Yancy L Shirley

Interests

Teaching

AST 202 (Life in the Universe), AST 250 (Fundamentals of Astronomy), AST 300b (Astrophysics - Radiation & Matter), AST 515 (ISM and Radiative Processes)

Research

Star and planet formation, the interstellar medium, astrochemistry, astrobiology, and atomic and molecular spectroscopy.

Courses

Scholarly Contributions

Journals/Publications

• Ambrose, H. E., Shirley, Y. L., & Scibelli, S. (2021). "A survey of CH$_{2$DOH towards starless and pre-stellar cores in the Taurus molecular cloud}". mnras, 501(1), 347-355.
• Anderson, M., Peretto, N., Ragan, S. E., Rigby, A. J., Avison, A., Duarte-Cabral, A., Fuller, G. A., Shirley, Y. L., Traficante, A., & Williams, G. M. (2021). "An ALMA study of hub-filament systems - I. On the clump mass concentration within the most massive cores". mnras, 508(2), 2964-2978.
• Choudhury, S., Pineda, J. E., Caselli, P., Offner, S. S., Rosolowsky, E., Friesen, R. K., Redaelli, E., Chac{'on-Tanarro}, A., Shirley, Y., Punanova, A., & Kirk, H. (2021). "Transition from coherent cores to surrounding cloud in L1688". aap, 648, A114.
• Kong, S., Arce, H. G., Shirley, Y., & Glasgow, C. (2021). "Evidence of Core Growth in the Dragon Infrared Dark Cloud: A Path for Massive Star Formation". apj, 912(2), 156.
• Okoda, Y., Oya, Y., Francis, L., Johnstone, D., Inutsuka, S., Ceccarelli, C., Codella, C., Chandler, C., Sakai, N., Aikawa, Y., Alves, F. O., Balucani, N., Bianchi, E., Bouvier, M., Caselli, P., Caux, E., Charnley, S., Choudhury, S., De, S. M., , Dulieu, F., et al. (2021). "FAUST. II. Discovery of a Secondary Outflow in IRAS 15398-3359: Variability in Outflow Direction during the Earliest Stage of Star Formation?". apj, 910(1), 11.
• Scibelli, S., Shirley, Y., Vasyunin, A., & Launhardt, R. (2021). "Detection of complex organic molecules in young starless core L1521E". mnras, 504(4), 5754-5767.
• Singh}, A., Matzner, C. D., Friesen, R. K., Martin, P. G., Pineda, J. E., Rosolowsky, E., Alves, F., Chac{'on-Tanarro}, A., Chen, H. H., Chen, M. C., Choudhury, S., Di, F. J., Keown, J., Kirk, H., Punanova, A., Seo, Y., Shirley, Y., Ginsburg, A., Offner, S. S., , Arce, H. G., et al. (2021). "Are Massive Dense Clumps Truly Subvirial? A New Analysis Using Gould Belt Ammonia Data". apj, 922(1), 87.
• Bianchi, E., Chandler, C., Ceccarelli, C., Codella, C., Sakai, N., L{'opez-Sepulcre}, A., Maud, L., Moellenbrock, G., Svoboda, B., Watanabe, Y., Sakai, T., M{'enard}, F., Aikawa, Y., Alves, F., Balucani, N., Bouvier, M., Caselli, P., Caux, E., Charnley, S., , Choudhury, S., et al. (2020). "FAUST I. The hot corino at the heart of the prototypical Class I protostar L1551 IRS5". mnras, 498(1), L87-L92.
• Chen, C., Behrens, E. A., Washington, J. E., Fissel, L. M., Friesen, R. K., Li, Z., Pineda, J. E., Ginsburg, A., Kirk, H., Scibelli, S., Alves, F., Redaelli, E., Caselli, P., Punanova, A., Di, F. J., Rosolowsky, E., Offner, S. S., Martin, P. G., Chac{'on-Tanarro}, A., , Chen, H., et al. (2020). "Relative alignment between dense molecular cores and ambient magnetic field: the synergy of numerical models and observations". mnras, 494(2), 1971-1987.
• Chen, M. C., Di, F. J., Rosolowsky, E., Keown, J., Pineda, J. E., Friesen, R. K., Caselli, P., Chen, H., Matzner, C. D., Offner, S. S., Punanova, A., Redaelli, E., Scibelli, S., & Shirley, Y. (2020). "Velocity-coherent Filaments in NGC 1333: Evidence for Accretion Flow?". apj, 891(1), 84.
• Choudhury, S., Pineda, J. E., Caselli, P., Ginsburg, A., Offner, S. S., Rosolowsky, E., Friesen, R. K., Alves, F. O., Chac{'on-Tanarro}, A., Punanova, A., Redaelli, E., Kirk, H., Myers, P. C., Martin, P. G., Shirley, Y., Chun-Yuan, C. M., Goodman, A. A., & Di, F. J. (2020). "Ubiquitous NH$_{3$ supersonic component in L1688 coherent cores}". aap, 640, L6.
• Ginsburg, A., Anderson, L., Dicker, S., Romero, C., Svoboda, B., Devlin, M., Galv{'an-Madrid}, R., Indebetouw, R., Liu, H. B., Mason, B., Mroczkowski, T., Armentrout, W., Bally, J., Brogan, C., Butterfield, N., Hunter, T. R., Reese, E. D., Rosolowsky, E., Sarazin, C., , Shirley, Y., et al. (2020). "The MUSTANG Galactic Plane Survey (MGPS90) Pilot". apjs, 248(2), 24.
• Harju, J., Pineda, J. E., Vasyunin, A. I., Caselli, P., Offner, S. S., Goodman, A. A., Juvela, M., Sipil{"a}, O., Faure, A., Le, G. R., Hily-Blant, P., Alves, J., Bizzocchi, L., Burkert, A., Chen, H., Friesen, R. K., G{"usten}, R., Myers, P. C., Punanova, A., , Rist, C., et al. (2020). "Efficient Methanol Production on the Dark Side of a Prestellar Core". apj, 895(2), 101.
• Scibelli, S., & Shirley, Y. (2020). "Prevalence of Complex Organic Molecules in Starless and Prestellar Cores within the Taurus Molecular Cloud". apj, 891(1), 73.
• Chen, H. H., Pineda, J. E., Offner, S. S., Goodman, A. A., Burkert, A., Friesen, R. K., Rosolowsky, E., Scibelli, S., & Shirley, Y. (2019). Droplets. II. Internal Velocity Structures and Potential Rotational Motions in Pressure-dominated Coherent Structures. apj, 886(2), 119.
• Chen}, H. H., Pineda, J. E., Goodman, A. A., Burkert, A., Offner, S. S., Friesen, R. K., Myers, P. C., Alves, F., Arce, H. G., Caselli, P., Chac{'on-Tanarro}, A., Chen, M. C., Di, F. J., Ginsburg, A., Keown, J., Kirk, H., Martin, P. G., Matzner, C., Punanova, A., , Redaelli, E., et al. (2019). Droplets. I. Pressure-dominated Coherent Structures in L1688 and B18. apj, 877(2), 93.
• Kerr, R., Kirk, H., Di, F. J., Keown, J., Chen, M., Rosolowsky, E., Offner, S. S., Friesen, R., Pineda, J. E., Shirley, Y., Redaelli, E., Caselli, P., Punanova, A., Seo, Y., Alves, F., Chac{'on-Tanarro}, A., & Chen, H. H. (2019). The Green Bank Ammonia Survey: A Virial Analysis of Gould Belt Clouds in Data Release 1. apj, 874(2), 147.
• Merello, M., Molinari, S., Rygl, K., Evans, N., Elia, D., Schisano, E., Traficante, A., Shirley, Y., Svoboda, B., & Goldsmith, P. (2019). Thermal balance and comparison of gas and dust properties of dense clumps in the Hi-GAL survey. mnras, 483(4), 5355-5379.
• Seo, Y. M., Majumdar, L., Goldsmith, P. F., Shirley, Y. L., Willacy, K., Ward-Thompson, D., Friesen, R., Frayer, D., Church, S. E., Chung, D., Cleary, K., Cunningham, N., Devaraj, K., Egan, D., Gaier, T., {Gawand, e. R., Gundersen, J. O., Harris, A. I., Kangaslahti, P., , Readhead, A. C., et al. (2019). An Ammonia Spectral Map of the L1495-B218 Filaments in the Taurus Molecular Cloud. II. CCS and HC$_7$N Chemistry and Three Modes of Star Formation in the Filaments. apj, 871(2), 134.
• Svoboda, B. E., Shirley, Y. L., Traficante, A., Battersby, C., Fuller, G. A., Zhang, Q., Beuther, H., Peretto, N., Brogan, C., & Hunter, T. (2019). ALMA Observations of Fragmentation, Substructure, and Protostars in High-mass Starless Clump Candidates. apj, 886(1), 36.
• Calahan, J., Shirley, Y., Svoboda, B., Ivanov, E., Schmid, J., Pulley, A., Lautenbach, J., Zawadzki, N., Bullivant, C., Cook, C., Gray, L., Henrici, A., Pascale, M., Bosse, C., Chance, Q., Choi, S., Dunn, M., Jaime-Frias, R. .., Kearsley, I., , Kelledy, J., et al. (2018). Searching for Inflow toward Massive Starless Clump Candidates Identified in the Bolocam Galactic Plane Survey. apj, 862, 63.
• French, K., Zabludoff, A., Yoon, I., Shirley, Y., Yang, Y., Smercina, A., Smith, J., & Narayanan, D. (2018). Why Post-starburst Galaxies Are Now Quiescent. apj, 861, 123.
• Seo, Y., Majumdar, L., Goldsmith, P., Shirley, Y., Willacy, K., Ward-Thompson, D. .., Friesen, R., Frayer, D., Church, S., Chung, D., Cleary, K., Cunningham, N., Devaraj, K., Egan, D., Gaier, T., Gawande, R., Gundersen, J., Harris, A., Kangaslahti, P., , Readhead, A., et al. (2018). An Ammonia Spectral Map of the L1495-B218 Filaments in the Taurus Molecular Cloud: II CCS amp HC$_7$N Chemistry and Three Modes of Star Formation in the Filaments. arXiv e-prints.
• Friesen, R., Pineda, J., co-PIs, ., Rosolowsky, E., Alves, F., Chac{'on-Tanarro}, A., How-Huan Chen, H., Chun-Yuan Chen, M., Di Francesco, J., Keown, J., Kirk, H., Punanova, A., Seo, Y., Shirley, Y., Ginsburg, A., Hall, C., Offner, S., Singh, A., Arce, H., , Caselli, P., et al. (2017). "The Green Bank Ammonia Survey: First Results of NH$_{3$ Mapping ofnbspthe Gould Belt}". apj, 843, 63.
• Harju, J., Daniel, F., Sipil{"a}, O., Caselli, P., Pineda, J., Friesen, R., Punanova, A., G{"usten}, R., Wiesenfeld, L., Myers, P., Faure, A., Hily-Blant, P. .., Rist, C., Rosolowsky, E., Schlemmer, S., & Shirley, Y. (2017). "Deuteration of ammonia in the starless core Ophiuchus/H-MM1". aap, 600, A61.
• Keown, J., Di Francesco, J., Kirk, H., Friesen, R., Pineda, J., Rosolowsky, E., Ginsburg, A., Offner, S., Caselli, P., Alves, F., Chac{'on-Tanarro}, A., Punanova, A., Redaelli, E., Seo, Y., Matzner, C., Chun-Yuan Chen, M., Goodman, A., Chen, H., Shirley, Y., , Singh, A., et al. (2017). "The Green Bank Ammonia Survey: Observations of Hierarchical Dense Gas Structures in Cepheus-L1251". apj, 850, 3.
• Kirk, H., Dunham, M., Di Francesco, J., Johnstone, D., Offner, S., Sadavoy, S., Tobin, J., Arce, H., Bourke, T., Mairs, S., Myers, P., Pineda, J., Schnee, S., & Shirley, Y. (2017). "ALMA Observations of Starless Core Substructure in Ophiuchus". apj, 838, 114.
• Kirk, H., Friesen, R., Pineda, J., Rosolowsky, E., Offner, S., Matzner, C., Myers, P., Di Francesco, J., Caselli, P., Alves, F., Chac{'on-Tanarro}, A., Chen, H., Chun-Yuan Chen, M., Keown, J., Punanova, A., Seo, Y., Shirley, Y., Ginsburg, A., Hall, C., , Singh, A., et al. (2017). "The Green Bank Ammonia Survey: Dense Cores under Pressure in Orion A". apj, 846, 144.
• Webb, K., Di Francesco, J., Sadavoy, S., Thanjavur, K., Launhardt, R., Shirley, Y., Stutz, A., Abreu Vicente, J., & Kainulainen, J. (2017). "Constraining the Dust Opacity Law in Three Small and Isolated Molecular Clouds". apj, 849, 13.
• Bally, J., Blake, G., Bolatto, A., Casey, C., Church, S., Francesco, J., Goldsmith, P., Goodman, A., Harris, A., Jackson, J., Leroy, A., Lockman, F., Lovell, A., Marscher, A., Marrone, D., Mason, B., Mroczkowski, T., Shirley, Y., & Yun, M. (2016). "The Case for a Publicly Available, Well-Instrumented GBT Operating at 20-115 GHz". ArXiv e-prints.
• Storm, S., Mundy, L., Lee, K., Fern{'andez-L'opez}, M., Looney, L., Teuben, P., Arce, H., Rosolowsky, E., Meisner, A., Isella, A., Kauffmann, J., Shirley, Y., Kwon, W., Plunkett, A., Pound, M., Segura-Cox, D., Tassis, K., Tobin, J., Volgenau, N., , Crutcher, R., et al. (2016). "CARMA Large Area Star Formation Survey: Dense Gas in the Young L1451 Region of Perseus". apj, 830, 127.
• Svoboda, B., Shirley, Y., Battersby, C., Rosolowsky, E., Ginsburg, A., Ellsworth-Bowers, T., Pestalozzi, M., Dunham, M., Evans, N., Bally, J., & Glenn, J. (2016). "The Bolocam Galactic Plane Survey. XIV. Physical Properties of Massive Starless and Star-forming Clumps". apj, 822, 59.
• Ellsworth-Bowers, T. P., Rosolowsky, E., Glenn, J., Ginsburg, A., Evans, N. J., Battersby, C., Shirley, Y. L., & Svoboda, B. (2015). The Bolocam Galactic Plane Survey. XII. Distance Catalog Expansion Using Kinematic Isolation of Dense Molecular Cloud Structures with $^13$CO(1-0). apj, 799, 29.
• French, K. D., Yang, Y., Zabludoff, A., Narayanan, D., Shirley, Y., Walter, F., Smith, J., & Tremonti, C. A. (2015). Discovery of Large Molecular Gas Reservoirs in Post-starburst Galaxies. apj, 801, 1.
• Mangum, J. G., & Shirley, Y. L. (2015). How to Calculate Molecular Column Density. pasp, 127, 266-298.
• Shirley, Y. L. (2015). The Critical Density and the Effective Excitation Density of Commonly Observed Molecular Dense Gas Tracers. pasp, 127, 299-310.
• {Ellsworth-Bowers}, T., {Glenn}, J., {Riley}, A., {Rosolowsky}, E., {Ginsburg}, A., {Evans}, N., {Bally}, J., {Battersby}, C., {Shirley}, Y., , M. (2015). "{The Bolocam Galactic Plane Survey. XIII. Physical Properties and Mass Functions of Dense Molecular Cloud Structures}". apj, 805, 157.
• {Gerner}, T., {Shirley}, Y., {Beuther}, H., {Semenov}, D., {Linz}, H., {Albertsson}, T., , T. (2015). "{Chemical evolution in the early phases of massive star formation. II. Deuteration}". aap, 579, A80.
• {Merello}, M., {Evans}, N., {Shirley}, Y., {Rosolowsky}, E., {Ginsburg}, A., {Bally}, J., {Battersby}, C., , M. (2015). "{The Bolocam Galactic Plane Survey. XI. Temperatures and Substructure of Galactic Clumps Based On 350 {$mu$}M Observations}". apjs, 218, 1.
• {Sadavoy}, S., {Shirley}, Y., {Di Francesco}, J., {Henning}, T., {Currie}, M., {Andr{'e}}, P., , S. (2015). "{The Kinematic and Chemical Properties of a Potential Core-forming Clump: Perseus B1-E}". apj, 806, 38.
• {Seo}, Y., {Shirley}, Y., {Goldsmith}, P., {Ward-Thompson}, D., {Kirk}, J., {Schmalzl}, M., {Lee}, J., {Friesen}, R., {Langston}, G., {Masters}, J., , R. (2015). "{An Ammonia Spectral Map of the L1495-B218 Filaments in the Taurus Molecular Cloud. I. Physical Properties of Filaments and Dense Cores}". apj, 805, 185.
• {Svoboda}, B., {Shirley}, Y., {Battersby}, C., {Rosolowsky}, E., {Ginsburg}, A., {Ellsworth-Bowers}, T., {Pestalozzi}, M., {Dunham}, M., {Evans}, N., {Bally}, J., , J. (2015). "{The Bolocam Galactic Plane Survey. XIV. Physical Properties of Massive Starless and Star Forming Clumps}". ArXiv e-prints.
• Bally, J., Ginsburg, A., Probst, R., Reipurth, B., Shirley, Y. L., & Stringfellow, G. S. (2014). Outflows, Dusty Cores, and a Burst of Star Formation in the North America and Pelican Nebulae. aj, 148, 120.
• Fern'andez-L'opez, M., Arce, H. G., Looney, L., Mundy, L. G., Storm, S., Teuben, P. J., Lee, K., Segura-Cox, D., Isella, A., Tobin, J. J., Rosolowsky, E., Plunkett, A., Kwon, W., Kauffmann, J., Ostriker, E., Tassis, K., Shirley, Y. L., & Pound, M. (2014). CARMA Large Area Star Formation Survey: Observational Analysis of Filaments in the Serpens South Molecular Cloud. apjl, 790, L19.
• Gerner, T., Beuther, H., Semenov, D., Linz, H., Vasyunina, T., Bihr, S., Shirley, Y. L., & Henning, T. (2014). Chemical evolution in the early phases of massive star formation. i. Astronomy and Astrophysics, 563.
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  Abstract: Understanding the chemical evolution of young (high-mass) star-forming regions is a central topic in star formation research. Chemistry is employed as a unique tool 1) to investigate the underlying physical processes and 2) to characterize the evolution of the chemical composition. With these aims in mind, we observed a sample of 59 high-mass star-forming regions at different evolutionary stages varying from the early starless phase of infrared dark clouds to high-mass protostellar objects to hot molecular cores and, finally, ultra-compact Hii regions at 1 mm and 3 mm with the IRAM 30 m telescope. We determined their large-scale chemical abundances and found that the chemical composition evolves along with the evolutionary stages. On average, the molecular abundances increase with time. We modeled the chemical evolution, using a 1D physical model where density and temperature vary from stage to stage coupled with an advanced gas-grain chemical model and derived the best-fit χ2 values of all relevant parameters. A satisfying overall agreement between observed and modeled column densities for most of the molecules was obtained. With the best-fit model we also derived a chemical age for each stage, which gives the timescales for the transformation between two consecutive stages. The best-fit chemical ages are ~10 000 years for the IRDC stage, ~60 000 years for the HMPO stage, ~40 000 years for the HMC stage, and ~10 000 years for the UCHii stage. Thus, the total chemical timescale for the entire evolutionary sequence of the high-mass star formation process is on the order of 105 years, which is consistent with theoretical estimates. Furthermore, based on the approach of a multiple-line survey of unresolved data, we were able to constrain an intuitive and reasonable physical and chemical model. The results of this study can be used as chemical templates for the different evolutionary stages in high-mass star formation. © 2014 ESO.
• Lee, K. I., Fern'andez-L'opez, M., Storm, S., Looney, L. W., Mundy, L. G., Segura-Cox, D., Teuben, P., Rosolowsky, E., Arce, H. G., Ostriker, E. C., Shirley, Y. L., Kwon, W., Kauffmann, J., Tobin, J. J., Plunkett, A. L., Pound, M. W., Salter, D. M., Volgenau, N. H., Chen, C., , Tassis, K., et al. (2014). CARMA Large Area Star Formation Survey: Structure and Kinematics of Dense Gas in Serpens Main. apj, 797, 76.
• Storm, S., Mundy, L. G., Fern'andez-L'opez, M., Lee, K. I., Looney, L. W., Teuben, P., Rosolowsky, E., Arce, H. G., Ostriker, E. C., Segura-Cox, D. M., Pound, M. W., Salter, D. M., Volgenau, N. H., Shirley, Y. L., Chen, C., Gong, H., Plunkett, A. L., Tobin, J. J., Kwon, W., , Isella, A., et al. (2014). CARMA Large Area Star Formation Survey: Project Overview with Analysis of Dense Gas Structure and Kinematics in Barnard 1. apj, 794, 165.
• Ellsworth-Bowers, T. P., Glenn, J., Rosolowsky, E., Mairs, S., Evans, N. J., Battersby, C., Ginsburg, A., Shirley, Y. L., & Bally, J. (2013). The bolocam galactic plane survey. VIII. A mid-infrared kinematic distance discrimination method. Astrophysical Journal, 770(1).
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  Abstract: We present a new distance estimation method for dust-continuum-identified molecular cloud clumps. Recent (sub-)millimeter Galactic plane surveys have cataloged tens of thousands of these objects, plausible precursors to stellar clusters, but detailed study of their physical properties requires robust distance determinations. We derive Bayesian distance probability density functions (DPDFs) for 770 objects from the Bolocam Galactic Plane Survey in the Galactic longitude range 7.°5 ≤ ℓ ≤ 65°. The DPDF formalism is based on kinematic distances, and uses any number of external data sets to place prior distance probabilities to resolve the kinematic distance ambiguity (KDA) for objects in the inner Galaxy. We present here priors related to the mid-infrared absorption of dust in dense molecular regions and the distribution of molecular gas in the Galactic disk. By assuming a numerical model of Galactic mid-infrared emission and simple radiative transfer, we match the morphology of (sub-)millimeter thermal dust emission with mid-infrared absorption to compute a prior DPDF for distance discrimination. Selecting objects first from (sub-)millimeter source catalogs avoids a bias towards the darkest infrared dark clouds (IRDCs) and extends the range of heliocentric distance probed by mid-infrared extinction and includes lower-contrast sources. We derive well-constrained KDA resolutions for 618 molecular cloud clumps, with approximately 15% placed at or beyond the tangent distance. Objects with mid-infrared contrast sufficient to be cataloged as IRDCs are generally placed at the near kinematic distance. Distance comparisons with Galactic Ring Survey KDA resolutions yield a 92% agreement. A face-on view of the Milky Way using resolved distances reveals sections of the Sagittarius and Scutum-Centaurus Arms. This KDA-resolution method for large catalogs of sources through the combination of (sub-)millimeter and mid-infrared observations of molecular cloud clumps is generally applicable to other dust-continuum Galactic plane surveys. © 2013. The American Astronomical Society. All rights reserved..
• Friesen, R. K., Kirk, H. M., & Shirley, Y. L. (2013). An analysis of the deuterium fractionation of star-forming cores in the perseus molecular cloud. Astrophysical Journal, 765(1).
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  Abstract: We have performed a pointed survey of N2D+ 2-1 and N2D+ 3-2 emission toward 64 N2H +-bright starless and protostellar cores in the Perseus molecular cloud using the Arizona Radio Observatory Submillimeter Telescope and Kitt Peak 12 m telescope. We find a mean deuterium fractionation in N2H +, RD = N(N2D+)/N(N 2H+), of 0.08, with a maximum RD = 0.2. In detected sources, we find no significant difference in the deuterium fractionation between starless and protostellar cores, nor between cores in clustered or isolated environments. We compare the deuterium fraction in N 2H+ with parameters linked to advanced core evolution. We only find significant correlations between the deuterium fraction and increased H2 column density, as well as with increased central core density, for all cores. Toward protostellar sources, we additionally find a significant anticorrelation between RD and bolometric temperature. We show that the Perseus cores are characterized by low CO depletion values relative to previous studies of star-forming cores, similar to recent results in the Ophiuchus molecular cloud. We suggest that the low average CO depletion is the dominant mechanism that constrains the average deuterium fractionation in the Perseus cores to small values. While current equilibrium and dynamic chemical models are able to reproduce the range of deuterium fractionation values we find in Perseus, reproducing the scatter across the cores requires variation in parameters such as the ionization fraction or the ortho-to-para-H2 ratio across the cloud, or a range in core evolution timescales. © 2013. The American Astronomical Society. All rights reserved.
• Ginsburg, A., Glenn, J., Rosolowsky, E., Ellsworth-Bowers, T. P., Battersby, C., Dunham, M., Merello, M., Shirley, Y., Bally, J., J., N., Stringfellow, G., & Aguirre, J. (2013). The Bolocam Galactic Plane Survey. IX. Data release 2 and outer galaxy extension. Astrophysical Journal, Supplement Series, 208(2).
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  Abstract: We present a re-reduction and expansion of the Bolocam Galactic Plane Survey (BGPS), first presented by Aguirre et al. and Rosolowsky et al. The BGPS is a 1.1 mm survey of dust emission in the Northern galactic plane, covering longitudes -10° < ℓ < 90°and latitudes |b| < 0.°5 with a typical 1σ rms sensitivity of 30-100 mJy in a c33″ beam. Version 2 of the survey includes an additional 20 deg2 of coverage in the third and fourth quadrants and 2 deg2 in the first quadrant. The new data release has improved angular recovery, with complete recovery out to 80″ and partial recovery to 300″, and reduced negative bowls around bright sources resulting from the atmospheric subtraction process. We resolve the factor of 1.5 flux calibration offset between the v1.0 data release and other data sets and determine that there is no offset between v2.0 and other data sets. The v2.0 pointing accuracy is tested against other surveys and is demonstrated to be accurate and an improvement over v1.0. We present simulations and tests of the pipeline and its properties, including measurements of the pipeline's angular transfer function. The Bolocat cataloging tool was used to extract a new catalog, which includes 8594 sources, with 591 in the expanded regions. We have demonstrated that the Bolocat 40″ and 80″ apertures are accurate even in the presence of strong extended background emission. The number of sources is lower than in v1.0, but the amount of flux and area included in identified sources is larger. © 2013. The American Astronomical Society. All rights reserved..
• Launhardt, R., Stutz, A. M., Schmiedeke, A., Henning, T., Krause, O., Balog, Z., Beuther, H., Birkmann, S., Hennemann, M., Kainulainen, J., Khanzadyan, T., Linz, H., Lippok, N., Nielbock, M., Pitann, J., Ragan, S., Risacher, C., Schmalzl, M., Shirley, Y. L., , Stecklum, B., et al. (2013). The Earliest Phases of Star Formation (EPoS): A Herschel key project: The thermal structure of low-mass molecular cloud cores. Astronomy and Astrophysics, 551.
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  Abstract: Context. The temperature and density structure of molecular cloud cores are the most important physical quantities that determine the course of the protostellar collapse and the properties of the stars they form. Nevertheless, density profiles often rely either on the simplifying assumption of isothermality or on observationally poorly constrained model temperature profiles. The instruments of the Herschel satellite provide us for the first time with both the spectral coverage and the spatial resolution that is needed to directly measure the dust temperature structure of nearby molecular cloud cores. Aims. With the aim of better constraining the initial physical conditions in molecular cloud cores at the onset of protostellar collapse, in particular of measuring their temperature structure, we initiated the guaranteed time key project (GTKP) "The Earliest Phases of Star Formation" (EPoS) with the Herschel satellite. This paper gives an overview of the low-mass sources in the EPoS project, the Herschel and complementary ground-based observations, our analysis method, and the initial results of the survey. Methods. We study the thermal dust emission of 12 previously well-characterized, isolated, nearby globules using FIR and submm continuum maps at up to eight wavelengths between 100 μm and 1.2 mm. Our sample contains both globules with starless cores and embedded protostars at different early evolutionary stages. The dust emission maps are used to extract spatially resolved SEDs, which are then fit independently with modified blackbody curves to obtain line-of-sight-averaged dust temperature and column density maps. Results. We find that the thermal structure of all globules (mean mass 7 M⊙) is dominated by external heating from the interstellar radiation field and moderate shielding by thin extended halos. All globules have warm outer envelopes (14-20 K) and colder dense interiors (8-12 K) with column densities of a few 10 22 cm-2. The protostars embedded in some of the globules raise the local temperature of the dense cores only within radii out to about 5000 AU, but do not significantly affect the overall thermal balance of the globules. Five out of the six starless cores in the sample are gravitationally bound and approximately thermally stabilized. The starless core in CB 244 is found to be supercritical and is speculated to be on the verge of collapse. For the first time, we can now also include externally heated starless cores in the Lsmm/Lbol vs. Tbol diagram and find that T bol < 25 K seems to be a robust criterion to distinguish starless from protostellar cores, including those that only have an embedded very low-luminosity object. © ESO, 2013.
• Seo, Y. M., Hong, S. S., & Shirley, Y. L. (2013). On the internal dynamics of starless cores: Stability of starless cores with internal motions and collapse dynamics. Astrophysical Journal, 769(1).
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  Abstract: In order to understand the collapse dynamics of observed low-mass starless cores, we revise the conventional stability condition of hydrostatic Bonnor-Ebert spheres to take internal motions into account. Because observed starless cores resemble Bonnor-Ebert density structures, the stability and dynamics of the starless cores are frequently analyzed by comparing to the conventional stability condition of a hydrostatic Bonnor-Ebert sphere. However, starless cores are not hydrostatic but have observed internal motions. In this study, we take gaseous spheres with a homologous internal velocity field and derive stability conditions of the spheres utilizing a virial analysis. We propose two limiting models of spontaneous gravitational collapse: the collapse of critical Bonnor-Ebert spheres and uniform density spheres. The collapse of these two limiting models is intended to provide the lower and the upper limits, respectively, of the infall speeds for a given density structure. The results of our study suggest that the stability condition sensitively depends on internal motions. A homologous inward motion with a transonic speed can reduce the critical size compared to the static Bonnor-Ebert sphere by more than a factor of two. As an application of the two limiting models of spontaneous gravitational collapse, we compare the density structures and infall speeds of the observed starless cores L63, L1544, L1689B, and L694-2 to the two limiting models. L1689B and L694-2 seem to have been perturbed to result in faster infall motions than for spontaneous gravitational collapse. © 2013. The American Astronomical Society. All rights reserved.
• Shirley, Y. L., Ellsworth-Bowers, T. P., Svoboda, B., Schlingman, W. M., Ginsburg, A., Rosolowsky, E., Gerner, T., Mairs, S., Battersby, C., Stringfellow, G., Dunham, M. K., Glenn, J., & Bally, J. (2013). The bolocam galactic plane survey. X. A complete spectroscopic catalog of dense molecular gas observed toward 1.1 mm dust continuum sources with 7.°5 ≤ l ≤ 194°. Astrophysical Journal, Supplement Series, 209(1).
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  Abstract: The Bolocam Galactic Plane Survey (BGPS) is a 1.1 mm continuum survey of dense clumps of dust throughout the Galaxy covering 170 deg2. We present spectroscopic observations using the Heinrich Hertz Submillimeter Telescope of the dense gas tracers, HCO+ and N2H + 3-2, for all 6194 sources in the BGPS v1.0.1 catalog between 7.°5 ≤ l ≤ 194°. This is the largest targeted spectroscopic survey of dense molecular gas in the Milky Way to date. We find unique velocities for 3126 (50.5%) of the BGPS v1.0.1 sources observed. Strong N2H + 3-2 emission (T mb > 0.5 K) without HCO+ 3-2 emission does not occur in this catalog. We characterize the properties of the dense molecular gas emission toward the entire sample. HCO+ is very sub-thermally populated and the 3-2 transitions are optically thick toward most BGPS clumps. The median observed line width is 3.3 km s-1 consistent with supersonic turbulence within BGPS clumps. We find strong correlations between dense molecular gas integrated intensities and 1.1 mm peak flux and the gas kinetic temperature derived from previously published NH 3 observations. These intensity correlations are driven by the sensitivity of the 3-2 transitions to excitation conditions rather than by variations in molecular column density or abundance. We identify a subset of 113 sources with stronger N2H+ than HCO+ integrated intensity, but we find no correlations between the N 2H+/HCO+ ratio and 1.1 mm continuum flux density, gas kinetic temperature, or line width. Self-absorbed profiles are rare (1.3%). © 2013. The American Astronomical Society. All rights reserved.
• Sakai, N., Shirley, Y. L., Sakai, T., Hirota, T., Watanabe, Y., & Yamamoto, S. (2012). Tentative detection of deuterated methane toward the low-mass protostar iras 04368+2557 in L1527. Astrophysical Journal Letters, 758(1).
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  Abstract: The millimeter-wave rotational transition line (JK = 1 0-00) of deuterated methane CH3D has tentatively been detected toward the low-mass Class 0 protostar IRAS 04368+2557 in L1527 with the Heinrich Hertz Submillimeter Telescope. This is the first detection of CH3D in interstellar clouds, if confirmed. The column density and fractional abundance of CH3D are determined to be (9.1 ± 3.4) × 1015cm-2 and (3.0 ± 1.1) × 10-7, respectively, where we assume the rotational temperature of 25K. The column density and fractional abundance of the gaseous CH4 are estimated to be (1.3-4.6) × 1017cm -2 and (4.3-15.2) × 10-6, respectively, by adopting the molecular D/H ratios of 2%-7% reported for various molecules in L1527. The fractional abundance of CH4 is higher than or comparable to that found in high-mass star-forming cores by infrared observations. It is sufficiently high to trigger the efficient production of various carbon-chain molecules in a lukewarm region near the protostar, which supports the scenario of warm carbon-chain chemistry. © © 2012. The American Astronomical Society. All rights reserved.
• Schwarz, K. R., Shirley, Y. L., & Dunham, M. M. (2012). A systematic search for molecular outflows toward candidate low-luminosity protostars and very low luminosity objects. Astronomical Journal, 144(4).
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  Abstract: We present a systematic single-dish search for molecular outflows toward a sample of nine candidate low-luminosity protostars and 30 candidate very low luminosity objects (VeLLOs; L int ≤ 0.1 L ⊙). The sources are identified using data from the Spitzer Space Telescope cataloged by Dunham etal. toward nearby (D < 400 pc) star-forming regions. Each object was observed in 12CO and 13CO J = 2 → 1 simultaneously using the sideband separating ALMA Band-6 prototype receiver on the Heinrich Hertz Telescope at 30″ resolution. Using five-point grid maps, we identify five new potential outflow candidates and make on-the-fly maps of the regions surrounding sources in the dense cores B59, L1148, L1228, and L1165. Of these new outflow candidates, only the map of B59 shows a candidate blue outflow lobe associated with a source in our survey. We also present larger and more sensitive maps of the previously detected L673-7 and the L1251-A-IRS4 outflows and analyze their properties in comparison to other outflows from VeLLOs. The accretion luminosities derived from the outflow properties of the VeLLOs with detected CO outflows are higher than the observed internal luminosity of the protostars, indicating that these sources likely had higher accretion rates in the past. The known L1251-A-IRS3 outflow is detected but not re-mapped. We do not detect clear, unconfused signatures of red and blue molecular wings toward the other 31 sources in the survey indicating that large-scale, distinct outflows are rare toward this sample of candidate protostars. Several potential outflows are confused with the kinematic structure in the surrounding core and cloud. Interferometric imaging is needed to disentangle large-scale molecular cloud kinematics from these potentially weak protostellar outflows. © © 2012. The American Astronomical Society. All rights reserved..
• Devine, K. E., Chandler, C. J., Brogan, C., Churchwell, E., Indebetouw, R., Shirley, Y., & Borg, K. J. (2011). Very large array observations of the infrared dark cloud G19.30+0.07. Astrophysical Journal, 733(1).
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  Abstract: We present Very Large Array observations of ammonia (NH3) (1,1), (2,2), and dicarbon sulfide (CCS) (21-10) emission toward the infrared dark cloud (IRDC) G19.30+0.07 at ∼22 GHz. The NH3 emission closely follows the 8 μm extinction. The NH3 (1,1) and (2,2) lines provide diagnostics of the temperature and density structure within the IRDC, with typical rotation temperatures of ∼10-20K and NH3 column densities of ∼1015cm-2. The estimated total mass of G19.30+0.07 is ∼1130 M⊙. The cloud comprises four compact NH3 clumps of mass ∼30-160 M⊙. Two coincide with 24 μm emission, indicating heating by protostars, and show evidence of outflow in the NH3 emission. We report a water maser associated with a third clump; the fourth clump is apparently starless. A non-detection of 8.4 GHz emission suggests that the IRDC contains no bright H II regions and places a limit on the spectral type of an embedded zero-age main-sequence star to early-B or later. From the NH3 emission, we find that G19.30+0.07 is composed of three distinct velocity components or "subclouds." One velocity component contains the two 24 μm sources and the starless clump, another contains the clump with the water maser, while the third velocity component is diffuse, with no significant high-density peaks. The spatial distribution of NH3 and CCS emission from G19.30+0.07 is highly anti-correlated, with the NH3 predominantly in the high-density clumps and the CCS tracing lower-density envelopes around those clumps. This spatial distribution is consistent with theories of evolution for chemically young low-mass cores, in which CCS has not yet been processed to other species and/or depleted in high-density regions. © 2011. The American Astronomical Society. All rights reserved..
• Ford, A. B., & Shirley, Y. L. (2011). C¹⁸O depletion in starless cores in Taurus. Astrophysical Journal, 728(2).
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  Abstract: We present here findings for C18O depletion in eight starless cores in Taurus: TMC-2, L1498, L1512, L1489, L1517B, L1521E, L1495A-S, and L1544. We compare observations of the C18O J = 2-1 transition taken with the ALMA prototype receiver on the Heinrich Hertz Submillimeter Telescope to results of radiative transfer modeling using RATRAN. We use temperature and density profiles calculated from dust continuum radiative transfer models to model the C18O emission. We present modeling of three cores, TMC-2, L1489, and L1495A-S, which have not been modeled before, and compare our results for the five cores with published models. We find that all of the cores but one, L1521E, are substantially depleted. We also find that varying the temperature profiles of these model cores has a discernable effect, and varying the central density has an even larger effect. We find no trends with depletion radius or depletion fraction with the density or temperature of these cores, suggesting that the physical structure alone is insufficient to fully constrain evolutionary state. We are able to place tighter constraints on the radius at which C18O is depleted than the absolute fraction of depletion. As the timeline of chemical depletion depends sensitively on the fraction of depletion, this difficulty in constraining depletion fraction makes comparison with other timescales, such as the free-fall timescale, very difficult. © 2011. The American Astronomical Society. All rights reserved. Printedin the U.S.A.
• Kim, H. J., J., N., Dunham, M. M., Chen, J., Lee, J., Bourke, T. L., Huard, T. L., Shirley, Y. L., & Vries, C. D. (2011). The Spitzer C2D survey of nearby dense cores. XI. Infrared and submillimeter observations of CB130. Astrophysical Journal, 729(2).
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  Abstract: We present new observations of the CB130 region composed of three separate cores. Using the Spitzer Space Telescope, we detected a Class 0 and a Class II object in one of these, CB130-1. The observed photometric data from Spitzer and ground-based telescopes are used to establish the physical parameters of the Class 0 object. Spectral energy distribution fitting with a radiative transfer model shows that the luminosity of the Class 0 object is 0.14-0.16 L 1, which is low for a protostellar object. In order to constrain the chemical characteristics of the core having the low-luminosity object, we compare our molecular line observations to models of lines including abundance variations. We tested both ad hoc step function abundance models and a series of self-consistent chemical evolution models. In the chemical evolution models, we consider a continuous accretion model and an episodic accretion model to explore how variable luminosity affects the chemistry. The step function abundance models can match observed lines reasonably well. The best-fitting chemical evolution model requires episodic accretion and the formation of CO2 ice from CO ice during the low-luminosity periods. This process removes C from the gas phase, providing a much improved fit to the observed gas-phase molecular lines and the CO2 ice absorption feature. Based on the chemical model result, the low luminosity of CB130-1 is explained better as a quiescent stage between episodic accretion bursts rather than being at the first hydrostatic core stage. © 2011. The American Astronomical Society. All rights reserved.
• Reiter, M., Shirley, Y. L., Jingwen, W. u., Brogan, C., Wootten, A., & Tatematsu, K. (2011). Evidence for inflow in high-mass star-forming clumps. Astrophysical Journal, 740(1).
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  Abstract: We analyze the HCO+ 3-2 and H13CO+ 3-2 line profiles of 27 high-mass star-forming regions to identify asymmetries that are suggestive of mass inflow. Three quantitative measures of line asymmetry are used to indicate whether a line profile is blue, red, or neither - the ratio of the temperature of the blue and red peaks, the line skew, and the dimensionless parameter δv. We find nine HCO+ 3-2 line profiles with a significant blue asymmetry and four with significant red asymmetric profiles. Comparing our HCO+ 3-2 results to HCN 3-2 observations from Wu et al., we find that eight of the blue and three of the red have profiles with the same asymmetry in HCN. The eight sources with blue asymmetries in both tracers are considered strong candidates for inflow. Quantitative measures of the asymmetry (e.g., δv) tend to be larger for HCN. This, combined with possible HCO+ abundance enhancements in outflows, suggests that HCN may be a better tracer of inflow. Understanding the behavior of common molecular tracers like HCO+ in clumps of different masses is important for properly analyzing the line profiles seen in a sample of sources representing a broad range of clump masses. Such studies will soon be possible with the large number of sources with possible self-absorption seen in spectroscopic follow-up observations of clumps identified in the Bolocam Galactic Plane Survey. © 2011. The American Astronomical Society. All rights reserved.
• Reiter, M., Shirley, Y. L., Jingwen, W. u., Brogan, C., Wootten, A., & Tatematsu, K. (2011). The physical properties of high-mass star-forming clumps: A systematic comparison of molecular tracers. Astrophysical Journal, Supplement Series, 195(1).
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  Abstract: We present observations of HCO+ and H13CO +, N2H+, HCS+, HNC and HN 13C, SO and 34SO, CCH, SO2, and CH 3OH-E toward a sample of 27 high-mass clumps coincident with water maser emission. All transitions are observed with or convolved to nearly identical resolution (30″), allowing for inter-comparison of the clump properties derived from the mapped transitions. We find that N2H + emission is spatially differentiated compared with the dust and the other molecules toward a few very luminous cores (10 of 27) and the N 2H+ integrated intensity does not correlate well with dust continuum flux. We calculate the effective excitation density, neff, the density required to excite a 1 K line in Tkin = 20 K gas for each molecular tracer. The intensity of molecular tracers with larger effective excitation densities (neff ≥ 105cm-3) appears to correlate more strongly with the submillimeter dust continuum intensity. The median sizes of the clumps are anti-correlated with the n eff of the tracers (which span more than three orders of magnitude). Virial mass is not correlated with neff, especially where the lines are optically thick as the linewidths may be broadened significantly by non-virial motions. The median mass surface density and median volume density of the clumps are correlated with neff indicating the importance of understanding the excitation conditions of the molecular tracer when deriving the average properties of an ensemble of cores. © 2011. The American Astronomical Society. All rights reserved.
• Schenck, D. E., Shirley, Y. L., Reiter, M., & Juneau, S. (2011). Testing the global star formation relation: An HCO⁺ (3-2) mapping study of RED MSX Sources in the Bolocam Galactic Plane Survey. Astronomical Journal, 142(3).
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  Abstract: We present an analysis of the relation between the star formation rate (SFR) and mass of dense gas in Galactic clumps and nearby galaxies. Using the bolometric luminosity as a measure of SFR and the molecular line luminosity of HCO+ (3-2) as a measure of dense gas mass, we find that the relation between SFR and M dense is approximately linear. This is similar to published results derived using HCN(1-0) as a dense gas tracer. HCO+ (3-2) and HCN(1-0) have similar conditions for excitation. Our work includes 16 Galactic clumps that are in both the Bolocam Galactic Plane Survey and the Red MSX Source Survey, 27 water maser sources from the literature, and the aforementioned HCN(1-0) data. Our results agree qualitatively with predictions of recent theoretical models which state that the nature of the relation should depend on how the critical density of the tracer compares with the mean density of the gas. © 2011. The American Astronomical Society. All rights reserved.
• Schlingman, W. M., Shirley, Y. L., Schenk, D. E., Rosolowsky, E., Bally, J., Battersby, C., Dunham, M. K., Ellsworth-Bowers, T. P., Evans, N. J., Ginsburg, A., & Stringfellow, G. (2011). The Bolocam Galactic Plane Survey. V. HCO⁺ and N ₂H⁺ spectroscopy of 1.1mm dust continuum sources. Astrophysical Journal, Supplement Series, 195(2).
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  Abstract: We present the results of observations of 1882 sources in the Bolocam Galactic Plane Survey (BGPS) at 1.1mm with the 10 m Henrich Hertz Telescope simultaneously in HCO+ J = 3-2 and N2H+ J = 3-2. We detect 77% of these sources in HCO+ and 51% in N 2H+ at greater than 3σ. We find a strong correlation between the integrated intensity of both dense gas tracers and the 1.1mm dust emission of BGPS sources. We determine kinematic distances for 529 sources (440 in the first quadrant breaking the distance ambiguity and 89 in the second quadrant). We derive the size, mass, and average density for this subset of clumps. The median size of BGPS clumps is 0.75pc with a median mass of 330 M⊙ (assuming T Dust = 20K). The median HCO + linewidth is 2.9kms-1 indicating that BGPS clumps are dominated by supersonic turbulence or unresolved kinematic motions. We find no evidence for a size-linewidth relationship for BGPS clumps. We analyze the effects of the assumed dust temperature on the derived clump properties with a Monte Carlo simulation and find that changing the temperature distribution will change the median source properties (mass, volume-averaged number density, surface density) by factors of a few. The observed differential mass distribution has a power-law slope that is intermediate between that observed for diffuse CO clouds and the stellar initial mass function. BGPS clumps represent a wide range of objects (from dense cores to more diffuse clumps) and are typically characterized by larger sizes and lower densities than previously published surveys of high-mass star-forming regions. This collection of objects is a less-biased sample of star-forming regions in the Milky Way that likely span a wide range of evolutionary states. © 2011. The American Astronomical Society. All rights reserved.
• Shirley, Y. L., Mason, B. S., Mangum, J. G., Bolin, D. E., Devlin, M. J., Dicker, S. R., & Korngut, P. M. (2011). Mustang 3.3 mm continuum observations of class 0 protostars. Astronomical Journal, 141(2).
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  Abstract: We present observations of six Class 0 protostars at 3.3 mm (90 GHz) using the 64 pixel MUSTANG bolometer camera on the 100 m Green Bank Telescope. The 3.3 mm photometry is analyzed along with shorter wavelength observations to derive spectral indices (Sv ∝ vα) of the measured emission. We utilize previously published dust continuum radiative transfer models to estimate the characteristic dust temperature within the central beam of our observations. We present constraints on the millimeter dust opacity index β between 0.862 mm, 1.25 mm, and 3.3 mm. βmm typically ranges from 1.0 to 2.4 for Class 0 sources. The relative contributions from disk emission and envelope emission are estimated at 3.3 mm. L483 is found to have negligible disk emission at 3.3 mm, while L1527 is dominated by disk emission within the central beam. The βdiskmm ≤0.8-1.4 for L1527 indicates that grain growth is likely occurring in the disk. The photometry presented in this paper may be combined with future interferometric observations of Class 0 envelopes and disks.© 2011. The American Astronomical Society.
• Bally, J., Aguirre, J., Battersby, C., Bradley, E. T., Cyganowski, C., Dowell, D., Drosback, M., Dunham, M. K., J., N., Ginsburg, A., Glenn, J., Harvey, P., Mills, E., Merello, M., Rosolowsky, E., Schlingman, W., Shirley, Y. L., Stringfellow, G. S., Walawender, J., & Williams, J. (2010). The Bolocam Galactic Plane Survey: λ = 1.1 and 0.35 mm dust continuum emission in the Galactic center region. Astrophysical Journal Letters, 721(1), 137-163.
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  Abstract: The Bolocam Galactic Plane Survey (BGPS) data for a 6 deg2 region of the Galactic plane containing the Galactic center are analyzed and compared to infrared and radio continuum data. The BGPS 1.1 mm emission consists of clumps interconnected by a network of fainter filaments surrounding cavities, a few of which are filled with diffuse near-IR emission indicating the presence of warm dust or with radio continuum characteristic of Hii regions or supernova remnants. New 350 μm images of the environments of the two brightest regions, Sgr A and B, are presented. Sgr B2 is the brightest millimeter-emitting clump in the Central Molecular Zone (CMZ) and may be forming the closest analog to a super star cluster in the Galaxy. The CMZ contains the highest concentration of millimeter- and submillimeter-emitting dense clumps in the Galaxy. Most 1.1 mm features at positive longitudes are seen in silhouette against the 3.6-24 μm background observed by the Spitzer Space Telescope. However, only a few clumps at negative longitudes are seen in absorption, confirming the hypothesis that positive longitude clumps in the CMZ tend to be on the near side of the Galactic center, consistent with the suspected orientation of the central bar in our Galaxy. Some 1.1 mm cloud surfaces are seen in emission at 8 μm, presumably due to polycyclic aromatic hydrocarbons. A ∼0°.2 (∼30 pc) diameter cavity and infrared bubble between l ≈ 0°.0 and 0°.2 surround the Arches and Quintuplet clusters and Sgr A. The bubble contains several clumpy dust filaments that point toward Sgr A*; its potential role in their formation is explored. Bania's Clump 2, a feature near l = 3°-3. ° 5 which exhibits extremely broad molecular emission lines (ΔV >150 km s-1), contains dozens of 1.1 mm clumps. These clumps are deficient in near- and mid-infrared emission in the Spitzer images when compared to both the inner Galactic plane and the CMZ. Thus, Bania's Clump 2 is either inefficient in forming stars or is in a pre-stellar phase of clump evolution. The Bolocat catalog of 1.1 mm clumps contains 1428 entries in the Galactic center between l = 358. ° 5 and l = 4. ° 5 of which about 80% are likely to be within about 500 pc of the center. The mass spectrum above about 80M⊙ can be described by a power-law ΔN/ΔM = N0M-2.14(+0.1,-0.4). The power-law index is somewhat sensitive to systematic grain temperature variations, may be highly biased by source confusion, and is very sensitive to the spatial filtering inherent in the data acquisition and reduction. © 2010. The American Astronomical Society. All rights reserved.
• Bally, J., Anderson, L. D., Battersby, C., Calzoletti, L., Digiorgio, A. M., Faustini, F., Ginsburg, A., Li, J. Z., Nguyen-Luong, Q., Molinari, S., Motte, F., Pestalozzi, M., Plume, R., Rodon, J., Schilke, P., Schlingman, W., Schneider-Bontemps, N., Shirley, Y., Stringfellow, G. S., , Testi, L., et al. (2010). Herschel observations of the W43 "mini-starburst". Astronomy and Astrophysics, 518(1).
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  Abstract: Aims. To explore the infrared and radio properties of one of the closest Galactic starburst regions. Methods. Images obtained with the Herschel Space Observatory at wavelengths of 70, 160, 250, 350, and 500 μm using the PACS and SPIRE arrays are analyzed and compared with radio continuum VLA data and 8 μm images from the Spitzer Space Observatory. The morphology of the far-infrared emission is combined with radial velocity measurements of millimeter and centimeter wavelength transitions to identify features likely to be associated with the W43 complex. Results. The W43 star-forming complex is resolved into a dense cluster of protostars, infrared dark clouds, and ridges of warm dust heated by massive stars. The 4 brightest compact sources with L > 1.5 × 104 L⊙ embedded within the Z-shaped ridge of bright dust emission in W43 remain single at 4" (0.1 pc) resolution These objects, likely to be massive protostars or compact clusters in early stages of evolution are embedded in clumps with masses of 103 to 104 M⊙, but contribute only 2% to the 3.6 × 106 L⊙ far-IR luminosity of W43 measured in a 16 by 16 pc box. The total mass of gas derived from the far-IR dust emission inside this region is ∼106 M⊙. Cometary dust clouds, compact 6 cm radio sources, and warm dust mark the locations of older populations of massive stars. Energy release has created a cavity blowing-out below the Galactic plane. Compression of molecular gas in the plane by the older H ii region near G30.684-0.260 and the bipolar structure of the resulting younger W43 H ii region may have triggered the current mini-star burst. © 2010 ESO.
• Bally, J., Anderson, L. D., Battersby, C., Calzoletti, L., Digiorgio, A. M., Faustini, F., Ginsburg, A., Li, J. Z., Nguyen-Luong, Q., Molinari, S., Motte, F., Pestalozzi, M., Plume, R., Rodon, J., Schilke, P., Schlingman, W., Schneider-Bontemps, N., Shirley, Y., Stringfellow, G. S., , Testi, L., et al. (2010). Herschel observations of the W43 "mini-starburst". Astronomy and Astrophysics, 518(4).
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  Abstract: Aims. To explore the infrared and radio properties of one of the closest Galactic starburst regions. Methods. Images obtained with the Herschel Space Observatory at wavelengths of 70, 160, 250, 350, and 500 μm using the PACS and SPIRE arrays are analyzed and compared with radio continuum VLA data and 8 μm images from the Spitzer Space Observatory. The morphology of the far-infrared emission is combined with radial velocity measurements of millimeter and centimeter wavelength transitions to identify features likely to be associated with the W43 complex. Results. The W43 star-forming complex is resolved into a dense cluster of protostars, infrared dark clouds, and ridges of warm dust heated by massive stars. The 4 brightest compact sources with L > 1.5 × 104 L⊙ embedded within the Z-shaped ridge of bright dust emission in W43 remain single at 4" (0.1 pc) resolution These objects, likely to be massive protostars or compact clusters in early stages of evolution are embedded in clumps with masses of 103 to 104 M⊙, but contribute only 2% to the 3.6 × 106 L⊙ far-IR luminosity of W43 measured in a 16 by 16 pc box. The total mass of gas derived from the far-IR dust emission inside this region is ∼106 M⊙. Cometary dust clouds, compact 6 cm radio sources, and warm dust mark the locations of older populations of massive stars. Energy release has created a cavity blowing-out below the Galactic plane. Compression of molecular gas in the plane by the older H ii region near G30.684-0.260 and the bipolar structure of the resulting younger W43 H ii region may have triggered the current mini-star burst. © ESO 2010.
• Battersby, C., Bally, J., Jackson, J. M., Ginsburg, A., Shirley, Y. L., Schlingman, W., & Glenn, J. (2010). An infrared through radio study of the properties and evolution of IRDC clumps. Astrophysical Journal Letters, 721(1), 222-250.
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  Abstract: We examine the physical properties and evolutionary stages of a sample of 17 clumps within 8 Infrared Dark Clouds (IRDCs) by combining existing infrared, millimeter, and radio data with new Bolocam Galactic Plane Survey (BGPS) 1.1 mm data, Very Large Array radio continuum data, and Heinrich Hertz Telescope dense gas (HCO+ and N2H+) spectroscopic data. We combine literature studies of star formation tracers and dust temperatures within IRDCs with our search for ultracompact (UC) HII regions to discuss a possible evolutionary sequence for IRDC clumps. In addition, we perform an analysis of mass tracers in IRDCs and find that 8μm extinction masses and 1.1 mm BGPS masses are complementary mass tracers in IRDCs except for the most active clumps (notably those containing UC Hii regions), for which both mass tracers suffer biases. We find that the measured virial masses in IRDC clumps are uniformly higher than the measured dust continuum masses on the scale of ∼1 pc. We use 13CO, HCO+, and N2H+ to study the molecular gas properties of IRDCs and do not see any evidence of chemical differentiation between hot and cold clumps on the scale of ∼1 pc. However, both HCO+ and N2H+ are brighter in active clumps, due to an increase in temperature and/or density. We report the identification of four UC HII regions embedded within IRDC clumps and find that UC Hii regions are associated with bright (≳1 Jy) 24μm point sources, and that the brightest UC HII regions are associated with "diffuse red clumps" (an extended enhancement at 8μm). The broad stages of the discussed evolutionary sequence (from a quiescent clump to an embedded HII region) are supported by literature dust temperature estimates; however, no sequential nature can be inferred between the individual star formation tracers. © 2010. The American Astronomical Society. All rights reserved.
• Doty, S. D., Tidman, R., Shirley, Y., & Jackson, A. (2010). Unbiased fitting of B335 dust continuum observations: Approach and evidence for variation of grain properties with position. Monthly Notices of the Royal Astronomical Society, 406(2), 1190-1200.
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  Abstract: We present the first published unbiased, automated approach to fitting infrared observations of interstellar dust clouds for the purposes of constraining their underlying physical properties. The dust radiative transfer problem is solved self-consistently for a given set of physical inputs. Spherical geometry is chosen to minimize the run time, given the large number (∼ millions) of models necessary. The model output is convolved with appropriate beams to produce simulated observations, which are then compared with observational data. A best fit is achieved using the Levenberg-Marquardt DNLS1 routine from the SLATEC library, to minimize the chi-squared deviation. The speed of the model allows a large number of initial starting conditions to be considered. While any number of parameters can be fitted, we concentrate on the dust density and grain property distribution. We apply the model to the well-studied source B335. While much of the envelope is well modelled by a power-law exponent ∼1.5-1.9, we find potential evidence for a different inner structure for r < ∼10 arcsec, as well as an outer tenuous envelope for r > 120 arcsec. We also find evidence of a variation in grain properties with radial position. The interior and exterior have larger concentrations of both thick ice mantles and bare grains. The properties in the interior would be consistent with a non-spherical structure seen by Harvey et al. (2003b) and Stutz et al. (2008), and the exterior would be consistent with incomplete refreezing of ice on to mantles after an evaporative event, such as a shock, in the last ∼105 yr. © 2010 The Authors. Journal compilation © 2010 RAS.
• Dunham, M. K., Rosolowsky, E., J., N., Cyganowski, C. J., Aguirre, J., Bally, J., Battersby, C., Bradley, E. T., Dowell, D., Drosback, M., Ginsburg, A., Glenn, J., Harvey, P., Merello, M., Schlingman, W., Shirley, Y. L., Stringfellow, G. S., Walawender, J., & Williams, J. P. (2010). The bolocam galactic plane survey. III. Characterizing physical properties of massive star-forming regions in the Gemini OB1 molecular cloud. Astrophysical Journal Letters, 717(2), 1157-1180.
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  Abstract: We present the 1.1 mm Bolocam Galactic Plane Survey (BGPS) observations of the Gemini OB1 molecular cloud complex, and targeted NH3 observations of the BGPS sources. When paired with molecular spectroscopy of a dense gas tracer, millimeter observations yield physical properties such as masses, radii, mean densities, kinetic temperatures, and line widths. We detect 34 distinct BGPS sources above 5σ = 0.37 Jy beam-1 with corresponding 5σ detections in the NH3(1,1) transition. Eight of the objects show water maser emission (20%). We find a mean millimeter source FWHM of 1.12 pc and a mean gas kinetic temperature of 20K for the sample of 34 BGPS sources with detections in the NH3(1,1) line. The observed NH3 line widths are dominated by non-thermal motions, typically found to be a few times the thermal sound speed expected for the derived kinetic temperature. We calculate the mass for each source from the millimeter flux assuming the sources are isothermal and find a mean isothermal mass within a 120″ aperture of 230±180 M ·. We find a total mass of 8400 M · for all BGPS sources in the Gemini OB1 molecular cloud, representing 6.5% of the cloud mass. By comparing the millimeter isothermal mass to the virial mass calculated from the NH3 line widths within a radius equal to the millimeter source size, we find a mean virial parameter (M vir/M iso) of 1.0±0.9 for the sample. We find mean values for the distributions of column densities of 1.0 × 1022 cm-2 for H2, and 3.0 × 1014 cm -2 for NH3, giving a mean NH3 abundance of 3.0 × 10-8 relative to H2. We find volume-averaged densities on the order of 103-104cm-3. The sizes and densities suggest that in the Gem OB1 region the BGPS is detecting the clumps from which stellar clusters form, rather than smaller, higher density cores where single stars or small multiple systems form. © 2010. The American Astronomical Society. All rights reserved.
• Friesen, R. K., Francesco, J. D., Myers, P. C., Belloche, A., Shirley, Y. L., Bourke, T. L., & André, P. (2010). The initial conditions of clustered star formation. III. the deuterium fractionation of the ophiuchus B2 core. Astrophysical Journal Letters, 718(2), 666-682.
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  Abstract: We present N2D+ 3-2 (IRAM), and H2D + 111-110 and N2H+ 4-3 (JCMT) maps of the small cluster-forming Ophiuchus B2 core in the nearby Ophiuchus molecular cloud. In conjunction with previously published N 2H+ 1-0 observations, the N2D+ data reveal the deuterium fractionation in the high-density gas across Oph B2. The average deuterium fractionation RD = N(N2D +)/N(N2H+) ∼ 0.03 over Oph B2, with several small scale RD peaks and a maximum RD = 0.1. The mean RD is consistent with previous results in isolated starless and protostellar cores. The column density distributions of both H2D + and N2D+ show no correlation with total H2 column density. We find, however, an anticorrelation in deuterium fractionation with proximity to the embedded protostars in Oph B2 to distances ≳0.04 pc. Destruction mechanisms for deuterated molecules require gas temperatures greater than those previously determined through NH3 observations of Oph B2 to proceed. We present temperatures calculated for the dense core gas through the equating of non-thermal line widths for molecules (i.e., N2D+ and H2D+) expected to trace the same core regions, but the observed complex line structures in B2 preclude finding a reasonable result in many locations. This method may, however, work well in isolated cores with less complicated velocity structures. Finally, we use RD and the H2D+ column density across Oph B2 to set a lower limit on the ionization fraction across the core, finding a mean xe,lim ≳ few × 10-8. Our results show that care must be taken when using deuterated species as a probe of the physical conditions of dense gas in star-forming regions. © 2010. The American Astronomical Society. All rights reserved.
• Jingwen, W. u., Evans, N. J., Shirley, Y. L., & Knez, C. (2010). The properties of massive, dense clumps: Mapping surveys of HCN and CS. Astrophysical Journal, Supplement Series, 188(2), 313-357.
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  Abstract: We have mapped over 50 massive, dense clumps with four dense gas tracers: HCN J = 1-0 and 3-2; and CS J = 2-1 and 7-6 transitions. Spectral lines of optically thin H13CN 3-2 and C34S 5-4 were also obtained toward the map centers. These maps usually demonstrate single well-peaked distributions at our resolution, even with higher J transitions. The size, virial mass, surface density, and mean volume density within a well-defined angular size (FWHM) were calculated from the contour maps for each transition. We found that transitions with higher effective density usually trace the more compact, inner part of the clumps but have larger linewidths, leading to an inverse linewidth-size relation using different tracers. The mean surface densities are 0.29, 0.33, 0.78, 1.09gcm-2 within FWHM contours of CS 2-1, HCN 1-0, HCN 3-2, and CS 7-6, respectively. We find no correlation of L IR with surface density and a possible inverse correlation with mean volume density, contrary to some theoretical expectations. Molecular line luminosities L′mol were derived for each transition. We see no evidence in the data for the relation between L′mol and mean density posited by modelers. The correlation between L′mol and the virial mass is roughly linear for each dense gas tracer. No obvious correlation was found between the line luminosity ratio and infrared luminosity, bolometric temperature, or the L IR/M Vir ratio. A nearly linear correlation was found between the infrared luminosity and the line luminosity of all dense gas tracers for these massive, dense clumps, with a lower cutoff in luminosity at LIR = 104.5 L ⊙. The L IR-L′HCN1-0 correlation agrees well with the one found in galaxies. These correlations indicate a constant star formation rate per unit mass from the scale of dense clumps to that of distant galaxies when the mass is measured for dense gas. These results support the suggestion that starburst galaxies may be understood as having a large fraction of gas in dense clumps. © 2010. The American Astronomical Society.
• Friesen, R. K., Francesco, J. D., Shirley, Y. L., & Myers, P. C. (2009). The initial conditions of clustered star formation. i. nh₃ observations of dense cores in ophiuchus. Astrophysical Journal Letters, 697(2), 1457-1480.
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  Abstract: We present combined interferometer and single dish telescope data of NH3 (J, K) = (1,1) and (2,2) emission toward the clustered star forming Ophiuchus B, C, and F Cores at high spatial resolution (1200AU) using the Australia Telescope Compact Array, the Very Large Array, and the Green Bank Telescope. While the large-scale features of the NH3 (1,1) integrated intensity appear similar to 850μm continuum emission maps of the Cores, on 15″ (1800AU) scales we find significant discrepancies between the dense gas tracers in Oph B, but good correspondence in Oph C and F. Using the CLUMPFIND structure identifying algorithm, we identify 15 NH3 clumps in Oph B, and three each in Oph C and F. Only five of the Oph B NH3 clumps are coincident within 30″ (3600AU) of a submillimeter clump. We find v LSR varies little across any of the cores, and additionally varies by only 1.5km s-1 between them. The observed NH3 line widths within the Oph B and F Cores are generally large and often mildly supersonic, while Oph C is characterized by narrow line widths which decrease to nearly thermal values. We find several regions of localized narrow line emission (Δv ≲ 0.4 km s-1), some of which are associated with NH3 clumps. We derive the kinetic temperatures of the gas, and find they are remarkably constant across Oph B and F, with a warmer mean value (TK = 15 K) than typically found in isolated regions and consistent with previous results in clustered regions. Oph C, however, has a mean T K = 12 K, decreasing to a minimum TK = 9.4 K toward the submillimeter continuum peak, similar to previous studies of isolated starless clumps. There is no significant difference in temperature toward protostars embedded in the Cores. NH3 column densities, N(NH3), and abundances, X(NH3), are similar to previous work in other nearby molecular clouds. We find evidence for a decrease in X(NH3) with increasing N(H2) in Oph B2 and C, suggesting the NH3 emission may not be tracing well the densest core gas. © 2009. The American Astronomical Society.
• Juneau, S., Narayanan, D. T., Moustakas, J., Shirley, Y. L., Bussmann, R. S., Kennicutt, R. C., & Bout, P. V. (2009). Enhanced dense gas fraction in ultraluminous infrared galaxies. Astrophysical Journal Letters, 707(2), 1217-1232.
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  Abstract: We present a detailed analysis of the relation between infrared luminosity and molecular line luminosity, for a variety of molecular transitions, using a sample of 34 nearby galaxies spanning a broad range of infrared luminosities (1010 L · < L IR < 10 12.5 L ·). We show that the power-law index of the relation is sensitive to the critical density of the molecular gas tracer used, and that the dominant driver in observed molecular line ratios in galaxies is the gas density. As most nearby ultraluminous infrared galaxies (ULIRGs) exhibit strong signatures of active galactic nuclei (AGNs) in their center, we revisit previous claims questioning the reliability of HCN as a probe of the dense gas responsible for star formation in the presence of AGNs. We find that the enhanced HCN(1-0)/CO(1-0) luminosity ratio observed in ULIRGs can be successfully reproduced using numerical models with fixed chemical abundances and without AGN-induced chemistry effects. We extend this analysis to a total of 10 molecular line ratios by combining the following transitions: CO(1-0), HCO+(1-0), HCO+(3-2), HCN(1-0), and HCN(3-2). Our results suggest that AGNs reside in systems with higher dense gas fraction, and that chemistry or other effects associated with their hard radiation field may not dominate (NGC 1068 is one exception). Galaxy merger could be the underlying cause of increased dense gas fraction, and the evolutionary stage of such mergers may be another determinant of the HCN/CO luminosity ratio. © 2009. The American Astronomical Society. All rights reserved.
• Young, C. H., Bourke, T. L., Dunham, M. M., Evans, N. J., Jørgensen, J. K., Shirley, Y. L., Young, K. E., Vries, C. D., Claussen, M. J., & Popa, V. (2009). The spitzer c2d survey of nearby dense cores. VI. the protostars of lynds dark nebula 1221. Astrophysical Journal Letters, 702(1), 340-351.
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  Abstract: Observations of Lynds Dark Nebula 1221 from the Spitzer Space Telescope are presented. These data show three candidate protostars toward L1221, only two of which were previously known. The infrared observations also show signatures of outflowing material, an interpretation which is also supported by radio observations with the Very Large Array. In addition, molecular line maps from the Five College Radio Astronomy Observatory are shown. One-dimensional dust continuum modeling of two of these protostars, IRS1 and IRS3, is described. These models show two distinctly different protostars forming in very similar environments. IRS1 shows a higher luminosity and a larger inner radius of the envelope than IRS3. The disparity could be caused by a difference in age or mass, orientation of outflow cavities, or the impact of a binary in the IRS1 core. © 2009. The American Astronomical Society. All rights reserved.
• Brogan, C. L., Hunter, T. R., Indebetouw, R., Chandler, C. J., Shirley, Y. L., Rao, R., & Sarma, A. P. (2008). High resolution submillimeter observations of massive protostars. Astrophysics and Space Science, 313(1-3), 53-57.
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  Abstract: We describe results from recent Submillimeter Array observations of massive protostellar objects (CepheusA-East, NGC7538 IRS1, and G5.89-0.39) with resolutions ranging from 0.8″ to 2″. A wide range of spectral and continuum properties are observed, with one unifying theme: at these resolutions all of the studied sources reveal multiple submillimeter cores. Some are observed to have cm-wavelength counterparts, and others not, suggesting a range of evolutionary stages coexisting in close proximity. In the presence of such complexity and multiplicity of sources, these data suggest that the interpretation of diagnostics such as kinematic velocity gradients and temperatures that are strongly dependent on spatial resolution should be approached cautiously. © 2007 Springer Science+Business Media B.V.
• Jørgensen, J. K., Johnstone, D., Kirk, H., Myers, P. C., Allen, L. E., & Shirley, Y. L. (2008). Current star formation in the ophiuchus and perseus molecular clouds: Constraints and comparisons from unbiased submillimeter and mid-infrared surveys. II. Astrophysical Journal, 683(2), 822-843.
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  Abstract: We present a census of the population of deeply embedded young stellar objects (YSOs) in the Ophiuchus molecular cloud complex based on a combination of Spitzer Space Telescope mid-infrared data from the "Cores to Disks" (c2d) legacy team and JCMT/SCUBA submillimeter maps from the COMPLETE team. We have applied a method developed for identifying embedded protostars in Perseus to these data sets and in this way construct a relatively unbiased sample of 27 candidate embedded protostars with envelopes more massive than our sensitivity limit (about 0.1 M⊙). As in Perseus, the mid-infrared sources are located close to the center of the SCUBA cores and the narrowness of the spatial distribution of mid-infrared sources around the peaks of the SCUBA cores suggests that no significant dispersion of the newly formed YSOs has occurred. Embedded YSOs are found in 35% of the SCUBA cores-fewer than in Perseus (58%). On the other hand the mid-infrared sources in Ophiuchus have less red midinfrared colors, possibly indicating that they are less embedded. We apply a nearest neighbor surface density algorithm to define the substructure in each of the clouds and calculate characteristic numbers for each subregion-including masses, star formation efficiencies, fraction of embedded sources, etc. Generally the main clusters in Ophiuchus and Perseus (L1688, NGC 1333, and IC 348) are found to have higher star formation efficiencies than small groups such as B1, L1455, and L1448, which on the other hand are completely dominated by deeply embedded protostars. We discuss possible explanations for the differences between the regions in Perseus and Ophiuchus, such as different evolutionary timescales for the YSOs or differences, e.g., in the accretion in the two clouds. © 2008. The American Astronomical Society. All rights reserved.
• Brogan, C. L., Chandler, C. J., Hunter, T. R., Shirley, Y. L., & Sarma, A. P. (2007). Arcsecond-scale kinematic and chemical complexity in Cepheus A East. Astrophysical Journal, 660(2 II), L133-L136.
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  Abstract: We present results from Submillimeter Array (SMA) observations of the star-forming region Cepheus A East at ∼340 GHz (875 μm) with 0.7″-2″ resolution. At least four compact submillimeter continuum sources have been detected as well as a rich forest of hot core line emission. Two kinematically, chemically, and thermally distinct regions of molecular emission are present in the vicinity of the HW2 thermal jet, both spatially distinct from the submillimeter counterpart to HW2. We propose that this emission is indicative of multiple protostars rather than a massive disk as reported by Patel et al. © 2007. The American Astronomical Society. All rights reserved.
• Shirley, Y. L., Claussen, M. J., Bourke, T. L., Young, C. H., & Blake, G. A. (2007). The detection and characterization of centimeter radio continuum emission from the low-mass protostar L1014-IRS. Astrophysical Journal, 667(1 I), 329-339.
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  Abstract: Observations by the Cores to Disk Legacy Team with the Spitzer Space Telescope have identified a low-luminosity, mid-infrared source within the dense core, Lynds 1014, which was previously thought to harbor no internal source. Follow-up near-infrared and submillimeter interferometric observations have confirmed the protostellar nature of this source by detecting scattered light from an outflow cavity and a weak molecular outflow. In this paper, we report the detection of centimeter continuum emission with the VLA. The emission is characterized by a quiescent, unresolved 90 μJy 6 cm source within 0.2″ of the Spitzer source. The spectral index of the quiescent component is σ = 0.37 ± 0.34 between 6 and 3.6 cm. A factor of 2 increase in 6 cm emission was detected during one epoch and circular polarization was marginally detected at the 5 σ level with Stokes V/I = 48% = 16%. We have searched for 22 GHz H2O maser emission toward L1014-IRS, but no masers were detected during seven epochs of observations between 2004 June and 2006 December. L1014-IRS appears to be a low-mass, accreting protostar, which exhibits centimeter emission from a thermal jet or a wind, with a variable nonthermal emission component. The quiescent cm radio emission is noticeably above the correlation of 3.6 and 6 cm luminosity versus bolometric luminosity, indicating more radio emission than expected. In this paper, we characterize the centimeter continuum emission in terms of observations of other low-mass protostars, including updated correlations of centimeter continuum emission with bolometric luminosity and outflow force, and discuss the implications of recent larger distance estimates on the physical attributes of the protostar and dense molecular core. © 2007. The American Astronomical Society. All rights reserved.
• Bourke, T. L., Myers, P. C., J., N., Dunham, M. M., Kauffmann, J., Shirley, Y. L., Crapsi, A., Young, C. H., Huard, T. L., Brooke, T. Y., Chapman, N., Cieza, L., Lee, C. W., Teuben, P., & Wahhaj, Z. (2006). The spitzer c2d survey of nearby dense cores. II. Discovery of a low-luminosity object in the "evolved starless core" L1521F. Astrophysical Journal Letters, 649(1 II), L37-L40.
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  Abstract: We present Spitzer Space Telescope observations of the "evolved starless coreπ L1521F that reveal the presence of a very low luminosity object (L < 0.07 L⊙). The object, L1521F-IRS, is directly detected at mid-infrared wavelengths (>5 μm), but only in scattered light at shorter infrared wavelengths, showing a bipolar nebula oriented east-west that is probably tracing an outflow cavity. The nebula strongly suggests that L1521F-IRS is embedded in the L152IF core. Thus, L1521F-IRS is similar to the recently discovered L1014-IRS and the previously known IRAM 04191 in its substellar luminosity and dense core environment. However, these objects differ significantly in their core density, core chemistry, and outflow properties, and some may be destined to be brown dwarfs rather than stars. © 2006. The American Astronomical Society. All rights reserved.
• Young, C. H., Bourke, T. L., Young, K. E., J., N., Jørgensen, J. K., Shirley, Y. L., F., E., & Hogerheijde, M. (2006). Submillimeter common-user bolometer array mapping of Spitzer c2d small clouds and cores. Astronomical Journal, 132(5), 1998-2013.
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  Abstract: We present submillimeter observations of dark clouds that are part of the Spitzer Legacy program "From Molecular Cores to Planet-Forming Disks" (c2d). We used the Submillimeter Common-User Bolometer Array to map the regions observed by Spitzer with the c2d program to create a census of dense molecular cores including data from the infrared to the submillimeter. In this paper we present the basic data from these observations: maps, fluxes, and source attributes. We also show data for an object just outside the Perseus cloud that was serendipitously observed in our program. We propose that this object is a newly discovered evolved protostar. © 2006. The American Astronomical Society. All rights reserved.
• Chandler, C. J., Brogan, C. L., Shirley, Y. L., & Loinard, L. (2005). IRAS 16293-2422: Proper motions, jet precession, the hot core, and the unambiguous detection of infall. Astrophysical Journal Letters, 632(1 I), 371-376.
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  Abstract: We present high spatial resolution observations of the multiple protostellar system IRAS 16293-2422 using the Submillimeter Array (SMA) at 300 GHz and the Very Large Array (VLA) at frequencies from 1.5 to 43 GHz. This source was already known to be a binary system with its main components, A and B, separated by ∼5″. The new SMA data now separate source A into two submillimeter continuum components, which we denote Aa and Ab. The strongest of these, Aa, peaks between the centimeter radio sources A1 and A2, but the resolution of the current submillimeter data is insufficient to distinguish whether this is a separate source or the centroid of submillimeter dust emission associated with A1 and A2. Archival VLA data spanning 18 yr show proper motion of sources A and B of 17 mas yr-11, associated with the motion of the ρ Ophiuchi cloud. We also find, however, significant relative motion between the centimeter sources A1 and A2, which excludes the possibility that these two sources are gravitationally bound unless A1 is in a highly eccentric orbit and is observed at periastron, the probability of which is low. A2 remains stationary relative to source B, and we identify it as the protostar that drives the large-scale northeast-southwest CO outflow. A1 is shock-ionized gas that traces the location of the interaction between a precessing jet and nearby dense gas. This jet probably drives the large-scale east-west outflow, and indeed its motion is consistent with the wide opening angle of this flow. The origin of this jet must be located close to A2 and may be the submillimeter continuum source Aa. Thus, source A is now shown to comprise three (proto)stellar components within 1″. Source B, on the other hand, is single, exhibits optically thick dust emission even at 8 GHz, has a high luminosity, and yet shows no sign of outflow. It is probably very young and may not even have begun a phase of mass loss yet. The SMA spectrum of IRAS 16293-2422 reports the first astronomical identification of many lines of organic and other molecules at 300 and 310 GHz. The species detected are typical of hot cores, the emission from which is mainly associated with source A. The abundances of second-generation species, especially of sulphur-bearing molecules, are significantly higher than predicted by chemical models for this source to date, and we suggest that shocks are probably needed to explain these enhancements. The peaks in the integrated emission from molecules having high rotation temperatures coincide with the centimeter source A1, also highlighting the key role of shocks in explaining the nature of hot cores. Finally, we use the high brightness temperature of the submillimeter dust emission from source B to demonstrate the unambiguous detection of infall by observing redshifted SO (77-66) absorption against the emission from its dust disk. © 2005. The American Astronomical Society. All rights reserved.
• Crapsi, A., DeVries, C. H., Huard, T. L., Lee, J. -., Myers, P. C., Ridge, N. A., Bourke, T. L., II, N. E., Jørgensen, J., Kauffmann, J., Lee, C. W., Shirley, Y. L., & Young, C. H. (2005). Dynamical and chemical properties of the "starless" core L1014. Astronomy and Astrophysics, 439(3), 1023-1032.
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  Abstract: Spitzer Space Telescope observations of a point-like source, L1014-IRS, close to the dust peak of the low-mass dense core L1014, have raised questions about its starless nature. These show the presence of an object with colors expected for an embedded protostar with the implication that L1014-IRS would be the lowest luminosity isolated protostar known, and an ideal target with which to test star formation theories at the low mass end. In order to study its molecular content and to search for the presence of a molecular outflow, we mapped L1014 in at least one transition of 12CO, N2H +, HCO+, CS, and of their isotopologues 13CO, C18O, C17O, N2D+, and H 13CO+, using the Five College Radio Astronomy Observatory (FCRAO), the IRAM 30 m antenna, and the Caltech Submillimeter Observatory (CSO). The data show physical and chemical properties in L1014 typical of moderately evolved dense cores: i.e. H2 central density of a few 105 molecules cm-3, estimated mass of ∼2 M⊙, CO integrated depletion factor less than 10, N(N2H+) ≃ 6 × 1012 cm-2, N(N2D+)/N(N 2H+) equal to 10%, and relatively broad N 2H+ and N2D+ lines (0.35 km s -1). Infall signatures and significant velocity shifts between optically thick and optically thin tracers are not observed in the line profiles. No classical signatures of molecular outflow are found in the 12CO and 13CO FCRAO observations. In particular, no high velocity wings are found, and no well-defined blue-red lobes of 12CO emission are seen in the channel maps. Sensitive, higher resolution observations will clarify the presence of a molecular outflow on a smaller scale than that probed by our observations. © ESO 2005.
• Doty, S. D., Everett, S. E., Shirley, Y. L., J., N., & Palotti, M. L. (2005). Constraining the structure of the non-spherical pre-protostellar core L1544. Monthly Notices of the Royal Astronomical Society, 359(1), 228-236.
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  Abstract: We present a study of the pre-protostellar core L1544. A series of self-consistent, three-dimensional continuum radiative transfer models is constructed. The outputs of these models are convolved with appropriate telescope beam responses, and compared with existing SCUBA data. The resulting comparison allows us to constrain the structure of L1544. We find that the source is well-fitted by a prolate spheroid, having an ellipsoidal power-law density distribution of index m ∼ 2(1.75 < m < 2.25) in to at least r ∼ 1600 au. For r < 1600 au, the data are consistent with either an extension of the power law to smaller radii, or a flattened (Bonner-Ebert-like) density distribution. Furthermore, we find an optical depth along the short axis at 1300 μm of τ1300,short = 5 × 10-3(2 × 10-3 < τ1300,short < 8 × 10 -3), a central luminosity L* = 0 (
• Jingwen, W. u., J., N., Gao, Y., Solomon, P. M., Shirley, Y. L., & A., P. (2005). Connecting dense gas tracers of star formation in our galaxy to high-z star formation. Astrophysical Journal Letters, 635(2 II), L173-L176.
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  Abstract: Observations have revealed prodigious amounts of star formation in starburst galaxies as traced by dust and molecular emission, even at large redshifts. Recent work shows that for both nearby spiral galaxies and distant starbursts, the global star formation rate, as indicated by the infrared luminosity, has a tight and almost linear correlation with the amount of dense gas as traced by the luminosity of HCN. Our surveys of Galactic dense cores in HCN 1-0 emission show that this correlation continues to a much smaller scale, with nearly the same ratio of infrared luminosity to HCN luminosity found over 7-8 orders of magnitude in LIR, with a lower cutoff around 10 4.5 L⊙ of infrared luminosity. The linear correlation suggests that we may understand distant star formation in terms of the known properties of local star-forming regions. Both the correlation and the luminosity cutoff can be explained if the basic unit of star formation in galaxies is a dense core, similar to those studied in our Galaxy. © 2005. The American Astronomical Society. All rights reserved.
• Shirley, Y. L., Nordhaus, M. K., Grcevich, J. M., J., N., Rawlings, J. M., & Tatematsu, K. (2005). Modeling the physical structure of the low-density pre-protostellar core Lynds 1498. Astrophysical Journal Letters, 632(2 I), 982-1000.
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  Abstract: Pre-protostellar cores likely represent the incipient stages of low-mass (≈1 M⊙) star formation. Lynds 1498 is a pre-protostellar core (PPC) and was one of the initial objects toward which molecular depletion and differentiation was detected. Despite the considerable scrutiny of L1498, there has not been an extensive study of the density and temperature structure as derived from radiative transfer modeling of dust continuum observations. We present deep SCUBA observations of L1498 at 850 and 450 μm, high-resolution BEARS maps of the N2H+ 1 → 0 transition, Caltech Submillimeter Observatory observations of the N2H+ 3 → 2 transition, and Green Bank Telescope observations of the C 38 4 → 3 transition. We also present a comparison of derived properties between L1498 and nearby PPCs that have been observed at far-infrared and submillimeter wavelengths. The L1498 continuum emission is modeled using a one-dimensional radiative transfer code that self-consistently calculates the temperature distribution and calculates the spectral energy distribution and intensity profiles at 850 and 450 μm. We present a more realistic treatment of PPC heating that varies the strength of the interstellar radiation field (sisrf) and includes attenuation of the ISRF due to dust grains at the outer radius of the core, AV. The best-fit model consists of a Bonner-Ebert sphere with a central density of (1-3) × 104 cm-3, R0 → 0.29 pc, 0.5 ≤ S isrf ≤ 1, AV ≈ 1 mag, and a nearly isothermal temperature profile of ≈10.5 K for OH8 opacities. C3S emission shows a central depletion hole, while N2H+ emission is centrally peaked. We derive a mean N2H+ abundance of 4.0 × 10-10 relative to H2 that is consistent with chemical models for a dynamically young yet chemically evolved source. The observed depletions of C3S and H2CO, the modest N 2H+ abundance, and a central density that is an order of magnitude lower than other modeled PPCs suggests that L1498 may be a forming PPC. Our derived temperature and density profile will improve modeling of molecular line observations that will explicate the core's kinematical and chemical state. © 2005. The American Astronomical Society. All rights reserved.
• Shephhrd, D. S., Borders, T., Claussen, M., Shirley, Y., & Kurtz, S. (2004). The circumstellar environment of the early B protostar G192.16-3.84 and the discovery of a low-mass, protostellar core. Astrophysical Journal Letters, 614(1 I), 211-220.
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  Abstract: We have observed the massive star-forming region associated with the early B protostar G192.16-3.84 in NH3(1, 1). 22.2 GHz H2O masers, 1.3 cm continuum emission, and at 850 μm. The dense gas associated with G192.16 is clumpy, is optically thin, and has a mass of 0.9 M ⊙. The NH3 core is gravitationally unstable, which may signal that the outflow phase of this system is coming to an end. Water masers trace an ionized jet 0″.8 (1600 AU at a distance of 2 kpc) north of G192.16. Masers are also located within 500 AU of G192.16; their velocity distribution is consistent with but does not strongly support the interpretation that the maser emission arises in a 1000 AU rotating disk centered on G192.16. Roughly 30″ south of G192.16 (0.3 pc) is a compact, optically thick (τ - 1.2) NH3 core (called G192 S3) with an estimated mass of 2.6 M⊙. Based on the presence of 850 μm and 1.2 mm continuum emission, G192 S3 probably harbors a very young, low-mass protostar or protocluster. The dense gas in the G192 S3 core is likely to be gravitationally bound and may represent the next site of star formation in this region.
• Young, C. H., Jørgensen, J. K., Shirley, Y. L., Kauffmann, J., Huard, T., Lai, S., Lee, C. W., Crapsi, A., Bourke, T. L., Dullemond, C. P., Brooke, T. Y., Porras, A., Spiesman, W., Allen, L. E., Blake, G. A., J., N., Harvey, P. M., Koerner, D. W., Mundy, L. G., , Myers, P. C., et al. (2004). A "starless" core that isn't: Detection of a source in the L1014 dense core with the Spitzer Space Telescope. Astrophysical Journal, Supplement Series, 154(1), 396-401.
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  Abstract: We present observations of L1014, a dense core in the Cygnus region previously thought to be starless, but data from the Spitzer Space Telescope show the presence of an embedded source. We propose a model for this source that includes a cold core, heated by the interstellar radiation field, and a low-luminosity internal source. The low luminosity of the internal source suggests a substellar object. If L1014 is representative, other "starless" cores may turn out to harbor central sources.
• Lee, J., J., N., Shirley, Y. L., & Tatematsu, K. (2003). Chemistry and dynamics in pre-protostellar cores. Astrophysical Journal Letters, 583(2 I), 789-808.
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  Abstract: We have compared molecular-line emission to dust continuum emission and modeled molecular lines using Monte Carlo simulations in order to study the depletion of molecules and the ionization fraction in three pre-protostellar cores, L1512, L1544, and L1689B. L1512 is much less dense than L1544 and L1689B, which have similar density structures. L1689B has a different environment from those of L1512 and L1544. We used density and temperature profiles, calculated by modeling dust continuum emission in the submillimeter, for modeling molecular-line profiles. In addition, we have used molecular-line profiles and maps observed in several different molecules toward the three cores. We find a considerable diversity in chemical state among the three cores. The molecules include those sensitive to different timescales of chemical evolution such as CCS, the isotopes of CO and HCO+, DCO+, and N 2H+. The CO molecule is significantly depleted in L1512 and L1544 but not in L1689B. CCS may be in the second enhancement of its abundance in L1512 and L1544 because of the significant depletion of CO molecules. N2H+ might already be starting to be depleted in L1512, but it traces very well the distribution of dust emission in L1544. On the other hand, L1689B may be so young that N2H+ has not reached its maximum yet. The ionization fraction has been calculated using H13CO+ and DCO+. The result shows that the ionization fraction is similar toward the centers of the three cores. This study suggests that chemical evolution depends on the absolute timescale during which a core stays in a given environment as well as its density structure.
• Shirley, Y. L., J., N., Young, K. E., Knez, C., & Jaffe, D. T. (2003). A CS J = 5 → 4 mapping survey toward high-mass star-forming cores associated with water masers. Astrophysical Journal, Supplement Series, 149(2), 375-403.
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  Abstract: We have mapped 63 regions forming high-mass stars in CS J = 5 → 4 using the CSO. The CS peak position was observed in C 34S J = 5 → 4 toward 57 cores and in 13CS J = 5 → 4 toward the nine brightest cores. The sample is a subset of a sample originally selected toward water masers; the selection on maser sources should favor sources in an early stage of evolution. The cores are located in the first and second Galactic quadrants with an average distance of 5.3 ± 3.7 kpc and were well detected with a median peak signal-to-noise ratio in the integrated intensity of 40. The integrated intensity of CS J = 5 → 4 correlates very well with the dust continuum emission at 350 μm. For 57 sufficiently isolated cores, a well-defined angular size (FWHM) was determined. The core radius (R CS), aspect ratio [(a/b) obs], virial mass (M vir), surface density (∑), and the luminosity in the CS J = 5 → 4 line (L(CS54)) are calculated. The distributions of size, virial mass, surface density, and luminosity are all peaked with a few cores skewed toward much larger values than the mean. The median values, μ 1/2, are as follows: μ 1/2 (R CS) = 0.32 pc, μ 1/2 ((a/b) obs) = 1.20, μ 1/2 (M vir) = 920 M ⊙, μ 1/2 (∑) = 0.60 g cm -2, μ 1/2 (L(CS54)) = 1.9 × 10 -2 L ⊙ and μ 1/2 (L bol/M vir) = 165 (L/M) ⊙. We find a weak correlation between C 34S line width and size, consistent with Δv ∼ R 0.3. The line widths are much higher than would be predicted by the usual relations between line width and size determined from regions of lower mass. These regions are very turbulent. The derived virial mass agrees within a factor of 2-3 with mass estimates from dust emission at 350 μm after corrections for the density structure are accounted for. The resulting cumulative mass spectrum of cores above 1000 M ⊙ can be approximated by a power law with a slope of about -0.9, steeper than that of clouds measured with tracers of lower density gas and close to that for the total masses of stars in OB associations. The median turbulent pressures are comparable to those in UCH II regions, and the pressures at small radii are similar to those in hypercompact H II regions (P/k ∼ 10 10 K cm -3). The filling factors for dense gas are substantial, and the median abundance of CS is about 10 -9. The ratio of bolometric luminosity to virial mass is much higher than the value found for molecular clouds as a whole, and the correlation of luminosity with mass is tighter.
• Young, C. H., Shirley, Y. L., J., N., & Rawlings, J. M. (2003). Tracing the mass during low-mass star formation. IV. Observations and modeling of the submillimeter continuum emission from Class I protostars. Astrophysical Journal, Supplement Series, 145(1), 111-145.
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  Abstract: We present results from the observations and modeling of 17 Class I cores with the Submillimetre Common Users Bolometer Array (SCUBA) on the James Clerk Maxwell Telescope (JCMT). Our sample consists of cores with 64 K < T bol < 270 K, 0.2 < Lobs/L⊙< 12, and 50 < Lobs/Lsmm < 1000. By modeling the transfer of radiation through the envelope for nine cores, we find, for a power-law distribution n(r) = nf(r/rf)-p, the average and standard deviation 〈p〉 = 1.6 ± 0.4 and a median of p = 1.8. However, the inclusion of a disk or other pointlike component can cause the derived p to be shallower by as much as 0.5. We discuss uncertainties due to the interstellar radiation field (ISRF), disks, dust opacity, and outer radii in our modeling results. We find no evidence for a truncated outer radius or radially variant dust properties in most sources. Uncertainty in the strength of the ISRF and possible existence of a disk contribute the greatest uncertainty in p. In addition, we test the Shu collapse model for our sources and discuss the application of simpler analyses that derive a density power-law distribution directly from the slope of the intensity radial profile. The total mass of the envelope in our sample has a range of 0.04 < M env/M⊙ < 5.0, but these masses disagree with the virial masses derived from molecular line observations, indicating that observations of molecular lines do not trace the mass in some Class I cores. We also discuss several sources individually. In particular, IRAS 03256+3055, with its unique morphology, is an ideal object for testing theories of fragmentation in the formation of low-mass protostars. Also, we note the possibility, through some simple calculations, that IRAS 04385+2550 is a young, forming substellar object. Finally, we discuss the nature of these sources in light of various evolutionary indicators and find that Tbol and Lobs/L smm are often inconsistent in distinguishing Class 0 from Class I cores. We note that, in this sample, the Lobs/Lsmm criterion redefines many of these Class I sources (by Tbol) as Class 0 sources.
• Mueller, K. E., Shirley, Y. L., J., N., & Jacobson, H. R. (2002). The physical conditions for massive star formation: Dust continuum maps and modeling. Astrophysical Journal, Supplement Series, 143(2), 469-497.
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  Abstract: Fifty-one dense cores associated with water masers were mapped at 350 μm. These cores are very luminous, 103 < Lbol/L ȯ
• Shirley, Y. L., J., N., & Rawlings, J. M. (2002). Tracing the mass during low-mass star formation. III. Models of the submillimeter dust continuum emission from class 0 protostars. Astrophysical Journal Letters, 575(1 I), 337-353.
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  Abstract: Seven Class 0 sources mapped with SCUBA at 850 and 450 μm are modeled using a one-dimensional radiative transfer code. The modeling takes into account heating from an internal protostar, heating from the interstellar radiation field (ISRF), realistic beam effects, and chopping to model the normalized intensity profile and spectral energy distribution. Power-law density models, n(r) ∝ r-p, fit all of the sources; best-fit values are mostly p = 1.8 ± 0.1, but two sources with aspherical emission contours have lower values (p ∼ 1.1). Including all sources, 〈p〈 = 1.63 ± 0.33. Based on studies of the sensitivity of the best-fit p to variations in other input parameters, uncertainties in p for an envelope model are Δp = ±0.2. If an unresolved source (e.g., a disk) contributes 70% of the flux at the peak, p is lowered in this extreme case and Δp = 0.2-0.6. The models allow a determination of the internal luminosity (〈Lint〉 = 4.0 L⊙) of the central protostar as well as a characteristic dust temperature for mass determination (〈Tiso〉 = 13.8 ± 2.4 K). We find that heating from the ISRF strongly affects the shape of the dust temperature profile and the normalized intensity profile, but it does not contribute strongly to the overall bolometric luminosity of Class 0 sources. There is little evidence for variation in the dust opacity as a function of distance from the central source. The data are well fitted by dust opacities for coagulated dust grains with ice mantles (Ossenkopf & Henning). The density profile from an inside-out collapse model (Shu) does not fit the data well, unless the infall radius is set so small as to make the density nearly a power law.
• J., N., M., J., Shirley, Y. L., & Mundy, L. G. (2001). Tracing the mass during low-mass star formation. II. Modeling the submillimeter emission from preprotostellar cores. Astrophysical Journal Letters, 557(1 PART 1), 193-208.
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  Abstract: We have modeled the emission from dust in preprotostellar cores, including a self-consistent calculation of the temperature distribution for each input density distribution. Model density distributions include Bonnor-Ebert spheres and power laws. The Bonnor-Ebert spheres fit the data well for all three cores that we have modeled. The dust temperatures decline to very low values (Td ∼ 7 K) in the centers of these cores, strongly affecting the dust emission. Compared to earlier models that assume constant dust temperatures, our models indicate higher central densities and smaller regions of relatively constant density. Indeed, for L1544, a power-law density distribution, similar to that of a singular, isothermal sphere, cannot be ruled out. For the three sources modeled herein, there seems to be a sequence of increasing central condensation, from L1512 to L1689B to L1544. The two denser cores, L1689B and L1544, have spectroscopic evidence for contraction, suggesting an evolutionary sequence for preprotostellar cores.
• Shirley, Y. L., J., N., Rawlings, J. M., & Gregersen, E. M. (2000). Tracing the mass during low-mass star formation. I. Submillimeter continuum observations. Astrophysical Journal, Supplement Series, 131(1), 249-271.
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  Abstract: We have obtained 850 and 450 μm continuum maps of 21 low-mass cores with SEDs ranging from pre-protostellar to Class I (18 K < Tbol < 370 K), using SCUBA at the JCMT. In this paper we present the maps, radial intensity profiles, and photometry. Pre-protostellar cores do not have power-law intensity profiles, whereas the intensity profiles of Class O and Class I sources can be fitted with power laws over a large range of radii. A substantial number of sources have companion sources within a few arcminutes (two out of five pre-protostellar cores, nine out of 16 Class 0/1 sources). The mean separation between sources is 10,800 AU. The median separation is 18,000 AU including sources without companions as a lower limit. The mean value of the spectral index between 450 and 850 μm is 2.8 ± 0.4, with pre-protostellar cores having slightly lower spectral indices (2.5 ± 0.4). The mean mass of the sample, based on the dust emission in a 120″ aperture, is 1.1 ± 0.9 M⊙. For the sources fitted by power-law intensity distributions (Iv(b)/Iv(0) = (b/b0)m), the mean value of m is 1.52 ± 0.45 for Class 0 and I sources at 850 μm and 1.44 ± 0.25 at 450 μm. Based on a simple analysis, assuming the emission is in the Rayleigh-Jeans limit and that Td(r) ∝ r-0.4, these values of m translate into power-law density distributions (n ∝ r-p) with p ∼ 2.1. However, we show that this result may be changed by more careful consideration of effects such as beam size and shape, finite outer radii, more realistic Td(r), and failure of the Rayleigh-Jeans approximation.

Proceedings Publications

• Shirley, Y. L. (2020, feb). "The Virial State of Starless Cores". In The 35th Annual New Mexico Symposium.
• Svoboda, B., Shirley, Y., Battersby, C., & Calahan, J. (2019, jan). Probing gas inflow with GBT/ALMA mapping towards starless clump candidates. In American Astronomical Society Meeting Abstracts #233, 233.
• Lee, K., Mundy, L. G., Fernandez Lopez, M., Storm, S., Looney, L., Segura-Cox, D., Teuben, P. J., Rosolowsky, E., Arce, H. G., Shirley, Y. L., Plunkett, A., Isella, A., & Tobin, J. J. (2014, jan). Kinematics and Temperature Structures of Filaments in Serpens Main and Serpens South. In American Astronomical Society Meeting Abstracts, 223, #214.05.
• Looney, L., Fernandez Lopez, M., Segura-Cox, D., Arce, H. G., Lee, K., Storm, S., Mundy, L. G., Teuben, P. J., Isella, A., Plunkett, A., Rosolowsky, E., Shirley, Y. L., Tobin, J. J., & Team, C. (2014, jan). Analysis of the Serpens South Filamentary Cloud: CLASSy Results. In American Astronomical Society Meeting Abstracts, 223, #244.12.
• Mundy, L. G., Storm, S., Fernandez Lopez, M., Lee, K., Looney, L., Teuben, P. J., Rosolowsky, E., Shirley, Y. L., Arce, H. G., Plunkett, A., Isella, A., & Team, C. (2014, jan). The Structure of Dense Gas in Perseus and Serpens: CLASSy Results. In American Astronomical Society Meeting Abstracts, 223, #244.11.
• Storm, S., Mundy, L. G., Teuben, P. J., Lee, K., Looney, L., Fernandez Lopez, M., Rosolowsky, E., Arce, H. G., Shirley, Y. L., Segura-Cox, D., Isella, A., & Team, C. (2014, jan). Dendrogram Analysis of Large-Area CARMA Images in Perseus: the Dense Gas in NGC 1333, Barnard 1, and L1451. In American Astronomical Society Meeting Abstracts, 223, #214.06.
• Walker-LaFollette, A., Shirley, Y. L., Amaya, H., Becker, S. L., Biddle, L. I., Lichtenberger, M., Nieberding, M. N., Raphael, B. A., Romine, J. M., Small, L., Stanford-Jones, C., Smith, C., Thompson, R., Towner, A. P., Turner, J., Watson, Z., Cates, I., McGraw, A. M., Pearson, K., , Robertson, A., et al. (2014, jan). Kinematic Results From a Systematic Search for Infall Signatures Towards the Starless Core Population in the Perseus Molecular Cloud. In American Astronomical Society Meeting Abstracts, 223, #454.33.
• Battersby, C., Bally, J., Ginsburg, A., Longmore, S., Dunham, M., Shirley, Y., Myers, P., & Kirk, H. (2013, jul). The Dynamic Role of Large-Scale Gas Flows in High-Mass Star-Forming Filaments. In Protostars and Planets VI Posters, 13.
• Launhardt, R., Stutz, A., Schmiedecke, A., Henning, T., Krause, O., Balog, Z., Beuther, H., Kainulainen, J., Linz, H., Lippok, N., Nielbock, M., Ragan, S., Schmalzl, M., Shirley, Y., & Steinacker, J. (2013, jul). The thermal structure of low-mass cloud cores. In Protostars and Planets VI Posters, 43.
• Looney, L., Lee, K., Fernandez Lopez, M., Arce, H. G., Chen, C., Crutcher, R., Gong, H., Hakobian, N., Isella, A., Kauffmann, J., Kwon, W., Mouschovias, T. C., Mundy, L. G., Ostriker, E. C., Plunkett, A., Pound, M. W., Rosolowsky, E., Salter, D. M., Shirley, Y. L., , Storm, S., et al. (2013, jan). CARMA Large Area Star-formation Survey: First Look at Serpens Main. In American Astronomical Society Meeting Abstracts, 221, #251.11.
• McGraw, A. M., Hardegree-Ullman, K. K., Turner, J. D., Shirley, Y. L., Walker-LaFollette, A. M., Robertson, A. N., Carleton, T. M., Smart, B. M., Towner, A. P., Wallace, S. C., Smith, C., Austin, C. L., Small, L. C., Daugherty, M. J., Guvenen, B. C., Crawford, B. E., & Schlingman, W. M. (2013, apr). Using Group Research to Stimulate Undergraduate Astronomy Major Learning. In Communicating Science: A National Conference on Science Education and Public Outreach, 473, 369.
• McGraw, A. M., Hardegree-Ullman, K., Turner, J., Shirley, Y. L., Walker-Lafollette, A., Scott, A., Guvenen, B., Raphael, B., Sanford, B., Smart, B., Nguyen, C., Jones, C., Smith, C., Cates, I., Romine, J., Cook, K., Pearson, K., Biddle, L., Small, L., , Donnels, M., et al. (2013, jan). Enhancing Astronomy Major Learning Through Group Research Projects. In American Astronomical Society Meeting Abstracts, 221, #255.08.
• Mundy, L. G., Storm, S., Pound, M. W., Salter, D. M., Arce, H. G., Chen, C., Crutcher, R., Fernandez Lopez, M., Gong, H., Hakobian, N., Isella, A., Kauffmann, J., Kwon, W., Lee, K., Looney, L., Mouschovias, T. C., Ostriker, E. C., Plunkett, A., Rosolowsky, E., , Shirley, Y. L., et al. (2013, jan). CARMA Large-Area Star-formation Survey: First Look at NGC 1333 SVS-13 Region. In American Astronomical Society Meeting Abstracts, 221, #251.12.
• Storm, S., Mundy, L. G., Teuben, P. J., Arce, H. G., Chen, C., Crutcher, R., Fernandez Lopez, M., Gong, H., Hakobian, N., Isella, A., Kauffmann, J., Kwon, W., Lee, K., Looney, L., Mouschovias, T. C., Ostriker, E. C., Plunkett, A., Pound, M. W., Rosolowsky, E., , Salter, D. M., et al. (2013, jan). CARMA Large Area Star-formation Survey: First Look at Barnard 1. In American Astronomical Society Meeting Abstracts, 221, #251.10.
• Svoboda, B., Shirley, Y., Rosolowsky, E., Dunham, M., Ellsworth-Bowers, T., & Ginsburg, A. (2013, jul). Physical properties of high-mass star-forming clumps in different evolutionary stages from the Bolocam Galactic Plane Survey. In Protostars and Planets VI Posters, 36.
• Walker-LaFollette, A., Shirley, Y. L., Towner, A. P., Biddle, L. I., Smith, C., Amaya, H., Becker, S. L., Lichtenberger, M., Nieberding, M. N., Raphael, B. A., Romine, J. M., Small, L., Stanford-Jones, C., Thompson, R., Turner, J., Watson, Z., Cates, I., Daugherty, M., Haberstroh, J., , Kwon, M., et al. (2013, jun). A Systematic Search for Infall Signatures Towards the Starless Core Population in the Perseus Molecular Cloud. In American Astronomical Society Meeting Abstracts, 222, #216.10.
• Friesen, R., Kirk, H., & Shirley, Y. (2012, jan). A Systematic Study of Deuteration of Dense Cores in Perseus. In American Astronomical Society Meeting Abstracts #219, 219, #220.05.
• Hardegree-Ullman, K., Shirley, Y. L., Rosolowsky, E. W., Burleigh, K. J., Bieging, J. H., Hardegree-Ullman, E. E., & Schlingman, W. M. (2012, may). Dense Core Properties in the Serpens North Molecular Cloud. In American Astronomical Society Meeting Abstracts #220, 220, #134.10.
• Jasso, S., Shirley, Y., Bieging, J., Rudolph, A., Lada, C., Forbrich, J., & Roman, C. (2012, jan). Analysis Of The California Molecular Cloud Through CS J(2-1), HCN J(1-0), And C18O J(2- 1)molecular Tracers. In American Astronomical Society Meeting Abstracts #219, 219, #349.20.
• McGraw, A. M., Hardegree-Ullman, K. K., Turner, J. D., Shirley, Y. L., Walker-LaFollette, A. M., Robertson, A. N., Carleton, T. M., Smart, B. M., Towner, A. P., Wallace, S. C., Smith, C. W., Small, L. C., Daugherty, M. J., Guvenen, B. C., Crawford, B. E., Austin, C. L., & Schlingman, W. M. (2012, may). Using Group Research Projects to Stimulate Undergraduate Astronomy Major Learning. In American Astronomical Society Meeting Abstracts #220, 220, #437.03.
• Robertson, A., & Shirley, Y. (2012, jan). Evaluating Early-time vs. Late-time Chemical Evolutionary Tracers in Starless Cores. In American Astronomical Society Meeting Abstracts #219, 219, #439.22.
• Schlingman, W. M., Shirley, Y. L., Langston, G., & Ginsburg, A. (2012, jan). KFPA Mapping of NH3 in the G111 Infrared Dark Cloud Filament. In American Astronomical Society Meeting Abstracts #219, 219, #341.14.
• Schwarz, K. R., Shirley, Y. L., & Dunham, M. M. (2012, may). A Systematic Search for Molecule Outflows Toward Candiate Low-Luminosity Protostars. In American Astronomical Society Meeting Abstracts #220, 220, #333.09.
• Shirley, Y. L. (2012, jan). Star Formation Studies with ALMA in Cycle 0 and Cycle 1. In American Astronomical Society Meeting Abstracts #219, 219, #309.03.
• Shirley, Y. L., Ellsworth-Bowers, T., Mairs, S., Rosolowsky, E., Ginsburg, A., Battersby, C., Stringfellow, G., Dunham, M., & Schlingman, W. (2012, may). A Complete Spectroscopic Survey of Dense Molecular Gas in Clumps in the Bolocam Galactic Plane Survey with $l $ backslash$geq 7.5 $ deg. In American Astronomical Society Meeting Abstracts #220, 220, #333.10.
• Shirley, Y. L., Stutz, A. M., Launhardt, R., & J orgensen, J. K. (2012, mar). Constraining the Physical Structure and Dust Opacities Toward the Class 0 Protostar B335. In From Atoms to Pebbles: Herschel's view of Star and Planet Formation.
• Walker-LaFollette, A., Shirley, Y. L., Hardegree-Ullman, K. K., Towner, A. P., Wallace, S. C., Smith, C. W., Turner, J. D., Robertson, A. N., Austin, C. L., Small, L. C., Carleton, T. M., McGraw, A. M., Daugherty, M. J., Guvenen, B. C., Johnson, K. L., Crawford, B. E., & Smart, B. M. (2012, may). AZTECAN C3PO: Arizona Three-millimeter Educational C18O And N2H+ Cold Core Census of Planck Objects. In American Astronomical Society Meeting Abstracts #220, 220, #134.12.

Presentations

• Shirley, Y. L. (2019, December). The Structure and Evolution of Starless and Prestellar Cores. ORIGINS talk. SO 208: Steward Observatory.
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  ORIGINS talk
• Shirley, Y. L. (2019, October). Deuteration on Dust Grains in Starless Cores. Steward Internal Symposium. LPL 308: Steward Observatory.
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  Talk at Internal Symposium
• Shirley, Y. L. (2019, September). The Physical and Chemical Evolution of Starless Cores. MPE Colloquium. Garching, Germany: Max Planck Institute for Extraterrestrial Physics.
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  Invited Colloquium talk
• Shirley, Y. L. (2018, Fall). Dark Clouds and Prestellar Cores – The Beginning Stage of Star and Planet Formation. Tucson Amateur Astronomy Association General Meeting. Steward Observatory, Tucson, AZ: TAAA.
• Shirley, Y. L. (2018, Fall). GAS - The Gould's Belt NH3 Imaging Survey with the KFPA on the GBT. Velocity-Resolved Far-Infrared Imaging Spectroscopy of the Future A Symposium Honoring Paul F. Goldsmith. Paris Observatory, Paris, France: Paris Observatory.
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  Invited talk
• Shirley, Y. L. (2018, Fall). The Structure and Evolution of Starless Cores. UNM Physics and Astronomy Department Invited Colloquium. University of New Mexico.
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  Invited colloquium
• Shirley, Y. L. (2018, Spring). Where do stars come from? Studying Star Formation in the Milky Way. Steward Observatory 100 Year Open House. Steward Observatory, Tucson, AZ: Steward Observatory.
• Shirley, Y. L. (2018, Summer). Star Formation in the Galaxy. Astrophysical Frontiers in the Next Decade and Beyond: Planets, Galaxies, Black Holes, and the Transient Universe. Portland, OR: NRAO.
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  Invited review talk
• Shirley, Y. L. (2017, Aug 28). Complex Organic Molecules in Prestellar Cores. ORIGINS Talk. SO N305: Steward Observatory.
• Shirley, Y. L. (2017, July 5). Complex Organic Molecules in Prestellar Cores. MPIA PSF Coffee Talk. Max Planck Institute fur Astronomie: MPIA.
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  30 min. PSF coffee talk at MPIA
• Shirley, Y. L. (2017, June 28). The Physical Properties of Clumps in Different Evolutionary Stages Identified in Galactic Plane Surveys. European Week of Astronomy and Space Sciences 2017. Prague.
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  Invited review talk to open the session "Understanding the environmental dependence of star formation: the importance of Big Data".
• Shirley, Y. L. (2017, Mar 3). Detection of Complex Organic Molecules toward a Young Prestellar Core. Steward Observatory Internal Symposium. Tucson: Steward Observatory.
• Shirley, Y. L. (2017, March 10). The Physical Properties of Massive Dense Clumps in Different Evolutionary Stages in the Milky Way. NRAO Invited Colloquium. NRAO Socorro: National Radio Astronomy Observatory.
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  Galactic Plane Surveys at Far-Infrared through Millimeter wavelengths have provided the most unbiased maps of dust continuum emission in the Milky Way. The Bolocam Galactic Plane Survey catalogued 10^4 dense clumps of a gas and dust - current and future sites of star formation within the Galaxy. Followup molecular line observations of several thousand clumps in lines of NH3 and HCO+ with the GBT and SMT determine the thermal and turbulent state of the clumps. The BGPS team has developed a Bayesian technique for constraining the heliocentric distance to the clumps and use Monte Carlo sampling of the posterior distance distributions to more properly account for uncertainties in calculations of the physical variable (i.e. size, mass, luminosity, etc.). Clumps have been sorted into evolutionary categories by comparing the 1.1mm continuum with near/mid/far-infrared surveys, masers surveys, and radio continuum (VLA) surveys. The distributions of flux density, flux concentration, kinetic temperature, mass surface density, radius, and mass all show strong progressions when sorted by star formation indicators with increasing luminosity. A population of over 2000 starless clump candidates have been identified which have no evidence from Galactic plane survey observations for star formation. The lifetime of the starless clump phase is found to be a function of the mass of the clumps (t ~ 1/M) with the majority of clumps having starless phase lifetimes longer than their average free-fall times. However, bew followup observations of the most massive starless clump candidates with ALMA indicate that current Galactic plane surveys from near-infrared through centimeter wavelengths are not sensitive enough to detect low-mass star formation within clumps at distances of a few kpc. Initial analysis of the ALMA observations probe fragmentation down to the core scales and are consistent with thermal Jean fragmentation in these massive clumps.
• Shirley, Y. L. (2017, Nov 3). Complex Organic Molecules Observed Towards Prestellar Cores. 33rd New Mexico Symposium. NRAO Socorro: NRAO.
• Shirley, Y. L. (2017, Oct 2). Studying the Earliest Phase of Massive Star and Cluster Formation - the Properties of Massive Starless Clump Candidates in the Milky Way. Inivted Colloquium Univ. British Columbia. Vancouver, B.C.: UBC.
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  Recent surveys of the dust continuum emission in the Milky Way Galaxyhave revealed tens of thousands of cold, dense clumps with enough massto form clusters of stars (some potentially massive stars) but no currentevidence for star formation. These massive starless clump candidatesrepresent the earliest phase of cluster formation. The typical starless clumpcandidate is ~1 pc in size, cold (Tk ~ 13 K), and with a mass of ~250 Msun.I shall present results from the 1.1mm Bolocam Galactic Plane Survey thatcharacterize the physical properties of the massive starless clump candidatesand compare those results to the properties of clumps in different evolutionarystages. I shall also present the results from ALMA and single dish observationsstudying the fragmentation and mass flow within massive starless clumpcandidates. I will show just how very difficult it is to identify the earliest phase ofmassive star formation, the elusive >30 Msun starless core.
• Shirley, Y. L. (2017, Oct 3). Studying the Earliest Phase of Massive Star and Cluster Formation – the Properties of Massive Starless Clump Candidates in the Milky Way. HIA Invited Colloquium. Victoria, B.C.: HIA.
• Shirley, Y. L. (2017, Oct 4). Complex Organic Molecules in Prestellar Cores. HIA Coffee Talk. Victoria, B.C.: HIA.
• Shirley, Y. L. (2016, 10). An Overview of Physical Properties of Clumps in the Bolocam Galactic Plane Survey. ViaLactea 2016 -. Rome, Italy: ESA.
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  ViaLactea 2016 was a meeting bringing together researchers that have studied the Milky Way Galaxy with far-infrared through millimeter continuum surveys.
• Shirley, Y. L. (2016, 2016-03-16). Characterizing the Properties of Massive Starless Clumps - The Initial Phase of Massive Star Formation. NRAO Colloquium. Green Bank, WV: NRAO.
• Shirley, Y. L. (2015, 2015-03-17). Deuteration in High-Mass Star-Forming Regions. The Soul of High-Mass Star Formation Conference. Puerto Varas, Chile: ALMA and Cerro Calan.
• Shirley, Y. L. (2015, 2015-03-23). The Properties and Evolution of Clumps and Cores. Star and Planet Formation in the Southwest (SPF1). Biosphere, Oracle, Arizona: University of Arizona.
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  Invited opening conference review of the properties of clumps and cores (the observational review paired with an opening theoretical review)
• Shirley, Y. L. (2015, 2015-10-05). Astrochemical probes from clouds to dense cores. From clouds to protoplanetary disks: the astrochemical link. Berlin, Germany: MPE and ERC.
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  Invited opening conference review at the Berlin Astrochemistry conference.
• Shirley, Y. L. (2015, 2015-12-18). ALMA Observations of Prestellar Cores. NOAO FLASH Lunch. NOAO Tucson, AZ: NOAO.
• Shirley, Y. L. (2014, April). Astrophysics with Submillimeter Galactic Plane Surveys. Univ. of Florida Invited Colloquium. University of Florida, Gainesville: Astronomy Dept..
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  Invited colloquium at The University of Florida
• Shirley, Y. L. (2014, August). The Effective Excitation Density of Molecular Tracers. MPIA PSF Colloquium. MPIA Heidelberg, Germany: Max Planck Institute for Astornomy.
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  Colloquium reviewing the concepts of critical density and the effective excitation density of molecular gas tracers.
• Shirley, Y. L. (2014, December). A Systematic Infall Survey of Starless Cores in Perseus. MPIA PSF Colloquium. MPIA Heidelberg, Germany: Max Planck Institute for Astornomy.
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  MPIA PSF colloquium.
• Shirley, Y. L. (2014, October). A Review of Molecular Tracers of Dense Filaments (NRAO). Filamentary Structure in Molecular Clouds. NRAO Charlottesville, VA: National Radio Astronomy Observatory.
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  Invited review talk.
• Shirley, Y. L. (2014, September). Properties of Clumps in Different Evolutionary Phases in the Bolocam Galactic Plane Survey. From Galactic to Extragalactic Star Formation (Marseille). Marseille, France: ESA.
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  Contributed conference talk.
• Shirley, Y. L. (2014, jan). A Systematic Deuteration Survey in the Gemini OB1 Molecular Cloud. American Astronomical Society Meeting Abstracts.

Creative Productions

• Shirley, Y. L. (2017. Active Galactic Video - VLBA/LBO Dish Walk. YouTube. LBO Station Kitt Peak. https://www.youtube.com/watch?v=1lfXsN45088
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  Organized a dish walk for the Active Galactic Videos team, consulted and contributed to the making of a YouTube video. The video was highlighted by Tom Scott's YouTube channel and has received over 22,000 views.