from CCD imaging to show that the galaxies we detect are about 0.5 mag bluer in V - H than normal galaxies. Such colors can arise from a heightened level of star formation compared with normal galaxies and are consistent with these galaxies having been the sites of luminous starbursts about 108 yr ago.
• Mcleod, K. K., & Rieke, G. H. (1994). Near-infrared imaging of low-redshift quasar host galaxies. II. High-luminosity quasars. Astrophysical Journal Letters, 431(1), 137-146.
  More info

  Abstract: We present H-band images of a complete sample of 26 high-luminosity quasars selected from the Bright Quasar Survey. We detect the quasar host galaxy in at least 23 of these objects. We compare these galaxies with host galaxies from a complementary sample of low-luminosity quasars and find the hosts of the high-luminosity quasars to be significantly brighter at H and possibly more massive. The average galaxy magnitude corresponds to a luminosity (and approximate mass) twice that of an L* galaxy. The high-luminosity quasars are possibly more likely to have brighter interacting companions than their low-luminosity counterparts. These results are consistent with suggestions that the highest levels of activity in radio-quiet quasars require a large host galaxy or a close interaction with a massive galaxy and that some of these interactions result in mergers. We also present what we believe is the first published infrared image of the jet of 3C 273, and we compare this image to optical and radio images from the literature. The results are consistent with suggestions that the knots at the end of the jet are due to rapid energy loss where the jet is burrowing into the surrounding medium.
• RIEKE, G., CUTRI, R., BLACK, J., KAILEY, W., MCALARY, C., LEBOFSKY, M., & ELSTON, R. (1994). 10(12)L. STARBURSTS AND SHOCKED MOLECULAR-HYDROGEN IN THE COLLIDING GALAXIES-ARP 220 (=IC-4553) AND NGC-6240. ASTROPHYSICAL JOURNAL, 290(1), 116-124.
• Rieke, G. H., & Young, E. T. (1994). Prospects for far infrared arrays. Experimental Astronomy, 3(1-4), 265-271.
  More info

  Abstract: We report initial performance measurements of a 1/8 scale version of a 32×32 pixel array under development for SIRTF. This array demonstrates that we can reach the sensitivity limits set by the natural backgrounds in space while providing good imaging and photometric performance. Based on the achieved performance levels, we project the imaging capabilities of SIRTF in the far infrared to exceed by a factor of more than 10,000 those achieved by any preceding telescope. © 1994 Kluwer Academic Publishers.
• Ruiz, M., Rieke, G. H., & Schmidt, G. D. (1994). New infrared observations of seyfert 2 galaxies and unification theories. Astrophysical Journal Letters, 423(2), 608-613.
  More info

  Abstract: We present infrared spectroscopy of He I 1.083 μm and Paβ for a sample of nine Seyfert 2 galaxies. These galaxies were selected for strong emission at ∼3 μm and spectral energy distributions similar to type 1 Seyferts. We find broad emission lines components (FWHM ∼1500 km s-1) in six galaxies of our sample and evidence for strong dust obscuration. Spectropolarimetry of Mrk 334 reveals that scattering screens are not a universal component of the broad-line region in Seyfert galaxies. The overall results show that the portion of Seyfert 1 galaxies is underestimated significantly in optically based studies and support current unified models for active galactic nuclei.
• Ruiz, M., Rieke, G. H., Rieke, M. J., Means, D., & Frawley, P. (1994). Near infrared spectroscopy of SL-9 impacts. Earth, Moon, and Planets, 66(1), 91-97.
  More info

  Abstract: We provide a preliminary description of the campaign of infrared spectroscopy of the SL-9 impacts carried out at the Steward Observatory 2.3m telescope. The data include high resolution (R = 3500) measurements of the impact sites, monitoring of auroral emissions, and spectra of two impact fireballs. © 1994 Kluwer Academic Publishers.
• Shier, L. M., Rieke, M. J., & Rieke, G. H. (1994). A comparison of dynamical and molecular gas masses in very luminous infrared galaxies. Astrophysical Journal Letters, 433(1 PART 2), L9-L12.
  More info

  Abstract: Observations of the 2.3 μm bands of CO have been used to measure the central stellar velocity dispersions in NGC 1614 and IC 694. K-band images were used to constrain models of the stellar mass distribution. With these data and a spectrum of Arp 220 from the literature, we have determined the total mass within the central regions of all three galaxies. The central molecular gas masses inferred from 12CO J = 1-0 fluxes are larger than the total masses determined from stellar kinematics. Subtraction of the likely stellar mass from the total mass yields upper limits for the H2 mass that are 4-10 times less than the previously reported masses. This result supports other arguments that the ICO/MH2 ratio is not the sme in ultraluminous galaxies as it is in Milky Way giant molecular clouds.
• CUTRI, R., WISNIEWSKI, W., RIEKE, G., & LEBOFSKY, M. (1993). VARIABILITY AND THE NATURE OF OSO OPTICAL-INFRARED CONTINUA. ASTROPHYSICAL JOURNAL, 296(2), 423-429.
• Comeron, F., Rieke, G. H., Burrows, A., & Rieke, M. J. (1993). The stellar population in the ρ Ophiuchi cluster. Astrophysical Journal Letters, 416(1), 185-203.
  More info

  Abstract: We report a near-infrared survey of 200 arcmin2 in the cores of the ρ Ophiuchi interstellar clouds, leading to the detection of 91 sources. We develop a new method for estimating the luminosities of these sources based on fitting of isochrones from theoretical models. Application of this method allows us to determine a luminosity function and accompanying initial mass function for the cluster of young stars forming in these clouds. The IMF extends to well below the bottom of the main sequence (0.08 M⊙) with no obvious feature at the transition between stellar and substellar masses. The power-law exponent of the IMF at low stellar and substellar masses is roughly -1.3 to - 1.1, with formal errors of 0.2. These values are consistent with extrapolation of many estimates of the local IMF to substellar masses. At least seven objects appear to be substellar, even allowing for the largest plausible errors in the observations, the analysis, and the theoretical evolutionary models for these sources. It therefore seems likely that brown dwarfs form in significant numbers and that the process of cloud fragmentation is not biased against substellar masses. These results indicate that the widespread difficulty in finding large numbers of brown dwarfs in older stellar populations arise from the rapid cooling and possibly from atmospheric absorptions that may depress the near infrared spectra outputs of these objects.
• Hubbard, W. B., Porco, C. C., Hunten, D. M., Rieke, G. H., Rieke, M. J., McCarthy, D. W., Haemmerle, V., Clark, R., Turtle, E. P., Haller, J., McLeod, B., Lebofsky, L. A., Marcialis, R., Holberg, J. B., Landau, R., Carrasco, L., Elias, J., Buie, M. W., Persson, S. E., , Boroson, T., et al. (1993). The Occultation of 28 Sgr by Saturn: Saturn Pole Position and Astrometry. Icarus, 103(2), 215-234.
  More info

  Abstract: We determine the geometry of the 3 July 1989 occultation of 28 Sgr by Saturn and use the results to derive Saturn's pole as defined by the ring plane. The analysis makes use of high-precision timings of 12 circular edges in the C-ring (radii = 84750 to 90615 km), three features in the Cassini division, the edges of the Encke gap, and the outer edge of the Keeler gap. Our group of observing sites includes one southern hemisphere station (CTIO) and five northern hemisphere stations (three Tucson-area stations, the UK Infrared Telescope in Hawaii, and San Pedro Mártir in Baja California), which provides a terrestrial chord separation ∼10,000 km. Assuming ring radii obtained from an analysis of Voyager radio- and stellar-occultation data (P. D. Nicholson, M. L. Cooke, and E. Pellon, 1990, Astron. J.100, 1339-1362), we use edge timings to solve for the position angle and opening angle of the apparent ring ellipses. The star 28 Sgr appears to be well represented as a uniformly illuminated disk with an apparent radius of 9.0 ± 0.3 km projected at Saturn at the wavelengths of observation (λ ∼ 3 μm). The internal consistency of the data set and redundancy of stations indicates that the relative positional error of a given sharp ring edge timing is at the level of 2 km or smaller; the absolute error is roughly 5 km. Our derived pole position, αP = 40.599° ± 0.020°, δP = 83.536° ± 0.005°, is consistent with the pole and ring radius scale deduced from Voyager stellar and radio occultation observations (P. D. Nicholson, M. L. Cooke, and E. Pelton, 1990, Astron. J.100, 1339-1362) and the solution found in the accompanying paper (French et al., 1993, this issue). © 1993 Academic Press. All rights reserved.
• Ivison, R., Greve, T., Serjeant, S., Bertoldi, F., Egami, E., Mortier, A., Alonso-Herrero, A., Barmby, P., Bei, L., Dole, H., Engelbracht, C., Fazio, G., Frayer, D., Gordon, K., Hines, D., Huang, J., Le Floc'h, E., Misselt, K., Miyazaki, S., , Morrison, J., et al. (1993). Spitzer observations of MAMBO galaxies: Weeding out active nuclei in starbursting protoellipticals. ASTROPHYSICAL JOURNAL SUPPLEMENT SERIES, 154(1), 124-129.
  More info

  We present 3.6 - 24 mum Spitzer observations of an unbiased sample of nine luminous, dusty galaxies selected at 1200 mum by MAMBO on the IRAM 30 m telescope, a population akin to the well-known submillimeter or SCUBA galaxies ( hereafter SMGs). Owing to the coarse resolution of submillimeter/millimeter cameras, SMGs have traditionally been difficult to identify at other wavelengths. We compare our multiwavelength catalogs to show that the overlap between 24 and 1200 mum must be close to complete at these flux levels. We find that all (4/4) of the most secure greater than or equal to4 sigma SMGs have greater than or equal to 4 sigma counterparts at 1.4 GHz, while the fraction drops to 7/9 using all greater than or equal to 3 sigma SMGs. We show that combining mid-infrared (MIR) and marginal ( greater than or equal to 3 sigma) radio detections provides plausible identifications in the remaining cases, enabling us to identify the complete sample. Accretion onto an obscured central engine is betrayed by the shape of the MIR continuum emission for several sources, confirming Spitzer's potential to weed out active galaxies. We demonstrate the power of an S-24 mum/S-8 mum versus S-8 mum/S-4.5 mum color-color plot as a diagnostic for this purpose. However, we conclude that the majority ( similar to 75%) of SMGs have rest-frame mid/far-IR spectral energy distributions commensurate with obscured starbursts. Sensitive 24 mum observations are clearly a useful route to identify and characterize reliable counterparts to high-redshift far-IR-bright galaxies, complementing what is possible via deep radio imaging.
• Kirkpatrick, J. D., Kelly, D. M., Rieke, G. H., Liebert, J., Allard, F., & Wehrse, R. (1993). M dwarf spectra from 0.6 to 1.5 microns: A spectral sequence, model atmosphere fitting, and the temperature scale. Astrophysical Journal Letters, 402(2), 643-654.
  More info

  Abstract: Red/infrared (0.6-1.5 μm) spectra are presented for a sequence of well-studied M dwarfs ranging from M2 through M9. A variety of temperature-sensitive features useful for spectral classification are identified. Using these features the spectral data are compared to recent theoretical models, from which a temperature scale is assigned. The red portion of the model spectra provide reasonably good fits for dwarfs earlier than M6. For later types, the infrared region provides a more reliable fit to the observations. In each case, the wavelength region used includes the broad peak of the energy distribution. For a given spectral type, the derived temperature sequence assigns higher temperatures than have earlier studies - the difference becoming more pronounced at lower luminosities. The positions of M dwarfs on the H-R diagram are, as a result, in closer agreement with theoretical tracks of the lower main sequence.
• Mcleod, K. K., Rieke, G. H., Rieke, M. J., & Kelly, D. M. (1993). M82: The saga continues. Astrophysical Journal Letters, 412(1), 111-126.
  More info

  Abstract: We present new near-infrared observations of the starburst galaxy M82, including high-resolution J, H, and K imagery, 1-5 μm spectrophotometry and photometry, and 1.05-1.35 μm spectroscopy. These measurements are used to examine the stellar population in the galaxy and conditions in the interstellar medium. We combine our observations with results from the literature to derive a new set of constraints for starburst models, which are presented in a companion paper. Our measurements of Paschen line fluxes in combination with the strengths of other recombination lines allow study of the reddening in M82. We find that a uniform foreground screen model for the dust geometry cannot explain the relative line strengths. A variety of other models can fit the data reasonably well, such as a nonuniform foreground screen or a homogeneous mix of dust and gas. The derived properties of the galaxy are not strongly dependent on which of these models is selected; we derive an ionizing flux of ≈1054 s-1 and an absolute magnitude of the starburst region of MK < -22.5. Depending on the reddening model, the visual extinction to the nucleus lies between AV = 12 and AV = 27; we show that the nucleus does not coincide with any feature that is bright at visual wavelengths. The stellar H2O index in the nuclear region is less than 0.06 and the CO index is ≈0.21; contamination of the CO band by emission by hot dust must be small. We use several lines in the 1.3 μm region to derive a lower limit to the electron density of ne > 104.5 cm-3 in the [Fe II] emission region. The [Fe II] line fluxes are consistent with excitation by fast shocks incident on dense gas. We report the tentative detection of several lines of H2, which, if confirmed, implicate UV fluorescence as the excitation mechanism.
• Rieke, G. H., Loken, K., Rieke, M. J., & Tamblyn, P. (1993). Starburst modeling of M82: Test case for a biased initial mass function. Astrophysical Journal Letters, 412(1), 99-110.
  More info

  Abstract: We compute starburst models for M82, making use of recent theoretical tracks of stellar evolution. Detailed comparisons of our models and those of others demonstrate this technique to be quite reliable, with relatively little change in output parameters as a function of the selection of theoretical tracks or of estimates of the observational characteristics of the stars along these tracks. The models are matched to the observational constraints for M82 summarized by McLeod et al. The rate of star formation and time of observation were thoroughly optimized to produce the most favorable fit to the observations, but we still found that the recently proposed forms for the solar-neighborhood initial mass function (IMF) cannot produce starbursts adequate to fit the observations of this galaxy. We then explored adjustments to the shape of the IMF to improve the fit to M82. We find (1) the shape of the IMF for high-mass stars need not be different from that observed locally; and (2) the most likely modification to the IMF in M82 is that stars with masses below a few M⊙ form much less commonly than in the solar neighborhood.
• Rieke, G., Su, K., Stansberry, J., Trilling, D., Bryden, G., Muzerolle, J., White, B., Gorlova, N., Young, E., Beichman, C., Stapelfeldt, K., & Hines, D. (1993). Decay of planetary debris disks. ASTROPHYSICAL JOURNAL, 620(2), 1010-1026.
  More info

  We report new Spitzer 24 mum photometry of 76 main-sequence A-type stars. We combine these results with previously reported Spitzer 24 mum data and 24 and 25 mum photometry from the Infrared Space Observatory and the Infrared Astronomy Satellite. The result is a sample of 266 stars withmass close to 2.5 M-., all detected to at least the similar to 7 sigma level relative to their photospheric emission. We culled ages for the entire sample from the literature and/or estimated them using the H-R diagram and isochrones; they range from 5 to 850 Myr. We identified excess thermal emission using an internally derived K - 24 ( or 25) mum photospheric color and then compared all stars in the sample to that color. Because we have excluded stars with strong emission lines or extended emission ( associated with nearby interstellar gas), these excesses are likely to be generated by debris disks. Younger stars in the sample exhibit excess thermal emission more frequently and with higher fractional excess than do the older stars. However, as many as 50% of the younger stars do not show excess emission. The decline in the magnitude of excess emission, for those stars that show it, has a roughly t(0)/ time dependence, with t(0) similar to 150 Myr. If anything, stars in binary systems ( including Algoltype stars) and lambda Boo stars show less excess emission than the other members of the sample. Our results indicate that ( 1) there is substantial variety among debris disks, including that a significant number of stars emerge from the protoplanetary stage of evolution with little remaining disk in the 10 - 60 AU region and ( 2) in addition, it is likely that much of the dust we detect is generated episodically by collisions of large planetesimals during the planet accretion end game, and that individual events often dominate the radiometric properties of a debris system. This latter behavior agrees generally with what we know about the evolution of the solar system, and also with theoretical models of planetary system formation.
• Tamblyn, P., & Rieke, G. H. (1993). IRS 16: The galaxy's central wimp?. Astrophysical Journal Letters, 414(2), 573-579.
  More info

  Abstract: We have constructed burst models of the stellar population in the Galactic center. Many classes of models can be excluded entirely. Models with an age of 7-8 Myr and an initial mass of less than 4 × 105 M⊙ can reproduce the red supergiant stars and stars with the continuum characteristics of IRS 16 and provide the ionizing flux. We show that if IRS 16 is the product of normal stellar evolution associated with a recent star formation burst that currently dominates the energetics of the region, then IRS 16 itself is inconsequential to Galactic center energetics.
• Kelly, D. M., Latter, W. B., & Rieke, G. H. (1992). Near-infrared observations of AFGL 618. II. The atomic spectrum. Astrophysical Journal Letters, 395(1), 174-184.
  More info

  Abstract: We measured the 0.84-1.35 μm spectrum for the eastern lobe and the 0.40-0.68 μm spectra for both lobes of the proto - planetary nebula AFGL 618. These rich emission spectra are highlighted by strong forbidden lines. We have compiled an extensive line list from these spectra, including many identifications in the poorly explored 1.0-1.35 μm region. The atomic line ratios indicate that there is both high- and low-temperature gas in the lobes. The apparently shock-excited hotter gas has an electron temperature of Te ≈ 25,000 K and an electron density of ne ≈ 8000 cm-3; the cooler gas has Te ≈ 10,000 K and ne ≈ 1600 cm-3. We used line strengths to determine the filling factors of these two components and found that the cool component fills most of the visible lobes. We compare our results with previous work.
• Latter, W. B., Maloney, P. R., Kelly, D. M., Black, J. H., Rieke, G. H., & Rieke, M. J. (1992). Near-infrared observations of the proto-planetary nebula AFGL 618. Astrophysical Journal Letters, 389(1), 347-356.
  More info

  Abstract: We present near-infrared images and spectroscopy of the bipolar proto-planetary nebula AFGL 618. Emission from molecular hydrogen is detected in the 0.90-1.34 μm spectrum. From molecular hydrogen line ratios, we derive a visual extinction of AV = 3.4+4.0-2.0 mag to the H2-emtting region. Models of collisionally excited and fluorescent H2 emission are compared with the data: the near-infrared H2 spectrum is dominated by emission from collisionally excited molecules at Tex ≈ 2000 K, but a component of fluorescent emission is also present. The low level of fluorescent emission might indicate a clumpy structure, or one which partly shields the emitting region from the stellar continuum. We show that this type of near-infrared spectrum is an excellent tool for discriminating relatively low levels of fluorescent H2 emission from a strong collisionally excited component. Images in the H- and K-bandpasses have been analyzed using models which assume single scattering of photons from the central object. The models indicate that the bipolar axis is inclined to the plane of the sky by i ∼ 45°. An unresolved, compact source is seen in both images and is reproduced in the models. It is found that the emission in the H- and K-bands is consistent with single scattering of photons by dust with a distribution such that the dust density decreases with increasing stellar latitude and is nearly zero at the poles. A total visual attenuation at the stellar equator of AV ∼ 87 mag is required to reproduce the images.
• Young, E. T., Scutero, M. J., Rieke, G. H., Milner, T. E., Low, F. J., Hubbard, W. P., Davis, J. T., Haller, E. E., & Beeman, J. (1992). Far-infrared focal-plane development for SIRTF. Proceedings of SPIE - The International Society for Optical Engineering, 1684, 63-74.
  More info

  Abstract: We describe the development of sensitive extrinsic germanium focal plane arrays for the Space Infrared Telescope Facility (SIRTF). The cryogenic telescope of SIRTF will be used for natural-background-limited astronomical observations, an application that requires arrays of far-infrared sensors of unprecedented sensitivity. For the 30 - 55 μm wavelength range, we describe the development of monolithic Ge:Be arrays with associated readouts bump- bonded to a common substrate. For the 55 - 120 μm wavelength range, we describe arrays based on a 1 × 32 building block that can be stacked into fully filled two- dimensional arrays. We show results from tests of a 3 × 32 demonstration array that operates at the SIRTF performance levels. This array demonstrates solutions to the problems of (1) maintaining the required detector operating temperature (< 2 K); (2) isolating the array from the heat and photon emission of the readout; (3) achieving long absorption paths in the detectors; and (4) maintaining constant detector bias and low noise from the readout amplifier. The array design permits stacking into the full 32 × 32 format required for SIRTF. The array thermally isolates the readout from the detectors to take advantage of the improved electronics noise performance at the elevated temperature of 20 K. We also show designs for improved versions of the array that emphasize manufacturability and the ability to be space qualified.
• Stauffer, J., Herter, T., Hamilton, D., Rieke, G. H., Rieke, M. J., Probst, R., & Forrest, W. (1991). Spectroscopy of Taurus cloud brown dwarf candidates. Astrophysical Journal Letters, 367(1 PART 2), L23-L26.
  More info

  Abstract: We have obtained low-dispersion optical spectra for six objects and infrared spectra for two objects originally proposed to be brown dwarf members of the Taurus cloud population. None of the brown dwarf candidates shows definite Hα emission, and only two objects display molecular absorption bands. In one case, the weak TiO bands and Hα emission indicate a spectral type of K7-M0e, but these features may be caused by contamination from the nearby, bright primary HBC 370. In the other object, the TiO bands are definitely present but relatively weak indicating a spectral type of about M1-M2. These characteristics are unlike those expected for brown dwarfs; thus it appears that the brown dwarf candidates identified by Forrest et al. are much more likely to be heavily reddened background G or K field stars.
• Currie, T., Kenyon, S. J., Balog, Z., Rieke, G., Bragg, A., & Bromley, B. (1990). The rise and fall of debris disks: MIPS observations of h and chi Persei and the evolution of mid-IR emission from planet formation. ASTROPHYSICAL JOURNAL, 672(1), 558-574.
  More info

  We describe Spitzer MIPS observations of the double cluster, h and chi Persei, covering a similar to 0.6 deg(2) area surrounding the cores of both clusters. The data are combined with IRAC and 2MASS data to investigate similar to 616 sources from 1.25-24 mu m. We use the long-baseline K-s - [24] color to identify two populations with IR excess indicative of circumstellar material: Be stars with 24 mu m excess from optically thin free-free emission, and 17 fainter sources (J similar to 14-15) with [24] excess consistent with a circumstellar disk. The frequency of IR excess for the fainter sources increases from 4.5 to 24 mu m. The IR excess is likely due to debris from the planet formation process. The wavelength-dependent behavior is consistent with an inside-out clearing of circumstellar disks. A comparison of the 24 mu m excess population in h and chi Per sources with results for other clusters shows that 24 mu m emission from debris disks "rises'' from 5 to 10 Myr, peaks at similar to 10-15 Myr, and then "falls'' from similar to 15-20 Myr to 1 Gyr.
• Keller, L. D., Sabol, B. A., & Rieke, G. H. (1990). Deep thermal infrared capability for the Multiple Mirror Telescope. Demands of multi-mirror telescope technology on infrared instrumentation. Proceedings of SPIE - The International Society for Optical Engineering, 1235 pt 1, 160-170.
  More info

  Abstract: Utilizing the light gathering advantages associated with multi-mirror telescope technology demands unique instrument design features, particularly in the thermal infrared. Specialized optics are needed to minimize the effects of the thermal emission of the telescope structure and the reflective surfaces as significant noise sources. Furthermore, it is unknown exactly how divided apertures perform in canceling the thermal fluctuations from the sky ('sky noise') which can exceed the effects of photon noise in determining the sensitivity. The Multiple Mirror Telescope (MMT) has just commissioned a new infrared bolometer system designed primarily for use in the thermal infrared from 2 to 25 microns. We report on the success with which the MMT system has addressed these issues. We find that the MMT competes well in sensitivity with similar detector systems currently operating on conventional single mirror telescopes--preliminary results indicate that the instrument will reach N (10.6micron) magnitudes of 10 or better (one standard deviation) in integrations of one hour through a 5.4 arcsecond aperture. Thus, multiple aperture telescope designs can be used with full effectiveness for observations in the deep thermal infrared.
• Kelly, D. M., & Rieke, G. H. (1990). 60 micron luminosity evolution of rich clusters of galaxies. Astrophysical Journal, 361(2), 354-361.
  More info

  Abstract: The average 60 μm flux has been determined for a collection of optically selected galaxy clusters at redshifts ranging from 0.30 to 0.92. The result, 26 mJy per cluster, represents the faintest flux determination we know of using the IRAS data base. The flux from this set of clusters has been compared to the 60 μm flux from a sample of nearby galaxy clusters. We find that the far-infrared luminosity evolution in cluster galaxies can be no more than a factor of 1.7 from z = 0.4 to the present epoch. This upper limit is close to the evolution predicted for simple aging of the stellar populations. Additional processes such as mergers, cannibalism, or enhanced rates of starbursts appear to occur at a low enough level that they have little influence on the farinfrared emission from clusters over this redshift range.
• Pompea, S. M., & Rieke, G. H. (1990). A test of the association of infrared activity with bars. Astrophysical Journal, 356(2), 416-429.
  More info

  Abstract: The hypothesis that high far-infrared luminosities in noninteracting galaxies are dependent on material fed into their nuclei or into circumnuclear rings along bars can be tested by near-infrared imaging. Except in extreme starbursts, the near-infrared emission arises from the stars that dominate the mass of the stellar populations; moreover, the effects of interstellar extinction are greatly reduced at these wavelengths compared with | the visible. We have selected a sample of 22 galaxies from the Revised Shapley-Ames Catalog that have farinfrared luminosities > 1010 L⊙ and hot colors between 60 and 100 μm (S60/S100 > 0.5), indicative of possible nuclear starbursts, but are not interacting or classified as Seyfert galaxies. Fifteen galaxies of the sample of 16 that are not clearly barred from optical data and are isolated were imaged at 1.6 and 2.2 μm. In an evaluation of the infrared images, at least eight of these galaxies do not appear to have bars. Strong bars therefore do not appear to be an absolute requirement for high infrared luminosity.
• Rieke, G. H., & Rieke, M. J. (1990). Possible substellar objects in the RHO Ophiuchi cloud. Astrophysical Journal, 362(1 PART 2), L21-L24.
  More info

  Abstract: Three sources have been discovered in the embedded population of the ρ Ophiuchi cloud that have dereddened MK ≥ 7. Comparison with theoretical models for evolution of low-mass stars shows that these sources are substantially less luminous than expected for objects evolving onto the main sequence and of the age of the embedded cluster. The sources are probably substellar in mass, i.e., they may be young brown dwarfs.
• Rix, H., Carleton, N. P., Rieke, G., & Rieke, M. (1990). Probing intermediate Seyfert galaxies by paβ spectroscopy. Astrophysical Journal, 363(2), 480-487.
  More info

  Abstract: We present high-resolution spectroscopy at Paβ of a sample of nearby Seyfert galaxies. These objects have been selected because of their observed steep Balmer decrements. We demonstrate the usefulness of Paβ in untangling whether dust obscuration or radiative transfer effects cause the large observed Hα/Hβ ratio and find that either mechanism can be dominant. In the cases where dust obscuration is present we find that the dereddened line strengths, relative to the hard X-ray flux, coincide with those found in unreddened objects. We propose a model for the dust distribution which accounts naturally for the frequency of severely reddened AGNs and their amount of reddening.
• Campins, H., Rieke, M. J., & Rieke, G. H. (1989). An infrared color gradient in the inner coma of Comet Halley. Icarus, 78(1), 54-62.
  More info

  Abstract: Near-infrared images of Comet Halley were obtained in the standard J, H, and K bandpasses, on 1985 November 3.5 UT with a HgCdTe camera at the University of Arizona 1.54-m telescope. A well-defined gradient in the J-H and H-K colors within ∼8000 km of the nucleus has been discovered with the bluest colors at the photocenter. Surface brightness profiles steeper than the "expected" 1/ρ{variant}, where "ρ{variant}" is the projected distance from the nucleus, are observed in the same region. A preliminary analysis indicates that the color gradient and the brightness profiles can both be explained by the presence of volatile (dirty ice) grains in the inner coma. An outburst of very small (Rayleigh scattering) dust particles could also account for the observations; however, this second model is not supported by the spacecraft measurements. No obvious jets or other structures are observed. © 1989.
• Currie, T., Balog, Z., Kenyon, S. J., Rieke, G., Prato, L., Young, E. T., Muzerolle, J., Clemens, D. P., Buie, M., Sarcia, D., Grabu, A., Tollestrup, E. V., Taylor, B., Dunham, E., & Mace, G. (1989). SPITZER IRAC and JHK(S) observations of h and chi Persei: Constraints on protoplanetary disk and massive cluster evolution at similar to 10(7) years. ASTROPHYSICAL JOURNAL, 659(1), 599-615.
  More info

  We describe IRAC 3.6-8 mu m observations and ground-based near-IR JHK(s) photometry from Mimir and 2MASS of the massive double cluster h and chi Persei complete to J = 15.5 (M similar to 1.3 M-circle dot). Within 25' of the cluster centers we detect similar to 11,000 sources with J
• RIEKE, G., LOKEN, K., RIEKE, M., & TAMBLYN, P. (1989). STARBURST MODELING OF M82 - TEST-CASE FOR A BIASED INITIAL MASS FUNCTION. ASTROPHYSICAL JOURNAL, 412(1), 99-110.
  More info

  We compute starburst models for M82, making use of recent theoretical tracks of stellar evolution. Detailed comparisons of our models and those of others demonstrate this technique to be quite reliable, with relatively little change in output parameters as a function of the selection of theoretical tracks or of estimates of the observational characteristics of the stars along these tracks. The models are matched to the observational constraints for M82 summarized by McLeod et al. The rate of star formation and time of observation were thoroughly optimized to produce the most favorable fit to the observations, but we still found that the recently proposed forms for the solar-neighborhood initial mass function (IMF) cannot produce starbursts adequate to fit the observations of this galaxy. We then explored adjustments to the shape of the IMF to improve the fit to M82. We find (1) the shape of the IMF for high-mass stars need not be different from that observed locally; and (2) the most likely modification to the IMF in M82 is that stars with masses below a few M . form much less commonly than in the solar neighborhood.
• Krause, O., Birkmann, S. M., Usuda, T., Hattori, T., Goto, M., Rieke, G. H., & Misselt, K. A. (1988). The Cassiopeia A supernova was of type IIb. SCIENCE, 320(5880), 1195-1197.
  More info

  Cassiopeia A is the youngest supernova remnant known in the Milky Way and a unique laboratory for supernova physics. We present an optical spectrum of the Cassiopeia A supernova near maximum brightness, obtained from observations of a scattered light echo more than three centuries after the direct light of the explosion swept past Earth. The spectrum shows that Cassiopeia A was a type IIb supernova and originated from the collapse of the helium core of a red supergiant that had lost most of its hydrogen envelope before exploding. Our finding concludes a long- standing debate on the Cassiopeia A progenitor and provides new insight into supernova physics by linking the properties of the explosion to the wealth of knowledge about its remnant.
• Donley, J., Rieke, G., Rigby, ., & Perez-Gonzalez, P. (1987). Unveiling a population of AGNs not detected in X-rays. ASTROPHYSICAL JOURNAL, 634(1), 169-182.
  More info

  We define a sample of 27 radio-excess AGNs in the Chandra Deep Field-North by selecting galaxies that do not obey the radio/infrared correlation for radio-quiet AGNs and star-forming galaxies. Approximately 60% of these radio-excess AGNs are undetected in X-rays in the 2 Ms Chandra catalog, even at exposures of >= 1 Ms; 25% lack even 2 sigma X-ray detections. The absorbing columns to the faint objects detected in X-rays are 1022 cm(-2) < NH < 10(24) cm(-2); i.e., they are obscured but unlikely to be Compton-thick. Using a local sample of radio-selected AGNs, we show that a low ratio of X-ray to radio emission, as seen in the samples of AGNs weakly detected and undetected in X-rays, is correlated with the viewing angle of the central engine and therefore with obscuration. Our technique can explore the proportion of obscured AGNs in the distant universe; the results reported here for radio-excess objects are consistent with, but at the low end of, the overall theoretical predictions for Compton-thick objects.
• Koch, D. G., Fazio, G. G., Hoffmann, W., Melnick, G., Rieke, G., Simpson, J., Witteborn, F., & Young, E. (1987). Infrared observations of contaminants from shuttle flight 51-F. Advances in Space Research, 7(5), 211-221.
  More info

  Abstract: A small helium cooled infrared telescope, IRT, was flown on the Shuttle in July/August 1985. The principle astrophysical objectives were to measure the large scale structure of sources and the background radiation. A cold shutter was incorporated to permit absolute flux measurements. Additionally, the engineering objectives included setting upper limits on the infrared radiation from the local environment. Even though the local background overwhelmed the astrophysical background, astronomical sources were still detectable superimposed on this background radiation. Data are presented covering the spectral range from 2μm to 120μm. The spatial, spectral and temporal variations are described. Based on the spectral character and variability in different wavelength bands, the background radiation does not appear to have a single origin. In this paper the results on the Shuttle environment will be presented. The astrophysical results will be presented elsewhere. © 1987.
• Marcialis, R. L., Rieke, G. H., & Lebofsky, L. A. (1987). The surface composition of Charon: Tentative identification of water ice. Science, 237(4820), 1349-1351.
  More info

  Abstract: The 3 March 1987 Charon occultation by Pluto was observed in the infrared at 1.5, 1.7, 2.0, and 2.35 micrometers. Subtraction of fluxes measured between second and third contacts from measurements made before and after the event has yielded individual spectral signatures for each body at these wavelengths. Charon's surface appears depleted in methane relative to Pluto. Constancy of flux at 2.0 micrometers throughout the event shows that Charon is effectively black at this wavelength, which is centered on a very strong water absorption band. Thus, the measurements suggest the existence of water ice on Pluto's moon.
• Haller, J., Rieke, M., Rieke, G., Tamblyn, P., Close, L., & Melia, F. (1986). Stellar kinematics and the black hole in the galactic center. ASTROPHYSICAL JOURNAL, 456(1), 194-205.
  More info

  We estimate the amount and distribution of matter in the Galactic center, based on measurements of stellar velocities. In addition to published data, we consider new observations of the CO (v = 2
• Rieke, G. (1986). European space telescope [5]. Science, 232(4757), 1487-.
• Rieke, G. H., Lada, C., Lebofsky, M., Low, F., Strittmatter, P., Young, E., Arens, J., Haller, E., Richards, P., Beichman, C., Gautier, T. N., Mould, J., Neugebauer, G., Gaalema, S., & Werner, M. (1986). MIPS: THE MULTIBAND IMAGING PHOTOMETER FOR SIRTF.. Proceedings of SPIE - The International Society for Optical Engineering, 619, 73-79.
  More info

  Abstract: The Multiband Imaging Photometer for SIRTF (MIPS) is to be designed to reach as closely as possible the fundamental sensitivity and angular resolution limits for SIRTF over the 3 to 700 mu m spectral region. It will use high performance photoconductive detectors from 3 to 200 mu m with integrating JFET amplifiers. From 200 to 700 mu m, the MIPS will use a bolometer cooled by an adiabatic demagnetization refrigerator. Over much of its operating range, the MIPS will make possible observations at and beyond the conventional Rayleigh diffraction limit of angular resolution.
• Rieke, G. H., Werner, M. W., Thompson, R. I., Becklin, E. E., Hoffmann, W. F., Houck, J. R., Low, F. J., Stein, W. A., & Witteborn, F. C. (1986). INFRARED ASTRONOMY AFTER IRAS.. Science, 231(4740), 807-814.
  More info

  Abstract: The 250,000 sources in the recently issued Infrared Astronomy Satellite (IRAS) all-sky infrared catalog are a challenge to astronomy. Many of these sources will be studied with existing and planned ground-based and airborne telescopes, but many others can no longer even be detected now that IRAS has ceased to operate. As anticipated by advisory panels of the National Academy of Sciences for a decade, study of the IRAS sources will require the Space Infrared Telescope Facility (SIRTF), a cooled, pointed telescope in space. This instrument may be the key to our understanding of cosmic birth - the formation of planets, stars, galaxies, actives galactic nuclei, and quasars. Compared with IRAS and existing telescopes, SIRTF's power derives from a thousandfold gain in sensitivity over five octaves of the spectrum.
• COMERON, F., RIEKE, G., BURROWS, A., & RIEKE, M. (1985). THE STELLAR POPULATION IN THE RHO OPHIUCHI CLUSTER. ASTROPHYSICAL JOURNAL, 416(1), 185-203.
  More info

  We report a near-infrared survey of 200 arcmin2 in the cores of the rho Ophiuchi interstellar clouds, leading to the detection of 91 sources. We develop a new method for estimating the luminosities of these sources based on fitting of isochrones from theoretical models. Application of this method allows us to determine a luminosity function and accompanying initial mass function for the cluster of young stars forming in these clouds. The IMF extends to well below the bottom of the main sequence (0.08 M.) with no obvious feature at the transition between stellar and substellar masses. The power-law exponent of the IMF at low stellar and substellar masses is roughly - 1.3 to - 1.1, with formal errors of 0.2. These values are consistent with extrapolation of many estimates of the local IMF to substellar masses. At least seven objects appear to be substellar, even allowing for the largest plausible errors in the observations, the analysis, and the theoretical evolutionary models for these sources. It therefore seems likely that brown dwarfs form in significant numbers and that the process of cloud fragmentation is not biased against substellar masses. These results indicate that the widespread difficulty in finding large numbers of brown dwarfs in older stellar populations arise from the rapid cooling and possibly from atmospheric absorptions that may depress the near infrared spectra outputs of these objects.
• Eisenhardt, P., Stern, D., Brodwin, M., Fazio, G., Rieke, G., Rieke, M., Werner, M., Wright, E., Allen, L., Arendt, R., Ashby, M., Barmby, P., Forrest, W., Hora, J., Huang, J., Huchra, J., Pahre, M., Pipher, J., Reach, W., , Smith, H., et al. (1985). The Infrared Array Camera (IRAC) shallow survey. ASTROPHYSICAL JOURNAL SUPPLEMENT SERIES, 154(1), 48-53.
  More info

  The Infrared Array Camera (IRAC) shallow survey covers 8.5 deg(2) in the NOAO Deep Wide-Field Survey in Bootes with three or more 30 s exposures per position. An overview of the survey design, reduction, calibration, star-galaxy separation, and initial results is provided. The survey includes approximate to370,000, 280,000, 38,000, and 34,000 sources brighter than the 5 sigma limits of 6.4, 8.8, 51, and 50 muJy at 3.6, 4.5, 5.8, and 8 mum, respectively, including some with unusual spectral energy distributions.
• MCLEOD, K., RIEKE, G., RIEKE, M., & KELLY, D. (1985). M82 - THE SAGA CONTINUES. ASTROPHYSICAL JOURNAL, 412(1), 111-126.
  More info

  We present new near-infrared observations of the starburst galaxy M82, including high-resolution J, H, and K imagery, 1-5 mum spectrophotometry and photometry, and 1.05-1.35 mum spectroscopy. These measurements are used to examine the stellar population in the galaxy and conditions in the interstellar medium. We combine our observations with results from the literature to derive a new set of constraints for starburst models, which are presented in a companion paper.
• Rieke, G. H., Lebofsky, L. A., & Lebofsky, M. J. (1985). A search for nitrogen on Triton. Icarus, 64(1), 153-155.
  More info

  Abstract: Improved spectrophotometry of Triton at 2.16 μm does not reveal an absorption feature due to liquid nitrogen. Either the absorption feature near this wavelength in the spectrum of this body is broader than expected for liquid nitrogen, or the liquid nitrogen is distributed nonuniformly over the surface. © 1985.
• Su, K., Rieke, G., Misselt, K., Stansberry, J., Moro-Martin, A., Stapelfeldt, K., Werner, M., Trilling, D., Bendo, G., Gordon, K., Hines, D., Wyatt, M., Holland, W., Marengo, M., Megeath, S., & Fazio, G. (1985). The vega debris disk: A surprise from Spitzer. ASTROPHYSICAL JOURNAL, 628(1), 487-500.
  More info

  We present high spatial resolution mid- and far-infrared images of the Vega debris disk obtained with the Multiband Imaging Photometer for Spitzer ( MIPS). The disk is well resolved, and its angular size is much larger than found previously. The radius of the disk is at least 43" (330 AU), 70" (543 AU), and 105" (815 AU) in extent at 24, 70, and 160 mu m, respectively. The disk images are circular, smooth, and without clumpiness at all three wavelengths. The radial surface brightness profiles follow radial power laws of r(-3) or r(-4) and imply an inner boundary at a radius of 11" +/- 2" (86 AU). Assuming an amalgam of amorphous silicate and carbonaceous grains, the disk can be modeled as an axially symmetric and geometrically thin disk, viewed face-on, with the surface particle number density following an inverse radial power law. The disk radiometric properties are consistent with a range of models using grains of sizes similar to 1 to similar to 50 mu m. The exact minimum and maximum grain size limits depend on the adopted grain composition. However, all of these models require an r(-1) surface number density profile and a total mass of (3 +/- 1.5) x 10(-3) M-circle plus in grains. We find that a ring, containing grains larger than 180 mu m and at radii of 86 - 200 AU from the star, can reproduce the observed 850 mu m flux, while its emission does not violate the observed MIPS profiles. This ring could be associated with a population of larger asteroidal bodies analogous to our own Kuiper Belt. Cascades of collisions starting with encounters among these large bodies in the ring produce the small debris that is blown outward by radiation pressure to much larger distances, where we detect its thermal emission. The relatively short lifetime (< 1000 yr) of these small grains and the observed total mass, similar to 3 x 10(-3) M-circle plus, set a lower limit on the dust production rate, similar to 10(15) g s(-1). This rate would require a very massive asteroidal reservoir for the dust to be produced in a steady state throughout Vega's life. Instead, we suggest that the disk we imaged is ephemeral and that we are witnessing the aftermath of a large and relatively recent collisional event, and a subsequent collisional cascade.
• Lebofsky, L. A., Tholen, D. J., Rieke, G. H., & Lebofsky, M. J. (1984). 2060 Chiron: Visual and thermal infrared observations. Icarus, 60(3), 532-537.
  More info

  Abstract: Five-color (λλ = 0.36-0.85 μm) and thermal infrared (λ = 22.5 μm) photometric observations of the unusual asteroid 2060 Chiron were made. Between 0.36 and 0.85 μm, Chiron's reflectance spectrum is similar to those of C-class asteroids as well as Saturn's satellite Phoebe. However, the thermal IR measurements imply an albedo ≥0.05 (i.e., a diameter ≤250 km at the level 2σ level) that is probably higher than those of C-class asteroids or Phoebe. © 1984.
• Campins, H., Rieke, G. H., & Lebofsky, M. J. (1983). Ice in Comet Bowell. Nature, 301(5899), 405-406.
  More info

  Abstract: It has been widely accepted that frozen volatiles are the major constituent of a comet nucleus1. However, the direct detection of these ices has proved to be difficult: bright comets which are easily observable are generally so close to the Sun that icy grains are too short lived to make an appreciable contribution to the coma brightness, while comets which are far enough from the Sun for ices to survive (heliocentric distance>2AU) ace usually too faint to be observed adequately. Observations of the reflected light from comets in the 1-5 m region of the spectrum are diagnostic of the presence of ices. Several attempts have been made to detect absorption bands in this region2-5 A weak, unidentified band near 2.2 m may have been detected in Comets Bowell and Panther, both of which are at large heliocentric distance5; although for Comet Bowell the result could not be confirmed4. We now report the detection of a deep absorption at 3.25 m in Comet Bowell which provides the first direct evidence for the presence of H2O ice in a comet. © 1983 Nature Publishing Group.
• Johnson, P. E., Kemp, J. C., Lebofsky, M. J., & Rieke, G. H. (1983). 10 μm polarimetry of ceres. Icarus, 56(3), 381-392.
  More info

  Abstract: Linear polarimetry of Ceres at 10 μm is presented. These data represent the first published polarization measurements of an asteroid in the thermal infrared. It is found that Ceres is polarized at the 0.2-0.6% level. This data set is compared with theoretical models of the linear polarization of emitted radiation from a spherical plane. These models are used to derive the pole position and thermal inertia of Ceres. Ceres is best fit with a thermal inertia of 0.0010±0.0003 cal cm-2 °K-1 sec 1 2 and a pole orientation of βp = 36° ± 5°, λp = 270° ± 3°. It is concluded that 10μm polarimetry is a potentially powerful technique for remotely sensing the pole orientation and thermal inertia of asteroids. © 1983.
• Middleditch, J., Cudaback, D., Oliver, B., Pennypacker, C., Lebofsky, M. J., Rieke, G. H., McGraw, J. T., Dearborn, D., Wisniewski, W., & Chini, R. (1983). A search for pulsed IR and near-IR emission from PSR1937 + 214. Nature, 306(5939), 163-164.
  More info

  Abstract: Backer et al.1,2 discovered PSR1937+214 at radiowavelengths. Djorgovski3 identified a candidate optical counterpart with a red-sensitive CCD on a 1-m telescope, although he found nothing on the paper prints of the Palomer Sky Survey. Manchester et al.4 at the Anglo-Australian Telescope reported optical pulses from a field including Djorgovski's red candidate, although they have not confirmedthis. Their 3.5 arcs field barely included the pulsar position. Two of us (M.J.L. and G.H.R.) have found a bright IR flux of 12.3 mag at 2.2 μm, an image at the plate limit on the red-sensitive glass print of the Sky Survey, and CO absorption bands, all for the red candidate5. We report here that it is probably an ordinary red giant. We do not find statistically significant pulsations at the pulsar frequency or any harmonic up to the fourth in 6 to 8 arc s fields including both the red candidate and the radio pulsar positions. © 1983 Nature Publishing Group.
• Young, E. T., Rieke, G. H., Gautier, T. N., Hoffmann, W. F., Low, F. J., Poteet, W., Fazio, G. G., Koch, D., Traub, W. A., & Urban, E. W. (1983). SENSITIVE OBSERVATIONS WITH THE SPACELAB 2 INFRARED TELESCOPE.. Proceedings of SPIE - The International Society for Optical Engineering, 363, 39-45.
• Campins, H., Rieke, G. H., & Lebofsky, M. J. (1982). Infrared photometry of periodic comets Encke, Chernykh, Kearns-Kwee, Stephan-Oterma, and Tuttle. Icarus, 51(3), 461-465.
  More info

  Abstract: Nearly simultaneous photometry of the reflected and thermal infrared spectra of periodic comets Encke, Chernykh, Kearns-Kwee, Stephan-Oterma, and Tuttle are presented. The 10-μm, silicate emission feature has been detected for the first time in periodic comets and was observed in three of these objects. The albedo of the dust particles in the comae of these comets is calculted and compared to that of Comet Kohoutek. The peculiar behavior of the dust in Comet Encke is discussed. © 1982.
• Koch, D., Fazio, G. G., Traub, W. A., Rieke, G. H., Gautier, T. N., Hoffmann, W. F., Low, F. J., Poteet, W., Young, E. T., Urban, E. W., & Katz, L. (1982). INFRARED TELESCOPE ON SPACELAB 2.. Optical Engineering, 21(1), 141-147.
  More info

  Abstract: The infrared telescope (IRT) on Spacelab 2 will be the first cryogenically cooled telescope operated from the Orbiter. The principal objectives, consistent with those of the second Spacelab mission, are to measure the induced environment about the Orbiter and to demonstrate the ability to manage a large volume of superfluid helium in space. The prime astrophysical objectives are to map extended sources of low surface brightness infrared emission, including the zodiacal light, the galactic plane, and extragalactic regions. The IRT consists of a 250 liter helium dewar and an articulated cryostat containing the telescope, which scans plus or minus 45 degrees about a single axis orthogonal to both the local vertical and the Orbiter pitch axis. The telescope is an f/4 15. 2 cm highly baffled Herschelian telescope cooled to 8K, which may scan to within 35 degrees of the sun. The focal plane cooled to 3K consists of nine discrete photoconductors covering a wavelength interval of 4. 5 to 120 microns in five bands. Each detector has a 0. 6 multiplied by 1. 0 degree field of view. A single 2 micron stellar detector is used for aspect determination. A cold shutter provides a zero flux reference. Overlapping scans, contiguous orbits, and a six degree per second scan rate permit rapid redundant coverage of 60% of the sky.
• MCLEOD, K., & RIEKE, G. (1982). NEAR-INFRARED IMAGING OF LOW-REDSHIFT QUASAR HOST GALAXIES. ASTROPHYSICAL JOURNAL, 420(1), 58-67.
  More info

  We present H-band images of a complete sample of 24 low-luminosity quasars selected from the Bright Quasar Survey. We detect the quasar host galaxy in at least 22 of these objects. We use a one-dimensional radial profile analysis to remove the contribution of the nucleus to the H-band light and to investigate the properties of the underlying galaxy. In most cases, the galaxy profiles are fitted better by exponential disk models than by de Vaucouleurs models. The average galaxy magnitude is [M(H)] = -23.9 mag, which is approximately the H magnitude of an L* galaxy. This result argues against the quasar activity being triggered by the merger of two large galaxies. No quasar host galaxies have inclinations greater than 60-degrees, suggesting that obscuration near the active nucleus hides many of these objects from our view; their space density could be underestimated by a factor of approximately 2. We combine our results with previously published results from CCD imaging to show that the galaxies we detect are about 0.5 mag bluer in V-H than normal galaxies. Such colors can arise from a heightened level of star formation compared with normal galaxies and are consistent with these galaxies having been the sites of luminous starbursts about 10(8) yr ago.
• Bregman, J. N., Lebofsky, M. J., Aller, M. F., Rieke, G. H., Aller, H. D., Hodge, P. E., Glassgold, A. E., & Huggins, P. J. (1981). Multifrequency observations of the red QSO 1413 + 135. Nature, 293(5835), 714-717.
  More info

  Abstract: The extremely red QSO 1413 + 135 shows characteristics typical of BL Lac objects - no emission lines, is embedded in a luminous galaxy, is subject to rapid radio and IR variability, has an inverted radio spectrum and shows substantial IR polarization. The rapid steepening of the nonthermal spectrum at λ < 5 μm is interpreted as synchrotron emission from an electron distribution that ends sharply at some maximum energy. The X-ray emission is probably inverse Compton radiation. We calculate that the optically thin emitting region is compact, has a large magnetic field and exhibits bulk relativistic motion towards the observer. The most energetic electrons in the emitting region have a Lorentz factor of 102-103. © 1981 Nature Publishing Group.
• Dye, S., Eales, S. A., Aretxaga, I., Serjeant, S., Dunlop, J. S., Babbedge, T. S., Chapman, S. C., Cirasuolo, M., Clements, D. L., Coppin, K. E., Dunne, L., Egami, E., Farrah, D., Ivison, R. J., van Kampen, E., Pope, A., Priddey, R., Rieke, G. H., Schael, A. M., , Scott, D., et al. (1981). The SCUBA HAlf degree extragalactic survey (SHADES) - VII. Optical/IR photometry and stellar masses of submillimetre galaxies. MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, 386(2), 1107-1130.
  More info

  We present estimates of the photometric redshifts, stellar masses and star formation histories of sources in the Submillimetre Common-User Bolometer Array (SCUBA) HAlf Degree Extragalactic Survey (SHADES). This paper describes the 60 SCUBA sources detected in the Lockman Hole covering an area of similar to 320 arcmin(2). Using photometry spanning the B band to 8 mu m, we find that the average SCUBA source forms a significant fraction of its stars in an early period of star formation and that most of the remainder forms in a shorter more intense burst around the redshift it is observed. This trend does not vary significantly with source redshift. However, the sources show a clear increase in stellar mass with redshift, consistent with downsizing. In terms of spectral energy distribution types, only two out of the 51 sources we have obtained photometric redshifts for are best fitted by a quasar-like spectrum, with approximately 80 per cent of the sources being best fitted with late-type spectra (Sc, Im and starburst). By including photometry at 850 mu m, we conclude that the average SCUBA source is forming stars at a rate somewhere between 6 and 30 times the rate implied from the rest-frame optical in a dust obscured burst and that this burst creates 15-65 per cent of the total stellar mass. Using a simplistic calculation, we estimate from the average star formation history that between one in five and one in 15 bright (L(*)+ 2 < L(optical) < L(*) - 1 mag) galaxies in the field over the interval 0 < z < 3 will at some point in their lifetime experience a similar energetic dusty burst of star formation. Finally, we compute the evolution of the star formation rate density and find it peaks around z similar to 2 .
• III, T. G., Poteet, W., Rieke, G. H., Low, F. J., & Hoffman, W. F. (1981). SMALL HELIUM-COOLED INFRARED TELESCOPE FOR SPACELAB 2.. Optical Engineering, 20(2), 285-290.
  More info

  Abstract: A helium-cooled telescope of 15 cm aperture is being constructed for high sensitivity IR astronomical observations from Spacelab 2. A focal plane array of ten detectors provides a total field of view of 3 degree and covers the wavelength regions 4. 5-8. 5 mu m, 6-7 mu m, 9-16 mu m, 18-30 mu m, and 60-120 mu m. A redundant all-sky survey will be conducted by repeated scanning of the sky during many orbits of the spacecraft. High redundancy will allow discrimination among variable and constant celestial sources and several types of variable nearby sources. The principal result of the survey will be the absolute flux measurement of low surface brightness, large scale celestial IR emissions, but it will also extend existing IR sky surveys by a factor of 10 in point-source sensitivity. The experiment will also measure contaminants in the Shuttle environment, test the technology of storage and utilization of large quantities of superfluid helium in space, demonstrate techniques for sensitive IR measurements from space, and test mechanical designs for future IR telescopes for the Space Shuttle.
• Koch, D., Fazio, G. G., Traub, W. A., Urban, E. W., Katz, L., Rieke, G. H., Gautier, T. N., Hoffmann, W. F., Low, F. J., Poteet, W., & Young, E. T. (1981). MAPPING THE INFRARED BACKGROUND RADIATION FROM THE SHUTTLE.. Proceedings of the Society of Photo-Optical Instrumentation Engineers, 265, 257-263.
  More info

  Abstract: The Spacelab-2 Small Helium-Cooled Infrared Telescope will be used to map extended astronomical sources of low surface brightness emission, to measure the Shuttle induced environment and to develop techniques for managing large volumes of superfluid helium in space. The instrument is an f/4 15. 2-cm Herschelian telescope with ten photoconductor detectors in the focal plane. The hardware and software aspects of the instrument with emphasis on mission operations are described. In particular, a description is given of the observing plan formulated to meet the scientific and engineering objectives, the scan drive system, the precautions in design and operation necessary to prevent the sun, moon, and earth from adversely affecting the observations, the implications of thruster firings, and the on-board experiment computer application software to control the scanning of the telescope and support on-board displays.
• Lebofsky, L. A., Rieke, G. H., & Lebofsky, M. J. (1981). Infrared reflectance spectra of Hyperion, Titania, and Triton. Icarus, 46(2), 169-174.
  More info

  Abstract: Medium-resolution infrared (1-2.5 μm; Δλ/λ {reversed tilde} 0.05) photometry of Triton, Titania, and Hyperion and medium-resolution (1.5-2.4 μm; Δλ/λ ≲ 0.01) spectroscopy of Triton are presented. Hyperion and Titania have spectra roughly similar to the laboratory spectrum of water frost, while the spectrum of Triton is inconsistent with the spectra of frosts likely to be major surface constituents. © 1981.
• Lebofsky, L. A., Veeder, G. J., Rieke, G. H., Lebofsky, M. J., Matson, D. L., Kowal, C., Wynn-Williams, C., & Becklin, E. E. (1981). The albedo and diameter of 1862 Apollo. Icarus, 48(2), 335-338.
  More info

  Abstract: We report infrared thermal emission measurements of 1862 Apollo, which is the type example of an Earth-crossing asteroid. We derive a geometric albedo of 0.21 ± 0.02 which is within the albedo range of the S class of asteroids. The effective diameter was observed to vary with rotation from 1.2 ± 0.1 to 1.5 ± 0.1 km. © 1981.
• Papovich, C., Rudnick, G., Le Floc'h, E., van Dokkum, P. G., Rieke, G. H., Taylor, E. N., Armus, L., Gawiser, E., Huang, J., Marcillac, D., & Franx, M. (1981). Spitzer mid- to far-infrared flux densities of distant galaxies. ASTROPHYSICAL JOURNAL, 668(1), 45-61.
  More info

  We study the infrared (IR) properties of high-redshift galaxies using deep Spitzer 24, 70, and 160 mu m data. Our primary interest is to improve the constraints on the total IR luminosities, L-IR, of these galaxies. We combine the Spitzer data in the southern Extended Chandra Deep Field with a K-s-band-selected galaxy sample and photometric redshifts from the Multiwavelength Survey by Yale-Chile. We used a stacking analysis to measure the average 70 and 160 mu m flux densities of 1.5 < z < 2.5 galaxies as a function of 24 mu m flux density, X-ray activity, and rest-frame near-IR color. Galaxies with 1.5 < z < 2.5 and S-24 = 53-250 mu Jy have L-IR derived fromtheir average 24-160 mu m flux densities within factors of 2-3 of those inferred from the 24 mu m flux densities only. However, L-IR derived from the average 24-160 mu m flux densities for galaxies with S-24 > 250 mu Jy and 1.5 < z < 2.5 are lower than those inferred using only the 24 mu m flux density by factors of 2-10. Galaxies with S-24 > 250 mu Jy have S-70/S-24 flux ratios comparable to sources with X-ray detections or red rest-frame IR colors, suggesting that warm dust possibly heated by AGNs may contribute to the high 24 mu m emission. Based on the average 24-160 mu m flux densities, nearly all 24 mu m-selected galaxies at 1.5 < z < 2.5 have L-IR < 6 x 10(12) L-circle dot, which, if attributed to star formation, corresponds to Psi < 1000 M-circle dot yr(-1). This suggests that high-redshift galaxies may have star formation efficiencies and feedback processes similar to those of local analogs. Objects with L-IR > 6 x 10(12) L-circle dot are quite rare, with a surface density similar to 30 +/- 10 deg(-2), corresponding to similar to 2 +/- 1 x 10(-6) Mpc(-3) over 1.5 < z < 2.5.
• Rieke, G. H., Lebofsky, L. A., Lebofsky, M. J., & Montgomery, E. F. (1981). Unidentified features in the spectrum of Triton. Nature, 294(5836), 59-60.
  More info

  Abstract: Water frost has been identified on the surfaces of the satellites of Jupiter1, Saturn2 and Uranus3,4; methane frost is dominant on Pluto5-7. However, although the IR spectrum of Triton, the largest satellite of Neptune, is similar to that of methane or methane frost8,this identification is not consistent with all the available data9,10. We have now used the Multiple Mirror Telescope (MMT) to obtain an improved IR spectrum of Triton. Our observations show features that are not in detailed agreement with the identification of methane, although the general spectral behaviour that led to this identification is confirmed. A satisfactory identification of the surface and/or atmospheric composition on Triton does not yet seem possible. © 1981 Nature Publishing Group.
• Rieke, G. H., Montgomery, E. F., Lebofsky, M. J., & Eisenhardt, P. R. (1981). HIGH SENSITIVITY OPERATION OF DISCRETE SOLID STATE DETECTORS AT 4 K.. Applied Optics, 20(4), 814-818.
  More info

  Abstract: Techniques are presented that allow operation of discrete solid state detectors at 4 K with optimized junction field effect transistor (JFET) amplifiers. Three detector types cover the 0. 6 - 4- mu m spectral range with a noise equivalent power (NEP) of approximately 10** minus **1**6 Hz** minus ** one-half for two of the types and potential improvement to this performance for the third. Lower NEPs can be anticipated at longer IR wavelengths.
• Stocke, J. T., Rieke, G. H., & Lebofsky, M. J. (1981). New observational constraints on the M87 jet. Nature, 294(5839), 319-322.
  More info

  Abstract: New observations at 1.6-3.45 μm confirm the presence of a dramatic (Δα ∼ 1) break between radio-IR wavelengths and 6,000 Å, in the spectrum of the M87 jet. These data, in combination with data taken in other spectral regions, show that the individual knots in the M87 jet have nearly the same spectral indices and nearly the same large (Δα ∼ 1) spectral break. This large spectral break and the constancy of spectral properties between the knots pose serious constraints for models of the M87 jet. © 1981 Nature Publishing Group.
• Young, E. T., Rieke, G. H., Gautier, T. N., Hoffmann, W. F., Low, F. J., Poteet, W., Fazio, G. G., Koch, D., Traub, W. A., Urban, E. W., & Katz, L. (1981). TEST RESULTS OF SPACELAB 2 INFRARED TELESCOPE FOCAL PLANE.. Proceedings of SPIE - The International Society for Optical Engineering, 280, 12-19.
• Gordon, K., Rieke, G., Engelbracht, C., Muzerolle, J., Stansberry, J., Misselt, K., Morrison, J., Cadien, J., Young, E., Dole, H., Kelly, D., Alonso-Herrero, A., Egami, E., Su, K., Papovich, C., Smith, P., Hines, D., Rieke, M., Blaylock, M., , Perez-Gonzalez, P., et al. (1980). Reduction algorithms for the multiband imaging photometer for Spitzer. PUBLICATIONS OF THE ASTRONOMICAL SOCIETY OF THE PACIFIC, 117(831), 503-525.
  More info

  We describe the data reduction algorithms for the Multiband Imaging Photometer for Spitzer (MIPS). These algorithms were based on extensive preflight testing and modeling of the Si: As (24 mm) and Ge:Ga (70 and 160 mm) arrays in MIPS and have been refined based on initial flight data. The behaviors we describe are typical of state-of-the-art infrared focal planes operated in the low backgrounds of space. The Ge arrays are bulk photoconductors and therefore show a variety of artifacts that must be removed to calibrate the data. The Si array, while better behaved than the Ge arrays, does show a handful of artifacts that must also be removed to calibrate the data. The data reduction to remove these effects is divided into three parts. The first part converts the nondestructively read data ramps into slopes while removing artifacts with time constants of the order of the exposure time. The second part calibrates the slope measurements while removing artifacts with time constants longer than the exposure time. The third part uses the redundancy inherent in the MIPS observing modes to improve the artifact removal iteratively. For each of these steps, we illustrate the relevant laboratory experiments or theoretical arguments, along with the mathematical approaches taken to calibrate the data. Finally, we describe how these preflight algorithms have performed on actual flight data.
• Lebofsky, M. J., & Rieke, G. H. (1980). Variations in the thermal emission of Seyfert galaxies. Nature, 284(5755), 410-412.
  More info

  Abstract: Accurate monitoring of five Seyfert galaxies demonstrates that they are all variable in the IR region. These fluctuations probably arise when variations in the nonthermal UV sources change the rate of heating of interstellar dust within the nuclei of these galaxies, as demonstrated quantitatively for III Zw 2. © 1980 Nature Publishing Group.
• Lebofsky, M. J., Rieke, G. H., Walsh, D., & Weymann, R. J. (1980). The IR spectrum of the double QSO. Nature, 285(5764), 385-386.
  More info

  Abstract: The hypothesis that the double QSO, 0957 + 561A,B (separation 6 arcs s and z = 1.4) is formed by a gravitational lens1 has found strong support from observations2 suggesting the presence of an intervening giant elliptical galaxy with z ≃ 0.4, separated from component B by
• RIEKE, G., & LEBOFSKY, M. (1980). SPECTRAL COMPONENTS OF NGC 4151. ASTROPHYSICAL JOURNAL, 250(1), 87-97.
• Dole, H., Le Floc'h, E., Perez-Gonzalez, P., Papovich, C., Egami, E., Lagache, G., Alonso-Herrero, A., Engelbracht, C., Gordon, K., Hines, D., Krause, O., Misselt, K., Morrison, J., Rieke, G., Rieke, M., Rigby, ., Young, E., Bai, L., Blaylock, M., , Neugebauer, G., et al. (1979). Far-infrared source counts at 70 and 160 microns in Spitzer deep surveys. ASTROPHYSICAL JOURNAL SUPPLEMENT SERIES, 154(1), 87-92.
  More info

  We derive galaxy source counts at 70 and 160 mum using the Multiband Imaging Photometer for Spitzer (MIPS) to map the Chandra Deep Field - South (CDF-S) and other fields. At 70 mum, our observations extend upward about 2 orders of magnitude in flux density from a threshold of 15 mJy, and at 160 mum they extend about an order of magnitude upward from 50 mJy. The counts are consistent with previous observations on the bright end. Significant evolution is detected at the faint end of the counts in both bands, by factors of 2 - 3 over no-evolution models. This evolution agrees well with models that indicate that most of the faint galaxies lie at redshifts between 0.7 and 0.9. The new Spitzer data already resolve about 23% of the cosmic far-infrared background at 70 mum and about 7% at 160 mum.
• III, T. G., Hoffmann, W. F., Low, F. J., Reed, M. A., & Rieke, G. H. (1979). CHOPPING SECONDARY MIRRORS FOR INFRARED ASTRONOMY WITH THE MULTIPLE MIRROR TELESCOPE.. Proceedings of the Society of Photo-Optical Instrumentation Engineers, 172, 54-59.
  More info

  Abstract: The technique of rapidly wobbling the secondary mirror of a reflecting telescope to modulate the energy from an astronomcial source by moving its image on and off of an aperture in the telescope's focal plane has been used with great success for a number of years on many ground based and airborne infrared telescopes. Such a secondary modulating system has been constructed and tested both in the laboratory and on the MMT itself. For image displacements up to about 20 arc seconds on the sky, the prototype is capable of a rise time of 2 ms and of operation at frequencies up to 80 Hz with a square wave driving signal. Larger displacements up to more than 120 arc seconds are available, but with a rise time of 4 ms. Adjustable hard stops and electronics to drive the secondary mechanism against these stops have been incorporated to provide a back up capability to the linear servo. Seven copies of the prototype are now in production and are expected to be in operation on the MMT in the spring of 1979.
• III, T. G., Rieke, G. H., Low, F. J., & Hoffmann, W. F. (1979). SMALL HELIUM-COOLED INFRARED TELESCOPE FOR SPACELAB 2.. Proceedings of the Society of Photo-Optical Instrumentation Engineers, 172, 264-270.
  More info

  Abstract: A helium cooled telescope of 15 cm aperture is being designed and constructed jointly by the University of Arizona, the Smithsonian Astrophysical Observatory and the Marshall Space Flight Center for high sensitivity infrared astronomical observations from Spacelab 2. A focal plane array of ten detectors provide a total field of view of 3 degree and cover the wavelength regions 4. 5 - 8. 5 mu m, 6 - 7 mu m, 9 - 16 mu m, 18 - 30 mu m and 80 - 120 mu m. a highly redundant all sky survey will be conducted by repeated scanning of the sky during many orbits of the spacecraft. High redundancy will allow discrimination among variable and constant celestial sources and several types of variable nearby sources. The principal astronomical result of the survey will be the absolute flux measurement of low surface brightness, large scale celestial infrared emissions but it will also extend existing IR sky surveys by a factor of 10 in point source sensitivity. The experiment will also make significant engineering measurements of contaminants in the Shuttle environment, test the technology of storage and utilization of large quantities of superfluid helium in space and test mechanical designs for future infrared telescopes for the Space Shuttle.
• Lebofsky, L. A., & Rieke, G. H. (1979). Thermal properties of 433 Eros. Icarus, 40(2), 297-308.
  More info

  Abstract: We report on radiometric and reflected light observations of 433 Eros at high time resolution, high accuracy, and broad spectral coverage. We use a thermal inertia model to estimate the thermal inertia, albedo, and size of Eros. We find an albedo of 0.125 ± 0.025 with axes of 39.3 ± 2.0 × 16.1 ± 0.8 km. Our estimate of the albedo is about 30% lower than previous estimates. © 1979.
• Lebofsky, L. A., Rieke, G. H., & Lebofsky, M. J. (1979). Surface composition of Pluto. Icarus, 37(3), 554-558.
  More info

  Abstract: Infrared photometric observations (1-4 μm) of Pluto have been made using broadband (Δλ/λ ∼ 0.3) and narrowband (Δλ/λ ∼ 0.05-0.1) filters. We confirm the probable presence of methane in some form, though, in detail the match between the spectrum of Pluto and the laboratory spectrum of methane frost is poor. © 1979.
• Luhman, K., & Rieke, G. (1979). The low-mass initial mass function in young clusters: L1495E. ASTROPHYSICAL JOURNAL, 497(1), 354-369.
  More info

  We have developed a technique of IR spectral classification in which we use K-band spectra (R similar to 1000) to derive the spectral types and continuum veilings of young, late-type stars (similar to 1 Myr, > GO). We show close agreement between the spectral types derived in this manner and those obtained optically. We complement previous optical spectroscopy with IR spectra of the most heavily embedded members of the young, embedded cluster L1495E. We critically analyze the translation between observable (spectral type, photometry) and theoretical (Teff, Lbol) parameters and use these data to construct an H-R diagram. We find that the evolutionary tracks of D'Antona & Mazzitelli imply a coeval population of II Myr and a plausible initial mass function (IMF). However, these models may underestimate the masses of objects near and below the hydrogen burning limit. The models of Swenson produce implausibly old ages and the models of Baraffe et al. yield somewhat old ages and an implausible IMF. We use infrared imaging to show that the spectroscopic sample for this cluster may be seriously incomplete below -0.15 hi,. After applying a completeness correction to the IILIF derived with the tracks of D'Antona & Mazzitelli, we find no evidence for a turnover at low masses; the IMF appears roughly flat in logarithmic mass units. Compared to the results of photometric studies of rho Oph and NGC 2024, the IMF appears roughly invariant among star-forming environments representing a 2 order of magnitude range in the density of young stars. However, the detailed behavior of the IMF from low stellar masses into the substellar regime will remain uncertain until (1) better evolutionary tracks are available and (2) the sources in the photometric completeness correction can be spectroscopically conarmed as low-mass cluster members.
• BREGMAN, J., GLASSGOLD, A., HUGGINS, P., NEUGEBAUER, G., SOIFER, B., MATTHEWS, K., ELIAS, J., WEBB, J., POLLOCK, J., PICA, A., LEACOCK, R., SMITH, A., ALLER, H., ALLER, M., HODGE, P., DENT, W., BALONEK, T., BARVAINIS, R., ROELLIG, T., , WISNIEWSKI, W., et al. (1978). MULTIFREQUENCY OBSERVATIONS OF THE SUPERLUMINAL QUASAR 3C 345. ASTROPHYSICAL JOURNAL, 301(2), 708-726.
• Kemp, J. C., Rudy, R. J., Lebofsky, M. J., & Rieke, G. H. (1978). Near-infrared polarization studies of Saturn and Jupiter. Icarus, 35(2), 263-271.
  More info

  Abstract: Polarization measurements of Jupiter, Saturn, and Saturn's rings from 1 to 3.5 μm are presented. At 1.6 μm on the discs of the two planets, the radially directed limb polarizations observed in the visible undergo, in some cases, a surprising 90° rotation to a tangential direction, particularly on the poles. The only immediate explanation for this effect is double Mie scattering, due to aerosols which must be of the order of a micrometer in size. On Jupiter the patterns are not uniform and are not stable, reflecting variable aerosol concentrations on the two poles. The ring polarization is uniformly negative (E vector parallel to the ecliptic plane) from the visible through 3.5 μm, and is inversely proportional to the albedo. This is as expected from Wolff's model for scattering from rough solid surfaces; but the degree of polarization seems uncommonly high, exceeding 2% at 3.5 μm. © 1978.
• Armstrong, K. R., Minton, R. B., Rieke, G. H., & Low, F. J. (1976). Jupiter at five microns. Icarus, 29(2), 287-298.
  More info

  Abstract: Maps of Jupiter at 5 um provide detailed information about the complex of emission features at this wavelength. Previous indications of a correlation between infrared sources and visual features are confirmed with a few significant exceptions. The behavior of Jupiter at 5 um is compared with that of other bodies in the outer solar system. Recent observations indicate emission features on Jupiter at other infrared wavelengths. © 1976.
• Bryden, G., Beichman, C., Trilling, D., Rieke, G., Holmes, E., Lawler, S., Stapelfeldt, K., Werner, M., Gautier, T., Blaylock, M., Gordon, K., Stansberry, J., & Su, K. (1976). Frequency of debris disks around solar-type stars: First results from a Spitzer MIPS survey. ASTROPHYSICAL JOURNAL, 636(2), 1098-1113.
  More info

  We have searched for infrared excesses around a well-defined sample of 69 FGK main-sequence field stars. These stars were selected without regard to their age, metallicity, or any previous detection of IR excess; they have a median age of similar to 4 Gyr. We have detected 70 mu m excesses around seven stars at the 3 sigma confidence level. This extra emission is produced by cool material (< 100 K) located beyond 10 AU, well outside the "habitable zones'' of these systems and consistent with the presence of Kuiper Belt analogs with similar to 100 times more emitting surface area than in our own planetary system. Only one star, HD 69830, shows excess emission at 24 mu m, corresponding to dust with temperatures greater than or similar to 300 K located inside of 1 AU. While debris disks with L(dust) /L(*) >= 10(-3) are rare around old FGK stars, we find that the disk frequency increases from 2% +/- 2% for L(dust)/L(*) >= 10(-4) to 12% +/- 5% for L(dust)/L(*) >= 10(-5). This trend in the disk luminosity distribution is consistent with the estimated dust in our solar system being within an order of magnitude greater or less than the typical level around similar nearby stars. Although there is no correlation of IR excess with metallicity or spectral type, there is a weak correlation with stellar age, with stars younger than a gigayear more likely to have excess emission.
• Morrison, D., Gradie, J. C., & Rieke, G. H. (1976). Radiometric diameter and albedo of the remarkable asteroid 1976AA. Nature, 260(5553), 691-.
  More info

  Abstract: THE minor planet 1976 A A (Fast-Moving Object Helin), discovered on January 7, 1976, is the first asteroid found with an orbital period of < 1 yr (orbital elements a=0.97, e=0.18; i=19°; ref. 1). Although it seems to be a likely speculation that 1976 AA is a former Apollo object that originally had its aphelion in the main asteroid belt, it is possible that this object is a member of a group of minor planets that is distinct in physical as well as orbital properties. Observations that reveal the physical nature (colour, albedo, texture, mineralogy) of its surface are needed to compare it with better studied objects in more orthodox orbits. This letter reports a determination by infrared radiometry of the diameter and albedo of 1977AA. © 1975 Nature Publishing Group.
• Rieke, G. H., Grasdalen, G. L., Kinman, T. D., Hintzen, P., Wills, B. J., & Wills, D. (1976). Photometric and spectroscopic observations of the BL Lacertae object AO 0235+164. Nature, 260(5554), 754-759.
• RIEKE, G., & LOW, F. (1975). NUCLEUS OF NGC 253. ASTROPHYSICAL JOURNAL, 197(1), 17-23.
• RIEKE, G., LEBOFSKY, M., & LOW, F. (1975). AN ABSOLUTE PHOTOMETRIC SYSTEM AT 10-MU-M AND 20-MU-M. ASTRONOMICAL JOURNAL, 90(5), 900-906.
• Rieke, G. H. (1975). The temperature of Amalthea. Icarus, 25(2), 333-334.
  More info

  Abstract: Infrared photometry of Amalthea (JV) indicates that it is at a temperature of 155±15 K and has a raduis of 120±30 km. There is no evidence for substantial heating by the Jovian radiation belts. © 1975.
• Rieke, G. H. (1975). The thermal radiation of Saturn and its rings. Icarus, 26(1), 37-44.
  More info

  Abstract: Infrared observations of Saturn from 5 to 40 μm are described. There is intense limb brightening at 12.35 μm over the southern polar cap. The C ring is anomalously bright at 10 and 20 μm and has bluer (hotter) colours than the A and B rings. The ring spectra have been extrapolated beyond 40 μm and subtracted from low-resolution far-infrared measurements to show that the far-infrared spectrum of the disk of Saturn is qualitatively similar to that of Jupiter and that Saturn radiates 2.5 ± 0.6 times the energy it absorbs from the Sun. © 1975.
• Low, F. J., & Rieke, G. H. (1974). 9. The Instrumentation and Techniques of Infrared Photometry. Methods in Experimental Physics, 12(PART A), 415-462.
• Rieke, G. H., & Lee, T. A. (1974). Photometry of Comet Kohoutek (1973f). Nature, 248(5451), 737-740.
  More info

  Abstract: Extensive photoelectric and infrared photometry of Comet Kohoutek (1973f) shows that its nucleus is 10 to 15 km in diameter and that the comet contains relatively little dust, and provides new information about the nature of cometary dust grains. © 1974 Nature Publishing Group.
• Maiolino, R., Ruiz, M., Rieke, G., & Papadopoulos, P. (1973). Molecular gas, morphology, and Seyfert galaxy activity. ASTROPHYSICAL JOURNAL, 485(2), 552-569.
  More info

  We probe the cause of the elevated star formation in host galaxies of Seyfert 2 nuclei compared with Seyfert 1 hosts and with field galaxies. (CO)-C-12 (1-0) observations of a large sam-pie of Seyfert galaxies indicate no significant difference in the total amount of molecular gas as a function of the Seyfert nuclear type, nor are Seyfert galaxies significantly different in this regard from a sample of field galaxies once selection effects are accounted for, Therefore, the total amount of molecular gas is not responsible for the enhanced star-forming activity in Seyfert 2 hosts.
• Balog, Z., Rieke, G. H., Su, K. Y., Muzerolle, J., & Young, E. T. (1972). Spitzer MIPS 24 mu m detection of photoevaporating protoplanetary disks. ASTROPHYSICAL JOURNAL, 650(1), L83-L86.
  More info

  We present 24 mm images of three protoplanetary disks being photoevaporated around high-mass O-type stars. These objects have "cometary" structure where the dust pulled away from the disk by the photoevaporating flow is forced away from the O star by photon pressure on the dust and heating and ionization of the gas. Models of the 24 and 8 mm brightness profiles agree with this hypothesis. These models show that the mass-loss rate needed to sustain such a configuration is in agreement with or somewhat less than the theoretical predictions for the photoevaporation process.
• Papovich, C., Dole, H., Egami, E., Le Floc'h, E., Perez-Gonzalez, P., Alonso-Herrero, A., Bai, L., Beichman, C., Blaylock, M., Engelbracht, C., Gordon, K., Hines, D., Misselt, K., Morrison, J., Mould, J., Muzerolle, J., Neugebauer, G., Richards, P., Rieke, G., , Rieke, M., et al. (1972). The 24 micron source counts in deep Spitzer space telescope surveys. ASTROPHYSICAL JOURNAL SUPPLEMENT SERIES, 154(1), 70-74.
  More info

  Galaxy source counts in the infrared provide strong constraints on the evolution of the bolometric energy output from distant galaxy populations. We present the results from deep 24 mum imaging from Spitzer surveys, which include approximate to5 x 10(4) sources to an 80% completeness of similar or equal to 60 muJy. The 24 mum counts rapidly rise at near-Euclidean rates down to 5 mJy, increase with a super-Euclidean rate between 0.4 and 4 mJy, and converge below similar to 0.3 mJy. The 24 mum counts exceed expectations from nonevolving models by a factor of greater than or similar to10 at S-nu similar to 0.1 mJy. The peak in the differential number counts corresponds to a population of faint sources that is not expected from predictions based on 15 mum counts from the Infrared Space Observatory. We argue that this implies the existence of a previously undetected population of infrared-luminous galaxies at z similar to 1-3. Integrating the counts to 60 muJy, we derive a lower limit on the 24 mum background intensity of 1.9 +/- 0.6 nW m(-2) sr(-1) of which the majority (similar to60%) stems from sources fainter than 0.4 mJy. Extrapolating to fainter flux densities, sources below 60 muJy contribute 0.8(-0.4)(+0.9) nW m(-2) sr(-1) to the background, which provides an estimate of the total 24 mum background of 2.7(-0.7)(+1.1) nW m(-2) sr(-1).
• Low, F. J., & Rieke, G. H. (1971). Physical sciences: Variations in the 10 μm flux from NGC 1068. Nature, 233(5317), 256-257.
  More info

  Abstract: ALTHOUGH there is considerable evidence of rapid variability of the intense infrared sources in the nuclei of galaxies and quasars, conclusive data have been lacking. NGC 1068 is one of the most powerful of the extragalactic infrared sources (LIR = 6×1045 erg s-1) and, with the exception of M82 which is extended, has the highest signal-to-noise ratio at 10 μm. We have therefore monitored NGC 1068 for several years to look for variations. The pertinent observations are summarized in Fig. 1, where data obtained during the past 3 yr have been combined into four points. The results of the individual observations are given in Table 1. © 1971 Nature Publishing Group.
• Rieke, G. H., & Low, F. J. (1971). Map of the galactic nucleus at 10 μm. Nature, 233(5314), 53-54.
  More info

  Abstract: WE have scanned the centre of our galaxy at a wavelength of 10 μm with a beam 5.5 arcsec in diameter. The scans have been combined to produce the map shown in Fig. 1. At 10 kpc, commonly assumed to be the distance to this region, 5.5 arcsec corresponds to 0.3 pc. © 1971 Nature Publishing Group.
• Fazio, G. G., Helmken, H. F., Rieke, G. H., & Weekes, T. C. (1968). Upper limits to gamma ray fluxes from three pulsating radio sources [2]. Nature, 220(5170), 892-893.
  More info

  Abstract: A SURVEY of possible celestial gamma ray sources was undertaken by the detection of Cerenkov light generated in the atmosphere by energetic particles in air showers. Upper limits for thirteen possible continuous sources of gamma rays of energy greater than 2 × 1012 eV, together with a description of the system and its operation, have been reported elsewhere1. Soon after the discovery of the pulsating radio sources2, the survey was extended to include observations of these objects. The results are presented here together with some preliminary observations of the same sources made with a new instrument with larger aperture (10 m) and lower threshold energy (4 × 1011 eV). Most of the observations were made at the 4,200 foot level of the Mount Hopkins observing station near Tucson, Arizona, by means of light detectors consisting of two 5 foot searchlight mirrors with RCA 4518 photomulipliers at their foci; these were operated in coincidence with a resolving time of 6 ns. The results of eleven drift scans on three of the pulsating radio sources are shown in Table 1. The location of CP 0950 near Leo XR-1 permitted an upper limit to be obtained for the former from re-examination of the previous drift scans on the latter. The upper limits to the gamma ray fluxes in Table 1 are at the three standard deviation level of significance. © 1968 Nature Publishing Group.

Proceedings Publications

• Alberts, S., Rujopakarn, W., & Rieke, G. H. (2020, jan). "Connecting black holes and galaxies in faint radio populations at cosmic noon". In Uncovering Early Galaxy Evolution in the ALMA and JWST Era, 352.
• Argyriou, I., Rieke, G. H., Ressler, M. E., G{'asp'ar}, A., & Vandenbussche, B. (2020, dec). "Characterization of the optical properties of the buried contact of the JWST MIRI Si: as infrared blocked impurity band detectors". In Society of Photo-Optical Instrumentation Engineers (SPIE) Conference Series, 11454.
• Glasse, A., Lee, D., Samara-Ratna, P. .., & Rieke, G. (2020, dec). "Modelling the path length of aluminium seen by the detectors in the MIRI instrument on the JWST". In Society of Photo-Optical Instrumentation Engineers (SPIE) Conference Series, 11443.
• Rieke, G. H., De, R., Shivaei, I., Bromm, V., & Lyu, J. (2020, jan). "The Far-Infrared emission of the first (z {ensuremath{sim} 6) massive galaxies}". In Uncovering Early Galaxy Evolution in the ALMA and JWST Era, 352.
• Leisawitz, D., Amatucci, E., Allen, L., Arenberg, J., Armus, L., Battersby, C., Beaman, B., Bauer, J., Bell, R., Beltran, P., Benford, D., Bergin, E., Bolognese, J., Bradford, C., Bradley, D., Burgarella, D., Carey, S., Carter, R., Chi, J., , Cooray, A., et al. (2019, sep). The Origins Space Telescope. In procspie, 11115.
• Ertel, S., Kennedy, G., Defr{`ere}, D., Hinz, P., Shannon, A., Mennesson, B., Danchi, W., Gelino, C., Hill, J., Hoffman, W., Rieke, G., Spalding, E., Stone, J., Vaz, A., Weinberger, A., Willems, P., Absil, O., Arbo, P., Bailey, V., , Beichman, C., et al. (2018, jul). The HOSTS survey for exo-zodiacal dust: preliminary results and future prospects. In Space Telescopes and Instrumentation 2018: Optical, Infrared, and Millimeter Wave, 10698.
• Garc{'{i}a, M. M., Rieke, G., Ressler, M., Dicken, D., Greene, T., Morrison, J., Kendrew, S., Alberts, S., Regan, M., Law, D., Fox, O., Temim, T., Hines, D., Lagage, P., Klaassen, P., Pye, J., Wright, G., & Glasse, A. (2018, jul). Observing recommendations for JWST MIRI users. In Observatory Operations: Strategies, Processes, and Systems VII, 10704.
• Kendrew, S., Dicken, D., Bouwman, J., Garcia Marin, M., Greene, T., Lagage, P., Ressler, M., Crouzet, N., Kreidberg, L., Batalha, N., Bean, J., Stevenson, K., Glasse, A., Wright, G., & Rieke, G. (2018, jul). Time series observations with the mid-infrared instrument (MIRI) on JWST. In Space Telescopes and Instrumentation 2018: Optical, Infrared, and Millimeter Wave, 10698.
• {Ballering}, N., {Rieke}, G., {Su}, K., , A. (2016, jan). "{The Dust Properties of the Beta Pictoris Debris Disk from an Analysis of its Thermal Emission and Scattered Light}". In American Astronomical Society Meeting Abstracts, 227.
• {Kilpatrick}, C., {Bieging}, J., , G. (2016, jan). "{A Survey For Broadened CO Lines Toward Galactic Supernova Remnants}". In American Astronomical Society Meeting Abstracts, 227.
• {Meng}, H., {Plavchan}, P., , G. (2016, jan). "{Photo-reverberation Mapping of a Protoplanetary Accretion Disk around a T Tauri Star}". In American Astronomical Society Meeting Abstracts, 227.
• {Su}, K., {Rieke}, G., {Defrere}, D., {Wang}, K., {Lai}, S., {Wilner}, D., {van Lieshout}, R., , C. (2016, jan). "{Does Fomalhaut A Have an Asteroid-belt Analog?}". In American Astronomical Society Meeting Abstracts, 227.
• {Su}, K., {Rieke}, G., {Marengo}, M., , K. (2016, jan). "{Nature of the Warm Excess in eps Eri: Asteroid belt or Dragged-in