Buell T. Jannuzi

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Journals/Publications

• Agudo, I., Marscher, A. P., Jorstad, S. G., Larionov, V. M., Gomez, J. L., Lahteenmaki, A., Smith, P. S., Nilsson, K., Readhead, A. C., Aller, M. F., Heidt, J., Gurwell, M., Thum, C., Wehrle, A. E., Nikolashvili, M. G., Aller, H. D., Benitez, E., Blinov, D. A., Hagen-Thorn, V. A., , Hiriart, D., et al. (2024). On the Location of the Gamma-ray Emission in the 2008 Outburst in the BL Lacertae Object AO 0235+164 through Observations across the Electromagnetic Spectrum.
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  We present observations of a major outburst at centimeter, millimeter,optical, X-ray, and gamma-ray wavelengths of the BL Lacertae object AO0235+164. We analyze the timing of multi-waveband variations in the flux andlinear polarization, as well as changes in Very Long Baseline Array (VLBA)images at 7mm with 0.15 milliarcsecond resolution. The association of theevents at different wavebands is confirmed at high statistical significance byprobability arguments and Monte-Carlo simulations. A series of sharp peaks inoptical linear polarization, as well as a pronounced maximum in the 7 mmpolarization of a superluminal jet knot, indicate rapid fluctuations in thedegree of ordering of the magnetic field. These results lead us to concludethat the outburst occurred in the jet both in the quasi-stationary "core" andin the superluminal knot, both parsecs downstream of the supermassive blackhole. We interpret the outburst as a consequence of the propagation of adisturbance, elongated along the line of sight by light-travel time delays,that passes through a standing recollimation shock in the core and propagatesdown the jet to create the superluminal knot. The multi-wavelength light curvesvary together on long time-scales (months/years), but the correspondence ispoorer on shorter time-scales. This, as well as the variability of thepolarization and the dual location of the outburst, agrees with theexpectations of a multi-zone emission model in which turbulence plays a majorrole in modulating the synchrotron and inverse Compton fluxes.[Journal_ref: ]
• Alberts, S., Lee, K., Pope, A., Brodwin, M., Chiang, Y., McKinney, J., Xue, R., Huang, Y., Brown, M., Dey, A., Eisenhardt, P. R., Jannuzi, B. T., Popescu, R., Ramakrishnan, V., Stanford, S. A., & Weiner, B. J. (2024). Measuring the total infrared light from galaxy clusters at z=0.5-1.6: connecting stellar populations to dusty star formation.
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  Massive galaxy clusters undergo strong evolution from z~1.6 to z~0.5, withoverdense environments at high-z characterized by abundant dust-obscured starformation and stellar mass growth which rapidly give way to widespreadquenching. Data spanning the near- to far-infrared (IR) spectrum can directlytrace this transformation; however, such studies have largely been limited tothe massive galaxy end of cluster populations. In this work, we present ``totallight" stacking techniques spanning 3.4-500{\mu}m aimed at revealing the totalcluster IR emission, including low mass members and potential intraclusterdust. We detail our procedures for WISE, Spitzer, and Herschel imaging,including corrections to recover the total stacked emission in the case of highfractions of detected galaxies. We apply our stacking techniques to 232well-studied massive (log M200/Msun~13.8) clusters across multiple z bins,recovering extended cluster emission at all wavelengths, typically at >5sigma.We measure the averaged near- to far-IR radial profiles and SEDs, quantifyingthe total stellar and dust content. The near-IR radial profiles are welldescribed by an NFW model with a high (c~7) concentration parameter. Dustemission is similarly concentrated, albeit suppressed at small radii(r10)cluster galaxies. Separating out the massive galaxy population reveals that themajority of cluster far-IR emission (~70-80%) is provided by the low massconstituents, which differs from field galaxies. This effect may be acombination of mass-dependent quenching and excess dust in low mass clustergalaxies.[Journal_ref: ]
• Alberts, S., Pope, A., Brodwin, M., Atlee, D. W., Lin, Y., Dey, A., Eisenhardt, P. R., Gettings, D. P., Gonzalez, A. H., Jannuzi, B. T., Mancone, C. L., Moustakas, J., Snyder, G. F., Stanford, A. S., Stern, D., Weiner, B. J., & Zeimann, G. R. (2024). The evolution of dust-obscured star formation activity in galaxy clusters relative to the field over the last 9 billion years.
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  We compare the star formation (SF) activity in cluster galaxies to the fieldfrom z=0.3-1.5 using $Herschel$ SPIRE 250$\mu$m imaging. We utilize 274clusters from the IRAC Shallow Cluster Survey (ISCS) selected as rest-framenear-infrared overdensities over the 9 square degree Bootes field . Thisanalysis allows us to quantify the evolution of SF in clusters over a longredshift baseline without bias against active cluster systems. Using a stackinganalysis, we determine the average star formation rates (SFRs) andspecific-SFRs (SSFR=SFR/M$_{\star}$) of stellar mass-limited (M>1.3x10$^{10}$M$_{\odot}$), statistical samples of cluster and field galaxies, probing boththe star forming and quiescent populations. We find a clear indication that theaverage SF in cluster galaxies is evolving more rapidly than in the field, withfield SF levels at z>1.2 in the cluster cores (r0.5 Mpc). Thesegeneral trends in the cluster cores and outskirts are driven by the lower massgalaxies in our sample. Blue cluster galaxies have systematically lower SSFRsthan blue field galaxies, but otherwise show no strong differential evolutionwith respect to the field over our redshift range. This suggests that thecluster environment is both suppressing the star formation in blue galaxies onlong time-scales and rapidly transitioning some fraction of blue galaxies tothe quiescent galaxy population on short time-scales. We argue that our resultsare consistent with both strangulation and ram pressure stripping acting inthese clusters, with merger activity occurring in the cluster outskirts.[Journal_ref: ]
• Alberts, S., Pope, A., Brodwin, M., Chung, S. M., Cybulski, R., Dey, A., Eisenhardt, P., Galametz, A., Gonzalez, A., Jannuzi, B., Stanford, A. S., Snyder, G., Stern, D., & Zeimann, G. (2024). Star Formation and AGN Activity in Galaxy Clusters from $z=1-2$: a Multi-wavelength Analysis Featuring $Herschel$/PACS.
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  We present a detailed, multi-wavelength study of star formation (SF) and AGNactivity in 11 near-infrared (IR) selected, spectroscopically confirmed,massive ($\gtrsim10^{14}\,\rm{M_{\odot}}$) galaxy clusters at $1
• Anugu, N., Durney, O., Morzinski, K. M., Hinz, P., Sivanandam, S., Males, J., Gardner, A., Fellows, C., Montoya, M., West, G., Vaz, A., Mailhot, E., Carlson, J., Chen, S., Lamb, M., Butko, A., Downey, E., Tylor, J., & Jannuzi, B. (2024). Design and development of a high-speed Visible Pyramid Wavefront Sensor for the MMT AO system.
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  MAPS, MMT Adaptive optics exoPlanet characterization System, is the upgradeof legacy 6.5m MMT adaptive optics system. It is an NSF MSIP-funded projectthat includes (i) refurbishing of the MMT Adaptive Secondary Mirror (ASM), (ii)new high sensitive and high spatial order visible and near-infrared pyramidwavefront sensors, and (iii) the upgrade of Arizona Infrared Imager and EchelleSpectrograph (ARIES) and MMT high Precision Imaging Polarimeter (MMTPol)science cameras. This paper will present the design and development of thevisible pyramid wavefront sensor. This system consists of an acquisitioncamera, a fast-steering tip-tilt modulation mirror, a double pyramid, a pupilimaging triplet lens, and a low noise and high-speed frame rate based CCID75camera. We will report on hardware and software and present the laboratorycharacterization results of the individual subsystems, and outline the on-skycommissioning plan.[Journal_ref: ]
• Appleton, P. N., Fadda, D. T., Marleau, F. R., Frayer, D. T., Helou, G., Condon, J. J., Choi, P. I., Yan, L., Lacy, M., Wilson, G., Armus, L., Chapman, S. C., Fang, F., Heinrichson, I., Im, M., Jannuzi, B. T., Storrie-Lombarsi, L. J., Shupe, D., Soifer, B. T., , Squires, G., et al. (2024). The Far- and Mid-Infrared/Radio Correlations in the Spitzer Extragalactic First Look Survey.
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  Using the SPITZER SPACE TELESCOPE and the VLA, we present the first DIRECTevidence that the well-known far-infrared/radio correlation is valid tocosmologically significant redshift. We also confirm, with improved statisticscompared with previous surveys, a similar result for the Mid-IR/radiocorrelation. We explore the dependence of monochromatic q_{24} and q_{70} on z.The results were obtained by matching Spitzer sources at 24 and 70 microns withVLA 1.4 GHz micro-Jy radio sources obtained for the SPITZER FLS. Spectroscopicredshifts have been obtained for over 500 matched IR/radio sources usingobservations at WIYN, Keck and archival SDSS data extending out to z > 2. Wefind that q_{24} shows significantly more dispersion than q_{70}. By comparingthe observed fluxes at 70, 24 and 4.5 microns with a library of SED templates,we find that the larger dispersion in q_{24} is predictable in terms ofsystematic variations in SED shape throughout the population. Although themodels are not able to encompass the full range of observed behavior (both thepresence of either extremely flat or extremely steep IR SEDs), the fittingparameters were used to `k-correct' the higher-z galaxies which resulted in areduced scatter in q. For comparison, we also corrected these data using theSED for M82. The results for 24 and 70 microns provide strong consistentevidence for the universality of the mid-IR/radio and far-IR/radio correlationsout to redshifts of at least z = 1.[Journal_ref: ]
• Ashby, M. L., Stanford, S. A., Brodwin, M., Gonzalez, A. H., Martinez, J., Bartlett, J. G., Benson, B. A., Bleem, L. E., Crawford, T. M., Dey, A., Dressler, A., Eisenhardt, P. R., Galametz, A., Jannuzi, B. T., Marrone, D. P., Mei, S., Muzzin, A., Pacaud, F., Pierre, M., , Stern, D., et al. (2024). The Spitzer-South Pole Telescope Deep Field: Survey Design and IRAC Catalogs.
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  The Spitzer-South Pole Telescope Deep Field (SSDF) is a wide-area surveyusing Spitzer's Infrared Array Camera (IRAC) to cover 94 square degrees ofextragalactic sky, making it the largest IRAC survey completed to date outsidethe Milky Way midplane. The SSDF is centered at 23:30,-55:00, in a region thatcombines observations spanning a broad wavelength range from numerousfacilities. These include millimeter imaging from the South Pole Telescope,far-infrared observations from Herschel/SPIRE, X-ray observations from the XMMXXL survey, near-infrared observations from the VISTA Hemisphere Survey, andradio-wavelength imaging from the Australia Telescope Compact Array, in apanchromatic project designed to address major outstanding questionssurrounding galaxy clusters and the baryon budget. Here we describe theSpitzer/IRAC observations of the SSDF, including the survey design,observations, processing, source extraction, and publicly available dataproducts. In particular, we present two band-merged catalogs, one for each ofthe two warm IRAC selection bands. They contain roughly 5.5 and 3.7 milliondistinct sources, the vast majority of which are galaxies, down to the SSDF5-sigma sensitivity limits of 19.0 and 18.2 Vega mag (7.0 and 9.4 microJy) at3.6 and 4.5 microns, respectively.[Journal_ref: ]
• Beckett, A., Morris, S. L., Fumagalli, M., Tejos, N., Jannuzi, B., & Cantalupo, S. (2024). Modelling gas around galaxy pairs and groups using the Q0107 quasar triplet.
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  We examine to what extent disk and outflow models can reproduce observationsof H I gas within a few virial radii of galaxies in pairs and groups. Usinghighly-sensitive HST/COS and FOS spectra of the Q0107 quasar triplet coveringLy$\alpha$ for z$\lesssim$1, as well as a deep galaxy redshift survey includingVIMOS, DEIMOS, GMOS and MUSE data, we test simple disk and outflow modelsagainst the H I absorption along three lines-of-sight (separated by 200-500kpc) through nine galaxy groups in this field. These can be compared with ourprevious results in which these models can often be fit to the absorptionaround isolated galaxies. Our models can reproduce $\approx$ 75$\%$ of the 28identified absorption components within 500 km/s of a group galaxy, so most ofthe H I around groups is consistent with a superposition of the CGM of theindividual galaxies. Gas stripped in interactions between galaxies may be aplausible explanation for some of the remaining absorption, but neither thegalaxy images nor the galaxy and absorber kinematics provide clear evidence ofsuch stripped material, and these unexplained absorbers do not preferentiallyoccur around close pairs of galaxies. We find H I column densities typicallyhigher than at similar impact parameters around isolated galaxies ($\approx$2.5$\sigma$), as well as more frequent detections of O VI than around isolatedgalaxies (30$\%$ of sightlines to 7$\%$).[Journal_ref: ]
• Beckett, A., Morris, S., Fumagalli, M., Bielby, R., Tejos, N., Schaye, J., Jannuzi, B., & Cantalupo, S. (2024). The relationship between gas and galaxies at z<1 using the Q0107 quasar triplet.
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  We study the distribution and dynamics of the circum- and intergalacticmedium using a dense galaxy survey covering the field around the Q0107 system,a unique z~1 projected quasar triplet. With full Ly$\alpha$ coverage along allthree lines-of-sight from z=0.18 to z=0.73, more than 1200 galaxy spectra, andtwo MUSE fields, we examine the structure of the gas around galaxies on100-1000 kpc scales. We search for H I absorption systems occurring at the sameredshift (within 500 $\textrm{km}$ $\textrm{s}^{-1}$) in multiple sightlines,finding with $>$ 99.9% significance that these systems are more frequent in theobserved quasar spectra than in a randomly distributed population of absorbers.This is driven primarily by absorption with column densities N(H I) $> 10^{14}$$\textrm{cm}^{-2}$, whilst multi-sightline absorbers with lower columndensities are consistent with a random distribution. Star-forming galaxies aremore likely to be associated with multi-sightline absorption than quiescentgalaxies. HST imaging provides inclinations and position angles for a subset ofthese galaxies. We observe a bimodality in the position angle of detectedgalaxy-absorber pairs, again driven mostly by high-column-density absorbers,with absorption preferentially along the major and minor axes of galaxies outto impact parameters of several hundred kpc. We find some evidence supporting adisk/outflow dichotomy, as H I absorbers near the projected major-axis of agalaxy show line-of-sight velocities that tend to align with the rotation ofthat galaxy, whilst minor-axis absorbers are twice as likely to exhibit O VI atthe same redshift.[Journal_ref: ]
• Brand, K., Weedman, D. W., Desai, V., Floc'H, E. L., Armus, L., Dey, A., Houck, J. R., Jannuzi, B. T., Smith, H. A., & Soifer, B. T. (2024). Spitzer Mid-Infrared Spectroscopy of Distant X-ray Luminous AGN.
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  We present mid-infrared spectroscopy of a sample of 16 optically faintinfrared luminous galaxies obtained with the Infrared Spectrograph (IRS) on theSpitzer Space Telescope. These sources were jointly selected from Spitzer andChandra imaging surveys in the NDWFS Bootes field and were selected from theirbright X-ray fluxes to host luminous AGN. None of the spectra show significantemission from polycyclic aromatic hydrocarbons (PAHs; 6.2um equivalent widths
• Brodwin, M., Gonzalez, A. H., Stanford, S. A., Plagge, T., Marrone, D. P., Carlstrom, J. E., Dey, A., Eisenhardt, P. R., Fedeli, C., Gettings, D., Jannuzi, B. T., Joy, M., Leitch, E. M., Mancone, C., Snyder, G. F., Stern, D., & Zeimann, G. (2024). IDCS J1426.5+3508: Sunyaev-Zel'dovich Measurement of a Massive IR-selected Cluster at z=1.75.
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  We report 31 GHz CARMA observations of IDCS J1426.5+3508, aninfrared-selected galaxy cluster at z = 1.75. A Sunyaev-Zel'dovich decrement isdetected towards this cluster, indicating a total mass of M200 = (4.3 +/- 1.1)x 10^{14} Msun in agreement with the approximate X-ray mass of ~5 x 10^{14}Msun. IDCS J1426.5+3508 is by far the most distant cluster yet detected via theSunyaev-Zel'dovich effect, and the most massive z >= 1.4 galaxy cluster foundto date. Despite the mere ~1% probability of finding it in the 8.82 deg^2 IRACDistant Cluster Survey, IDCS J1426.5+3508 is not completely unexpected in LCDMonce the area of large, existing surveys is considered. IDCS J1426.5+3508 is,however, among the rarest, most extreme clusters ever discovered, and indeed isan evolutionary precursor to the most massive known clusters at all redshifts.We discuss how imminent, highly sensitive Sunyaev-Zel'dovich experiments willcomplement infrared techniques for statistical studies of the formation of themost massive galaxy clusters in the z > 1.5 Universe, including potentialprecursors to IDCS J1426.5+3508.[Journal_ref: ]
• Brodwin, M., Stanford, S. A., Gonzalez, A. H., Zeimann, G. R., Snyder, G. F., Mancone, C. L., Pope, A., Eisenhardt, P. R., Stern, D., Alberts, S., Ashby, M. L., Brown, M. J., Chary, R. -., Dey, A., Galametz, A., Gettings, D. P., Jannuzi, B. T., Miller, E. D., Moustakas, J., & Moustakas, L. A. (2024). The Era of Star Formation in Galaxy Clusters.
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  We analyze the star formation properties of 16 infrared-selected,spectroscopically confirmed galaxy clusters at $1 < z < 1.5$ from theSpitzer/IRAC Shallow Cluster Survey (ISCS). We present new spectroscopicconfirmation for six of these high-redshift clusters, five of which are at$z>1.35$. Using infrared luminosities measured with deep Spitzer/MIPSobservations at 24 $\mu$m, along with robust optical+IRAC photometric redshiftsand SED-fitted stellar masses, we present the dust-obscured star-formingfractions, star formation rates and specific star formation rates in theseclusters as functions of redshift and projected clustercentric radius. We findthat $z\sim 1.4$ represents a transition redshift for the ISCS sample, withclear evidence of an unquenched era of cluster star formation at earlier times.Beyond this redshift the fraction of star-forming cluster members increasesmonotonically toward the cluster centers. Indeed, the specific star formationrate in the cores of these distant clusters is consistent with field values atsimilar redshifts, indicating that at $z>1.4$ environment-dependent quenchinghad not yet been established in ISCS clusters. Combining these observationswith complementary studies showing a rapid increase in the AGN fraction, astochastic star formation history, and a major merging episode at the sameepoch in this cluster sample, we suggest that the starburst activity is likelymerger-driven and that the subsequent quenching is due to feedback frommerger-fueled AGN. The totality of the evidence suggests we are witnessing thefinal quenching period that brings an end to the era of star formation ingalaxy clusters and initiates the era of passive evolution.[Journal_ref: ]
• Brodwin, M., Stern, D., Vikhlinin, A., Stanford, S. A., Gonzalez, A. H., Eisenhardt, P. R., Ashby, M. L., Bautz, M., Dey, A., Forman, W. R., Gettings, D., Hickox, R. C., Jannuzi, B. T., Jones, C., Mancone, C., Miller, E. D., Moustakas, L. A., Ruel, J., Snyder, G., & Zeimann, G. (2024). X-Ray Emission from Two Infrared-Selected Galaxy Clusters at z>1.4 in the IRAC Shallow Cluster Survey.
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  We report the X-ray detection of two z>1.4 infrared-selected galaxy clustersfrom the IRAC Shallow Cluster Survey (ISCS). We present new data from theHubble Space Telescope and the W. M. Keck Observatory that spectroscopicallyconfirm cluster ISCS J1432.4+3250 at z=1.49, the most distant of 18 confirmedz>1 clusters in the ISCS to date. We also present new spectroscopy for ISCSJ1438.1+3414, previously reported at z = 1.41, and measure its dynamical mass.Clusters ISCS J1432.4+3250 and ISCS J1438.1+3414 are detected in 36ks and 143ksChandra exposures at significances of 5.2 sigma and 9.7 sigma, from which wemeasure total masses of log(M_{200,Lx}/Msun) = 14.4 +/- 0.2 and14.35^{+0.14}_{-0.11}, respectively. The consistency of the X-ray and dynamicalproperties of these high redshift clusters further demonstrates that the ISCSis robustly detecting massive clusters to at least z = 1.5.[Journal_ref: ]
• Brown, M. J., Jannuzi, B. T., Floyd, D. J., & Mould, J. R. (2024). The Ubiquitous Radio Continuum Emission from the Most Massive Early-Type Galaxies.
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  We have measured the radio continuum emission of 396 early-type galaxiesbrighter than K = 9, using 1.4 GHz imagery from the NRAO VLA Sky Survey, GreenBank 300-ft Telescope and 64-m Parkes Radio Telescope. For M_K < -24 early-typegalaxies, the distribution of radio powers at fixed absolute magnitude spans 4orders of magnitude and the median radio power is proportional to K-bandluminosity to the power 2.78\pm0.16. The measured flux densities of M_K < -25.5early-type galaxies are greater than zero in all cases. It is thus highlylikely that the most massive galaxies always host an active galactic nucleus orhave recently undergone star formation.[Journal_ref: ]
• Brown, M. J., Moustakas, J., Caldwell, N., Palamara, D., Cool, R. J., Dey, A., Hickox, R., Jannuzi, B. T., Murray, S. S., & Zaritsky, D. (2024). Active Galactic Nuclei and the Truncation of Star Formation in K+A Galaxies.
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  We have searched for active galactic nuclei (AGNs) in K+A galaxies, usingmultiwavelength imaging and spectroscopy in the Bootes field of the NOAO DeepWide-Field Survey. The K+A galaxies, which have had their star formationrapidly truncated, are selected via their strong Balmer absorption lines andweak H-alpha emission. Our sample consists of 24 K+A galaxies selected from6594 0.10
• Bussmann, R. S., Dey, A., Armus, L., Brown, M. J., Desai, V., Gonzalez, A. H., Jannuzi, B. T., Melbourne, J., & Soifer, B. T. (2024). The Star-Formation Histories of z~2 DOGs and SMGs.
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  The Spitzer Space Telescope has identified a population of ultra-luminousinfrared galaxies (ULIRGs) at z ~ 2 that may play an important role in theevolution of massive galaxies. We measure the stellar masses of two populationsof Spitzer-selected ULIRGs, both of which have extremely red R-[24] colors(dust-obscured galaxies, or DOGs) and compare our results with sub-millimeterselected galaxies (SMGs). One set of 39 DOGs has a local maximum in theirmid-IR spectral energy distribution (SED) at rest-frame 1.6um associated withstellar emission ("bump DOGs"), while the other set of 51 DOGs has a power-lawdominated mid-IR SED with spectral features typical of obscured AGN ("power-lawDOGs"). We use stellar population synthesis models applied self-consistently tobroad-band photometry in the rest-frame ultra-violet, optical, andnear-infrared of each of these populations and test a variety of stellarpopulation synthesis codes, star-formation histories (SFHs), and initial massfunctions (IMFs). Assuming a simple stellar population SFH and a Chabrier IMF,we find that the median and inner quartile stellar masses of SMGs, bump DOGsand power-law DOGs are given by log(M_*/M_sun) = 10.42_-0.36^+0.42,10.62_-0.32^+0.36, and 10.71_-0.34^+0.40, respectively. Implementing morecomplicated SFHs with multiple age components increases these mass estimates byup to 0.5 dex. Our stellar mass estimates are consistent with physicalmechanisms for the origin of z~2 ULIRGs that result in high star-formationrates for a given stellar mass. Such mechanisms are usually driven by a majormerger of two gas-rich systems, rather than smooth accretion of gas and smallsatellites.[Journal_ref: ]
• Bussmann, R. S., Dey, A., Lotz, J., Armus, L., Brown, M. J., Desai, V., Eisenhardt, P., Higdon, J., Higdon, S., Jannuzi, B. T., Floc'H, L. E., Melbourne, J., Soifer, B. T., & Weedman, D. (2024). HST Morphologies of z ~ 2 Dust-Obscured Galaxies II: Bump Sources.
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  We present Hubble Space Telescope (HST) imaging of 22 ultra-luminous infraredgalaxies (ULIRGs) at z~2 with extremely red R-[24] colors (called dust-obscuredgalaxies, or DOGs) which have a local maximum in their spectral energydistribution (SED) at rest-frame 1.6um associated with stellar emission. Thesesources, which we call "bump DOGs", have star-formation rates of 400-4000Msun/yr and have redshifts derived from mid-IR spectra which show strongpolycyclic aromatic hydrocarbon emission --- a sign of vigorous on-goingstar-formation. Using a uniform morphological analysis, we look forquantifiable differences between bump DOGs, power-law DOGs (Spitzer-selectedULIRGs with mid-IR SEDs dominated by a power-law and spectral features that aremore typical of obscured active galactic nuclei than starbursts),sub-millimeter selected galaxies (SMGs), and other less-reddened ULIRGs fromthe Spitzer extragalactic First Look Survey (XFLS). Bump DOGs are larger thanpower-law DOGs (median Petrosian radius of 8.4 +/- 2.7 kpc vs. 5.5 +/- 2.3 kpc)and exhibit more diffuse and irregular morphologies (median M_20 of -1.08 +/-0.05 vs. -1.48 +/- 0.05). These trends are qualitatively consistent withexpectations from simulations of major mergers in which merging systems duringthe peak star-formation rate period evolve from M_20 = -1.0 to M_20 = -1.7.Less obscured ULIRGs (i.e., non-DOGs) tend to have more regular, centrallypeaked, single-object morphologies rather than diffuse and irregularmorphologies. This distinction in morphologies may imply that less obscuredULIRGs sample the merger near the end of the peak star-formation rate period.Alternatively, it may indicate that the intense star-formation in theseless-obscured ULIRGs is not the result of a recent major merger.[Journal_ref: ]
• Chen, C. J., Hickox, R. C., Alberts, S., Brodwin, M., Jones, C., Murray, S. S., Alexander, D. M., Assef, R. J., Brown, M. J., Dey, A., Forman, W. R., Gorjian, V., Goulding, A. D., Floc'H, E. L., Jannuzi, B. T., Mullaney, J. R., & Pope, A. (2024). A correlation between star formation rate and average black hole accretion in star forming galaxies.
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  We present a measurement of the average supermassive black hole accretionrate (BHAR) as a function of star formation rate (SFR) for galaxies in theredshift range 0.25
• Chung, S. M., Kochanek, C. S., Assef, R., Brown, M. J., Stern, D., Jannuzi, B. T., Gonzalez, A. H., Hickox, R. C., & Moustakas, J. (2024). A UV to Mid-IR Study of AGN Selection.
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  We classify the spectral energy distributions (SEDs) of 431,038 sources inthe 9 sq. deg Bootes field of the NOAO Deep Wide-Field Survey (NDWFS). Thereare up to 17 bands of data available per source, including ultraviolet (GALEX),optical (NDWFS), near-IR (NEWFIRM), and mid-infrared (IRAC/MIPS) data, as wellas spectroscopic redshifts for ~20,000 objects, primarily from the AGN andGalaxy Evolution Survey (AGES). We fit galaxy, AGN, stellar, and brown dwarftemplates to the observed SEDs, which yield spectral classes for the Galacticsources and photometric redshifts and galaxy/AGN luminosities for theextragalactic sources. The photometric redshift precision of the galaxy and AGNsamples are sigma/(1+z)=0.040 and sigma/(1+z)=0.169, respectively, with theworst 5% outliers excluded. Based on the reduced chi-squared of the SED fit foreach SED model, we are able to distinguish between Galactic and extragalacticsources for sources brighter than I=23.5. We compare the SED fits for agalaxy-only model and a galaxy+AGN model. Using known X-ray and spectroscopicAGN samples, we confirm that SED fitting can be successfully used as a methodto identify large populations of AGN, including spatially resolved AGN withsignificant contributions from the host galaxy and objects with the emissionline ratios of "composite" spectra. We also use our results to compare to theX-ray, mid-IR, optical color and emission line ratio selection techniques. Foran F-ratio threshold of F>10 we find 16,266 AGN candidates brighter than I=23.5and a surface density of ~1900 AGN per deg^2.[Journal_ref: ]
• Churchill, C. W., Mellon, R. R., Charlton, J. C., Jannuzi, B. T., Kirhakos, S., Steidel, C. C., & Schneider, D. P. (2024). Low and High Ionization Absorption Properties of Mg II Absorption-Selected Galaxies at Intermediate Redshifts. II. Taxonomy, Kinematics, and Galaxies.
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  [Abridged] We examine a sample of 45 Mg II absorption-selected systems overthe redshift range 0.4 to 1.4. Mg II and Fe II absorption profiles wereobserved at a resolution of ~6 km/s with HIRES/Keck. Lyman-alpha and C IV datawere measured in archival FOS/HST spectra (~230 km/s). We perform amultivariate analysis of W(MgII), W(FeII), W(CIV) and W(Lya) (rest-frame)equivalent widths and the Mg II kinematic spread. We find five categories of MgII absorbers: "Classic", "C IV-deficient", "Single/Weak", "Double", and"DLA/HI-Rich". There is a strong connection between low-ionization kinematicsand the location of an absorber on the W(CIV)-W(MgII) plane. In most absorbersa significant fraction of the C IV arises in a phase separate from Mg II. Manyof the C IV profiles are resolved in the FOS spectra due to velocitystructure.. For 16 galaxies, we compare the available absorption-lineproperties (taken from Churchill et al. 2000, Paper I) to the galaxy propertiesbut find no significant (greater than 3-sigma) correlations, although severalsuggestive trends are apparent. We compare the locations of our intermediateredshift absorbers on the W(CIV)-W(MgII) plane with those of lower and higherredshift data taken from the literature and find evidence for evolution that isconnected with the Mg II kinematics. We discuss the potential of using theabove categorizations of absorbers to understand the evolution in theunderlying physical processes giving rise to the gas and governing itsionization phases and kinematics.[Journal_ref: ]
• Churchill, C. W., Mellon, R. R., Charlton, J. C., Jannuzi, B. T., Kirhakos, S., Steidel, C. C., & Schneider, D. P. (2024). The CIV-MgII Kinematics Connection in ~0.7 Galaxies.
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  We have examined Faint Object Spectrograph data from the Hubble SpaceTelescope Archive for CIV 1548,1550 absorption associated with 40 MgII2796,2803 absorption-selected galaxies at 0.4 < z < 1.4. We report a strongcorrelation between MgII kinematics, measured in 6 km/s resolution HIRES/Keckspectra, and W_r(1548); this implies a physical connection between theprocesses that produce "outlying velocity" MgII clouds and high ionizationgalactic/halo gas. We found no trend in ionization condition,W_r(1548)/W_r(2796), with galaxy-QSO line-of-sight separation for 13 systemswith confirmed associated galaxies, suggesting no obvious ionization gradientwith galactocentric distance in these higher redshift galaxies. We findtentative evidence (2-sigma) that W_r(1548)/W_r(2796) is anti-correlated withgalaxy color; if further data corroborate this trend, in view of thestrong CIV-MgII kinematics correlation, it could imply a connection betweenstellar populations, star formation episodes, and the kinematics and ionizationconditions of halo gas at z~1.[Journal_ref: ]
• Cool, R. J., Eisenstein, D. J., Kochanek, C. S., Brown, M. J., Caldwell, N., Dey, A., Forman, W. R., Hickox, R. C., Jannuzi, B. T., Jones, C., Moustakas, J., & Murray, S. S. (2024). The Galaxy Optical Luminosity Function from the AGN and Galaxy Evolution Survey (AGES).
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  We present the galaxy optical luminosity function for the redshift range0.05
• Crighton, N. H., Bechtold, J., Carswell, R. F., Davé, R., Foltz, C. B., Jannuzi, B. T., Morris, S. L., O'Meara, J. M., Prochaska, X. J., Schaye, J., & Tejos, N. (2024). A high molecular fraction in a sub-damped absorber at z=0.56.
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  Measuring rest-frame ultraviolet rotational transitions from the Lyman andWerner bands in absorption against a bright background continuum is one of thefew ways to directly measure molecular hydrogen (H2). Here we report thedetection of Lyman-Werner absorption from H2 at z=0.56 in a sub-damped Ly-alphasystem with neutral hydrogen column density N(HI) = 10^(19.5 +/- 0.2) cm^-2.This is the first H2 system analysed at a redshift < 1.5 beyond the Milky Wayhalo. It has a surprisingly high molecular fraction: log f(H2) > -1.93 +/- 0.36based on modelling the line profiles, with a robust model-independent lowerlimit of f(H2) > 10^-3. This is higher than f(H2) values seen along sightlineswith similar N(HI) through the Milky Way disk and the Magellanic clouds. Themetallicity of the absorber is 0.19 +0.21 -0.10 solar, with a dust-to-gas ratio< 0.36 times the value in the solar neighbourhood. Absorption from associatedlow-ionisation metal transitions such as OI and FeII is observed in addition toOVI. Using Cloudy models we show that there are three phases present; a ~100 Kphase giving rise to H2, a ~10^4 K phase where most of the low-ionisation metalabsorption is produced; and a hotter phase associated with OVI. Based onsimilarities to high velocity clouds in the Milky Way halo showing H2 and thepresence of two nearby galaxy candidates with impact parameters of ~10 kpc, wesuggest that the absorber may be produced by a tidally-stripped structuresimilar to the Magellanic Stream.[Journal_ref: ]
• Crighton, N. H., Morris, S. L., Bechtold, J., Crain, R. A., Jannuzi, B. T., Shone, A., & Theuns, T. (2024). Galaxies at Redshift ~0.5 Around Three Closely Spaced Quasar Sightlines.
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  We examine the relationship between galaxies and the intergalactic medium atz < 1 using a group of three closely spaced background QSOs with z_em ~1observed with the Hubble Space Telescope. Using a new grouping algorithm, weidentify groups of galaxies and absorbers across the three QSO sightlines thatmay be physically linked. There is an excess number of such groups compared tothe number we expect from a random distribution of absorbers at a confidencelevel of 99.9%. The same search is performed with mock spectra generated usinga hydrodynamic simulation, and we find the vast majority of such groups arisein dense regions of the simulation. We find that at z
• Croft, S., van Breugel, W., Brown, M. J., de Vries, W., Dey, A., Eisenhardt, P., Jannuzi, B., Röttgering, H., Stanford, S. A., Stern, D., & Willner, S. P. (2024). Radio-loud high-redshift protogalaxy candidates in Bootes.
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  We used the Near Infrared Camera on Keck I to obtain Ks-band images of fourcandidate high-redshift radio galaxies selected using optical and radio data inthe NOAO Deep Wide-Field Survey in Bootes. Our targets have 1.4 GHz radio fluxdensities greater than 1 mJy, but are undetected in the optical to fainter than24 Vega mag. Spectral energy distribution fitting suggests that three of theseobjects are at z > 3, with radio luminosities near the FR-I / FR-II break. Theother has photometric redshift 1.2, but may in fact be at higher redshift. Twoof the four objects exhibit diffuse morphologies in Ks -band, suggesting thatthey are still in the process of forming.[Journal_ref: ]
• Dawson, K. S., Aldering, G., Amanullah, R., Barbary, K., Barrientos, L. F., Brodwin, M., Connolly, N., Dey, A., Doi, M., Donahue, M., Eisenhardt, P., Ellingson, E., Faccioli, L., Fadeyev, V., Fakhouri, H. K., Fruchter, A. S., Gilbank, D. G., Gladders, M. D., Goldhaber, G., , Gonzalez, A. H., et al. (2024). An Intensive HST Survey for z>1 Supernovae by Targeting Galaxy Clusters. Astronomical Journal, Volume, 1271-1283.
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  We present a new survey strategy to discover and study high redshift Type Iasupernovae (SNe Ia) using the Hubble Space Telescope (HST). By targetingmassive galaxy clusters at 0.9
• Dawson, S., Rhoads, J. E., Malhotra, S., Stern, D., Wang, J., Dey, A., Spinrad, H., & Jannuzi, B. T. (2024). A Luminosity Function of Lyman Alpha Emitting Galaxies at Redshift 4.5.
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  We present a catalog of 59 z=4.5 Lyman alpha emitting galaxiesspectroscopically confirmed in a campaign of Keck/DEIMOS follow-up observationsto candidates selected in the Large Area Lyman Alpha (LALA) narrow-band imagingsurvey. We targeted 97 candidates for spectroscopic follow-up; by accountingfor the variety of conditions under which we performed spectroscopy, weestimate a selection reliability of about 76%. Together with our previoussample of Keck/LRIS confirmations, the 59 sources confirmed herein bring thetotal catalog to 73 spectroscopically confirmed z=4.5 Lyman alpha emittinggalaxies in the 0.7 square degrees covered by the LALA imaging. As with theKeck/LRIS sample, we find that a non-negligible fraction of the confirmed Lymanalpha lines have rest-frame equivalent widths (w_{rest}) which exceed themaximum predicted for normal stellar populations: 17% -- 31% (93% confidence)of the detected galaxies show w_{rest} > 190 AA, and 12% -- 27% (90%confidence) show w_{rest} > 240 AA. We construct a luminosity function of z=4.5Lyman alpha emission lines for comparison to Lyman alpha luminosity functionsspanning 3.1 < z < 6.6. We find no significant evidence for Lyman alphaluminosity function evolution from z ~ 3 to z ~ 6. This result supports theconclusion that the intergalactic medium remains largely reionized from thelocal universe out to z=6.5. It is somewhat at odds with the pronounced drop inthe cosmic star formation rate density recently measured between z~3 and z~6 incontinuum-selected Lyman-break galaxies, and therefore potentially sheds lighton the relationship between the two populations.[Journal_ref: ]
• Desai, V., Soifer, B. T., Dey, A., Floc'H, E. L., Armus, L., Brand, K., Brown, M. J., Brodwin, M., Jannuzi, B. T., Houck, J. R., Weedman, D. W., Ashby, M. L., Gonzalez, A., Huang, J., Smith, H. A., Teplitz, H., Willner, S. P., & Melbourne, J. (2024). Strong PAH Emission from z~2 ULIRGs. Astrophys.J., 700, 1190-1204.
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  Using the Infrared Spectrograph on board the Spitzer Space Telescope, wepresent low-resolution (64 < lambda / dlambda < 124), mid-infrared (20-38micron) spectra of 23 high-redshift ULIRGs detected in the Bootes field of theNOAO Deep Wide-Field Survey. All of the sources were selected to have 1) fnu(24micron) > 0.5 mJy; 2) R-[24] > 14 Vega mag; and 3) a prominent rest-frame 1.6micron stellar photospheric feature redshifted into Spitzer's 3-8 micron IRACbands. Of these, 20 show emission from polycyclic aromatic hydrocarbons (PAHs),usually interpreted as signatures of star formation. The PAH features indicateredshifts in the range 1.5 < z < 3.0, with a mean of =1.96 and a dispersionof 0.30. Based on local templates, these sources have extremely large infraredluminosities, comparable to that of submillimeter galaxies. Our results confirmprevious indications that the rest-frame 1.6 micron stellar bump can beefficiently used to select highly obscured starforming galaxies at z~2, andthat the fraction of starburst-dominated ULIRGs increases to faint 24 micronflux densities. Using local templates, we find that the observed narrowredshift distribution is due to the fact that the 24 micron detectability ofPAH-rich sources peaks sharply at z = 1.9. We can analogously explain thebroader redshift distribution of Spitzer-detected AGN-dominated ULIRGs based onthe shapes of their SEDs. Finally, we conclude that z~2 sources with adetectable 1.6 micron stellar opacity feature lack sufficient AGN emission toveil the 7.7 micron PAH band.[Journal_ref: Astrophys.J.700:1190-1204,2009]
• Desai, V., Soifer, B. T., Dey, A., Jannuzi, B. T., Floc'H, E. L., Bian, C., Brand, K., Brown, M. J., Armus, L., Weedman, D. W., Cool, R., Stern, D., & Brodwin, M. (2024). Redshift Distribution of Extragalactic 24 micron Sources.
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  We present the redshift distribution of a complete, unbiased sample of 24micron sources down to fnu(24 micron) = 300 uJy (5-sigma). The sample consistsof 591 sources detected in the Bootes field of the NOAO Deep Wide-Field Survey.We have obtained optical spectroscopic redshifts for 421 sources (71%). Thesehave a redshift distribution peaking at z~0.3, with a possible additional peakat z~0.9, and objects detected out to z=4.5. The spectra of the remaining 170(29%) exhibit no strong emission lines from which to determine a redshift. Wedevelop an algorithm to estimate the redshift distribution of these sources,based on the assumption that they have emission lines but that these lines arenot observable due to the limited wavelength coverage of our spectroscopicobservations. The redshift distribution derived from all 591 sources exhibitsan additional peak of extremely luminous (L(8-1000 micron) > 3 x 10^{12} Lsun)objects at z~2, consisting primarily of sources without observable emissionlines. We use optical line diagnostics and IRAC colors to estimate that 55% ofthe sources within this peak are AGN-dominated. We compare our results topublished models of the evolution of infrared luminous galaxies. The modelswhich best reproduce our observations predict a large population ofstar-formation dominated ULIRGs at z > 1.5 rather than the AGN-dominatedsources we observe.[Journal_ref: ]
• Dey, A., Lee, K., Reddy, N., Cooper, M., Inami, H., Hong, S., Gonzalez, A. H., & Jannuzi, B. T. (2024). Spectroscopic Confirmation of a Protocluster at z=3.786.
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  We present new observations of the field containing the z=3.786 protocluster,PC217.96+32.3. We confirm that it is one of the largest and most overdensehigh-redshift structures known. Such structures are rare even in the largestcosmological simulations. We used the Mayall/MOSAIC1.1 imaging camera to imagea 1.2x0.6 deg area (~150x75 comoving Mpc) surrounding the protocluster's coreand discovered 165 candidate Lyman Alpha emitting galaxies (LAEs) and 788candidate Lyman Break galaxies (LBGs). There are at least 2 overdense regionstraced by the LAEs, the largest of which shows an areal overdensity in its core(i.e., within a radius of 2.5 comoving Mpc) of 14+/-7 relative to the averageLAE spatial density in the imaged field. Further, the average LAE spatialdensity in the imaged field is twice that derived by other field LAE surveys.Spectroscopy with Keck/DEIMOS yielded redshifts for 164 galaxies (79 LAEs and85 LBGs); 65 lie at a redshift of 3.785+/-0.010. The velocity dispersion ofgalaxies near the core is 350+/-40 km/s, a value robust to selection effects.The overdensities are likely to collapse into systems with present-day massesof >10^{15} solar masses and >6x10^{14} solar masses. The low velocitydispersion may suggest a dynamically young protocluster. We find a weak trendbetween narrow-band (Lyman Alpha) luminosity and environmental density: theLyman Alpha luminosity is enhanced on average by 1.35X within the protoclustercore. There is no evidence that the Lyman Alpha equivalent width depends onenvironment. These suggest that star-formation and/or AGN activity is enhancedin the higher density regions of the structure. PC217.96+32.3 is a Coma clusteranalog, witnessed in the process of formation.[Journal_ref: ]
• Dey, A., Schlegel, D. J., Lang, D., Blum, R., Burleigh, K., Fan, X., Findlay, J. R., Finkbeiner, D., Herrera, D., Juneau, S., Landriau, M., Levi, M., McGreer, I., Meisner, A., Myers, A. D., Moustakas, J., Nugent, P., Patej, A., Schlafly, E. F., , Walker, A. R., et al. (2024). Overview of the DESI Legacy Imaging Surveys.
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  The DESI Legacy Imaging Surveys are a combination of three public projects(the Dark Energy Camera Legacy Survey, the Beijing-Arizona Sky Survey, and theMayall z-band Legacy Survey) that will jointly image approximately 14,000 deg^2of the extragalactic sky visible from the northern hemisphere in three opticalbands (g, r, and z) using telescopes at the Kitt Peak National Observatory andthe Cerro Tololo Inter-American Observatory. The combined survey footprint issplit into two contiguous areas by the Galactic plane. The optical imaging isconducted using a unique strategy of dynamically adjusting the exposure timesand pointing selection during observing that results in a survey of nearlyuniform depth. In addition to calibrated images, the project is delivering acatalog, constructed by using a probabilistic inference-based approach toestimate source shapes and brightnesses. The catalog includes photometry fromthe grz optical bands and from four mid-infrared bands (at 3.4, 4.6, 12 and 22micorons) observed by the Wide-field Infrared Survey Explorer (WISE) satelliteduring its full operational lifetime. The project plans two public datareleases each year. All the software used to generate the catalogs is alsoreleased with the data. This paper provides an overview of the Legacy Surveysproject.[Journal_ref: ]
• Dey, A., Soifer, B. T., Desai, V., Brand, K., LeFloc'h, E., Brown, M. J., Jannuzi, B. T., Armus, L., Bussmann, S., Brodwin, M., Bian, C., Eisenhardt, P., Higdon, S., Weedman, D., & Willner, S. (2024). A Significant Population of Very Luminous Dust-Obscured Galaxies at Redshift z ~ 2.
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  Observations with Spitzer Space Telescope have recently revealed asignificant population of high-redshift z~2 dust-obscured galaxies (DOGs) withlarge mid-IR to UV luminosity ratios. These galaxies have been missed intraditional optical studies of the distant universe. We present a simple methodfor selecting this high-z population based solely on the ratio of the observedmid-IR 24um to optical R-band flux density. In the 8.6 sq.deg Bootes NDWFSField, we uncover ~2,600 DOG candidates (= 0.089/sq.arcmin) with 24um fluxdensities F24>0.3mJy and (R-[24])>14 (i.e., F[24]/F[R] > 1000). These galaxieshave no counterparts in the local universe, and become a larger fraction of thepopulation at fainter F24, representing 13% of the sources at 0.3~mJy. DOGsexhibit evidence of both star-formation and AGN activity, with the brighter24um sources being more AGN- dominated. We have measured spectroscopicredshifts for 86 DOGs, and find a broad z distribution centered at ~2.0.Their space density is 2.82E-5 per cubic Mpc, similar to that of brightsub-mm-selected galaxies at z~2. These redshifts imply very large luminositiesLIR>~1E12-14 Lsun. DOGs contribute ~45-100% of the IR luminosity densitycontributed by all z~2 ULIRGs, suggesting that our simple selection criterionidentifies the bulk of z~2 ULIRGs. DOGs may be the progenitors of ~4L*present-day galaxies seen undergoing a luminous,short- lived phase of bulge andblack hole growth. They may represent a brief evolution phase between SMGs andless obscured quasars or galaxies. [Abridged][Journal_ref: ]
• Dolley, T., Brown, M. J., Weiner, B. J., Brodwin, M., Kochanek, C. S., Pimbblet, K. A., Palamara, D. P., Jannuzi, B. T., Dey, A., Atlee, D. W., & Beare, R. (2024). The Clustering and Halo Masses of Star Forming Galaxies at z<1.
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  We present clustering measurements and halo masses of star forming galaxiesat 0.2 < z < 1.0. After excluding AGN, we construct a sample of 22553 24 {\mu}msources selected from 8.42 deg^2 of the Spitzer MIPS AGN and Galaxy EvolutionSurvey of Bo\"otes. Mid-infrared imaging allows us to observe galaxies with thehighest star formation rates (SFRs), less biased by dust obscuration afflictingthe optical bands. We find that the galaxies with the highest SFRs have opticalcolors which are redder than typical blue cloud galaxies, with many residingwithin the green valley. At z > 0.4 our sample is dominated by luminousinfrared galaxies (LIRGs, L_TIR > 10^11 Lsun) and is comprised entirely ofLIRGs and ultra-luminous infrared galaxies (ULIRGs, L_TIR > 10^12 Lsun) at z >0.6. We observe weak clustering of r_0 = 3-6 Mpc/h for almost all of our starforming samples. We find that the clustering and halo mass depend on L_TIR atall redshifts, where galaxies with higher L_TIR (hence higher SFRs) havestronger clustering. Galaxies with the highest SFRs at each redshift typicallyreside within dark matter halos of M_halo ~ 10^12.9 Msun/h. This is consistentwith a transitional halo mass, above which star formation is largely truncated,although we cannot exclude that ULIRGs reside within higher mass halos. Bymodeling the clustering evolution of halos, we connect our star forming galaxysamples to their local descendants. Most star forming galaxies at z < 1.0 arethe progenitors of L < 2.5L* blue galaxies in the local universe, but starforming galaxies with the highest SFRs (L_TIR >10^11.7 Lsun) at 0.6
• Douglas, E. S., Aldering, G., Allan, G. W., Anche, R., Angel, R., Ard, C. C., Chakrabarti, S., Close, L. M., Derby, K., Edelstein, J., Ford, J., Gersh-Range, J., Haffert, S. Y., Ingraham, P. J., Kang, H., Kelly, D. M., Kim, D., Lesser, M., Leisenring, J. M., , Lin, Y., et al. (2024). Approaches to lowering the cost of large space telescopes.
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  New development approaches, including launch vehicles and advances insensors, computing, and software, have lowered the cost of entry into space,and have enabled a revolution in low-cost, high-risk Small Satellite (SmallSat)missions. To bring about a similar transformation in larger space telescopes,it is necessary to reconsider the full paradigm of space observatories. Here wewill review the history of space telescope development and cost drivers, anddescribe an example conceptual design for a low cost 6.5 m optical telescope toenable new science when operated in space at room temperature. It uses amonolithic primary mirror of borosilicate glass, drawing on lessons and toolsfrom decades of experience with ground-based observatories and instruments, aswell as flagship space missions. It takes advantage, as do large launchvehicles, of increased computing power and space-worthy commercial electronicsin low-cost active predictive control systems to maintain stability. We willdescribe an approach that incorporates science and trade study results thataddress driving requirements such as integration and testing costs,reliability, spacecraft jitter, and wavefront stability in this newrisk-tolerant "LargeSat" context.[Journal_ref: ]
• Eisenhardt, P. R., Stern, D., Brodwin, M., Fazio, G. G., Rieke, G. H., Rieke, M. J., Werner, M. W., Wright, E. L., Allen, L. E., Arendt, R. G., Ashby, M. L., Barmby, P., Forrest, W. J., Hora, J. L., Huang, J. -., Huchra, J., Pahre, M. A., Pipher, J. L., Reach, W. T., , Smith, H. A., et al. (2024). The IRAC Shallow Survey.
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  The IRAC shallow survey covers 8.5 square degrees in the NOAO Deep Wide-FieldSurvey in Bootes with 3 or more 30 second exposures per position. An overviewof the survey design, reduction, calibration, star-galaxy separation, andinitial results is provided. The survey includes approximately 370,000,280,000, 38,000, and 34,000 sources brighter than the 5 sigma limits of 6.4,8.8, 51, and 50 microJy at 3.6, 4.5, 5.8, and 8 microns respectively, includingsome with unusual spectral energy distributions.[Journal_ref: ]
• Fadda, D., Jannuzi, B., Ford, A., & Storrie-Lombardi, L. J. (2024). The Spitzer Space Telescope First-Look Survey: KPNO MOSAIC-1 R-band Images and Source Catalogs.
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  (Abridged) We present R-band images covering more than 11 square degrees ofsky obtained with the KPNO 4-m telescope in preparation for the Spitzer SpaceTelescope First Look Survey. The FLS was designed to characterize themid-infrared sky at depths 2 orders of magnitude deeper than previous surveys.The extragalactic component is the first cosmological survey done with Spitzer.Two relatively large regions of the sky were observed: the main FLS extragalactic field (17h18m+59d30m) and ELAIS-N1 field (16h10m+54d30m). The overall quality of the images is high. The relative astrometric accuracyis better than 0.1'' and the typical seeing is 1.1''. Images are relativelydeep since they reach a median 5-sigma depth limiting magnitude of R=25.5(Vega). Catalogs have been extracted using SExtractor using thresholds in areaand flux for which the number of false detections is below 1% at R=25. Onlysources with S/N greater than 3 have been retained in the final catalogs.Comparing the galaxy number counts from our images with those of deeper R-bandsurveys, we estimate that our observations are 50% complete at R=24.5. Theselimits in depth are sufficient to identify a substantial fraction of theinfrared sources which will be detected by Spitzer.[Journal_ref: ]
• Finkelstein, K. D., Finkelstein, S. L., Tilvi, V., Malhotra, S., Rhoads, J. E., Grogin, N. A., Pirzkal, N., Dey, A., Jannuzi, B. T., Mobasher, B., Pakzad, S., Salmon, B., & Wang, J. (2024). Probing the Physical Properties of z=4.5 Lyman Alpha Emitters with Spitzer.
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  We present the results from a stellar population modeling analysis of asample of 162 z=4.5, and 14 z=5.7 Lyman alpha emitting galaxies (LAEs) in theBootes field, using deep Spitzer/IRAC data at 3.6 and 4.5 um from the SpitzerLyman Alpha Survey, along with Hubble Space Telescope NICMOS and WFC3 imagingat 1.1 and 1.6 um for a subset of the LAEs. This represents one of the largestsamples of high-redshift LAEs imaged with Spitzer IRAC. We find that 30/162(19%) of the z=4.5 LAEs and 9/14 (64%) of the z=5.7 LAEs are detected at>3-sigma in at least one IRAC band. Individual z=4.5 IRAC-detected LAEs have alarge range of stellar mass, from 5x10^8 to 10^11 Msol. One-third of theIRAC-detected LAEs have older stellar population ages of 100 Myr - 1 Gyr, whilethe remainder have ages < 100 Myr. A stacking analysis of IRAC-undetected LAEsshows this population to be primarily low mass (8 -- 20 x 10^8 Msol) and young(64 - 570 Myr). We find a correlation between stellar mass and thedust-corrected ultraviolet-based star-formation rate (SFR) similar to that atlower redshifts, in that higher mass galaxies exhibit higher SFRs. However, thez=4.5 LAE correlation is elevated 4-5 times in SFR compared tocontinuum-selected galaxies at similar redshifts. The exception is the mostmassive LAEs which have SFRs similar to galaxies at lower redshifts suggestingthat they may represent a different population of galaxies than the traditionallower-mass LAEs, perhaps with a different mechanism promoting Lyman alphaphoton escape.[Journal_ref: ]
• Galametz, A., Stern, D., Eisenhardt, P. R., Brodwin, M., Brown, M. J., Dey, A., Gonzalez, A. H., Jannuzi, B. T., Moustakas, L. A., & Stanford, A. S. (2024). The Cosmic Evolution of AGN in galaxy clusters. Astrophys.J., 694, 1309-1316.
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  We present the surface density of luminous active galactic nuclei (AGN)associated with a uniformly selected galaxy cluster sample identified in the8.5 square degree Bootes field of the NOAO Deep Wide-Field Survey. The clustersare distributed over a large range of redshift (0 < z < 1.5) and we identifyAGN using three different selection criteria: mid-IR color, radio luminosity,and X-ray luminosity. Relative to the field, we note a clear overdensity of thenumber of AGN within 0.5 Mpc of the cluster centers at z > 0.5. The amplitudeof this AGN overdensity increases with redshift. Although there are significantdifferences between the AGN populations probed by each selection technique, therise in cluster AGN surface density generally increases more steeply than thatof field quasars. In particular, X-ray selected AGN are at least three timesmore prevalent in clusters at 1 < z < 1.5 compared to clusters at 0.5 < z < 1.This effect is stronger than can be explained by the evolving median richnessof our cluster sample. We thus confirm the existence of a Butcher-Oemler typeeffect for AGN in galaxy clusters, with the number of AGN in clustersincreasing with redshift.[Journal_ref: Astrophys.J.694:1309-1316,2009]
• Glikman, E., Bogosavljevic, M., Djorgovski, S. G., Stern, D., Dey, A., Jannuzi, B. T., & Mahabal, A. (2024). The Faint End of the Quasar Luminosity Function at z~4. Astrophys.J., 710, 1498-1514.
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  We have conducted a spectroscopic survey to find faint quasars (-26.0
• Glikman, E., Djorgovski, S. G., Stern, D., Dey, A., Jannuzi, B. T., & Lee, K. (2024). The Faint End of the Quasar Luminosity Function at z~4: Implications for Ionization of the Intergalactic Medium and Cosmic Downsizing.
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  We present an updated determination of the z ~ 4 QSO luminosity function(QLF), improving the quality of the determination of the faint end of the QLFpresented in Glikman et al. (2010). We have observed an additional 43candidates from our survey sample, yielding one additional QSO at z = 4.23 andincreasing the completeness of our spectroscopic follow-up to 48% forcandidates brighter than R = 24 over our survey area of 3.76 deg2. We study theeffect of using K-corrections to compute the rest-frame absolute magnitude at1450A compared with measuring M1450 directly from the object spectra. We find aluminosity-dependent bias: template-based K-corrections overestimate theluminosity of low-luminosity QSOs, likely due to their reliance on templatesderived from higher luminosity QSOs. Combining our sample with bright quasarsfrom the Sloan Digital Sky Survey and using spectrum-based M1450 for all thequasars, we fit a double-power-law to the binned QLF. Our best fit has abright-end slope, {\alpha} = 3.3\pm0.2, and faint-end slope, {\beta} =1.6(+0.8/-0.6). Our new data revise the faint-end slope of the QLF down toflatter values similar to those measured at z ~ 3. The break luminosity, thoughpoorly constrained, is at M* = -24.1(+0.7/-1.9), approximately 1 - 1.5 magfainter than at z ~ 3. This QLF implies that QSOs account for about half theradiation needed to ionize the IGM at these redshifts.[Journal_ref: ]
• Gorjian, V., Brodwin, M., Kochanek, C. S., Murray, S., Stern, D., Brand, K., Eisenhardt, P. R., Ashby, M. L., Barmby, P., Brown, M. J., Dey, A., Forman, W., Jannuzi, B. T., Jones, C., Kenter, A. T., Pahre, M. A., Shields, J. C., Werner, M. W., & Willner, S. P. (2024). The Mid-Infrared Properties of X-ray Sources.
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  We combine the results of the Spitzer IRAC Shallow Survey and the ChandraXBootes Survey of the 8.5 square degrees Bootes field of the NOAO Deep Wide-Field Survey to produce the largest comparison of mid-IR and X-ray sources todate. The comparison is limited to sources with X-ray fluxes >8x10-15 ergcm-2s-1 in the 0.5-7.0 keV range and mid-IR sources with 3.6 um fluxes brighterthan 18.4 mag (12.3 uJy). In this most sensitive IRAC band, 85% of the 3086X-ray sources have mid-IR counterparts at an 80% confidence level based on aBayesian matching technique. Only 2.5% of the sample have no IRAC counterpartat all based on visual inspection. Even for a smaller but a significantlydeeper Chandra survey in the same field, the IRAC Shallow Survey recovers mostof the X-ray sources. A majority (65%) of the Chandra sources detected in allfour IRAC bands occupy a well-defined region of IRAC [3.6] - [4.5] vs [5.8] -[8.0] color-color space. These X-ray sources are likely infrared luminous,unobscured type I AGN with little mid-infrared flux contributed by the AGN hostgalaxy. Of the remaining Chandra sources, most are lower luminosity type I andtype II AGN whose mid-IR emission is dominated by the host galaxy, whileapproximately 5% are either Galactic stars or very local galaxies.[Journal_ref: ]
• Graur, O., Poznanski, D., Maoz, D., Yasuda, N., Totani, T., Fukugita, M., Filippenko, A. V., Foley, R. J., Silverman, J. M., Gal-Yam, A., Horesh, A., & Jannuzi, B. T. (2024). Supernovae in the Subaru Deep Field: the rate and delay-time distribution of type Ia supernovae out to redshift 2.
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  The type Ia supernova (SN Ia) rate, when compared to the cosmic starformation history (SFH), can be used to derive the delay-time distribution(DTD) of SNe Ia, which can distinguish among progenitor models. We present theresults of a SN survey in the Subaru Deep Field (SDF). Over a period of 3years, we have observed the SDF on 4 independent epochs with Suprime-Cam on theSubaru 8.2-m telescope, with 2 nights of exposure per epoch, in the R, i', andz' bands. We have discovered 150 SNe out to redshift z~2. Using 11 photometricbands from the observer-frame far-ultraviolet to the near-infrared, we derivephotometric redshifts for the SN host galaxies (for 24 we also havespectroscopic redshifts). This information is combined with the SN photometryto determine the type and redshift distribution of the SN sample. Our finalsample includes 28 SNe Ia in the range 1.0
• Green, P. J., Kochanek, C., Siemiginowska, A., Kim, D., Markevitch, M., Silverman, J., Dosaj, A., Jannuzi, B. T., & Smith, C. (2024). Chandra Observations of the QSO Pair Q2345+007: Binary Quasar or Massive Dark Lens?.
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  The components of the wide (7.3") separation quasar pair Q2345+007A,B(z=2.15) have the most strikingly similar optical spectra seen to date (Steidel& Sargent 1991) yet no detected lensing mass, making this system the bestcandidate known for a massive (1e14 Msun) dark matter lens system. Here wepresent results from a 65ksec Chandra observation designed to investigatewhether it is a binary quasar or a gravitational lens. We find no X-rayevidence for a lensing cluster to a (0.5-2keV) flux limit of 2e-15 cgs, whichis consistent with lensing only for a reduced baryon fraction. Using theChandra X-ray observations of the quasars themselves, together with new andpublished optical measurements, we use the observed emission properties of thequasars for further tests between the lens and binary hypotheses. Assumingsimilar line-of-sight absorption to the images, we find that their X-raycontinuum slopes are inconsistent (Gamma_A=2.30 and Gamma_B=0.83) as are theirX-ray to optical flux ratios. The probability that B suffers absorptionsufficient to account for these spectral differences is negligible. We presentnew optical evidence that the flux ratio of the pair is variable, so thetime-delay in a lens scenario could cause some of the discrepancies. However,adequately large variations in overall spectral energy distribution are rare inindividual QSOs. All new evidence here weighs strongly toward the binaryinterpretation. Q2345+007 thus may represent the highest redshift example knownof interaction-triggered but as-yet unmerged luminous AGN.[Journal_ref: ]
• Han, J. J., Dey, A., Price-Whelan, A. M., Najita, J., Schlafly, E. F., Saydjari, A., Wechsler, R. H., Bonaca, A., Schlegel, D. J., Conroy, C., Raichoor, A., Drlica-Wagner, A., Kollmeier, J. A., Koposov, S. E., Besla, G., Rix, H., Goodman, A., Finkbeiner, D., Anand, A., , Ashby, M., et al. (2024). NANCY: Next-generation All-sky Near-infrared Community surveY.
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  The Nancy Grace Roman Space Telescope is capable of delivering anunprecedented all-sky, high-spatial resolution, multi-epoch infrared map to theastronomical community. This opportunity arises in the midst of numerousground- and space-based surveys that will provide extensive spectroscopy andimaging together covering the entire sky (such as Rubin/LSST, Euclid, UNIONS,SPHEREx, DESI, SDSS-V, GALAH, 4MOST, WEAVE, MOONS, PFS, UVEX, NEO Surveyor,etc.). Roman can uniquely provide uniform high-spatial-resolution (~0.1 arcsec)imaging over the entire sky, vastly expanding the science reach and precisionof all of these near-term and future surveys. This imaging will not onlyenhance other surveys, but also facilitate completely new science. By imagingthe full sky over two epochs, Roman can measure the proper motions for starsacross the entire Milky Way, probing 100 times fainter than Gaia out to thevery edge of the Galaxy. Here, we propose NANCY: a completely public, all-skysurvey that will create a high-value legacy dataset benefiting innumerableongoing and forthcoming studies of the universe. NANCY is a pure expression ofRoman's potential: it images the entire sky, at high spatial resolution, in abroad infrared bandpass that collects as many photons as possible. The majorityof all ongoing astronomical surveys would benefit from incorporatingobservations of NANCY into their analyses, whether these surveys focus onnearby stars, the Milky Way, near-field cosmology, or the broader universe.[Journal_ref: ]
• Hickox, R. C., Myers, A. D., Brodwin, M., Alexander, D. M., Forman, W. R., Jones, C., Murray, S. S., Brown, M. J., Cool, R. J., Assef, R. J., Kochanek, C. S., Dey, A., Jannuzi, B. T., Eisenstein, D., Eisenhardt, P. R., Gorjian, V., Stern, D., Floc'H, E. L., Caldwell, N., , Goulding, A. D., et al. (2024). Clustering of obscured and unobscured quasars in the Bootes field: Placing rapidly growing black holes in the cosmic web.
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  We present the first measurement of the spatial clustering of mid-infraredselected obscured and unobscured quasars, using a sample in the redshift range0.7 < z < 1.8 selected from the 9 deg^2 Bootes multiwavelength survey. Recentlythe Spitzer Space Telescope and X-ray observations have revealed largepopulations of obscured quasars that have been inferred from models of theX-ray background and supermassive black hole evolution. To date, little isknown about obscured quasar clustering, which allows us to measure the massesof their host dark matter halos and explore their role in the cosmic evolutionof black holes and galaxies. In this study we use a sample of 806 mid-infraredselected quasars and ~250,000 galaxies to calculate the projected quasar-galaxycross-correlation function w_p(R). The observed clustering yieldscharacteristic dark matter halo masses of log (M_halo [h^-1 M_sun]) =12.7^+0.4_-0.6 and 13.3^+0.3_-0.4 for unobscured quasars (QSO-1s) and obscuredquasars (Obs-QSOs), respectively. The results for QSO-1s are in excellentagreement with previous measurements for optically-selected quasars, while weconclude that the Obs-QSOs are at least as strongly clustered as the QSO-1s. Wetest for the effects of photometric redshift errors on the optically-faintObs-QSOs, and find that our method yields a robust lower limit on theclustering; photo-z errors may cause us to underestimate the clusteringamplitude of the Obs-QSOs by at most ~20%. We compare our results to previousstudies, and speculate on physical implications of stronger clustering forobscured quasars.[Journal_ref: ]
• Jannuzi, B. T. (2024). Quasar Absorption Lines and the Intergalactic Medium.
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  The importance of HST for the study of quasar absorption lines and of thenature of the intergalactic medium is illustrated by reviewing selected resultsfrom past HST observations. Topics reviewed include the study of Ly-alphaabsorbers at low redshift and the search for a diffuse IGM at high redshifts.[Journal_ref: ]
• Jannuzi, B. T., Elston, R., Schmidt, G. D., Smith, P. S., & Stockman, H. S. (2024). Detection of Extended Polarized Ultraviolet Radiation from the z = 1.82 Radio Galaxy 3C 256.
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  We have detected spatially extended linear polarized UV emission from thehigh-redshift radio galaxy 3C~256 ($z=1.82$). A spatially integrated ($7.8''$diameter aperture) measurement of the degree of polarization of the $V-$band(rest frame 0.19 $\mu$m) emission yields a value of 16.4\% ($\pm 2.2$\%) with aposition angle of $42{}\rlap{\rm .}^\circ 4$ ($\pm 3{}\rlap{\rm .}^\circ 9$),orthogonal to the position angle on the sky of the major axis of the extendedemission. The peak emission measured with a $3.6''$ diameter circular apertureis 11.7\% ($\pm 1.5$\%) polarized with a position angle of $42{}\rlap{\rm.}^\circ 4$ ($\pm 3{}\rlap{\rm .}^\circ 6$). An image of the polarized flux ispresented, clearly displaying that the polarized flux is extended and presentover the entire extent of the object. While it has been suggested that the UVcontinuum of 3C~256 might be due to star formation (Elston 1988) or aprotogalaxy (Eisenhardt \& Dickinson 1993) based on its extremely blue spectralenergy distribution and similar morphology at UV and visible wavelengths, weare unable to reconcile the observed high degree of polarization with such amodel. While the detection of polarized emission from HZRGs has been shown tobe a common phenomena, 3C~256 is only the third object for which a measurementof the extended polarized UV emission has been presented. These data lendadditional support to the suggestion first made by di Serego Alighieri andcollaborators that the ``alignment effect'', the tendency for the extended UVcontinuum radiation and line emission from HZRGs to be aligned with the majoraxis of the extended radio emission, is in large part due to scattering ofanisotropic nuclear emission.[Journal_ref: ]
• Johnson, J. A., Vaz, A., Montoya, M., Anugu, N., Ard, C., Carlson, J., Chapman, K., Durney, O., Fellows, C., Gardner, A., Guyon, O., Jannuzi, B., Jones, R., Kulesa, C., Long, J., McEwen, E., Males, J., Mailhot, E., Sanchez, J., , Sivanandam, S., et al. (2024). The MAPS Adaptive Secondary Mirror: First Light, Laboratory Work, and Achievements.
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  The MMT Adaptive Optics exoPlanet Characterization System (MAPS) is acomprehensive update to the first generation MMT adaptive optics system(MMTAO), designed to produce a facility class suite of instruments whosepurpose is to image nearby exoplanets. The system's adaptive secondary mirror(ASM), although comprised in part of legacy components from the MMTAO ASM,represents a major leap forward in engineering, structure and function. Thesubject of this paper is the design, operation, achievements and technicalissues of the MAPS adaptive secondary mirror. We discuss laboratory preparationfor on-sky engineering runs, the results of those runs and the issues wediscovered, what we learned about those issues in a follow-up period oflaboratory work, and the steps we are taking to mitigate them.[Journal_ref: ]
• Kenter, A., Murray, S. S., Forman, W. R., Jones, C., Green, P., Kochanek, C. S., Vikhlinin, A., Fabricant, D., Fazio, G., Brand, K., Brown, M. J., Dey, A., Jannuzi, B. T., Najita, J., McNamara, B., Shields, J., & Rieke, M. (2024). The XBootes Chandra Survey Paper II: The X-ray Source Catalog.
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  We present results from a Chandra survey of the nine square degree Bootesfield of the NOAO Deep Wide-Field Survey (NDWFS). This XBootes survey consistsof 126 separate contiguous ACIS-I observations each of approximately 5000seconds in duration. These unique Chandra observations allow us to search forlarge scale structure and to calculate X-ray source statistics o ver a wide,contiguous field of view with arcsecond angular resolution and uniformcoverage. Optical spectroscopic follow-up observations and the rich NDWFS dataset will allow us to identify and classify these X-ray selected sources. Using wavelet decomposition, we detect 4642 point sources with n $\ge$ 2counts. In order to keep our detections ~99% reliable, we limit our list tosources with n $\ge$ 4 counts. The full 0.5--7 keV band n $\ge$ 4 count list has 3293 point sources. Inaddition to the point sources, 43 extended sources have been detectedconsistent, with the depth of these observations and the number counts ofclusters. We present here the X-ray catalog for the XBootes survey, includingsource positions, X-ray fluxes, hardness ratios and their uncertainties. We calculate and present the differential number of sources per flux densit yinterval, $N(S)$, for the point sources.[Journal_ref: ]
• Kim, E., Yang, Y., Zabludoff, A., Smith, P., Jannuzi, B., Lee, M. G., Hwang, N., & Park, B. (2024). What Makes Ly$α$ Nebulae Glow? Mapping the Polarization of LABd05.
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  "Ly$\alpha$ nebulae" are giant ($\sim$100 kpc), glowing gas clouds in thedistant universe. The origin of their extended Ly$\alpha$ emission remains amystery. Some models posit that Ly$\alpha$ emission is produced when the cloudis photoionized by UV emission from embedded or nearby sources, while otherssuggest that the Ly$\alpha$ photons originate from an embedded galaxy or AGNand are then resonantly scattered by the cloud. At least in the latterscenario, the observed Ly$\alpha$ emission will be polarized. To test thesepossibilities, we are conducting imaging polarimetric observations of sevenLy$\alpha$ nebulae. Here we present our results for LABd05, a cloud at $z$ =2.656 with an obscured, embedded AGN to the northeast of the peak of Ly$\alpha$emission. We detect significant polarization. The highest polarizationfractions $P$ are $\sim$10-20% at $\sim$20-40 kpc southeast of the Ly$\alpha$peak, away from the AGN. The lowest $P$, including upper-limits, are $\sim$5%and lie between the Ly$\alpha$ peak and AGN. In other words, the polarizationmap is lopsided, with $P$ increasing from the Ly$\alpha$ peak to the southeast.The measured polarization angles $\theta$ are oriented northeast, roughlyperpendicular to the $P$ gradient. This unique polarization pattern suggeststhat 1) the spatially-offset AGN is photoionizing nearby gas and 2) escapingLy$\alpha$ photons are scattered by the nebula at larger radii and into oursightline, producing tangentially-oriented, radially-increasing polarizationaway from the photoionized region. Finally we conclude that the interplaybetween the gas density and ionization profiles produces the observed centralpeak in the Ly$\alpha$ emission. This also implies that the structure of LABd05is more complex than assumed by current theoretical spherical or cylindricalmodels.[Journal_ref: ]
• Kochanek, C. S., Eisenstein, D. J., Cool, R. J., Caldwell, N., Assef, R. J., Jannuzi, B. T., Jones, C., Murray, S. S., Forman, W. R., Dey, A., Brown, M. J., Eisenhardt, P., Gonzalez, A. H., Green, P., & Stern, D. (2024). AGES: The AGN and Galaxy Evolution Survey.
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  The AGN and Galaxy Evolution Survey (AGES) is a redshift survey covering, inits standard fields, 7.7 square degrees of the Bootes field of the NOAO DeepWide-Field Survey (NDWFS). The final sample consists of 23745 redshifts. Thereare well-defined galaxy samples in ten bands (the Bw, R, I, J, K, IRAC 3.6,4.5, 5.8 and 8.0 micron and MIPS 24 micron bands) to a limiting magnitude ofI
• Kocherlakota, P., Rezzolla, L., Falcke, H., Fromm, C. M., Kramer, M., Mizuno, Y., Nathanail, A., Olivares, H., Younsi, Z., Akiyama, K., Alberdi, A., Alef, W., Algaba, J. C., Anantua, R., Asada, K., Azulay, R., Baczko, A., Ball, D., Balokovic, M., , Barrett, J., et al. (2024). Constraints on black-hole charges with the 2017 EHT observations of M87*.
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  Our understanding of strong gravity near supermassive compact objects hasrecently improved thanks to the measurements made by the Event HorizonTelescope (EHT). We use here the M87* shadow size to infer constraints on thephysical charges of a large variety of nonrotating or rotating black holes. Forexample, we show that the quality of the measurements is already sufficient torule out that M87* is a highly charged dilaton black hole. Similarly, whenconsidering black holes with two physical and independent charges, we are ableto exclude considerable regions of the space of parameters for thedoubly-charged dilaton and the Sen black holes.[Journal_ref: ]
• Kozlowski, S., Kochanek, C. S., Stern, D., Prieto, J. L., Stanek, K. Z., Thompson, T. A., Assef, R. J., Drake, A. J., Szczygiel, D. M., Wozniak, P. R., Nugent, P., Ashby, M. L., Beshore, E., Brown, M. J., Dey, A., Griffith, R., Harrison, F., Jannuzi, B. T., Larson, S., , Madsen, K., et al. (2024). SDWFS-MT-1: A Self-Obscured Luminous Supernova at z~0.2.
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  We report the discovery of a six-month-long mid-infrared transient,SDWFS-MT-1 (aka SN 2007va), in the Spitzer Deep, Wide-Field Survey of the NOAODeep Wide-Field Survey Bootes field. The transient, located in a z=0.19 lowluminosity (M_[4.5]~-18.6 mag, L/L_MilkyWay~0.01) metal-poor (12+log(O/H)~7.8)irregular galaxy, peaked at a mid-infrared absolute magnitude of M_[4.5]~-24.2in the 4.5 micron Spitzer/IRAC band and emitted a total energy of at least10^51 ergs. The optical emission was likely fainter than the mid-infrared,although our constraints on the optical emission are poor because the transientpeaked when the source was "behind" the Sun. The Spitzer data are consistentwith emission by a modified black body with a temperature of ~1350 K. We ruleout a number of scenarios for the origin of the transient such as a Galacticstar, AGN activity, GRB, tidal disruption of a star by a black hole andgravitational lensing. The most plausible scenario is a supernova explodinginside a massive, optically thick circumstellar medium, composed of multipleshells of previously ejected material. If the proposed scenario is correct,then a significant fraction (~10%) of the most luminous supernova may beself-enshrouded by dust not only before but also after the supernova occurs.The spectral energy distribution of the progenitor of such a supernova would bea slightly cooler version of eta Carina, peaking at 20-30 microns.[Journal_ref: ]
• Kulkarni, V. P., Hill, J. M., Schneider, G., Weymann, R. J., Storrie-Lombardi, L. J., Rieke, M. J., Thompson, R. I., & Jannuzi, B. T. (2024). NICMOS Imaging of a Damped Lyman-alpha Absorber at z=1.89 toward LBQS 1210+1731 : Constraints on Size and Star Formation Rate.
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  We report results of a high-resolution imaging search (in rest frameH-$\alpha$ and optical continuum) for the galaxy associated with the dampedLyman-$\alpha$ (DLA) absorber at $z=1.892$ toward the $z_{em}=2.543$ quasarLBQS 1210+1731, using HST/NICMOS. After PSF subtraction, a feature is seen inboth the broad-band and narrow-band images, at a projected separation of0.25$\arcsec$ from the quasar. If associated with the DLA, the object would be$\approx 2-3$ $h_{70}^{-1}$ kpc in size with a flux of $9.8 \pm 2.4$ $\mu$Jy inthe F160W filter, implying a luminosity at $\lambda_{central}=5500$ {\AA} inthe rest frame of $1.5 \times 10^{10}$ $h_{70}^{-2}$ L$_{\odot}$ at $z=1.89$,for $q_{0}=0.5$. However, no significant H-$\alpha$ emission is seen,suggesting a low star formation rate (SFR) (3 $\sigma$ upper limit of 4.0$h_{70}^{-2}$ M$_{\odot}$ yr$^{-1}$), or very high dust obscuration.Alternatively, the object may be associated with the host galaxy of the quasar.H-band images obtained with the NICMOS camera 2 coronagraph show a much fainterstructure $\approx 4-5$ $h_{70}^{-1}$ kpc in size and containing four knots ofcontinuum emission, located 0.7$\arcsec$ away from the quasar. We have probedregions far closer to the quasar sight-line than in most previous studies ofhigh-redshift intervening DLAs. The two objects we report mark the closestdetected high-redshift DLA candidates yet to any quasar sight line. If thefeatures in our images are associated with the DLA, they suggest faint,compact, somewhat clumpy objects rather than large, well-formed proto-galacticdisks or spheroids.[Journal_ref: ]
• Laor, A., Jannuzi, B. T., Green, R. F., & Boroson, T. A. (2024). The HST Spectrum of I Zw 1: Implications of the C III^* λ1176 Emission Line.
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  I Zw 1 is a well known narrow line quasar with very strong Fe II emission.High S/N spectra obtained with the HST FOS show a remarkably rich emission linespectrum. The C III$^* \lambda 1176$ line is clearly detected in emission forthe first time in AGNs. This line arises from radiative decay to the$2s2p^3P^o_{0,1,2}$ metastable levels of C III. The observed flux is 50 largerthan expected from collisional excitation, or dielectronic recombination, inphotoionized gas. The most plausible mechanism for the large enhancement in theC III^* \lambda 1176 flux is resonance scattering of continuum photons by CIII^* ions. This mechanism requires large velocity gradients 1000 km/s withineach emitting cloud in the BLR. Such large velocity gradients can be induced byforces external to the gas in the BLR clouds, such as tidal disruption, orradiation pressure.[Journal_ref: ]
• Laor, A., Jannuzi, B. T., Green, R. F., & Boroson, T. A. (2024). The UV Properties of the Narrow Line Quasar I Zwicky 1.
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  I Zw 1 is the prototype narrow line quasar. We report here the results of ourstudy of the UV emission of I Zw 1 using a high S/N (50-120) spectrum obtainedwith the HST FOS. The following main new results are obtained: 1. The Mg II andAl III doublets are partially/fully resolved. The measured doublet ratiosverify theoretical predictions that the lines are thermalized in the BLR. 2. Aweak associated UV absorption system is detected in N~V, and possibly also in CIV and Lya, suggesting an outflow with a velocity of 1870 km/s and velocitydispersion
• Lee, K., Alberts, S., Atlee, D., Dey, A., Pope, A., Jannuzi, B. T., Reddy, N., & Brown, M. J. (2024). Herschel Detection of Dust Emission from UV-Luminous Star-Forming Galaxies at 3.3
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  We report the Herschel SPIRE detection of dust emission arising fromUV-luminous (L>~L*) star-forming galaxies at 3.3
• Lee, K., Dey, A., Cooper, M. C., Reddy, N., & Jannuzi, B. T. (2024). Probing High-Redshift Galaxy Formation at the Highest Luminosities: New Insights from DEIMOS Spectroscopy.
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  We present DEIMOS spectroscopic observations of the most UV-luminousstar-forming galaxies at 3.2
• Lee, K., Dey, A., Hong, S., Reddy, N., Wilson, C., Jannuzi, B. T., Inami, H., & Gonzalez, A. H. (2024). Discovery of a Very Large Structure at Z=3.78.
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  We report the discovery of a large-scale structure containing multipleprotoclusters at z=3.78 in the Bo\"otes field. The spectroscopic discovery offive galaxies at z=3.783+/-0.002 lying within 1 Mpc of one another led us toundertake a deep narrow- and broad-band imaging survey of the surroundingfield. Within a comoving volume of 72x72x25 Mpc^3, we have identified 65 Lymanalpha emitter (LAE) candidates at z=3.795+/-0.015, and four additional galaxiesat z_spec=3.730,3.753,3.780,3.835. The galaxy distribution within the field ishighly non-uniform, exhibiting three large (~3-5x) overdensities separated by8-14 Mpc (physical) and possibly connected by filamentary structures traced byLAEs. The observed number of LAEs in the entire field is nearly twice theaverage expected in field environments, based on estimates of the Lyaluminosity function at these redshifts. We estimate that by z=0 the largestoverdensity will grow into a cluster of mass 10^15 Msun; the two smalleroverdensities will grow into clusters of mass (2-6)x10^14 Msun. The highestconcentration of galaxies is located at the southern end of the image,suggesting that the current imaging may not map the true extent of the largescale structure. Finding three large protocluster candidates within a single0.3 deg^2 field is highly unusual; expectations from theory suggest that suchalignments should occur less than 2% of the time. Searching for andcharacterizing such structures and accurately measuring their volume spacedensity can therefore place constraints on the theory of structure formation.Such regions can also serve as laboratories for the study of galaxy formationin dense environments.[Journal_ref: ]
• Lee, K., Dey, A., Matheson, T., Shi, K., Hung, C., Xue, R., Inami, H., Huang, Y., Lee, K., Ashby, M. L., Jannuzi, B., Reddy, N., Hong, S., Mo, W., & Malavasi, N. (2024). Discovery of a Very Large (~20 kpc) Galaxy at z=3.72.
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  We report the discovery and spectroscopic confirmation of a very largestar-forming Lyman Break galaxy, G6025, at z_spec=3.721+/-0.003. In therest-frame ~2100A, G6025 subtends ~24 kpc in physical extent when measured fromthe 1.5-sigma isophote, in agreement with the parametric size measurementswhich yield the half-light radius of 4.9+/-0.5 kpc and the semi-major axis of12.5+/-0.1 kpc. G6025 is also very UV-luminous (~5L*(z~4}) and young (~140+/-60Myr). Despite its unusual size and luminosity, the stellar populationparameters and dust reddening (M_star~M*(z~4)$, and E(B-V)=0.18+/-0.05)estimated from the integrated light, are similar to those of smaller galaxiesat comparable redshifts. The ground-based morphology and spectroscopy show twodominant components, both located off-center, embedded in more diffuseemission. We speculate that G6025 may be a scaled-up version of chain galaxiesseen in deep HST imaging, or alternatively, a nearly equal-mass mergerinvolving two super-L* galaxies in its early stage. G6025 lies close to but notwithin a known massive protocluster at z=3.78. We find four companions within 6Mpc from G6025, two of which lie within 1.6 Mpc. While the limited sensitivityof the existing spectroscopy does not allow us to robustly characterize thelocal environment of G6025, it likely resides in a locally overdenseenvironment. The luminosity, size, and youth of G6025 make it uniquely suitedto study the early formation of massive galaxies in the universe.[Journal_ref: ]
• Lee, K., Dey, A., Reddy, N., Brown, M. J., Gonzalez, A. H., Jannuzi, B. T., Cooper, M. C., Fan, X., Bian, F., Glikman, E., Stern, D., Brodwin, M., & Cooray, A. (2024). The Average Physical Properties and Star Formation Histories of the UV-Brightest Star-Forming Galaxies at z~3.7.
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  [Abridged] We investigate the average physical properties and star formationhistories of the most UV-luminous star-forming galaxies at z~3.7. Our resultsare derived from analyses of the average spectral energy distributions (SEDs),constructed from stacked optical to infrared photometry, of a sample of the1,902 most UV-luminous star-forming galaxies found in 5.3 square degrees of theNOAO Deep Wide-Field Survey. We bin the sample according to UV luminosity, andfind that the shape of the average SED in the rest-frame optical and infraredis fairly constant with UV luminosity: i.e., more UV luminous galaxies are, onaverage, also more luminous at longer wavelengths. In the rest-UV, however, thespectral slope (measured at 0.13-0.28 um) rises steeply with the median UVluminosity from -1.8 at L L* to -1.2 in the brightest bin (L~4-5L*). We usepopulation synthesis analyses to derive the average physical properties ofthese galaxies and find that: (1) L_UV, and thus star formation rates (SFRs),scale closely with stellar mass such that more UV-luminous galaxies are alsomore massive; (2) The median ages indicate that the stellar populations arerelatively young (200-400 Myr) and show little correlation with UV luminosity;and (3) More UV-luminous galaxies are dustier than their less-luminouscounterparts, such that L~4-5L* galaxies are extincted up to A(1600)=2 magwhile L L* galaxies have A(1600)=0.7-1.5 mag. Based on these observations, weargue that the average star formation histories of UV-luminous galaxies arebetter described by models in which SFR increases with time in order tosimultaneously reproduce the tight correlation between the observed SFR andstellar mass, and the universally young ages of these galaxies. We demonstratethe potential of measurements of the SFR-M* relation at multiple redshifts todiscriminate between simple models of star formation histories.[Journal_ref: ]
• Lundquist, M. J., Paterson, K., Fong, W., Sand, D. J., Andrews, J. E., Shivaei, I., Daly, P. N., Valenti, S., Yang, S., Christensen, E., Gibbs, A. R., Shelly, F., Wyatt, S., Kuhn, O., Amaro, R. C., Arcavi, I., Behroozi, P., Butler, N., Chomiuk, L., , Corsi, A., et al. (2024). Searches After Gravitational-waves Using ARizona Observatories (SAGUARO): System Overview and First Results from Advanced LIGO/Virgo's Third Observing Run.
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  We present Searches After Gravitational-waves Using ARizona Observatories(SAGUARO), a comprehensive effort dedicated to the discovery andcharacterization of optical counterparts to gravitational wave (GW) events.SAGUARO utilizes ground-based facilities ranging from 1.5m to 10m in diameter,located primarily in the Northern Hemisphere. We provide an overview ofSAGUARO's telescopic resources, pipeline for transient detection, and databasefor candidate visualization. We describe SAGUARO's discovery component, whichutilizes the $5$~deg$^2$ field-of-view optical imager on the Mt. Lemmon 1.5mtelescope, reaching limits of $\approx 21.3$~AB mag while rapidly tiling largeareas. We also describe the follow-up component of SAGUARO, used for rapidvetting and monitoring of optical candidates. With the onset of AdvancedLIGO/Virgo's third observing run, we present results from the first threeSAGUARO searches following the GW events S190408an, S190425z and S190426c,which serve as a valuable proof-of-concept of SAGUARO. We triggered andsearched 15, 60 and 60 deg$^{2}$ respectively, 17.6, 1.4 and 41.8 hrs after theinitial GW alerts. We covered 7.8, 3.0 and 5.1\% of the total probabilitywithin the GW event localizations, reaching 3$\sigma$ limits of 19.8, 21.3 and20.8 AB mag, respectively. Although no viable counterparts associated withthese events were found, we recovered 6 known transients and ruled out 5potential candidates. We also present Large Binocular Telescope spectroscopy ofPS19eq/SN2019ebq, a promising kilonova candidate that was later determined tobe a supernova. With the ability to tile large areas and conduct detailedfollow-up, SAGUARO represents a significant addition to GW counterpartsearches.[Journal_ref: ]
• Malhotra, S., Rhoads, J., Dey, A., Jannuzi, B., Stern, D., & Spinrad, H. (2024). Large Area Lyman Alpha survey: finding young galaxies at z=4.5.
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  Strong Lyman-alpha emission is a signpost of young stars and the absence ofdust and thus indicates young galaxies. To find such a population of younggalaxies at z=4.5 we started the Large Area Lyman Alpha survey (LALA). Thissurvey achieves an unprecedented combination of volume and sensitivity by usingnarrow-band filters on a large format (36x36 square-arcminutes) camera on the 4meter telescope at KPNO. The volume density and star-formation contribution ofthe Lyman-alpha emitters at z=4.5 is comparable to that of Lyman breakgalaxies. With many candidates and a few spectroscopic confirmations in hand wediscuss what the properties of Ly-alpha emitters imply for galaxy and starformation in the early universe.[Journal_ref: ]
• Martini, P., Miller, E. D., Brodwin, M., Stanford, S. A., Gonzalez, A. H., Bautz, M., Hickox, R. C., Stern, D., Eisenhardt, P. R., Galametz, A., Norman, D., Jannuzi, B. T., Dey, A., Murray, S., Jones, C., & Brown, M. J. (2024). The Cluster and Field Galaxy AGN Fraction at z = 1 to 1.5: Evidence for a Reversal of the Local Anticorrelation Between Environment and AGN Fraction.
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  The fraction of cluster galaxies that host luminous AGN is an important probeof AGN fueling processes, the cold ISM at the centers of galaxies, and howtightly black holes and galaxies co-evolve. We present a new measurement of theAGN fraction in a sample of 13 clusters of galaxies (M >= 10^{14} Msun) at1
• Masini, A., Hickox, R. C., Carroll, C. M., Aird, J., Alexander, D. M., Assef, R. J., Bower, R., Brodwin, M., Brown, M. J., Chatterjee, S., Chen, C. -., Dey, A., DiPompeo, M. A., Duncan, K. J., Eisenhardt, P. R., Forman, W. R., Gonzalez, A. H., Goulding, A. D., Hainline, K. N., , Jannuzi, B. T., et al. (2024). The Chandra Deep Wide-Field Survey: A New Chandra Legacy Survey in the Boötes Field I. X-ray Point Source Catalog, Number Counts and Multi-Wavelength Counterparts.
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  We present a new, ambitious survey performed with the Chandra X-rayObservatory of the 9.3 deg$^2$ Bo\"otes field of the NOAO Deep Wide-FieldSurvey. The wide field probes a statistically representative volume of theUniverse at high redshift. The Chandra Deep Wide-Field Survey exploits theexcellent sensitivity and angular resolution of Chandra over a wide area,combining 281 observations spanning 15 years, for a total exposure time of 3.4Ms, and detects 6891 X-ray point sources down to limiting fluxes of$4.7\times10^{-16}$, $1.5\times10^{-16}$, and $9\times10^{-16}$ erg cm$^{-2}$s$^{-1}$, in the $0.5-7$ keV, $0.5-2$ keV, and $2-7$ keV bands, respectively.The robustness and reliability of the detection strategy is validated throughextensive, state-of-the-art simulations of the whole field. Accurate numbercounts, in good agreement with previous X-ray surveys, are derived thanks tothe uniquely large number of point sources detected, which resolve $65.0 \pm12.8\%$ of the cosmic X-ray background between $0.5-2$ keV and $81.0 \pm11.5\%$ between $2-7$ keV. Exploiting the wealth of multi-wavelength dataavailable on the field, we assign redshifts to $\sim 94\%$ of the X-raysources, estimate their obscuration and derive absorption-correctedluminosities. We provide an electronic catalog containing all the relevantquantities needed for future investigations.[Journal_ref: ]
• McNamara, B. R., Jannuzi, B. T., Sarazin, C. L., Elston, R., & Wise, M. (2024). An Alignment Effect in FR I Radio Galaxies: U-band Polarimetry of the Abell 2597 Cluster Central Galaxy.
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  We have obtained U-band polarimetry of the spatially extended, blue opticalcontinuum associated with the FR I radio source PKS 2322-122. PKS 2322-122 islocated in the Abell 2597 cluster central galaxy. We find a three sigma upperlimit to the degree of polarization of the optical continuum of less than 6%.This limit is inconsistent with the blue continuum being primarily scatteredlight or synchrotron radiation. We can therefore exclude models which attributethe blue continuum to scattered light from an active nucleus that is hiddenfrom direct view. Essentially all of the data pertaining to the blue continuumalong the radio source-the ``blue lobes''-indicate that they are regions ofrecent star formation that may have been induced by an interaction between theradio source and the cool ($
• Melbourne, J., Bussman, S., Brand, K., Desai, V., Armus, L., Dey, A., Jannuzi, B. T., Houck, J. R., Matthews, K., & Soifer, B. T. (2024). High Redshift Dust Obscured Galaxies, A Morphology-SED Connection Revealed by Keck Adaptive Optics.
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  A simple optical to mid-IR color selection, R-[24] > 14, i.e. f_nu(24) /f_nu(R) > 1000, identifies highly dust obscured galaxies (DOGs) with typicalredshifts of z~2 +/- 0.5. Extreme mid-IR luminosities (L_{IR} > 10^{12-14})suggest that DOGs are powered by a combination of AGN and star formation,possibly driven by mergers. In an effort to compare their photometricproperties with their rest frame optical morphologies, we obtained high spatialresolution (0.05 -0.1") Keck Adaptive Optics (AO) K'-band images of 15 DOGs.The images reveal a wide range of morphologies, including: small exponentialdisks (8 of 15), small ellipticals (4 of 15), and unresolved sources (2 of 15).One particularly diffuse source could not be classified because of low signalto noise ratio. We find a statistically significant correlation between galaxyconcentration and mid-IR luminosity, with the most luminous DOGs exhibitinghigher concentration and smaller physical size. DOGs with high concentrationalso tend to have spectral energy distributions (SEDs) suggestive of AGNactivity. Thus central AGN light may be biasing the morphologies of the moreluminous DOGs to higher concentration. Conversely, more diffuse DOGs tend toshow an SED shape suggestive of star formation. Two of fifteen in the sampleshow multiple resolved components with separations of ~1 kpc, circumstantialevidence for ongoing mergers.[Journal_ref: ]
• Melbourne, J., Desai, V., Armus, L., Dey, A., Brand, K., Thompson, D., Soifer, B. T., Matthews, K., Jannuzi, B. T., & Houck, J. R. (2024). Morphologies of High Redshift, Dust Obscured Galaxies from Keck Laser Guide Star Adaptive Optics.
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  Spitzer MIPS images in the Bootes field of the NOAO Deep Wide-Field Surveyhave revealed a class of extremely dust obscured galaxy (DOG) at z~2. The DOGsare defined by very red optical to mid-IR (observed-frame) colors, R - [24 um]> 14 mag, i.e. f_v (24 um) / f_v (R) > 1000. They are Ultra-Luminous InfraredGalaxies with L_8-1000 um > 10^12 -10^14 L_sun, but typically have very faintoptical (rest-frame UV) fluxes. We imaged three DOGs with the Keck Laser GuideStar Adaptive Optics (LGSAO) system, obtaining ~0.06'' resolution in theK'-band. One system was dominated by a point source, while the other two wereclearly resolved. Of the resolved sources, one can be modeled as a exponentialdisk system. The other is consistent with a de Vaucouleurs profile typical ofelliptical galaxies. The non-parametric measures of their concentration andasymmetry, show the DOGs to be both compact and smooth. The AO images rule outdouble nuclei with separations of greater than 0.1'' (< 1 kpc at z=2), makingit unlikely that ongoing major mergers (mass ratios of 1/3 and greater) aretriggering the high IR luminosities. By contrast, high resolution images of z~2SCUBA sources tend to show multiple components and a higher degree ofasymmetry. We compare near-IR morphologies of the DOGs with a set of z=1luminous infrared galaxies (LIRGs; L_IR ~ 10^11 L_sun) imaged with Keck LGSAOby the Center for Adaptive Optics Treasury Survey. The DOGs in our sample havesignificantly smaller effective radii, ~1/4 the size of the z=1 LIRGs, and tendtowards higher concentrations. The small sizes and high concentrations may helpexplain the globally obscured rest-frame blue-to-UV emission of the DOGs.[Journal_ref: ]
• Melbourne, J., Soifer, B. T., Desai, V., Pope, A., Armus, L., Dey, A., Bussmann, R. S., Jannuzi, B. T., & Alberts, S. (2024). The Spectral Energy Distributions and Infrared Luminosities of z \approx 2 Dust Obscured Galaxies from Herschel and Spitzer.
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  Dust-obscured galaxies (DOGs) are a subset of high-redshift (z \approx 2)optically-faint ultra-luminous infrared galaxies (ULIRGs, e.g. L_{IR} > 10^{12}Lsun). We present new far-infrared photometry, at 250, 350, and 500 um(observed-frame), from the Herschel Space Telescope for a large sample of 113DOGs with spectroscopically measured redshifts. Approximately 60% of the sampleare detected in the far-IR, confirming their high IR luminosities, which rangefrom 10^{11.6} Lsun < L_{IR} (8-1000 um) 10^{13} Lsun. Therest-frame near-IR (1 - 3 um) SEDs of the Herschel detected DOGs are predictorsof their SEDs at longer wavelengths. DOGs with "power-law" SEDs in therest-frame near-IR show observed-frame 250/24 um flux density ratios similar tothe QSO-like local ULIRG, Mrk 231. DOGs with a stellar "bump" in theirrest-frame near-IR show observed-frame 250/24 um flux density ratios similar tolocal star-bursting ULIRGs like NGC 6240. For the Herschel detected DOGs,accurate estimates (within \approx 25%) of total IR luminosity can be predictedfrom their rest-frame mid-IR data alone (e.g. from Spitzer observed-frame 24 umluminosities). Herschel detected DOGs tend to have a high ratio of infraredluminosity to rest-frame 8 um luminosity (the IR8= L_{IR}(8-1000 um)/v L_{v}(8um) parameter of Elbaz et al. 2011). Instead of lying on the z=1-2 "infraredmain-sequence" of star forming galaxies (like typical LIRGs and ULIRGs at thoseepochs) the DOGs, especially large fractions of the bump sources, tend to liein the starburst sequence. While, Herschel detected DOGs are similar to scaledup versions of local ULIRGs in terms of 250/24 um flux density ratio, and IR8,they tend to have cooler far-IR dust temperatures (20-40 K for DOGs vs. 40-50 Kfor local ULIRGs). Abridged.[Journal_ref: ]
• Milne, P. A., Williams, G. G., Porter, A., Smith, P. S., Smith, N., Leising, M. D., Jannuzi, B. T., & Green, E. M. (2024). Multi-epoch Spectropolarimetry of SN 2011fe.
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  We present multiple spectropolarimetric observations of the nearby Type Iasupernova (SN) 2011fe in M101, obtained before, during, and after the time ofmaximum apparent visual brightness. The excellent time coverage of ourspectropolarimetry has allowed better monitoring of the evolution ofpolarization features than is typical, which has allowed us new insight intothe nature of normal SNe Ia. SN 2011fe exhibits time-dependent polarization inboth the continuum and strong absorption lines. At early epochs, redwavelengths exhibit a degree of continuum polarization of up to 0.4\%, likelyindicative of a mild asymmetry in the electron-scattering photosphere. Thisbehavior is more common in sub-luminous SNe Ia than in normal events, such asSN2011fe. The degree of polarization across a collection of absorption linesvaries dramatically from epoch to epoch. During the earliest epoch a$\lambda$4600-5000 \AA\ complex of absorption lines shows enhanced polarizationat a different position angle than the continuum. We explore the origin ofthese features, presenting a few possible interpretations, without arriving ata single favored ion. During two epochs near maximum, the dominant polarizationfeature is associated with the Si{\sc ii} $\lambda$6355 \AA\ absorption line.This is common for SNeIa, but for SN2011fe the polarization of this featureincreases after maximum light, whereas for other SNeIa, that polarizationfeature was strongest before maximum light.[Journal_ref: ]
• Morris, S. L., Jannuzi, B., & Weymann, R. (2024). Low Redshift Lyman Alpha absorbers and their Connection with Galaxies.
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  We review the ongoing debate about the relationship between low redshiftLyman Alpha absorbers and luminous galaxies. In particular, we discuss thedifficulty of `assigning' a particular absorber to a particular galaxy, andconsider methods of circumventing this problem. We also provide a status reporton an ongoing project collecting more data to address this issue, and show someresults for a close together pair of QSOs providing two adjacent lines of sightthrough the inter-galactic medium.[Journal_ref: ]
• Mould, J., Reynolds, T., Readhead, T., Floyd, D., Jannuzi, B., Cotter, G., Ferrarese, L., Matthews, K., Atlee, D., & Brown, M. (2024). Infrared spectroscopy of nearby radio active elliptical galaxies.
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  In preparation for a study of their circumnuclear gas we have surveyed 60% ofa complete sample of elliptical galaxies within 75 Mpc that are radiosources.Some 20% of our nuclear spectra have infrared emission lines, mostly Paschenlines, Brackett gamma and [FeII]. We consider the influence of radio power andblack hole mass in relation to the spectra. Access to the spectra is providedas a community resource.[Journal_ref: ]
• Moustakas, J., Zaritsky, D., Brown, M., Cool, R., Dey, A., Eisenstein, D. J., Gonzalez, A. H., Jannuzi, B., Jones, C., Kochanek, C. S., Murray, S. S., & Wild, V. (2024). Evolution of the Stellar Mass-Metallicity Relation Since z=0.75.
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  We measure the gas-phase oxygen abundances of ~3000 star-forming galaxies atz=0.05-0.75 using optical spectrophotometry from the AGN and Galaxy EvolutionSurvey (AGES), a spectroscopic survey of I_AB
• Murray, S. S., Kenter, A., Forman, W. R., Jones, C., Green, P. J., Kochanek, C. S., Vikhlinin, A., Fabricant, D., Fazio, G., Brand, K., Brown, M. J., Dey, A., Jannuzi, B. T., Najita, J., McNamara, B., Shields, J., & Rieke, M. (2024). XBootes: An X-Ray Survey of the NDWFS Bootes Field - Paper I Overview and Initial Results.
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  We obtained a 5 ksec deep Chandra X-ray Observatory ACIS-I map of the 9.3square degree Bootes field of the NOAO Deep Wide-Field Survey. Here we describethe data acquisition and analysis strategies leading to a catalog of 4642(3293) point sources with 2 or more (4 or more) counts, corresponding to alimiting flux of roughly 4(8)x10^{-15} erg cm^{-2}s^{-1} in the 0.5-7 keV band.These Chandra XBootes data are unique in that they consitute the widestcontiguous X-ray field yet observed to such a faint flux limit. Because of theextraordinarily low background of the ACIS, we expect only 14% (0.7%) of thesources to be spurious. We also detected 43 extended sources in this survey.The distribution of the point sources among the 126 pointings (ACIS-I has a 16x 16 arcminute field of view) is consistent with Poisson fluctuations about themean of 36.8 sources per pointing. While a smoothed image of the point sourcedistribution is clumpy, there is no statistically significant evidence of largescale filamentary structure. We do find however, that for theta>1 arcminute,the angular correlation function of these sources is consistent with previousmeasurements, following a power law in angle with slope -0.7. In a 1.4 deg^{2}sample of the survey, approximately 87% of the sources with 4 or more countshave an optical counterpart to R ~26 mag. As part of a larger program ofoptical spectroscopy of the NDWFS Bootes area, spectra have been obtained for\~900 of the X-ray sources, most of which are QSOs or AGN.[Journal_ref: ]
• Pilachowski, C., Badenes, C., Bailey, S., Barth, A., Beaton, R., Bell, E., Bernstein, R., Bian, F., Blanton, M., Blum, R., Bolton, A., Bond, H., Brodwin, M., Bullock, J., Carlin, J., Chary, R., Cinabro, D., Cooper, M., Cota, J. L., , Davis, M., et al. (2024). Addressing Decadal Survey Science through Community Access to Highly Multiplexed Spectroscopy with BigBOSS on the KPNO Mayall Telescope.
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  This document summarizes the results of a community-based discussion of thepotential science impact of the Mayall+BigBOSS highly multiplexed multi-objectspectroscopic capability. The KPNO Mayall 4m telescope equipped with the DOE-and internationally-funded BigBOSS spectrograph offers one of the mostcost-efficient ways of accomplishing many of the pressing scientific goalsidentified for this decade by the "New Worlds, New Horizons" report. TheBigBOSS Key Project will place unprecedented constraints on cosmologicalparameters related to the expansion history of the universe. With the additionof an open (publicly funded) community access component, the scientific impactof BigBOSS can be extended to many important astrophysical questions related tothe origin and evolution of galaxies, stars, and the IGM. Massive spectroscopyis the critical missing ingredient in numerous ongoing and planned ground- andspace-based surveys, and BigBOSS is unique in its ability to provide this tothe US community. BigBOSS data from community-led projects will play a vitalrole in the education and training of students and in maintaining US leadershipin these fields of astrophysics. We urge the NSF-AST division to supportcommunity science with the BigBOSS multi-object spectrograph through the periodof the BigBOSS survey in order to ensure public access to the extraordinaryspectroscopic capability.[Journal_ref: ]
• Poznanski, D., Maoz, D., Yasuda, N., Foley, R. J., Doi, M., Filippenko, A. V., Fukugita, M., Gal-Yam, A., Jannuzi, B. T., Morokuma, T., Oda, T., Schweiker, H., Sharon, K., Silverman, J. M., & Totani, T. (2024). Supernovae in the Subaru Deep Field: An Initial Sample, and Type Ia Rate, out to Redshift 1.6.
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  Large samples of high-redshift supernovae (SNe) are potentially powerfulprobes of cosmic star formation, metal enrichment, and SN physics. We presentinitial results from a new deep SN survey, based on re-imaging in the R, i', z'bands, of the 0.25 deg2 Subaru Deep Field (SDF), with the 8.2-m Subarutelescope and Suprime-Cam. In a single new epoch consisting of two nights ofobservations, we have discovered 33 candidate SNe, down to a z'-band magnitudeof 26.3 (AB). We have measured the photometric redshifts of the SN hostgalaxies, obtained Keck spectroscopic redshifts for 17 of the host galaxies,and classified the SNe using the Bayesian photometric algorithm of Poznanski etal. (2007) that relies on template matching. After correcting for biases in theclassification, 55% of our sample consists of Type Ia supernovae and 45% ofcore-collapse SNe. The redshift distribution of the SNe Ia reaches z ~ 1.6,with a median of z ~ 1.2. The core-collapse SNe reach z ~ 1.0, with a median ofz ~ 0.5. Our SN sample is comparable to the Hubble Space Telescope/GOODS sampleboth in size and redshift range. The redshift distributions of the SNe in theSDF and in GOODS are consistent, but there is a trend (which requiresconfirmation using a larger sample) for more high-z SNe Ia in the SDF. Thistrend is also apparent when comparing the SN Ia rates we derive to those basedon GOODS data. Our results suggest a fairly constant rate at high redshift thatcould be tracking the star-formation rate. Additional epochs on this field,already being obtained, will enlarge our SN sample to the hundreds, anddetermine whether or not there is a decline in the SN Ia rate at z >~ 1.[Journal_ref: ]
• Prather, B. S., Dexter, J., Moscibrodzka, M., Pu, H., Bronzwaer, T., Davelaar, J., Younsi, Z., Gammie, C. F., Gold, R., Wong, G. N., Akiyama, K., Alberdi, A., Alef, W., Algaba, J. C., Anantua, R., Asada, K., Azulay, R., Bach, U., Baczko, A., , Ball, D., et al. (2024). Comparison of Polarized Radiative Transfer Codes used by the EHT Collaboration.
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  Interpretation of resolved polarized images of black holes by the EventHorizon Telescope (EHT) requires predictions of the polarized emissionobservable by an Earth-based instrument for a particular model of the blackhole accretion system. Such predictions are generated by general relativisticradiative transfer (GRRT) codes, which integrate the equations of polarizedradiative transfer in curved spacetime. A selection of ray-tracing GRRT codesused within the EHT collaboration is evaluated for accuracy and consistency inproducing a selection of test images, demonstrating that the various methodsand implementations of radiative transfer calculations are highly consistent.When imaging an analytic accretion model, we find that all codes produce imagessimilar within a pixel-wise normalized mean squared error (NMSE) of 0.012 inthe worst case. When imaging a snapshot from a cell-based magnetohydrodynamicsimulation, we find all test images to be similar within NMSEs of 0.02, 0.04,0.04, and 0.12 in Stokes I, Q, U , and V respectively. We additionally find thevalues of several image metrics relevant to published EHT results to be inagreement to much better precision than measurement uncertainties.[Journal_ref: ]
• Psaltis, D., Medeiros, L., Christian, P., Ozel, F., Akiyama, K., Alberdi, A., Alef, W., Asada, K., Azulay, R., Ball, D., Balokovic, M., Barrett, J., Bintley, D., Blackburn, L., Boland, W., Bower, G. C., Bremer, M., Brinkerink, C. D., Brissenden, R., , Britzen, S., et al. (2024). Gravitational Test Beyond the First Post-Newtonian Order with the Shadow of the M87 Black Hole.
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  The 2017 Event Horizon Telescope (EHT) observations of the central source inM87 have led to the first measurement of the size of a black-hole shadow. Thisobservation offers a new and clean gravitational test of the black-hole metricin the strong-field regime. We show analytically that spacetimes that deviatefrom the Kerr metric but satisfy weak-field tests can lead to large deviationsin the predicted black-hole shadows that are inconsistent with even the currentEHT measurements. We use numerical calculations of regular, parametric,non-Kerr metrics to identify the common characteristic among these differentparametrizations that control the predicted shadow size. We show that theshadow-size measurements place significant constraints on deviation parametersthat control the second post-Newtonian and higher orders of each metric andare, therefore, inaccessible to weak-field tests. The new constraints arecomplementary to those imposed by observations of gravitational waves fromstellar-mass sources.[Journal_ref: ]
• Rhoads, J. E., Dey, A., Malhotra, S., Stern, D., Spinrad, H., Jannuzi, B. T., Dawson, S., & Brown, M. (2024). Spectroscopic Confirmation of Three Redshift 5.7 Lyman-alpha Emitters from the Large Area Lyman Alpha Survey. Astron.J., 125.
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  Narrow-band searches for Lyman alpha emission are an efficient way ofidentifying star-forming galaxies at high redshifts. We present Keck telescopespectra confirming redshifts z = 5.7 for three objects discovered in the LargeArea Lyman Alpha (LALA) survey at Kitt Peak National Observatory. All three spectra show strong, narrow emission lines with the asymmetricprofile that is characteristically produced in high redshift Lyman alphaemitters by preferential HI absorption in the blue wing of the line. Theseobjects are undetected in deep Bw, V, R, and 6600A narrow-band images from theNOAO Deep Wide-Field Survey and from LALA, as expected from Lyman break andLyman alpha forest absorption at redshift z = 5.7. All three objects show largeequivalent widths (>= 150A in the rest-frame), suggesting at least one of thefollowing: a top-heavy initial mass function, very low stellar metallicity, orthe presence of an active nucleus. We consider the case for an active nucleusto be weak in all three objects due to the limited width of the Lyman alphaemission line (< 500 km/s) and the absence of any other indicator of quasaractivity. The three confirmed high redshift objects were among four spectroscopicallyobserved targets drawn from the sample of 18 candidates presented by Rhoads andMalhotra (2001). Thus, these spectra support the Lyman alpha emitter populationstatistics from our earlier photometric study, which imply little evolution innumber density from z=5.7 to z=4.5 and provide strong evidence that thereionization redshift is greater than 5.7.[Journal_ref: Astron.J.125:1006,2003]
• Rhoads, J. E., Malhotra, S., Dey, A., Jannuzi, B. T., Stern, D., & Spinrad, H. (2024). The Large Area Lyman Alpha Survey.
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  The Lyman-$\alpha$ line is expected to be strong in the presence of activestar formation and the absence of dust, making it a good tool for findingchemically primitive galaxies in the early universe. We report on a new surveyfor high redshift Lyman-$\alpha$ sources, the Large Area Lyman Alpha (LALA)survey. Our survey achieves an unprecedented combination of volume andsensitivity by using narrow-band filters on the new $8192^2$ pixel CCD MosaicCamera at the 4 meter Mayall telescope of Kitt Peak National Observatory. Well-detected sources with flux and equivalent width matching known highredshift Lyman-$\alpha$ galaxies have an observed surface density correspondingto $11000 \pm 700$ per square degree per unit redshift at $z=4.5$. Earlyspectroscopic followup from the Keck telescope suggests that $\sim 1/3$ ofthese are actually at $z\approx 4.5$, and has confirmed five $z > 4$Lyman-$\alpha$ emitters so far. Combining our photometric survey withspectroscopic results, we estimate a net density of $\sim 4000 $ Lyman-$\alpha$emitters per square degree per unit redshift at $z\approx 4.5$. The starformation rate density (estimated both from UV continuum and from lineemission) is comparable to that of the Lyman break galaxy population withinpresent uncertainties. The most extreme Lyman-$\alpha$ emitters in our samplehave rest frame equivalent widths $> 100\AA$, consistent with the expectationsfor the first burst of star formation in a primitive, dust-free galaxy.[Journal_ref: ]
• Roelofs, F., Janssen, M., Natarajan, I., Deane, R., Davelaar, J., Olivares, H., Porth, O., Paine, S. N., Bouman, K. L., Tilanus, R. P., Bemmel, V. I., Falcke, H., Akiyama, K., Alberdi, A., Alef, W., Asada, K., Azulay, R., Baczko, A., Ball, D., , Baloković, M., et al. (2024). SYMBA: An end-to-end VLBI synthetic data generation pipeline.
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  Realistic synthetic observations of theoretical source models are essentialfor our understanding of real observational data. In using synthetic data, onecan verify the extent to which source parameters can be recovered and evaluatehow various data corruption effects can be calibrated. These studies areimportant when proposing observations of new sources, in the characterizationof the capabilities of new or upgraded instruments, and when verifyingmodel-based theoretical predictions in a comparison with observational data. Wepresent the SYnthetic Measurement creator for long Baseline Arrays (SYMBA), anovel synthetic data generation pipeline for Very Long Baseline Interferometry(VLBI) observations. SYMBA takes into account several realistic atmospheric,instrumental, and calibration effects. We used SYMBA to create syntheticobservations for the Event Horizon Telescope (EHT), a mm VLBI array, which hasrecently captured the first image of a black hole shadow. After testing SYMBAwith simple source and corruption models, we study the importance of includingall corruption and calibration effects. Based on two example generalrelativistic magnetohydrodynamics (GRMHD) model images of M87, we performedcase studies to assess the attainable image quality with the current and futureEHT array for different weather conditions. The results show that the effectsof atmospheric and instrumental corruptions on the measured visibilities aresignificant. Despite these effects, we demonstrate how the overall structure ofthe input models can be recovered robustly after performing calibration steps.With the planned addition of new stations to the EHT array, images could bereconstructed with higher angular resolution and dynamic range. In our casestudy, these improvements allowed for a distinction between a thermal and anon-thermal GRMHD model based on salient features in reconstructed images.[Journal_ref: ]
• Sabra, B. M., Hamann, F., Shields, J. C., George, I., & Jannuzi, B. (2024). X-Ray Absorption Associated with High-Velocity UV Absorbers.
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  We present Chandra observations of two radio-quiet QSOs, PG 2302+029 and PG1254+047. PG 2302+029 has an ultra high-velocity UV absorption system -56,000km/s, while PG 1254+047 is a Broad Absorption Line (BAL) QSO with detachedtroughs. Both objects are X-ray weak, consistent with the known correlationbetween alpha_ox and the strength of the UV absorption lines. The data suggestthat there is evidence that both objects are intrinsically weak X-ray sources,in addition to being heavily X-ray absorbed. The X-ray absorption columndensities are N_H > 10^22 cm^-2 for neutral gas and the intrinsic emissionspectra have alpha_ox > 2. The data are fit best by including ionized (ratherthan neutral) absorbers, with column densities N_H(PG2302) > 2.98 x 10^22 cm^-2and N_H(PG1254) > 17.3 x 10^22 cm^-2. The degrees of ionization are consistentwith the UV lines, as are the total column densities if the strongest lines aresaturated.[Journal_ref: ]
• Sarajedini, V. L., Green, R. F., & Jannuzi, B. T. (2024). Requirements for Investigating the Connection Between Lyman Alpha Absorption Clouds and the Large-Scale Distribution of Galaxies.
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  We model the requirements on observational data that would allow an accuratedetermination of the degree of association between Lyman alpha absorbers andpeaks in the redshift distribution of galaxies (large-scale structures likeclusters of galaxies). We compare simulated distributions of low-redshift Lymanalpha absorption systems, constrained to be consistent with the distributionobserved with HST, with the large-scale distribution of galaxies determinedfrom pencil-beam redshift surveys. We estimate the amount of observational datarequired from catalogues of Lyman alpha absorbers and galaxies to allow astatistically significant test of the association of absorbers with large-scalestructures of galaxies. We find that for each line-of-sight observed for Lyman alpha absorption lines(assuming that the entire redshift range out to z=0.4 is observable), redshiftsmust be obtained for at least 18 galaxies brighter than Mb=-18 and havingredshifts between 0.2 and 0.4. Based on the redshift surveys used in thisstudy, a search radius of 10' from the quasar line-of-sight is required. Thiswill ensure that all peaks in the galaxy redshift distribution are representedby at least one galaxy in the observed sample. If Lyman alpha absorbers areintrinsically uncorrelated with galaxies, we find that 8 lines-of-sight must beobserved to show that the distributions are different at the 95% confidencelevel. However, if a fraction of the Lyman alpha absorbers are distributed withthe peaks in the galaxy distribution, 38 lines-of-sight must be mapped for thedistribution of both Lyman alpha absorbers and galaxies in order to determinethe fraction of absorbers distributed with the peaks of the galaxy distributionto an accuracy of 10%.[Journal_ref: ]
• Satapathy, K., Psaltis, D., Ozel, F., Medeiros, L., Dougall, S. T., Chan, C., Wielgus, M., Prather, B. S., Wong, G. N., Gammie, C. F., Akiyama, K., Alberdi, A., Alef, W., Algaba, J. C., Anantua, R., Asada, K., Azulay, R., Baczko, A., Ball, D. R., , Baloković, M., et al. (2024). The Variability of the Black-Hole Image in M87 at the Dynamical Time Scale.
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  The black-hole images obtained with the Event Horizon Telescope (EHT) areexpected to be variable at the dynamical timescale near their horizons. For theblack hole at the center of the M87 galaxy, this timescale (5-61 days) iscomparable to the 6-day extent of the 2017 EHT observations. Closure phasesalong baseline triangles are robust interferometric observables that aresensitive to the expected structural changes of the images but are free ofstation-based atmospheric and instrumental errors. We explored the day-to-dayvariability in closure phase measurements on all six linearly independentnon-trivial baseline triangles that can be formed from the 2017 observations.We showed that three triangles exhibit very low day-to-day variability, with adispersion of $\sim3-5^\circ$. The only triangles that exhibit substantiallyhigher variability ($\sim90-180^\circ$) are the ones with baselines that crossvisibility amplitude minima on the $u-v$ plane, as expected from theoreticalmodeling. We used two sets of General Relativistic magnetohydrodynamicsimulations to explore the dependence of the predicted variability on variousblack-hole and accretion-flow parameters. We found that changing the magneticfield configuration, electron temperature model, or black-hole spin has amarginal effect on the model consistency with the observed level ofvariability. On the other hand, the most discriminating image characteristic ofmodels is the fractional width of the bright ring of emission. Models that bestreproduce the observed small level of variability are characterized by thinring-like images with structures dominated by gravitational lensing effects andthus least affected by turbulence in the accreting plasmas.[Journal_ref: ]
• Schlegel, D. J., Bebek, C., Heetderks, H., Ho, S., Lampton, M., Levi, M., Mostek, N., Padmanabhan, N., Perlmutter, S., Roe, N., Sholl, M., Smoot, G., White, M., Dey, A., Abraham, T., Jannuzi, B., Joyce, D., Liang, M., Merrill, M., , Olsen, K., et al. (2024). BigBOSS: The Ground-Based Stage IV Dark Energy Experiment.
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  The BigBOSS experiment is a proposed DOE-NSF Stage IV ground-based darkenergy experiment to study baryon acoustic oscillations (BAO) and the growth ofstructure with an all-sky galaxy redshift survey. The project is designed tounlock the mystery of dark energy using existing ground-based facilitiesoperated by NOAO. A new 4000-fiber R=5000 spectrograph covering a 3-degreediameter field will measure BAO and redshift space distortions in thedistribution of galaxies and hydrogen gas spanning redshifts from 0.2
• Shi, K., Lee, K., Dey, A., Huang, Y., Malavasi, N., Hung, C., Inami, H., Ashby, M., Duncan, K., Xue, R., Reddy, N., Hong, S., Jannuzi, B. T., Cooper, M. C., Gonzalez, A. H., Röttgering, H. J., Best, P. N., & Tasse, C. (2024). A census of galaxy constituents in a Coma Progenitor observed at z>3.
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  We present a detailed census of galaxies in and around PC217.96+32.3, aspectroscopically confirmed Coma analog at z=3.78. Diverse galaxy typesidentified in the field include Lya emitters (LAEs), massive star-forminggalaxies, and ultra-massive galaxies (log (Mstar/Msun)>= 11) which may havealready halted their star formation. The sky distribution of the star-forminggalaxies suggests the presence of a significant overdensity (delta_g=8+/-2),which is spatially offset from the previously confirmed members by 3-4 Mpc tothe west. Candidate quiescent and post-starburst galaxies are also found inlarge excess (a factor of ~ 8-15 higher surface density than the field)although their redshifts are less certain. We estimate that the total enclosedmass traced by star-forming galaxy candidates is roughly comparable to that ofPC217.96+32.3 traced by the LAEs. We speculate that the true extent ofPC217.96+32.3 may be larger than previously known, a half of which is missed byour LAE selection. Alternatively, the newly discovered overdensity may belongto another Coma progenitor not associated with PC217.96+32.3. Expectations fromtheory suggest that both scenarios are equally unlikely (
• Shipley, H. V., Papovich, C., Rieke, G. H., Dey, A., Jannuzi, B. T., Moustakas, J., & Weiner, B. (2024). Spitzer Spectroscopy of Infrared-Luminous Galaxies: Diagnostics of AGN and Star Formation and Contribution to Total Infrared Luminosity.
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  We use Spitzer IRS spectroscopy to study the nature 65 IR-luminous galaxiesat 0.02 < z < 0.6 with F(24micron) > 1.2mJy. The IRS spectra cover wavelengthsspanning the PAH features and important atomic diagnostic lines. Our samplecorresponds to L(IR) = L(8-1000micron) = 10^10-10^12 Lsun. We divide ourgalaxies into those with Spitzer IRAC colors indicative of warm dust heated byan AGN (IRAGN) and those whose colors indicate star-formation processes(non-IRAGN). Compared to the non-IRAGN, the IRAGN show smaller PAH emissionEWs, which we attribute to an increase in mid-IR continuum from the AGN. Wefind that in both the IRAGN and non-IRAGN samples, the PAH luminositiescorrelate strongly with the [Ne II] emission, from which we conclude that thePAH luminosity directly traces the instantaneous SFR in both the IRAGN andnon-IRAGN galaxies. We compare the ratio of PAH luminosity to the total IRluminosity and show that for most IRAGN star-formation accounts for 10-50% ofthe L(IR). We also find no measurable difference between the PAH luminosityratios of L(11.3)/L(7.7) and L(6.2)/L(7.7) for the IRAGN and non-IRAGN,suggesting that AGN do not significantly excite or destroy PAH molecules ongalaxy-wide scales. A small subset of galaxies show excess of [O IV] emissioncompared to their PAH emission, which indicates the presence ofheavily-obscured AGN, including 3 galaxies that are not otherwise selected asIRAGN. The low PAH emission and low [Ne II] emission of the IRAGN and [OIV]-excess objects imply they have low SFRs and their IR luminosity isdominated by processes associated with the AGN.[Journal_ref: ]
• Silverman, J. D., Green, P. J., Barkhouse, W. A., Kim, D. -., Kim, M., Wilkes, B. J., Cameron, R. A., Hasinger, G., Jannuzi, B. T., Smith, M. G., Smith, P. S., & Tananbaum, H. (2024). The Luminosity Function of X-ray Selected Active Galactic Nuclei: Evolution of Supermassive Black Holes at High Redshift.
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  We present a measure of the hard (2-8 keV) X-ray luminosity function (XLF) ofActive Galactic Nuclei up to z~5. At high redshifts, the wide area coverage ofthe Chandra Multiwavength Project is crucial to detect rare and luminous (Lx >10^44 erg s^-1) AGN. The inclusion of samples from deeper published surveys,such as the Chandra Deep Fields, allows us to span the lower Lx range of theXLF. Our sample is selected from both the hard (z < 3; f(2-8 keV) > 6.3x10^-16erg cm^-2 s^-1) and soft (z > 3; f(0.5-2.0 keV) > 1.0x10^-16 erg cm^-2 s^-1)energy band detections. Within our optical magnitude limits (r',i' < 24), weachieve an adequate level of completeness (>50%) regarding X-ray sourceidentification (i.e., redshift). We find that the luminosity function issimilar to that found in previous X-ray surveys up to z~3 with an evolutiondependent upon both luminosity and redshift. At z > 3, there is a significantdecline in the numbers of AGN with an evolution rate similar to that found bystudies of optically-selected QSOs. Based on our XLF, we assess the resolvedfraction of the Cosmic X-ray Background, the cumulative mass density ofSupermassive Black Holes (SMBHs), and the comparison of the mean accretion rateonto SMBHs and the star formation history of galaxies as a function ofredshift. A coevolution scenario up to z~2 is plausible though at higherredshifts the accretion rate onto SMBHs drops more rapidly. Finally, wehighlight the need for better statistics of high redshift AGN at z > 3, whichis achievable with the upcoming Chandra surveys.[Journal_ref: ]
• Silverman, J. D., Green, P. J., Kim, D. W., Wilkes, B. J., Cameron, R. A., Morris, D., Dosaj, A., Smith, C., Infante, L., Smith, P. S., Jannuzi, B. T., & Mathur, S. (2024). Discovery of a z=4.93, X-ray selected quasar by the Chandra Multiwavelength Project (ChamP).
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  We present X-ray and optical observations of CXOMP J213945.0-234655, a highredshift (z=4.93) quasar discovered through the Chandra Multiwavelength Project(ChaMP). This object is the most distant X-ray selected quasar published, withan X-ray luminosity of L(X)=5.9x10^44 erg/s (measured in the 0.3-2.5 keV bandand corrected for Galactic absorption). CXOMP J213945.0-234655 is a g' dropoutobject (>26.2), with r'=22.87 and i'=21.36. The rest-frame X-ray to opticalflux ratio is similar to quasars at lower redshifts and slightly X-ray brightrelative to z>4 optically-selected quasars observed with Chandra. The ChaMP isbeginning to acquire significant numbers of high redshift quasars toinvestigate the unobscured X-ray luminosity function out to z~5.[Journal_ref: ]
• Simpson, C., Eisenhardt, P., Armus, L., Chokshi, A., Dickinson, M., Djorgovski, S. G., Elston, R., Jannuzi, B. T., McCarthy, P. J., Pahre, M. A., & Soifer, B. T. (2024). Young stars and non-stellar emission in the aligned radio galaxy 3C 256.
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  We present ground-based images of the z=1.824 radio galaxy 3C 256 in thestandard BVRIJHK filters and an interference filter centered at 8800A, a HubbleSpace Telescope image in a filter dominated by Ly-alpha emission (F336W), andspectra covering rest-frame wavelengths from Ly-alpha to [O III] 5007. Togetherwith published polarimetry observations, we use these to decompose the overallspectral energy distribution into nebular continuum emission, scattered quasarlight, and stellar emission. The nebular continuum and scattered light togethercomprise half (one third) of the V-band (K-band) light within a 4-arcsecaperture, and are responsible for the strong alignment between theoptical/near-infrared light and the radio emission. The stellar emission isdominated by a population estimated to be 100-200 Myr old (assuming a SalpeterIMF), and formed in a short burst with a peak star formation rate of 1-4x10^3Msun/yr. The total stellar mass is estimated to be no more than 2x10^{11} Msun,which is far less than other luminous radio galaxies at similar redshifts, andsuggests that 3C 256 will undergo further star formation or mergers.[Journal_ref: ]
• Smith, P. S., Montiel, E., Rightley, S., Turner, J., Schmidt, G. D., & Jannuzi, B. T. (2024). Coordinated Fermi/Optical Monitoring of Blazars and the Great 2009 September Gamma-ray Flare of 3C 454.3.
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  We describe the optical spectropolarimetric monitoring program at StewardObservatory centered around gamma-ray-bright blazars and the LAT MonitoredSource List planned for Fermi Cycles 2-4. The large number of measurements madeduring Cycle 1 of the Fermi mission are available to the research community andthe data products are summarized (seehttp://james.as.arizona.edu/~psmith/Fermi). The optical data includespectropolarimetry at a resolution of ~20 A, broad-band polarization and fluxmeasurements, and flux-calibrated spectra spanning 4000-7600 A. These dataprovide a comprehensive view of the optical variability of an important sampleof objects during the Fermi Era. In addition to broad-band flux and linearpolarization monitoring, the spectra allow for the tracking of changes to thespectral index of the synchrotron continuum, importance of non-synchrotronemission features, and how and when the polarization varies with wavelength, animportant clue as to the structure of the emission region or the identificationof multiple nonthermal components. As an illustration, we present observationsof 3C 454.3 obtained in 2009 September during an exceptionally bright gamma-rayflare. The blazar was optically bright during the flare, but except for a fewshort periods, it showed surprisingly low polarization (P < 5%). Opportunitiesexist within the Fermi research community to coordinate with our long-termoptical monitoring program toward the goal of maximum scientific value to boththe Fermi and associated radio VLBI monitoring of blazars.[Journal_ref: ]
• Smith, P. S., Schmidt, G. D., & Jannuzi, B. T. (2024). The Optical Properties of PKS 1222+216 During the Fermi Mission.
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  The optical properties of the z = 0.435 quasar PKS 1222+216 (4C+21.35) aresummarized since the discovery of impressive gamma-ray activity in this sourceby Fermi/LAT. Unlike several other gamma-ray-bright blazars, there appears tobe little connection between optical and gamma-ray activity. Spectropolarimetryshows this object to be a composite system with optical emission from both apolarized, variable synchrotron power-law and unpolarized light from a stableblue continuum source (+broad emission-line region) contributing to theobserved spectrum. Spectrophotometry over a period of about two years does notdetect significant variability in the strong, broad emission lines, despitelarge optical continuum variations. This suggests that the relativistic jet haslittle influence on the output of the broad emission-line region, possiblyeither because the highly beamed continuum ionizes only a small portion of theline-emitting gas, or the observed non-thermal continuum originates parsecsdownstream from the base of the jet, further away from the central engine thanthe broad emission-line region.[Journal_ref: ]
• Stanford, S. A., Eisenhardt, P. R., Brodwin, M., Gonzalez, A. H., Stern, D., Jannuzi, B., Dey, A., Brown, M. J., McKenzie, E., & Elston, R. (2024). An IR-Selected Galaxy Cluster at z = 1.41.
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  We report the discovery of a galaxy cluster at z = 1.41. ISCS J143809+341419was found in the Spitzer/IRAC Shallow Survey of the Bootes field in the NOAODeep Wide-Field Survey carried out by IRAC. The cluster candidate was initiallyidentified as a high density region of objects with photometric redshifts inthe range 1.3 < z < 1.5. Optical spectroscopy of a limited number of objects inthe region shows that 5 galaxies within a ~120 arcsec diameter region lie at z= 1.41 +/- 0.01. Most of these member galaxies have broad--band colorsconsistent with the expected spectral energy distribution of apassively--evolving elliptical galaxy formed at high redshift. The redshift ofISCS J143809+341419 is the highest currently known for aspectroscopically-confirmed cluster of galaxies.[Journal_ref: ]
• Tejos, N., Morris, S. L., Finn, C. W., Crighton, N. H., Bechtold, J., Jannuzi, B. T., Schaye, J., Theuns, T., Altay, G., Fevre, O. L., Ryan-Weber, E., & Dave, R. (2024). On the connection between the intergalactic medium and galaxies: The HI-galaxy cross-correlation at z < 1.
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  We present a new optical spectroscopic survey of 1777 'star-forming' ('SF')and 366 'non-star-forming' ('non-SF') galaxies at redshifts z < 1 (2143 intotal), 22 AGN and 423 stars, observed by instruments such as DEIMOS, VIMOS andGMOS, in 3 fields containing 5 quasi-stellar objects (QSOs) with HST UVspectroscopy. We also present a new spectroscopic survey of 165 'strong' (10^14< NHI < 10^17 cm^-2), and 489 'weak' (10^13 < NHI < 10^14 cm^-2) intervening HIabsorption line systems at z < 1 (654 in total), observed in the spectra of 8QSOs by COS and FOS on the HST. Combining these new data with previouslypublished galaxy catalogs such as VVDS and GDDS, we have gathered a sample of654 HI absorption systems and 17509 galaxies at transverse scales < 50 Mpc. Wepresent observational results on the HI-galaxy and galaxy-galaxy correlationsat transverse scales r < 10 Mpc, and the HI-HI auto-correlation at transversescales r < 2 Mpc. The two-point correlation functions are measured both alongand transverse to the line-of-sight. We constrain the HI-galaxy statisticalconnection, as a function of both HI column density and galaxy star-formingactivity. Our results are consistent with the following conclusions: (1) thebulk of HI systems on Mpc scales have little velocity dispersion (
• Thompson, R., Green, J., Rieke, G., Robertson, D. Z., Schneider, G., Stark, D., Jannuzi, B., Ebbets, D., Kaplan, M., & Gracey, R. (2024). WFIRST Science with a Probe Class Mission.
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  WFIRST is the highest priority space mission of the Decadal review, however,it is unlikely to begin in this decade primarily due to a anticipated NASAbudget that is unlikely to have sufficient resources to fund such a mission.For this reason we present a lower cost mission that accomplishes all of theWFIRST science as described in the Design Reference Mission 1 with a probeclass design. This is effort is motivated by a desire to begin WFIRST in atimely manner and within a budget that can fit within the assets available toNASA on a realistic basis. The design utilizes dichroics to form four focalplanes all having the same field of view to use the majority of availablephotons from a 1.2 meter telescope.[Journal_ref: ]
• Torne, P., Liu, K., Eatough, R. P., Wongphechauxsorn, J., Cordes, J. M., Desvignes, G., de Laurentis, M., Kramer, M., Ransom, S. M., Chatterjee, S., Wharton, R., Karuppusamy, R., Blackburn, L., Janssen, M., Chan, C., Crew, G. B., Matthews, L. D., Goddi, C., Rottmann, H., , Wagner, J., et al. (2024). A search for pulsars around Sgr A* in the first Event Horizon Telescope dataset.
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  The Event Horizon Telescope (EHT) observed in 2017 the supermassive blackhole at the center of the Milky Way, Sagittarius A* (Sgr A*), at a frequency of228.1 GHz ($\lambda$=1.3 mm). The fundamental physics tests that even a singlepulsar orbiting Sgr A* would enable motivate searching for pulsars in EHTdatasets. The high observing frequency means that pulsars - which typicallyexhibit steep emission spectra - are expected to be very faint. However, italso negates pulse scattering, an effect that could hinder pulsar detections inthe Galactic Center. Additionally, magnetars or a secondary inverse Comptonemission could be stronger at millimeter wavelengths than at lower frequencies.We present a search for pulsars close to Sgr A* using the data from the threemost-sensitive stations in the EHT 2017 campaign: the Atacama LargeMillimeter/submillimeter Array, the Large Millimeter Telescope and the IRAM 30m Telescope. We apply three detection methods based on Fourier-domain analysis,the Fast-Folding-Algorithm and single pulse search targeting both pulsars andburst-like transient emission; using the simultaneity of the observations toconfirm potential candidates. No new pulsars or significant bursts were found.Being the first pulsar search ever carried out at such high radio frequencies,we detail our analysis methods and give a detailed estimation of thesensitivity of the search. We conclude that the EHT 2017 observations are onlysensitive to a small fraction ($\lesssim$2.2%) of the pulsars that may existclose to Sgr A*, motivating further searches for fainter pulsars in the region.[Journal_ref: ]
• Tran, H. D., Filippenko, A. V., Schmidt, G. D., Bjorkman, K. S., Jannuzi, B. T., & Smith, P. S. (2024). Probing the Geometry and Circumstellar Environment of SN 1993J in M81.
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  We have monitored the polarized radiation of the Type IIb SN 1993J in M81over a period of 41 days, starting from 7 days after the explosion on 1993March 27.5 (UT). Our data show clear evidence that the intrinsic continuumpolarization of SN 1993J evolved from being essentially negligible on April3-4, to a peak value of ~ 1% in late April 1993, and started to decline by themiddle of May. The polarized flux spectrum in late April strongly resembledspectra of Type Ib supernovae, with prominent He I lines but redshifted ~ 3380km/s relative to the total flux spectrum. These data are consistent with modelsof Hoflich; they suggest that the polarization was most likely produced byeither an asymmetric helium core configuration of material and/or flux, orscattering from an asymmetric circumstellar distribution of dusty material. Acombination of electron and dust scattering, as well as a clumpy or stratifieddistribution of the emitting gas, are possible as the polarization mechanism ofthe continuum and emission lines. The latter interpretation is supported by thefact that 1-2 months after the explosion, the observed rotations ofpolarization position angle across prominent line features remain even aftercorrection for effects of interstellar polarization. This indicates thatemission lines of He I, Fe II, [O I], and H are all intrinsically polarized atposition angles different from that of the continuum, with the non-Balmer linesgenerally being most highly polarized. If the supernova had an oblate geometry,our data are consistent with a small viewing angle (i.e., more or lessequator-on), although the degree of asphericity that gave rise to thepolarization at early times is probably smaller (minor to major axis ratio >0.7) than has been previously suggested.[Journal_ref: ]
• Trichas, M., Green, P. J., Silverman, J. D., Aldcroft, T., Barkhouse, W., Cameron, R. A., Constantin, A., Ellison, S. L., Foltz, C., Haggard, D., Jannuzi, B. T., Kim, D., Marshall, H. L., Mossman, A., Perez, L. M., Romero-Colmenero, E., Ruiz, A., Smith, M. G., Smith, P. S., , Torres, G., et al. (2024). The Chandra Multi-Wavelength Project: Optical Spectroscopy and the Broadband Spectral Energy Distributions of X-ray Selected AGN.
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  From optical spectroscopy of X-ray sources observed as part of ChaMP, wepresent redshifts and classifications for a total of 1569 Chandra sources fromour targeted spectroscopic follow up using the FLWO, SAAO, WIYN, CTIO, KPNO,Magellan, MMT and Gemini telescopes, and from archival SDSS spectroscopy. Weclassify the optical counterparts as 50% BLAGN, 16% NELG, 14% ALG, and 20%stars. We detect QSOs out to z~5.5 and galaxies out to z~3. We have compiledextensive photometry from X-ray to radio bands. Together with our spectroscopicinformation, this enables us to derive detailed SEDs for our extragalacticsources. We fit a variety of templates to determine bolometric luminosities,and to constrain AGN and starburst components where both are present. While~58% of X-ray Seyferts require a starburst event to fit observed photometryonly 26% of the X-ray QSO population appear to have some kind of star formationcontribution. This is significantly lower than for the Seyferts, especially ifwe take into account torus contamination at z>1 where the majority of our X-rayQSOs lie. In addition, we observe a rapid drop of the percentage of starburstcontribution as X-ray luminosity increases. This is consistent with thequenching of star formation by powerful QSOs, as predicted by the merger model,or with a time lag between the peak of star formation and QSO activity. We havetested the hypothesis that there should be a strong connection between X-rayobscuration and star-formation but we do not find any association between X-raycolumn density and star formation rate both in the general population or thestar-forming X-ray Seyferts. Our large compilation also allows us to reporthere the identification of 81 XBONG, 78 z>3 X-ray sources and 8 Type-2 QSOcandidates. Also we have identified the highest redshift (z=5.4135) X-rayselected QSO with optical spectroscopy.[Journal_ref: ]
• Veilleux, S., & Jannuzi, B. T. (2024). The Maryland-NOAO Instrument Partnership (2003-2009).
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  Seven years ago, with the encouragement of the NSF and AURA, NOAO requestedproposals from the community to partner with the national observatory toimprove instrumentation and/or telescope capabilities at KPNO and CTIO. Of theproposals that were selected, one came from the University of Maryland with thegoals of helping NOAO complete the development, construction, and deployment ofa new, wide-field, near-IR imager (NEWFIRM) and of working with NOAO to developdata reduction pipelines and data archiving capabilities at NOAO. By allmeasures, the Maryland-NOAO instrument partnership has been a resoundingsuccess. In this article, we briefly describe the positive impact thispartnership has had on Maryland, NOAO, and the astronomical community.[Journal_ref: ]
• Wagg, J., Pope, A., Alberts, S., Armus, L., Brodwin, M., Bussmann, R. S., Desai, V., Dey, A., Jannuzi, B., Floc'H, E. L., Melbourne, J., & Stern, D. (2024). CO J=2-1 line emission in cluster galaxies at z~1: fueling star formation in dense environments.
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  We present observations of CO J=2-1 line emission in infrared-luminouscluster galaxies at z~1 using the IRAM Plateau de Bure Interferometer. Our twoprimary targets are optically faint, dust-obscured galaxies (DOGs) found to liewithin 2 Mpc of the centers of two massive (>10^14 Msun) galaxy clusters. COline emission is not detected in either DOG. We calculate 3-sigma upper limitsto the CO J=2-1 line luminosities, L'_CO < 6.08x10^9 and < 6.63x10^9 K km/spc^2. Assuming a CO-to-H_2 conversion factor derived for ultraluminous infraredgalaxies in the local Universe, this translates to limits on the cold moleculargas mass of M_H_2 < 4.86x10^9 Msun and M_H_2 < 5.30x10^9 Msun. Both DOGsexhibit mid-infrared continuum emission that follows a power-law, suggestingthat an AGN contributes to the dust heating. As such, estimates of the starformation efficiencies in these DOGs are uncertain. A third cluster member withan infrared luminosity, L_IR < 7.4x10^11 Lsun, is serendipitously detected inCO J=2-1 line emission in the field of one of the DOGs located roughly twovirial radii away from the cluster center. The optical spectrum of this objectsuggests that it is likely an obscured AGN, and the measured CO line luminosityis L'_CO = (1.94 +/- 0.35)x10^10 K km/s pc^2, which leads to an estimated coldmolecular gas mass M_H_2 = (1.55+/-0.28)x10^10 Msun. A significant reservoir ofmolecular gas in a z~1 galaxy located away from the cluster center demonstratesthat the fuel can exist to drive an increase in star-formation and AGN activityat the outskirts of high-redshift clusters.[Journal_ref: ]
• Wang, J. X., Malhotra, S., Rhoads, J. E., Brown, M. J., Dey, A., Heckman, T. M., Jannuzi, B. T., Norman, C. A., Tiede, G. P., & Tozzi, P. (2024). 172 ks Chandra Exposure of the LALA Boötes Field: X-ray Source Catalog.
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  We present an analysis of a deep, 172 ks Chandra observation of the LargeArea Lyman Alpha Survey (LALA) Bo\"{o}tes field, obtained with the Advanced CCDImaging Spectrometer (ACIS-I) on the Chandra X-ray Observatory. This is one ofthe deepest Chandra images of the extragalactic sky; only the 2 Ms CDF-N and 1Ms CDF-S are substantially deeper. A total of 168 X-ray sources were detected.The X-ray source counts were derived and compared with those from other Chandradeep surveys; the hard X-ray source density of the LALA Bo\"{o}tes field is 33%higher than that of CDF-S at the flux level of 2.0E-15 ergs/cm^2/s, confirmingthe field-to-field variances of the hard band source counts reported byprevious studies. The deep exposure resolves > 72% of the 2-10 keV X-raybackground. Our primary optical data are R-band imaging from NOAO Deep Wide-Field Survey(NDWFS), with limiting magnitude of R = 25.7 (Vega, 3sigma, 4" diameteraperture). We have found optical counterparts for 152 of the 168 Chandrasources (90%). Among the R-band non-detected sources, not more than 11 of themcan possibly be at z > 5, based on the hardness ratios of their X-ray emissionand nondetections in bluer bands. The majority (~76%) of the X-ray sources arefound to have log(f_X/f_R) within 0.0+-1, which are believed to be AGNs.Most ofthe X-ray faint/optically bright sources (log(f_X/f_R) < -1.0) are opticallyextended, which are low-z normal galaxies or low luminosity AGNs. There is alsoa population of sources which are X-ray overluminous for their opticalmagnitudes (log(f_X/f_R) > 1.0), which are harder in X-ray and are probablyobscured AGNs. (abridged)[Journal_ref: ]
• Watson, C. R., Kochanek, C. S., Forman, W. R., Hickox, R. C., Jones, C. J., Brown, M. J., Brand, K., Dey, A., Jannuzi, B. T., Kenter, A. T., Murray, S. S., Vikhlinin, A., Eisenstein, D. J., Fazio, G. G., Green, P. J., McNamara, B. R., Rieke, M., & Shields, J. C. (2024). The Star Formation and Nuclear Accretion Histories of Normal Galaxies in the AGES Survey. Astrophys.J., 696, 2206-2219.
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  We combine IR, optical and X-ray data from the overlapping, 9.3 square degreeNOAO Deep Wide-Field Survey (NDWFS), AGN and Galaxy Evolution Survey (AGES),and XBootes Survey to measure the X-ray evolution of 6146 normal galaxies as afunction of absolute optical luminosity, redshift, and spectral type over thelargely unexplored redshift range 0.1 < z < 0.5. Because only the closest orbrightest of the galaxies are individually detected in X-rays, we use astacking analysis to determine the mean properties of the sample. Our resultssuggest that X-ray emission from spectroscopically late-type galaxies isdominated by star formation, while that from early-type galaxies is dominatedby a combination of hot gas and AGN emission. We find that the mean starformation and supermassive black hole accretion rate densities evolve like(1+z)^3, in agreement with the trends found for samples of bright, individuallydetectable starburst galaxies and AGN. Our work also corroborates the resultsof many previous stacking analyses of faint source populations, with improvedstatistics.[Journal_ref: Astrophys.J.696:2206-2219,2009]
• Weiner, B. J., Sand, D., Gabor, P., Johnson, C., Swindell, S., Kubanek, P., Gasho, V., Golota, T., Jannuzi, B., Milne, P., Smith, N., & Zaritsky, D. (2024). Development of the Arizona Robotic Telescope Network. Proc. SPIE.
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  The Arizona Robotic Telescope Network (ARTN) project is a long term effort todevelop a system of telescopes to carry out a flexible program of PI observing,survey projects, and time domain astrophysics including monitoring, rapidresponse, and transient/target-of-opportunity followup. Steward Observatoryoperates and shares in several 1-3m class telescopes with quality sites andinstrumentation, largely operated in classical modes. Science programs suitedto these telescopes are limited by scheduling flexibility and people-power ofavailable observers. Our goal is to adapt these facilities for multipleco-existing queued programs, interrupt capability, remote/robotic operation,and delivery of reduced data. In the long term, planning for the LSST era, weenvision an automated system coordinating across multiple telescopes and sites,where alerts can trigger followup, classification, and triggering of furtherobservations if required, such as followup imaging that can triggerspectroscopy. We are updating telescope control systems and software toimplement this system in stages, beginning with the Kuiper 61'' and VaticanObservatory 1.8-m telescopes. The Kuiper 61'' and its Mont4K camera can now becontrolled and queue-scheduled by the RTS2 observatory control software, andoperated from a remote room at Steward. We discuss science and technicalrequirements for ARTN, and some of the challenges in adapting heterogenouslegacy facilities, scheduling, data pipelines, and maintaining capabilities fora diverse user base.[Journal_ref: Proc. SPIE 10704, 107042H (10 July 2018)]
• Wilkes, B. J., Green, P., Brissenden, R., Cameron, R., Dobrzycki, A., Drake, J., Evans, N., Fruscione, A., Gaetz, T., Garcia, M., Ghosh, H., Grimes, J., Grindlay, J., Hooper, E., Karovska, M., Kashyap, V., Kim, D. -., Kowal, K., Marshall, H., , Mossman, A., et al. (2024). The Chandra Multi-wavelength Project (ChaMP): a serendipitous survey with Chandra archival data.
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  The launch of the Chandra X-ray Observatory in July 1999 opened a new era inX-ray astronomy. Its unprecedented,
• Xue, R., Lee, K., Dey, A., Reddy, N., Hong, S., Prescott, M. K., Inami, H., Jannuzi, B. T., & Gonzalez, A. H. (2024). The Diversity of Diffuse Ly$α$ Nebulae around Star-Forming Galaxies at High Redshift.
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  We report the detection of diffuse Ly$\alpha$ emission, or Ly$\alpha$ halos(LAHs), around star-forming galaxies at $z\approx3.78$ and $2.66$ in the NOAODeep Wide-Field Survey Bo\"otes field. Our samples consist of a total of$\sim$1400 galaxies, within two separate regions containing spectroscopicallyconfirmed galaxy overdensities. They provide a unique opportunity toinvestigate how the LAH characteristics vary with host galaxy large-scaleenvironment and physical properties. We stack Ly$\alpha$ images of differentsamples defined by these properties and measure their median LAH sizes bydecomposing the stacked Ly$\alpha$ radial profile into a compact galaxy-likeand an extended halo-like component. We find that the exponential scale-lengthof LAHs depends on UV continuum and Ly$\alpha$ luminosities, but not onLy$\alpha$ equivalent widths or galaxy overdensity parameters. The fullsamples, which are dominated by low UV-continuum luminosity Ly$\alpha$ emitters($M_{\rm UV} \gtrsim -21$), exhibit LAH sizes of 5$\,-\,6\,$kpc. However, themost UV- or Ly$\alpha$-luminous galaxies have more extended halos withscale-lengths of 7$\,-\,9\,$kpc. The stacked Ly$\alpha$ radial profiles declinemore steeply than recent theoretical predictions that include the contributionsfrom gravitational cooling of infalling gas and from low-level star formationin satellites. On the other hand, the LAH extent matches what one would expectfor photons produced in the galaxy and then resonantly scattered by gas in anoutflowing envelope. The observed trends of LAH sizes with host galaxyproperties suggest that the physical conditions of the circumgalactic medium(covering fraction, HI column density, and outflow velocity) change with halomass and/or star-formation rates.[Journal_ref: ]
• You, C., Zabludoff, A., Smith, P., Yang, Y., Kim, E., Jannuzi, B., Prescott, M. K., Matsuda, Y., & Lee, M. G. (2024). Mapping the Polarization of the Radio-Loud Ly$α$ Nebula B3 J2330+3927.
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  Lya nebulae, or "Lya blobs", are extended (up to ~100 kpc), bright (L[Lya] >10^43 erg/s) clouds of Lya emitting gas that tend to lie in overdense regionsat z ~ 2--5. The origin of the Lya emission remains unknown, but recenttheoretical work suggests that measuring the polarization might discriminateamong powering mechanisms. Here we present the first narrowband, imagingpolarimetry of a radio-loud Lya nebula, B3 J2330+3927 at z=3.09, with anembedded active galactic nucleus (AGN). The AGN lies near the blob's Lyaemission peak and its radio lobes align roughly with the blob's major axis.With the SPOL polarimeter on the 6.5m MMT telescope, we map the total (Lya +continuum) polarization in a grid of circular apertures of radius 0.6"(4.4kpc), detecting a significant (>2sigma) polarization fraction P in nineapertures and achieving strong upper-limits (as low as 2%) elsewhere. Pincreases from
• Beckett, A., Cantalupo, S., Fumagalli, M., Jannuzi, B., Morris, S. L., & Tejos, N. (2023). Modelling gas around galaxy pairs and groups using the Q0107 quasar triplet. Monthly Notices of the Royal Astronomical Society, 521(1), 1113-1143. doi:10.1093/mnras/stad596
• Janssen, M., Falcke, H., Kadler, M., Ros, E., Wielgus, M., Akiyama, K., Baloković, M., Blackburn, L., Bouman, K. L., Chael, A., Chan, C., Chatterjee, K., Davelaar, J., Edwards, P. G., Fromm, C. M., Gómez, J. L., Goddi, C., Issaoun, S., Johnson, M. D., , Kim, J., et al. (2021). Event Horizon Telescope observations of the jet launching and collimation in Centaurus A. Nature Astronomy, July, 1017-1028.
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  Very-long-baseline interferometry (VLBI) observations of active galacticnuclei at millimeter wavelengths have the power to reveal the launching andinitial collimation region of extragalactic radio jets, down to $10-100$gravitational radii ($r_g=GM/c^2$) scales in nearby sources. Centaurus A is theclosest radio-loud source to Earth. It bridges the gap in mass and accretionrate between the supermassive black holes (SMBHs) in Messier 87 and ourgalactic center. A large southern declination of $-43^{\circ}$ has howeverprevented VLBI imaging of Centaurus A below ${\lambda}1$cm thus far. Here, weshow the millimeter VLBI image of the source, which we obtained with the EventHorizon Telescope at $228$GHz. Compared to previous observations, we imageCentaurus A's jet at a tenfold higher frequency and sixteen times sharperresolution and thereby probe sub-lightday structures. We reveal ahighly-collimated, asymmetrically edge-brightened jet as well as the faintercounterjet. We find that Centaurus A's source structure resembles the jet inMessier 87 on ${\sim}500r_g$ scales remarkably well. Furthermore, we identifythe location of Centaurus A's SMBH with respect to its resolved jet core at${\lambda}1.3$mm and conclude that the source's event horizon shadow should bevisible at THz frequencies. This location further supports the universal scaleinvariance of black holes over a wide range of masses.[Journal_ref: Nature Astronomy, July 2021, Volume 5, p. 1017-1028]
• Narayan, R., Palumbo, D. C., Johnson, M. D., Gelles, Z., Himwich, E., Chang, D. O., Ricarte, A., Dexter, J., Gammie, C. F., Chael, A. A., Collaboration, T. E., , :., Akiyama, K., Alberdi, A., Alef, W., Algaba, J. C., Anantua, R., Asada, K., Azulay, R., , Baczko, A., et al. (2021). The Polarized Image of a Synchrotron Emitting Ring of Gas Orbiting a Black Hole. ApJ.
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  Synchrotron radiation from hot gas near a black hole results in a polarizedimage. The image polarization is determined by effects including theorientation of the magnetic field in the emitting region, relativistic motionof the gas, strong gravitational lensing by the black hole, and paralleltransport in the curved spacetime. We explore these effects using a simplemodel of an axisymmetric, equatorial accretion disk around a Schwarzschildblack hole. By using an approximate expression for the null geodesics derivedby Beloborodov (2002) and conservation of the Walker-Penrose constant, weprovide analytic estimates for the image polarization. We test this model usingcurrently favored general relativistic magnetohydrodynamic simulations of M87*,using ring parameters given by the simulations. For a subset of these withmodest Faraday effects, we show that the ring model broadly reproduces thepolarimetric image morphology. Our model also predicts the polarizationevolution for compact flaring regions, such as those observed from Sgr A* withGRAVITY. With suitably chosen parameters, our simple model can reproduce theEVPA pattern and relative polarized intensity in Event Horizon Telescope imagesof M87*. Under the physically motivated assumption that the magnetic fieldtrails the fluid velocity, this comparison is consistent with the clockwiserotation inferred from total intensity images.[Journal_ref: ApJ 912 35 (2021)]
• Berlind, A., Pratt, C., Oppenheimer, B., Danforth, C., Keeney, B., Stocke, J., Jannuzi, B. T., & Impey, C. D. (2019). The Ultraviolet Detection of Diffuse Gas in Galaxy Groups. The Astrophysical Journal Supplement Series, 240(1). doi:10.3847/1538-4365/aaf73d
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  A small survey of the UV-absorbing gas in 12 low-z galaxy groups has been conducted using the Cosmic Origins Spectrograph on board the Hubble Space Telescope. Targets were selected from a large, homogeneously selected sample of groups found in the Sloan Digital Sky Survey. A critical selection criterion excluded sight lines that pass close (
• Pratt, C., Berlind, A., Oppenheimer, B., Jannuzi, B. T., Danforth, C., Keeney, B., Stocke, J., & Impey, C. D. (2019). VizieR Online Data Catalog: HST/COS UV obs. of low-z SDSS galaxy groups. The Astrophysical Journal Supplement Series, 240, 15.
• Stocke, J. T., Keeney, B. A., Danforth, C. W., Oppenheimer, B. D., Pratt, C. T., Berlind, A. A., Impey, C., & Jannuzi, B. (2019). The Ultraviolet Detection of Diffuse Gas in Galaxy Groups. , ApJS,.
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  A small survey of the UV-absorbing gas in 12 low-$z$ galaxy groups has beenconducted using the Cosmic Origins Spectrograph (COS) on-board the Hubble SpaceTelescope (HST). Targets were selected from a large, homogeneously-selectedsample of groups found in the Sloan Digital Sky Survey (SDSS). A criticalselection criterion excluded sight lines that pass close ($
• Kozlowski, S., Kochanek, C. S., Ashby, M. L., Assef, R. J., Brodwin, M., Eisenhardt, P. R., Jannuzi, B. T., & Stern, D. (2016). Quasar Variability in the Mid-Infrared. , The Astrophysical Journal,.
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  The Decadal IRAC Bootes Survey is a mid-IR variability survey of the ~9 sq.deg. of the NDWFS Bootes Field and extends the time baseline of itspredecessor, the Spitzer Deep, Wide-Field Survey (SDWFS), from 4 to 10 years.The Spitzer Space Telescope visited the field five times between 2004 and 2014at 3.6 and 4.5 microns. We provide the difference image analysis photometry fora half a million mostly extragalactic sources. In mid-IR color-color plane,sources with quasar colors constitute the largest variability class (75%), 16%of the variable objects have stellar colors and the remaining 9% have thecolors of galaxies. Adding the fifth epoch doubles the number of variableactive galactic nuclei (AGNs) for the same false positive rates as in SDWFS, orincreases the number of sources by 20% while decreasing the false positiverates by factors of 2-3 for the same variability amplitude. We quantify theensemble mid-IR variability of ~1500 spectroscopically confirmed AGNs usingsingle power-law structure functions (SFs), which we find to be steeper (index$\gamma=0.45$) than in the optical ($\gamma=0.3$), leading to much loweramplitudes at short time-lags. This provides evidence for large emissionregions, smoothing out any fast UV/optical variations, as the origin ofinfrared quasar variability. The mid-IR AGN SF slope $\gamma$ seems to beuncorrelated with both the luminosity and rest-frame wavelength, while theamplitude shows an anti-correlation with the luminosity and a correlation withthe rest-frame wavelength.[Journal_ref: 2016, The Astrophysical Journal, 817, 119]
• Tejos, N., Morris, S. L., Finn, C. W., H., N., Bechtold, J., Jannuzi, B. T., Schaye, J., Theuns, T., Altay, G., Fèvre, O. L., Ryan-Weber, E., & Dav́e, R. (2014). On the connection between the intergalactic medium and galaxies: The hi-galaxy cross-correlation at z < 1*. Monthly Notices of the Royal Astronomical Society, 437(3), 2017-2075.
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  Abstract: We present a new optical spectroscopic survey of 1777 'star-forming' ('SF') and 366 'non-starforming' ('non-SF') galaxies at redshifts z ~ 0-1 (2143 in total), 22 AGN and 423 stars, observed by instruments such as the Deep Imaging Multi-Object Spectrograph, the Visible Multi- Object Spectrograph and the GeminiMulti-Object Spectrograph, in three fields containing five quasi-stellar objects (QSOs) with Hubble Space Telescope (HST) ultraviolet spectroscopy.We also present a new spectroscopic survey of 173 'strong' (1014 < NHI < 1017 cm-2) and 496 'weak' (1013 < NHI ≤ 1014 cm-2) intervening HI (Lyα) absorption-line systems at z < 1 (669 in total), observed in the spectra of eight QSOs at z ~ 1 by the Cosmic Origins Spectrograph and the Faint Object Spectrograph on the HST. Combining these new data with previously published galaxy catalogues such as the Very Large Telescope Visible Multi-Object Spectrograph Deep Survey and the Gemini Deep Deep Survey, we have gathered a sample of 654 HI absorption systems and 17 509 galaxies at transverse scales ≤50 Mpc, suitable for a two-point correlation function analysis. We present observational results on the HI-galaxy (ξgg) and galaxy-galaxy (ξ;gg) correlations at transverse scales r⊥ ≤ 10 Mpc, and the HI-H I autocorrelation (ξ;gg) at transverse scales r⊥ ≤ 2Mpc. The two-point correlation functions are measured both along and transverse to the line of sight, ξ (r⊥, r). We also infer the shape of their corresponding 'real-space' correlation functions, ξ (r), from the projected along the line-of-sight correlations, assuming power laws of the form ξ (r)=(r/r0)-γ; . Comparing the results from ξag, ξgg and ξa, we constrain the HI-galaxy statistical connection, as a function of both HI column density and galaxy star formation activity. Our results are consistent with the following conclusions: (i) the bulk of HI systems on ~Mpc scales have little velocity dispersion (≤120 km s-1) with respect to the bulk of galaxies (i.e. no strong galaxy outflow/inflow signal is detected); (ii) the vast majority (~100 per cent) of 'strong' HI systems and 'SF' galaxies are distributed in the same locations, together with 75 ± 15 per cent of 'non-SF' galaxies, all of which typically reside in dark matter haloes of similar masses; (iii) 25 ± 15 per cent of 'non-SF' galaxies reside in galaxy clusters and are not correlated with 'strong' HI systems at scales
• Alberts, S., Pope, A., Brodwin, M., Atlee, D. W., Lin, Y., Dey, A., Eisenhardt, P. R., Gettings, D. P., Gonzalez, A. H., Jannuzi, B. T., Mancone, C. L., Moustakas, J., Snyder, G. F., Stanford, S. A., Stern, D., Weiner, B. J., & Zeimann, G. R. (2013). The evolution of dust-obscured star formation activity in galaxy clusters relative to the field over the last 9 billion years. Monthly Notices of the Royal Astronomical Society, 437(1), 437-457.
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  Abstract: We compare the star formation (SF) activity in cluster galaxies to the field from z = 0.3 to 1.5 using Herschel Spectral and Photometric Imaging REceiver 250 μm imaging and utilizing 274 clusters from the IRAC Shallow Cluster Survey (ISCS). These clusters were selected as rest-frame near-infrared overdensities over the 9 square degree Boötes field. This sample allows us to quantify the evolution of SF in clusters over a long redshift baseline without bias against active cluster systems. Using a stacking analysis, we determine the average star formation rates (SFRs) and specific SFRs (SSFR = SFR/M*) of stellar mass-limited (M ≥ 1.3 × 1010M⊙), statistical samples of cluster and field galaxies, probing both the star-forming and quiescent populations. We find a clear indication that the average SF in cluster galaxies is evolving more rapidly than in the field, with field SF levels at z ≳ 1.2 in the cluster cores (r < 0.5 Mpc), in good agreement with previous ISCS studies. By quantifying the SF in cluster and field galaxies as an exponential function of cosmic time, we determine that cluster galaxies are evolving approximately two times faster than the field. Additionally, we see enhanced SF above the field level at z ~ 1.4 in the cluster outskirts (r > 0.5Mpc). These general trends in the cluster cores and outskirts are driven by the lower mass galaxies in our sample. Blue cluster galaxies have systematically lower SSFRs than blue field galaxies, but otherwise show no strong differential evolution with respect to the field over our redshift range. This suggests that the cluster environment is both suppressing the SF in blue galaxies on long time-scales and rapidly transitioning some fraction of blue galaxies to the quiescent galaxy population on short time-scales. We argue that our results are consistent with both strangulation and ram pressure stripping acting in these clusters, with merger activity occurring in the cluster outskirts. © 2013 The Authors Published by Oxford University Press on behalf of the Royal Astronomical Society.
• Ashby, M. L., Stanford, S. A., Brodwin, M., Gonzalez, A. H., Martinez-Manso, J., Bartlett, J. G., Benson, B. A., Bleem, L. E., Crawford, T. M., Dey, A., Dressler, A., Eisenhardt, P. R., Galametz, A., Jannuzi, B. T., Marrone, D. P., Mei, S., Muzzin, A., Pacaud, F., Pierre, M., , Stern, D., et al. (2013). The Spitzer South Pole Telescope Deep Field: Survey design and infrared array camera catalogs. Astrophysical Journal, Supplement Series, 209(2).
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  Abstract: The Spitzer South Pole Telescope Deep Field (SSDF) is a wide-area survey using Spitzer's Infrared Array Camera (IRAC) to cover 94 deg2 of extragalactic sky, making it the largest IRAC survey completed to date outside the Milky Way midplane. The SSDF is centered at (α, δ) = (23:30, -55:00), in a region that combines observations spanning a broad wavelength range from numerous facilities. These include millimeter imaging from the South Pole Telescope, far-infrared observations from Herschel/SPIRE, X-ray observations from the XMM XXL survey, near-infrared observations from the VISTA Hemisphere Survey, and radio-wavelength imaging from the Australia Telescope Compact Array, in a panchromatic project designed to address major outstanding questions surrounding galaxy clusters and the baryon budget. Here we describe the Spitzer/IRAC observations of the SSDF, including the survey design, observations, processing, source extraction, and publicly available data products. In particular, we present two band-merged catalogs, one for each of the two warm IRAC selection bands. They contain roughly 5.5 and 3.7 million distinct sources, the vast majority of which are galaxies, down to the SSDF 5σ sensitivity limits of 19.0 and 18.2 Vega mag (7.0 and 9.4 μJy) at 3.6 and 4.5 μm, respectively. © 2013. The American Astronomical Society. All rights reserved.
• Assef, R. J., Stern, D., Kochanek, C. S., Blain, A. W., Brodwin, M., Brown, M. J., Donoso, E., Eisenhardt, P. R., Jannuzi, B. T., Jarrett, T. H., Stanford, A. S., Tsai, C., Wu, J., & Yan, L. (2013). Mid-Infrared Selection of Active Galactic Nuclei with the Wide-Field Infrared Survey Explorer. II. Properties of WISE-Selected Active Galactic Nuclei in the NDWFS Boötes Field. , ApJ,.
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  Stern et al.(2012) presented a study of WISE selection of AGN in the 2 deg^2COSMOS field, finding that a simple criterion W1-W2>=0.8 provides a highlyreliable and complete AGN sample for W2
• Assef, R. J., Stern, D., Kochanek, C. S., Blain, A. W., Brodwin, M., Brown, M. J., Donoso, E., Eisenhardt, P. R., Jannuzi, B. T., Jarrett, T. H., Stanford, S. A., Tsai, C. -., Wu, J., & Yan, L. (2013). Mid-infrared selection of active galactic nuclei with the wide-field infrared survey explorer. II. Properties of wise-selected active galactic nuclei in the NDWFS boötes field. Astrophysical Journal, 772(1).
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  Abstract: Stern et al. presented a study of Wide-field Infrared Survey Explorer (WISE) selection of active galactic nuclei (AGNs) in the 2 deg2 COSMOS field, finding that a simple criterion W1-W2 ≥ 0.8 provides a highly reliable and complete AGN sample for W2 < 15.05, where the W1 and W2 passbands are centered at 3.4 μm and 4.6 μm, respectively. Here we extend this study using the larger 9 deg2 NOAO Deep Wide-Field Survey Boötes field which also has considerably deeper WISE observations than the COSMOS field, and find that this simple color cut significantly loses reliability at fainter fluxes. We define a modified selection criterion combining the W1-W2 color and the W2 magnitude to provide highly reliable or highly complete AGN samples for fainter WISE sources. In particular, we define a color-magnitude cut that finds 130 ± 4 deg-2 AGN candidates for W2 < 17.11 with 90% reliability. Using the extensive UV through mid-IR broadband photometry available in this field, we study the spectral energy distributions of WISE AGN candidates. We find that, as expected, the WISE AGN selection can identify highly obscured AGNs, but that it is biased toward objects where the AGN dominates the bolometric luminosity output. We study the distribution of reddening in the AGN sample and discuss a formalism to account for sample incompleteness based on the step-wise maximum-likelihood method of Efstathiou et al. The resulting dust obscuration distributions depend strongly on AGN luminosity, consistent with the trend expected for a receding torus. At L AGN ∼ 3 × 1044 erg s-1, 29% ± 7% of AGNs are observed as Type 1, while at ∼4 × 1045 erg s-1 the fraction is 64% ± 13%. The distribution of obscuration values suggests that dust in the torus is present as both a diffuse medium and in optically thick clouds. © 2013. The American Astronomical Society. All rights reserved.
• Brodwin, M., Stanford, S. A., Gonzalez, A. H., Zeimann, G. R., Snyder, G. F., Mancone, C. L., Pope, A., Eisenhardt, P. R., Stern, D., Alberts, S., Ashby, M. L., Brown, M. J., Chary, R. -., Dey, A., Galametz, A., Gettings, D. P., Jannuzi, B. T., Miller, E. D., Moustakas, J., & Moustakas, L. A. (2013). The era of star formation in galaxy clusters. Astrophysical Journal, 779(2).
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  Abstract: We analyze the star formation properties of 16 infrared-selected, spectroscopically confirmed galaxy clusters at 1 < z < 1.5 from the Spitzer/IRAC Shallow Cluster Survey (ISCS). We present new spectroscopic confirmation for six of these high-redshift clusters, five of which are at z > 1.35. Using infrared luminosities measured with deep Spitzer/Multiband Imaging Photometer for Spitzer observations at 24 μm, along with robust optical + IRAC photometric redshifts and spectral-energy-distribution-fitted stellar masses, we present the dust-obscured star-forming fractions, star formation rates, and specific star formation rates in these clusters as functions of redshift and projected clustercentric radius. We find that z ∼ 1.4 represents a transition redshift for the ISCS sample, with clear evidence of an unquenched era of cluster star formation at earlier times. Beyond this redshift, the fraction of star-forming cluster members increases monotonically toward the cluster centers. Indeed, the specific star formation rate in the cores of these distant clusters is consistent with field values at similar redshifts, indicating that at z > 1.4 environment-dependent quenching had not yet been established in ISCS clusters. By combining these observations with complementary studies showing a rapid increase in the active galactic nucleus (AGN) fraction, a stochastic star formation history, and a major merging episode at the same epoch in this cluster sample, we suggest that the starburst activity is likely merger-driven and that the subsequent quenching is due to feedback from merger-fueled AGNs. The totality of the evidence suggests we are witnessing the final quenching period that brings an end to the era of star formation in galaxy clusters and initiates the era of passive evolution. © 2013. The American Astronomical Society. All rights reserved.
• Chen, C. J., Hickox, R. C., Alberts, S., Brodwin, M., Jones, C., Murray, S. S., Alexander, D. M., Assef, R. J., J., M., Dey, A., Forman, W. R., Gorjian, V., Goulding, A. D., Floc'H, E. L., Jannuzi, B. T., Mullaney, J. R., & Pope, A. (2013). A correlation between star formation rate and average black hole accretion in star-forming galaxies. Astrophysical Journal, 773(1).
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  Abstract: We present a measurement of the average supermassive black hole accretion rate (BHAR) as a function of the star formation rate (SFR) for galaxies in the redshift range 0.25 < z < 0.8. We study a sample of 1767 far-IR-selected star-forming galaxies in the 9 deg2 Boötes multi-wavelength survey field. The SFR is estimated using 250 μm observations from the Herschel Space Observatory, for which the contribution from the active galactic nucleus (AGN) is minimal. In this sample, 121 AGNs are directly identified using X-ray or mid-IR selection criteria. We combined these detected AGNs and an X-ray stacking analysis for undetected sources to study the average BHAR for all of the star-forming galaxies in our sample. We find an almost linear relation between the average BHAR (in M⊙ yr-1) and the SFR (in M⊙ yr-1) for galaxies across a wide SFR range 0.85 < log SFR < 2.56: log BHAR = (- 3.72 ± 0.52) + (1.05 ± 0.33)log SFR. This global correlation between SFR and average BHAR is consistent with a simple picture in which SFR and AGN activity are tightly linked over galaxy evolution timescales. © 2013. The American Astronomical Society. All rights reserved.
• Crighton, N. H., Bechtold, J., Carswell, R. F., Davé, R., Foltz, C. B., Jannuzi, B. T., Morris, S. L., O'Meara, J. M., Prochaska, J. X., Schaye, J., & Tejos, N. (2013). A high molecular fraction in a subdamped absorber at z = 0.56. Monthly Notices of the Royal Astronomical Society, 433(1), 178-193.
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  Abstract: Measuring rest-fram ultraviolet rotational transitions from the Lyman and Werner bands in absorption against a bright background continuum is one of the few ways to directly measure molecular hydrogen (H2). Here, we report the detection of absorption from H2 at z = 0.56 in a subdamped Lyα system with neutral hydrogen column density NHI = 1019.5±0.2 cm-2. This is the first H2 system analysed at a redshift of -1.93 ± 0.36 based on modelling the line profiles, with a robust model-independent lower limit of fH2 > 10-3. This is higher than fH2 values seen along sightlines with similar NHI through the Milky Way disc and the Magellanic Clouds. The metallicity of the absorber is 0.19+0.21-0.10 solar, with a dust-to-gas ratio of
• K., M., Dey, A., & Jannuzi, B. T. (2013). A successful broadband survey for giant Lyα nebulae. II. Spectroscopic confirmation. Astrophysical Journal, 762(1).
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  Abstract: Using a systematic broadband search technique, we have carried out a survey for large Lyα nebulae (or Lyα "blobs") at 2 ≲ z ≲ 3 within 8.5 deg2 of the NOAO Deep Wide-Field Survey Boötes field, corresponding to a total survey comoving volume of ≈108 h -370 Mpc3. Here, we present our spectroscopic observations of candidate giant Lyα nebulae. Of 26 candidates targeted, 5 were confirmed to have Lyα emission at 1.7 ≲ z ≲ 2.7, 4 of which were new discoveries. The confirmed Lyα nebulae span a range of Lyα equivalent widths, colors, sizes, and line ratios, and most show spatially extended continuum emission. The remaining candidates did not reveal any strong emission lines, but instead exhibit featureless, diffuse, blue continuum spectra. Their nature remains mysterious, but we speculate that some of these might be Lyα nebulae lying within the redshift desert (i.e., 1.2 ≲ z ≲ 1.6). Our spectroscopic follow-up confirms the power of using deep broadband imaging to search for the bright end of the Lyα nebula population across enormous comoving volumes. © 2013. The American Astronomical Society. All rights reserved.
• Lee, K., Dey, A., Cooper, M. C., Reddy, N., & Jannuzi, B. T. (2013). Probing high-redshift galaxy formation at the highest luminosities: New insights from deimos spectroscopy. Astrophysical Journal, 771(1).
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  Abstract: We present Keck DEIMOS spectroscopic observations of the most UV-luminous star-forming galaxies at redshifts 3.2 < z < 4.6. Our sample, selected in the Boötes field of the NOAO Deep Wide-Field Survey, contains galaxies with luminosities of L* ≲ L UV ≲ 7 L* and is one of the largest samples to date of the most UV-luminous galaxies at these redshifts. Our spectroscopic data confirm 41 candidates as star-forming galaxies at 3.2 < z < 4.6 and validate the relatively clean selection of the photometric candidates with a contamination rate of 11%-28%. We find that the fraction of Lyα emitting galaxies increases with decreasing UV luminosity. None of the 12 galaxies with M UV < -22 (i.e., L UV > 3 L*) exhibit strong Lyα emission. We find strong evidence of large-scale outflows, transporting the neutral/ionized gas in the interstellar medium away from the galaxy. Galaxies exhibiting both interstellar absorption and Lyα emission lines show a significant offset between the two features, with a relative velocity of 200-1150 km s-1. We find tentative evidence that this measure of the outflow velocity increases with UV luminosity and/or stellar mass. The luminosity- and mass-dependent outflow strengths suggest that the efficiency of feedback and enrichment of the surrounding medium depend on these galaxy parameters. We also stack the individual spectra to construct composite spectra of the absorption-line-only and Lyα-emitting subsets of the UV luminous galaxies at z ≃ 3.7. The composite spectra are very similar to those of lower-redshift and lower-luminosity Lyman break galaxy (LBG) samples, but with some subtle differences. Analyses of the composite spectra suggest that the UV luminous LBGs at z ≃ 3.7 may have a higher covering fraction of absorbing gas, and may be older (or have had more prolonged star formation histories) than their lower-redshift and lower-luminosity counterparts. In addition, we have discovered that five galaxies in the sample belong to a massive overdensity at z = 3.78. Finally, two galaxies each show two distinct sets of interstellar absorption features. The latter may be a sign of a final stage of major merger, or clumpy disk formation. These systems are not expected in our sample: their presence implies that the frequency of such sources among our luminous z ≃ 3.7 LBGs may be an order of magnitude higher than in lower-redshift and lower-luminosity samples. © 2013. The American Astronomical Society. All rights reserved.
• Martini, P., Miller, E. D., Brodwin, M., Stanford, S. A., Gonzalez, A. H., Bautz, M., Hickox, R. C., Stern, D., Eisenhardt, P. R., Galametz, A., Norman, D., Jannuzi, B. T., Dey, A., Murray, S., Jones, C., & Brown, M. J. (2013). The cluster and field galaxy active galactic nucleus fraction at Z = 1-1.5: Evidence for a reversal of the local anticorrelation between environment and agn fraction. Astrophysical Journal, 768(1).
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  Abstract: The fraction of cluster galaxies that host luminous active galactic nuclei (AGNs) is an important probe of AGN fueling processes, the cold interstellar medium at the centers of galaxies, and how tightly black holes and galaxies co-evolve. We present a new measurement of the AGN fraction in a sample of 13 clusters of galaxies (M ≥ 1014 MȮ) at 1 < z < 1.5 selected from the Spitzer/IRAC Shallow Cluster Survey, as well as the field fraction in the immediate vicinity of these clusters, and combine these data with measurements from the literature to quantify the relative evolution of cluster and field AGN from the present to z ∼ 3. We estimate that the cluster AGN fraction at 1 < z < 1.5 is % for AGNs with a rest-frame, hard X-ray luminosity greater than LȮ X, H ≥ 1044 erg s-1. This fraction is measured relative to all cluster galaxies more luminous than , where is the absolute magnitude of the break in the galaxy luminosity function at the cluster redshift in the IRAC 3.6 μm bandpass. The cluster AGN fraction is 30 times greater than the 3σ upper limit on the value for AGNs of similar luminosity at z ∼ 0.25, as well as more than an order of magnitude greater than the AGN fraction at z ∼ 0.75. AGNs with LȮ X, H ≥ 1043 erg s-1 exhibit similarly pronounced evolution with redshift. In contrast to the local universe, where the luminous AGN fraction is higher in the field than in clusters, the X-ray and MIR-selected AGN fractions in the field and clusters are consistent at 1 < z < 1.5. This is evidence that the cluster AGN population has evolved more rapidly than the field population from z ∼ 1.5 to the present. This environment-dependent AGN evolution mimics the more rapid evolution of star-forming galaxies in clusters relative to the field. © 2013. The American Astronomical Society. All rights reserved.
• Palamara, D. P., Brown, M. J., Jannuzi, B. T., Dey, A., Stern, D., Pimbblet, K. A., Weiner, B. J., Ashby, M. L., Kochanek, C. S., Gonzalez, A., Brodwin, M., Floc'H, E. L., & Rieke, M. (2013). The Clustering of Extremely Red Objects. ApJ,.
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  We measure the clustering of Extremely Red Objects (EROs) in ~8 deg^2 of theNOAO Deep Wide Field Survey Bo\"otes field in order to establish robust linksbetween ERO z~1.2 and local galaxy z5.0 (28,724 galaxies), (I-K_s)>4.0 (22,451 galaxies) and (I-[3.6])>5.0(64,370 galaxies). Magnitude-limited samples show the correlation length (r_0)to increase for more luminous EROs, implying a correlation with stellar mass.We can separate star-forming and passive ERO populations using the (K_s-[24])and ([3.6]-[24]) colors to K_s=18.4 and [3.6]=17.5, respectively. Star-formingand passive EROs in magnitude limited samples have different clusteringproperties and host dark halo masses, and cannot be simply understood as asingle population. Based on the clustering, we find that bright passive EROsare the likely progenitors of >4L^* elliptical galaxies. Bright EROs withongoing star formation were found to occupy denser environments thanstar-forming galaxies in the local Universe, making these the likelyprogenitors of >L^* local ellipticals. This suggests that the progenitors ofmassive >4L^* local ellipticals had stopped forming stars by z>1.2, but thatthe progenitors of less massive ellipticals (down to L^*) can still showsignificant star formation at this epoch.[Journal_ref: ApJ, 764, 31, 2013]
• Palamara, D. P., J., M., Jannuzi, B. T., Dey, A., Stern, D., Pimbblet, K. A., Weiner, B. J., L., M., Kochanek, C. S., Gonzalez, A., Brodwin, M., Floc'H, E. L., & Rieke, M. (2013). The clustering of extremely red objects. Astrophysical Journal, 764(1).
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  Abstract: We measure the clustering of extremely red objects (EROs) in 8 deg 2 of the NOAO Deep Wide Field Survey Boötes field in order to establish robust links between ERO (z 1.2) and local galaxy (z < 0.1) populations. Three different color selection criteria from the literature are analyzed to assess the consequences of using different criteria for selecting EROs. Specifically, our samples are (R-Ks ) > 5.0 (28, 724 galaxies), (I-Ks ) > 4.0 (22, 451 galaxies), and (I-[3.6]) > 5.0 (64, 370 galaxies). Magnitude-limited samples show the correlation length (r 0) to increase for more luminous EROs, implying a correlation with stellar mass. We can separate star-forming and passive ERO populations using the (Ks-[24]) and ([3.6]-[24]) colors to Ks = 18.4 and [3.6] = 17.5, respectively. Star-forming and passive EROs in magnitude-limited samples have different clustering properties and host dark halo masses and cannot be simply understood as a single population. Based on the clustering, we find that bright passive EROs are the likely progenitors of ≳ 4L* elliptical galaxies. Bright EROs with ongoing star formation were found to occupy denser environments than star-forming galaxies in the local universe, making these the likely progenitors of ≳ L* local ellipticals. This suggests that the progenitors of massive ≳ 4L* local ellipticals had stopped forming stars by z ≳ 1.2, but that the progenitors of less massive ellipticals (down to L*) can still show significant star formation at this epoch. © 2013. The American Astronomical Society. All rights reserved.
• Prescott, M. K., Dey, A., & Jannuzi, B. T. (2013). A Successful Broad-band Survey for Giant Lya Nebulae II: Spectroscopic Confirmation. Astrophys.J., 38-45.
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  Using a systematic broad-band search technique, we have carried out a surveyfor large Lya nebulae (or Lya "blobs") at 2
• Shipley, H. V., Papovich, C., Rieke, G. H., Dey, A., Jannuzi, B. T., Moustakas, J., & Weiner, B. (2013). Spitzer spectroscopy of infrared-luminous galaxies: Diagnostics of active galactic nuclei and star formation and contribution to total infrared luminosity. Astrophysical Journal, 769(1).
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  Abstract: We use mid-infrared (MIR) spectroscopy from the Spitzer Infrared Spectrograph to study the nature of star-formation and supermassive black hole accretion for a sample of 65 IR-luminous galaxies at 0.02 < z < 0.6 with F(24 μm) > 1.2 mJy. The MIR spectra cover wavelengths 5-38 μm, spanning the polycyclic aromatic hydrocarbon (PAH) features and important atomic diagnostic lines. Our sample of galaxies corresponds to a range of total IR luminosity, L IR = L(8-1000 μm) = 1010-1012L (median LIR of 3.0 × 1011L). We divide our sample into a subsample of galaxies with Spitzer Infrared Array Camera 3.6-8.0 μm colors indicative of warm dust heated by an active galactic nucleus (AGN; IRAGN) and those galaxies whose colors indicate star-formation processes (non-IRAGN). Compared to the non-IRAGN, the IRAGN show smaller PAH emission equivalent widths, which we attribute to an increase in mid-IR continuum from the AGN. We find that in both the IRAGN and star-forming samples, the luminosity in the PAH features correlates strongly with [Ne II] λ12.8 μm emission line, from which we conclude that the PAH luminosity directly traces the instantaneous star-formation rate (SFR) in both the IRAGN and star-forming galaxies. We compare the ratio of PAH luminosity to the total IR luminosity, and we show that for most IRAGN star-formation accounts for 10%-50% of the total IR luminosity. We also find no measurable difference between the PAH luminosity ratios of L 11.3/L7.7 and L 6.2/L7.7 for the IRAGN and non-IRAGN, suggesting that AGN do not significantly excite or destroy PAH molecules on galaxy-wide scales. Interestingly, a small subset of galaxies (8 of 65 galaxies) show a strong excess of [O IV] λ25.9 μm emission compared to their PAH emission, which indicates the presence of heavily-obscured AGN, including 3 galaxies that are not otherwise selected as IRAGN. The low PAH emission and low [Ne II] emission of the IRAGN and [O IV]-excess objects imply the IR luminosity of these objects is dominated by processes associated with the AGN. Because these galaxies lie in the "green valley" of the optical color-magnitude relation and have low implied SFRs, we argue their hosts have declining SFRs and these objects will transition to the red sequence unless some process restarts their star-formation. © 2013. The American Astronomical Society. All rights reserved.
• Brodwin, M., Gonzalez, A. H., Stanford, S. A., Plagge, T., Marrone, D. P., Carlstrom, J. E., Dey, A., Eisenhardt, P. R., Fedeli, C., Gettings, D., Jannuzi, B. T., Joy, M., Leitch, E. M., Mancone, C., Snyder, G. F., Stern, D., & Zeimann, G. (2012). IDCS J1426.5+3508: Sunyaev-Zel'dovich measurement of a massive infrared-selected cluster at z = 1.75. Astrophysical Journal, 753(2).
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  Abstract: We report 31GHz CARMA observations of IDCSJ1426.5+3508, an infrared-selected galaxy cluster at z = 1.75. A Sunyaev-Zel'dovich (SZ) decrement is detected toward this cluster, indicating a total mass of M 200, m = (4.3 ± 1.1) × 10 14 M ⊙ in agreement with the approximate X-ray mass of 5 × 10 14 M ȯ. IDCSJ1426.5+3508 is by far the most distant cluster yet detected via the SZ effect, and the most massive z ≥ 1.4 galaxy cluster found to date. Despite the mere 1% probability of finding it in the 8.82deg 2 IRAC Distant Cluster Survey, IDCSJ1426.5+3508 is not completely unexpected in ΛCDM once the area of large, existing surveys is considered. IDCSJ1426.5+3508 is, however, among the rarest, most extreme clusters ever discovered and indeed is an evolutionary precursor to the most massive known clusters at all redshifts. We discuss how imminent, highly sensitive SZ experiments will complement infrared techniques for statistical studies of the formation of the most massive galaxy clusters in the z > 1.5 universe, including potential precursors to IDCSJ1426.5+3508. © 2012. The American Astronomical Society. All rights reserved..
• Bussmann, R. S., Dey, A., Armus, L., Brown, M. J., Desai, V., Gonzalez, A. H., Jannuzi, B. T., Melbourne, J., & Soifer, B. T. (2012). The star formation histories of z ∼ 2 dust-obscured galaxies and submillimeter-selected galaxies. Astrophysical Journal, 744(2).
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  Abstract: The Spitzer Space Telescope has identified a population of ultraluminous infrared galaxies (ULIRGs) at z ∼ 2 that may play an important role in the evolution of massive galaxies. We measure the stellar masses (M *) of two populations of Spitzer-selected ULIRGs that have extremely red R - [24] colors (dust-obscured galaxies, or DOGs) and compare our results with submillimeter-selected galaxies (SMGs). One set of 39 DOGs has a local maximum in their mid-infrared (mid-IR) spectral energy distribution (SED) at rest frame 1.6μm associated with stellar emission ("bump DOGs"), while the other set of 51 DOGs have power-law mid-IR SEDs that are typical of obscured active galactic nuclei ("power-law DOGs"). We measure M * by applying Charlot & Bruzual stellar population synthesis models to broadband photometry in the rest-frame ultraviolet, optical, and near-infrared of each of these populations. Assuming a simple stellar population and a Chabrier initial mass function, we find that power-law DOGs and bump DOGs are on average a factor of 2 and 1.5 more massive than SMGs, respectively (median and inter-quartile M * values for SMGs, bump DOGs, and power-law DOGs are log(M */M) = 10.42 +0.42- 0.36, 10.62+0.36- 0.32, and 10.71+0.40- 0.34, respectively). More realistic star formation histories drawn from two competing theories for the nature of ULIRGs at z 2 (major merger versus smooth accretion) can increase these mass estimates by up to 0.5dex. A comparison of our stellar masses with the instantaneous star formation rate (SFR) in these z 2 ULIRGs provides a preliminary indication supporting high SFRs for a given M *, a situation that arises more naturally in major mergers than in smooth accretion-powered systems. © 2012 The American Astronomical Society. All rights reserved.
• Cool, R. J., Eisenstein, D. J., Kochanek, C. S., J., M., Caldwell, N., Dey, A., Forman, W. R., Hickox, R. C., Jannuzi, B. T., Jones, C., Moustakas, J., & Murray, S. S. (2012). The galaxy optical luminosity function from the AGN and galaxy evolution survey. Astrophysical Journal, 748(1).
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  Abstract: We present the galaxy optical luminosity function for the redshift range 0.05 < z < 0.75 from the AGN and Galaxy Evolution Survey, a spectroscopic survey of 7.6 deg 2 in the Boötes field of the NOAO Deep Wide-Field Survey. Our statistical sample is composed of 12,473 galaxies with known redshifts down to I = 20.4 (AB). Our results at low redshift are consistent with those from Sloan Digital Sky Survey; at higher redshift, we find strong evidence for evolution in the luminosity function, including differential evolution between blue and red galaxies. We find that the luminosity density evolves as (1 + z) (0.54 0.64) for red galaxies and (1 + z) (1.64 0.39) for blue galaxies. © 2012 The American Astronomical Society. All rights reserved.
• K., M., Dey, A., & Jannuzi, B. T. (2012). A successful broadband survey for giant Lyα nebulae. I. Survey design and candidate selection. Astrophysical Journal, 748(2).
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  Abstract: Giant Lyα nebulae (or Lyα "blobs") are likely sites of ongoing massive galaxy formation, but the rarity of these powerful sources has made it difficult to form a coherent picture of their properties, ionization mechanisms, and space density. Systematic narrowband Lyα nebula surveys are ongoing, but the small redshift range covered and the observational expense limit the comoving volume that can be probed by even the largest of these surveys and pose a significant problem when searching for such rare sources. We have developed a systematic search technique designed to find large Lyα nebulae at 2 ≲ z ≲ 3 within deep broadband imaging and have carried out a survey of the 9.4deg 2 NOAO Deep Wide-Field Survey Boötes field. With a total survey comoving volume of 10 8h -370Mpc 3, this is the largest volume survey for Lyα nebulae ever undertaken. In this first paper in the series, we present the details of the survey design and a systematically selected sample of 79 candidates, which includes one previously discovered Lyα nebula. © 2012. The American Astronomical Society. All rights reserved..
• K., M., Dey, A., Brodwin, M., Chaffee, F. H., Desai, V., Eisenhardt, P., Floc'H, E. L., Jannuzi, B. T., Kashikawa, N., Matsuda, Y., & Soifer, B. T. (2012). Resolving the galaxies within a giant Lyα nebula: Witnessing the formation of a galaxy group?. Astrophysical Journal, 752(2).
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  Abstract: Detailed analysis of the substructure of Lyα nebulae can put important constraints on the physical mechanisms at work and the properties of galaxies forming within them. Using high-resolution Hubble Space Telescope (HST) imaging of a Lyα nebula at z 2.656, we have taken a census of the compact galaxies in the vicinity, used optical/near-infrared colors to select system members, and put constraints on the morphology of the spatially extended emission. The system is characterized by (1) a population of compact, low-luminosity (0.1 L*) sources - 17 primarily young, small (R e 1-2kpc), disky galaxies including an obscured active galactic nucleus - that are all substantially offset (≳20kpc) from the line-emitting nebula; (2) the lack of a central galaxy at or near the peak of the Lyα emission; and (3) several nearly coincident, spatially extended emission components - Lyα, He II, and UV continuum - that are extremely smooth. These morphological findings are difficult to reconcile with theoretical models that invoke outflows, cold flows, or resonant scattering, suggesting that while all of these physical phenomena may be occurring, they are not sufficient to explain the powering and large extent of Lyα nebulae. In addition, although the compact galaxies within the system are irrelevant as power sources, the region is significantly overdense relative to the field galaxy population (by at least a factor of four). These observations provide the first estimate of the luminosity function of galaxies within an individual Lyα nebula system and suggest that large Lyα nebulae may be the seeds of galaxy groups or low-mass clusters. © 2012. The American Astronomical Society. All rights reserved.
• Kochanek, C. S., Eisenstein, D. J., Cool, R. J., Caldwell, N., Assef, R. J., Jannuzi, B. T., Jones, C., Murray, S. S., Forman, W. R., Dey, A., Brown, M. J., Eisenhardt, P., Gonzalez, A. H., Green, P., & Stern, D. (2012). AGES: The AGN and galaxy evolution survey. Astrophysical Journal, Supplement Series, 200(1).
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  Abstract: The AGN and Galaxy Evolution Survey (AGES) is a redshift survey covering, in its standard fields, 7.7deg 2 of the Boötes field of the NOAO Deep Wide-Field Survey. The final sample consists of 23,745 redshifts. There are well-defined galaxy samples in 10 bands (the B W , R, I, J, K, IRAC 3.6, 4.5, 5.8, and 8.0 μm, and MIPS 24 μm bands) to a limiting magnitude of I < 20mag for spectroscopy. For these galaxies, we obtained 18,163 redshifts from a sample of 35,200 galaxies, where random sparse sampling was used to define statistically complete sub-samples in all 10 photometric bands. The median galaxy redshift is 0.31, and 90% of the redshifts are in the range 0.085 < z < 0.66. Active galactic nuclei (AGNs) were selected as radio, X-ray, IRAC mid-IR, and MIPS 24 μmsources to fainter limiting magnitudes (I < 22.5mag for point sources). Redshifts were obtained for 4764 quasars and galaxies with AGN signatures, with 2926, 1718, 605, 119, and 13 above redshifts of 0.5, 1, 2, 3, and 4, respectively. We detail all the AGES selection procedures and present the complete spectroscopic redshift catalogs and spectral energy distribution decompositions. Photometric redshift estimates are provided for all sources in the AGES samples. © 2012. The American Astronomical Society. All rights reserved..
• Krug, H. B., Veilleux, S., Tilvi, V., Malhotra, S., Rhoads, J., Hibon, P., Swaters, R., Probst, R., Dey, A., Dickinson, M., & Jannuzi, B. T. (2012). Searching for z 7.7 Lyα emitters in the cosmos field with newfirm. Astrophysical Journal, 745(2).
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  Abstract: The study of Lyα emission in the high-redshift universe is a useful probe of the epoch of reionization, as the Lyα line should be attenuated by the intergalactic medium (IGM) at low to moderate neutral hydrogen fractions. Here we present the results of a deep and wide imaging search for Lyα emitters in the Cosmological Evolution Survey field. We have used two ultra-narrowband filters (filter width of 8-9 ) on the NOAO Extremely Wide-Field Infrared Mosaic camera, installed on the Mayall 4 m telescope at Kitt Peak National Observatory, in order to isolate Lyα emitters at z = 7.7; such ultra-narrowband imaging searches have proved to be excellent at detecting Lyα emitters. We found 5σ detections of four candidate Lyα emitters in a survey volume of 2.8 × 10 4Mpc 3 (total survey area 760 arcmin 2). Each candidate has a line flux greater than 8 × 10 -18ergs -1cm -2. Using these results to construct a luminosity function and comparing to previously established Lyα luminosity functions at z = 5.7 and z = 6.5, we find no conclusive evidence for evolution of the luminosity function between z = 5.7 and z = 7.7. Statistical Monte Carlo simulations suggest that half of these candidates are real z = 7.7 targets, and spectroscopic follow-up will be required to verify the redshift of these candidates. However, our results are consistent with no strong evolution in the neutral hydrogen fraction of the IGM between z = 5.7 and z = 7.7, even if only one or two of the z = 7.7 candidates are spectroscopically confirmed. © 2012. The American Astronomical Society. All rights reserved.
• Krug, H., Veilleux, S., Tilvi, V., Malhotra, S., Rhoads, J., Hibon, P., Swaters, R., Probst, R., Dey, A., Dickinson, M., & Jannuzi, B. T. (2012). Searching for z~7.7 Lyman Alpha Emitters in the COSMOS Field with NEWFIRM. Astrophysical Journal.
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  The study of Ly-alpha emission in the high-redshift universe is a usefulprobe of the epoch of reionization, as the Ly-alpha line should be attenuatedby the intergalactic medium (IGM) at low to moderate neutral hydrogenfractions. Here we present the results of a deep and wide imaging search forLy-alpha emitters in the COSMOS field. We have used two ultra-narrowbandfilters (filter width of ~8-9 {\deg}A) on the NEWFIRM camera, installed on theMayall 4m telescope at Kitt Peak National Observatory, in order to isolateLy-alpha emitters at z = 7.7; such ultra-narrowband imaging searches haveproved to be excellent at detecting Ly-alpha emitters. We found 5-sigmadetections of four candidate Ly-alpha emitters in a survey volume of 2.8 x 10^4Mpc^3 (total survey area ~760 arcmin^2). Each candidate has a line flux greaterthan 8 x 10^-18 erg s^-1 cm^-2. Using these results to construct a luminosityfunction and comparing to previously established Ly-alpha luminosity functionsat z = 5.7 and z = 6.5, we find no conclusive evidence for evolution of theluminosity function between z = 5.7 and z = 7.7. Statistical Monte Carlosimulations suggest that half of these candidates are real z = 7.7 targets, andspectroscopic follow-up will be required to verify the redshift of thesecandidates. However, our results are consistent with no strong evolution in theneutral hydrogen fraction of the IGM between z = 5.7 and z = 7.7, even if onlyone or two of the z = 7.7 candidates are spectroscopically confirmed.[Journal_ref: Astrophysical Journal 745 (2012) 122]
• Lee, K., Alberts, S., Atlee, D., Dey, A., Pope, A., Jannuzi, B. T., Reddy, N., & J., M. (2012). Herschel detection of dust emission from UV-luminous star-forming galaxies at 3.3 ≲ z ≲ 4.3. Astrophysical Journal Letters, 758(2).
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  Abstract: We report the Herschel/SPIRE detection of dust emission arising from UV-luminous (L ≳ L*) star-forming galaxies at 3.3 ≲ z ≲ 4.3. Our sample of 1913 Lyman break galaxy (LBG) candidates is selected over an area of 5.3deg2 in the Boötes field of the NOAO Deep Wide-Field Survey. This is one of the largest samples of UV-luminous galaxies at this epoch and enables an investigation of the bright end of the galaxy luminosity function. We divide our sample into three luminosity bins and stack the Herschel/SPIRE data to measure the average spectral energy distribution (SED) of LBGs at far-infrared (FIR) wavelengths. We find that these galaxies have average IR luminosities of (3-5) × 1011 L and 60%-70% of their star formation obscured by dust. The FIR SEDs peak at λrest ≳ 100 μm suggesting dust temperatures (Td = 27-30 K) significantly colder than that of local galaxies of comparable IR luminosities. The observed IR-to-UV luminosity ratio (IRX ≡ L IR/L UV) is low (3-4) compared with that observed for z 2 LBGs (IRX z 2 7.1 ± 1.1). The correlation between the slope of the UV continuum and IRX for galaxies in the two lower luminosity bins suggests dust properties similar to those of local starburst galaxies. However, the galaxies in the highest luminosity bin appear to deviate from the local relation, suggesting that their dust properties may differ from those of their lower-luminosity and low-redshift counterparts. We speculate that the most UV-luminous galaxies at this epoch are being observed in a short-lived and young evolutionary phase. © © 2012. The American Astronomical Society. All rights reserved.
• Melbourne, J., Soifer, B. T., Desai, V., Pope, A., Armus, L., Dey, A., Bussmann, R. S., Jannuzi, B. T., & Alberts, S. (2012). The spectral energy distributions and infrared luminosities of z ≈ 2 dust-obscured galaxies from Herschel and Spitzer. Astronomical Journal, 143(5).
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  Abstract: Dust-obscured galaxies (DOGs) are a subset of high-redshift (z ≈ 2) optically-faint ultra-luminous infrared galaxies (ULIRGs, e.g., L IR > 10 12 L ⊙). We present new far-infrared photometry, at 250, 350, and 500 μm (observed-frame), from the Herschel Space Telescope for a large sample of 113 DOGs with spectroscopically measured redshifts. Approximately 60% of the sample are detected in the far-IR. The Herschel photometry allows the first robust determinations of the total infrared luminosities of a large sample of DOGs, confirming their high IR luminosities, which range from 10 11.6 L ⊙ 10 13 L ⊙. The rest-frame near-IR (1-3 μm) spectral energy distributions (SEDs) of the Herschel-detected DOGs are predictors of their SEDs at longer wavelengths. DOGs with "power-law" SEDs in the rest-frame near-IR show observed-frame 250/24 μm flux density ratios similar to the QSO-like local ULIRG, Mrk 231. DOGs with a stellar "bump" in their rest-frame near-IR show observed-frame 250/24 μm flux density ratios similar to local star-bursting ULIRGs like NGC6240. None show 250/24 μm flux density ratios similar to extreme local ULIRG, Arp 220; though three show 350/24 μm flux density ratios similar to Arp 220. For the Herschel-detected DOGs, accurate estimates (within ∼25%) of total IR luminosity can be predicted from their rest-frame mid-IR data alone (e.g., from Spitzer observed-frame 24 μm luminosities). Herschel-detected DOGs tend to have a high ratio of infrared luminosity to rest-frame 8 μm luminosity (the IR8 = L IR(8-1000 μm)/νL ν(8 μm) parameter of Elbaz et al.). Instead of lying on the z = 1-2 "infrared main sequence" of star-forming galaxies (like typical LIRGs and ULIRGs at those epochs) the DOGs, especially large fractions of the bump sources, tend to lie in the starburst sequence. While, Herschel-detected DOGs are similar to scaled up versions of local ULIRGs in terms of 250/24 μm flux density ratio, and IR8, they tend to have cooler far-IR dust temperatures (20-40 K for DOGs versus 40-50 K for local ULIRGs) as measured by the rest-frame 80/115 μm flux density ratios (e.g., observed-frame 250/350 μm ratios at z = 2). DOGs that are not detected by Herschel appear to have lower observed-frame 250/24 μm ratios than the detected sample, either because of warmer dust temperatures, lower IR luminosities, or both. © 2012. The American Astronomical Society. All rights reserved.
• Mould, J., Reynolds, T., Readhead, T., Floyd, D., Jannuzi, B., Cotter, G., Ferrarese, L., Matthews, K., Atlee, D., & Brown, M. (2012). Infrared spectroscopy of nearby radio active elliptical galaxies. Astrophysical Journal, Supplement Series, 203(1).
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  Abstract: In preparation for a study of their circumnuclear gas we have surveyed 60% of a complete sample of elliptical galaxies within 75 Mpc that are radio sources. Some 20% of our nuclear spectra have infrared emission lines, mostly Paschen lines, Brackett γ, and [Fe II]. We consider the influence of radio power and black hole mass in relation to the spectra. Access to the spectra is provided here as a community resource. © 2012. The American Astronomical Society. All rights reserved..
• Prescott, M. K., Dey, A., & Jannuzi, B. T. (2012). A Successful Broad-band Survey for Giant Lya Nebulae I: Survey Design and Candidate Selection. Astrophys.J., 125-144.
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  Giant Lya nebulae (or Lya "blobs") are likely sites of ongoing massive galaxyformation, but the rarity of these powerful sources has made it difficult toform a coherent picture of their properties, ionization mechanisms, and spacedensity. Systematic narrow-band Lya nebula surveys are ongoing, but the smallredshift range covered and the observational expense limit the comoving volumethat can be probed by even the largest of these surveys and pose a significantproblem when searching for such rare sources. We have developed a systematicsearch technique designed to find large Lya nebulae at 2
• Prescott, M. K., Dey, A., Brodwin, M., Chaffee, F. H., Desai, V., Eisenhardt, P., Floc'H, E. L., Jannuzi, B. T., Kashikawa, N., Matsuda, Y., & Soifer, B. T. (2012). Resolving the Galaxies within a Giant Lya Nebula: Witnessing the Formation of a Galaxy Group?. Astrophys.J., 86-110.
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  Detailed analysis of the substructure of Lya nebulae can put importantconstraints on the physical mechanisms at work and the properties of galaxiesforming within them. Using high resolution HST imaging of a Lya nebula atz~2.656, we have taken a census of the compact galaxies in the vicinity, usedoptical/near-infrared colors to select system members, and put constraints onthe morphology of the spatially-extended emission. The system is characterizedby (a) a population of compact, low luminosity (~0.1 L*) sources --- 17primarily young, small (Re~1-2 kpc), disky galaxies including an obscured AGN--- that are all substantially offset (>20 kpc) from the line-emitting nebula;(b) the lack of a central galaxy at or near the peak of the Lya emission; and(c) several nearly coincident, spatially extended emission components --- Lya,HeII, and UV continuum --- that are extremely smooth. These morphologicalfindings are difficult to reconcile with theoretical models that invokeoutflows, cold flows, or resonant scattering, suggesting that while all ofthese physical phenomena may be occurring, they are not sufficient to explainthe powering and large extent of Lya nebulae. In addition, although the compactgalaxies within the system are irrelevant as power sources, the region issignificantly overdense relative to the field galaxy population (by at least afactor of 4). These observations provide the first estimate of the luminosityfunction of galaxies within an individual Lya nebula system, and suggest thatlarge Lya nebulae may be the seeds of galaxy groups or low-mass clusters.[Journal_ref: Astrophys.J. 752 (2012) 86-110]
• Snyder, G. F., Brodwin, M., Mancone, C. M., Zeimann, G. R., Stanford, S. A., Gonzalez, A. H., Stern, D., Eisenhardt, P. R., Brown, M. J., Dey, A., Jannuzi, B., & Perlmutter, S. (2012). Assembly of the Red Sequence in Infrared-Selected Galaxy Clusters from the IRAC Shallow Cluster Survey. Astrophys.J..
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  We present results for the assembly and star formation histories of massive(~L*) red sequence galaxies in 11 spectroscopically confirmed,infrared-selected galaxy clusters at 1.0 < z < 1.5, the precursors topresent-day massive clusters with M ~ 10^15 M_sun. Using rest-frame opticalphotometry, we investigate evolution in the color and scatter of the redsequence galaxy population, comparing with models of possible star formationhistories. In contrast to studies of central cluster galaxies at lower redshift(z < 1), these data are clearly inconsistent with the continued evolution ofstars formed and assembled primarily at a single, much-earlier time.Specifically, we find that the colors of massive cluster galaxies at z = 1.5imply that the bulk of star formation occurred at z ~ 3, whereas by z = 1 theircolors imply formation at z ~ 2; therefore these galaxies exhibit approximatelythe same luminosity-weighted stellar age at 1 < z < 1.5. This likely reflectsstar formation that occurs over an extended period, the effects of significantprogenitor bias, or both. Our results generally indicate that massive clustergalaxy populations began forming a significant mass of stars at z >~ 4,contained some red spheroids by z ~ 1.5, and were actively assembling much oftheir final mass during 1 < z < 2 in the form of younger stars. Qualitatively,the slopes of the cluster color-magnitude relations are consistent with nosignificant evolution relative to local clusters.[Journal_ref: Astrophys.J. 756 (2012) 114]
• Snyder, G. F., Brodwin, M., Mancone, C. M., Zeimann, G. R., Stanford, S. A., Gonzalez, A., Stern, D., R., P., J., M., Dey, A., Jannuzi, B., & Perlmutter, S. (2012). Assembly of the red sequence in infrared-selected galaxy clusters from the irac shallow cluster survey. Astrophysical Journal, 756(2).
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  Abstract: We present results for the assembly and star formation histories (SFHs) of massive (∼L*) red sequence galaxies (RSGs) in 11 spectroscopically confirmed, infrared-selected galaxy clusters at 1.0 < z < 1.5, the precursors to present-day massive clusters with M ∼10 15 M ⊙. Using rest-frame optical photometry, we investigate evolution in the color and scatter of the RSG population, comparing with models of possible SFHs. In contrast to studies of central cluster galaxies at lower redshift (z < 1), these data are clearly inconsistent with the continued evolution of stars formed and assembled primarily at a single, much earlier time. Specifically, we find that the colors of massive cluster galaxies at z ≈1.5 imply that the bulk of star formation occurred at z ∼3, whereas by z ≈1 their colors imply formation at z ∼2; therefore these galaxies exhibit approximately the same luminosity-weighted stellar age at 1 < z < 1.5. This likely reflects star formation that occurs over an extended period, the effects of significant progenitor bias, or both. Our results generally indicate that massive cluster galaxy populations began forming a significant mass of stars at z ≳ 4, contained some red spheroids by z ≈1.5, and were actively assembling much of their final mass during 1 < z < 2 in the form of younger stars. Qualitatively, the slopes of the cluster color-magnitude relations are consistent with no significant evolution relative to local clusters. © 2012. The American Astronomical Society. All rights reserved.
• Trichas, M., Green, P. J., Silverman, J. D., Aldcroft, T., Barkhouse, W., Cameron, R. A., Constantin, A., Ellison, S. L., Foltz, C., Haggard, D., Jannuzi, B. T., Kim, D., Marshall, H. L., Mossman, A., Pérez, L. M., Romero-Colmenero, E., Ruiz, A., Smith, M. G., Smith, P. S., , Torres, G., et al. (2012). The chandra multi-wavelength project: Optical spectroscopy and the broadband spectral energy distributions of X-ray-selected AGNs. Astrophysical Journal, Supplement Series, 200(2).
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  Abstract: From optical spectroscopy of X-ray sources observed as part of the Chandra Multi-wavelength Project (ChaMP), we present redshifts and classifications for a total of 1569 Chandra sources from our targeted spectroscopic follow-up using the FLWO/1.5m, SAAO/1.9m, WIYN 3.5m, CTIO/4m, KPNO/4m, Magellan/6.5m, MMT/6.5m, and Gemini/8m telescopes, and from archival Sloan Digital Sky Survey (SDSS) spectroscopy. We classify the optical counterparts as 50% broad-line active galactic nuclei (AGNs), 16% emission line galaxies, 14% absorption line galaxies, and 20% stars. We detect QSOs out to z ∼ 5.5 and galaxies out to z ∼ 3. We have compiled extensive photometry, including X-ray (ChaMP), ultraviolet (GALEX), optical (SDSS and ChaMP-NOAO/MOSAIC follow-up), near-infrared (UKIDSS, Two Micron All Sky Survey, and ChaMP-CTIO/ISPI follow-up), mid-infrared (WISE), and radio (FIRST and NVSS) bands. Together with our spectroscopic information, this enables us to derive detailed spectral energy distributions (SEDs) for our extragalactic sources. We fit a variety of template SEDs to determine bolometric luminosities, and to constrain AGNs and starburst components where both are present. While 58% of X-ray Seyferts (10 42 erg s -1 < L 2 - 10 keV 5% starburst contribution to bolometric luminosity) to fit observed photometry only 26% of the X-ray QSO (L 2 - 10 keV >10 44ergs -1) population appear to have some kind of star formation contribution. This is significantly lower than for the Seyferts, especially if we take into account torus contamination at z > 1 where the majority of our X-ray QSOs lie. In addition, we observe a rapid drop of the percentage of starburst contribution as X-ray luminosity increases. This is consistent with the quenching of star formation by powerful QSOs, as predicted by the merger model, or with a time lag between the peak of star formation and QSO activity. We have tested the hypothesis that there should be a strong connection between X-ray obscuration and star formation but we do not find any association between X-ray column density and star formation rate both in the general population or the star-forming X-ray Seyferts. Our large compilation also allows us to report here the identification of 81 X-ray Bright Optically inactive Galaxies, 78 z > 3 X-ray sources, and eight Type-2 QSO candidates. Also, we have identified the highest redshift (z = 5.4135) X-ray-selected QSO with optical spectroscopy. © 2012. The American Astronomical Society. All rights reserved..
• Wagg, J., Pope, A., Alberts, S., Armus, L., Brodwin, M., Bussmann, R. S., Desai, V., Dey, A., Jannuzi, B., Floc'H, E. L., Melbourne, J., & Stern, D. (2012). CO J = 2-1 line emission in cluster galaxies at z ̃ 1: Fueling star formation in dense environments. Astrophysical Journal, 752(2).
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  Abstract: We present observations of CO J = 2-1 line emission in infrared-luminous cluster galaxies at z 1 using the IRAM Plateau de Bure Interferometer. Our two primary targets are optically faint, dust-obscured galaxies (DOGs) found to lie within 2Mpc of the centers of two massive (>10 14 M) galaxy clusters. CO line emission is not detected in either DOG. We calculate 3σ upper limits to the CO J = 2-1 line luminosities, L′ CO < 6.08 × 10 9 and
• Agudo, I., Marscher, A. P., Jorstad, S. G., Larionov, V. M., Gómez, J. L., Lähteenmäki, A., Smith, P. S., Nilsson, K., C., A., Aller, M. F., Heidt, J., Gurwell, M., Thum, C., Wehrle, A. E., Nikolashvili, M. G., Aller, H. D., Benítez, E., Blinov, D. A., Hagen-Thorn, V. A., , Hiriart, D., et al. (2011). On the location of the γ-ray outburst emission in the BL Lacertae object AO 0235+164 through observations across the electromagnetic spectrum. Astrophysical Journal Letters, 735(1).
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  Abstract: We present observations of a major outburst at centimeter, millimeter, optical, X-ray, and γ-ray wavelengths of the BL Lacertae object AO 0235+164. We analyze the timing of multi-waveband variations in the flux and linear polarization, as well as changes in Very Long Baseline Array images at λ = 7mm with 0.15 milliarcsec resolution. The association of the events at different wavebands is confirmed at high statistical significance by probability arguments and Monte Carlo simulations. A series of sharp peaks in optical linear polarization, as well as a pronounced maximum in the 7 mm polarization of a superluminal jet knot, indicate rapid fluctuations in the degree of ordering of the magnetic field. These results lead us to conclude that the outburst occurred in the jet both in the quasi-stationary "core" and in the superluminal knot, both parsecs downstream of the supermassive black hole. We interpret the outburst as a consequence of the propagation of a disturbance, elongated along the line of sight by light-travel time delays, that passes through a standing recollimation shock in the core and propagates down the jet to create the superluminal knot. The multi-wavelength light curves vary together on long timescales (months/years), but the correspondence is poorer on shorter timescales. This, as well as the variability of the polarization and the dual location of the outburst, agrees with the expectations of a multi-zone emission model in which turbulence plays a major role in modulating the synchrotron and inverse Compton fluxes. © 2011. The American Astronomical Society. All rights reserved.
• Assef, R. J., Kochanek, C. S., Ashby, M. L., Brodwin, M., Brown, M. J., Cool, R., Forman, W., Gonzalez, A. H., Hickox, R. C., Jannuzi, B. T., Jones, C., Floc'H, L. E., Moustakas, J., Murray, S. S., & Stern, D. (2011). The Mid-IR and X-ray Selected QSO Luminosity Function. Astrophys. J..
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  We present the J-band luminosity function of 1838 mid-infrared and X-rayselected AGNs in the redshift range 0
• Assef, R. J., Kochanek, C. S., Ashby, M. L., Brodwin, M., Brown, M. J., Cool, R., Forman, W., Gonzalez, A. H., Hickox, R. C., Jannuzi, B. T., Jones, C., Floc'h, E. L., Moustakas, J., Murray, S. S., & Stern, D. (2011). The mid-IR-and X-ray-selected QSO luminosity function. Astrophysical Journal, 728(1).
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  Abstract: We present the J-band luminosity function (LF) of 1838 mid-infrared and X-ray-selected active galactic nuclei (AGNs) in the redshift range 0 < z < 5.85. These LFs are constructed by combining the deep multi-wavelength broadband observations from the UV to the mid-IR of the NDWFS Bootes field with the X-ray observations of the XBootes survey and the spectroscopic observations of the same field by AGES. Our sample is primarily composed of IRAC-selected AGNs, targeted using modifications of the Stern et al. criteria, complemented by MIPS 24 μm and X-ray-selected AGNs to alleviate the biases of IRAC mid-IR selection against z ∼ 4.5 quasars and AGNs faint with respect to their hosts. This sample provides an accurate link between low-and high-redshift AGN LFs and does not suffer from the usual incompleteness of optical samples at z ∼ 3. We use a set of low-resolution spectral energy distribution templates for AGNs and galaxies presented in a previous paper by Assef et al. to model the selection function of these sources and apply host and reddening corrections. We find that the space density of the brightest quasars strongly decreases from z = 3 to z = 0, while the space density of faint quasars is at least flat, and possibly increasing, over the same redshift range. At z > 3, we observe a decrease in the space density of quasars of all brightnesses. We model the LF by a double power law and find that its evolution cannot be described by either pure luminosity or pure density evolution, but must be a combination of both. We used the bright-end slope determined by Croom et al. (2QZ) as a prior to fit the data in order to minimize the effects of our small survey area. The bright-end power-law index of our best-fit model remains consistent with the prior, while the best-fit faint-end index is consistent with the low-redshift measurements based on the 2QZ and 2SLAQ surveys. Our best-fit model generally agrees with the number of bright quasars predicted by other LFs at all redshifts. If we construct the QSO luminosity function using only the IRAC-selected AGNs, we find that the biases inherent to this selection method significantly modify the behavior of the characteristic density Φ*(z) only for z < 1 and have no significant impact upon the characteristic magnitude M*,J(z). © 2011. The American Astronomical Society. All rights reserved. Printed in the U.S.A.
• Brodwin, M., Stern, D., Vikhlinin, A., Stanford, S. A., Gonzalez, A. H., Eisenhardt, P. R., Ashby, M. L., Bautz, M., Dey, A., Forman, W. R., Gettings, D., Hickox, R. C., Jannuzi, B. T., Jones, C., Mancone, C., Miller, E. D., Moustakas, L. A., Ruel, J., Snyder, G., & Zeimann, G. (2011). X-ray emission from two infrared-selected galaxy clusters at z > 1.4 in the IRAC Shallow Cluster Survey. Astrophysical Journal, 732(1).
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  Abstract: We report the X-ray detection of two z > 1.4 infrared-selected galaxy clusters from the IRAC Shallow Cluster Survey (ISCS). We present new data from the Hubble Space Telescope and the W. M. Keck Observatory that spectroscopically confirm cluster ISCS J1432.4+3250 at z = 1.49, the most distant of 18 confirmed z > 1 clusters in the ISCS to date. We also present new spectroscopy for ISCS J1438.1+3414, previously reported at z = 1.41, and measure its dynamical mass. Clusters ISCS J1432.4+3250 and ISCS J1438.1+3414 are detected in 36 ks and 143 ks Chandra exposures at significances of 5.2σ and 9.7σ, from which we measure total masses of log (M200,Lx/M⊙) = 14.4 ± 0.2 and 14.35 +0.14- 0.11, respectively. The consistency of the X-ray and dynamical properties of these high-redshift clusters further demonstrates that the ISCS is robustly detecting massive clusters to at least z = 1.5. © 2011. The American Astronomical Society. All rights reserved.
• Brown, M. J., Jannuzi, B. T., Floyd, D. J., & Mould, J. R. (2011). The ubiquitous radio continuum emission from the most massive early-type galaxies. Astrophysical Journal Letters, 731(2 PART II).
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  Abstract: We have measured the radio continuum emission of 396 early-type galaxies brighter than K = 9, using 1.4 GHz imagery from the NRAO Very Large Array Sky Survey, Green Bank 300 ft Telescope, and 64 m Parkes Radio Telescope. For M K < -24 early-type galaxies, the distribution of radio powers at fixed absolute magnitude spans four orders of magnitude and the median radio power is proportional to K-band luminosity to the power 2.78 ± 0.16. The measured flux densities of MK < -25.5 early-type galaxies are greater than zero in all cases. It is thus highly likely that the most massive galaxies always host an active galactic nucleus or have recently undergone star formation. © 2011. The American Astronomical Society. All rights reserved.
• Bussmann, R. S., Dey, A., Lotz, J., Armus, L., Brown, M. J., Desai, V., Eisenhardt, P., Higdon, J., Higdon, S., Jannuzi, B. T., Floc'H, E. L., Melbourne, J., Soifer, B. T., & Weedman, D. (2011). Hubble space telescope morphologies of z ∼ 2 dust-obscured galaxies. II. Bump sources. Astrophysical Journal, 733(1).
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  Abstract: We present Hubble Space Telescope imaging of 22 ultra-luminous infrared galaxies (ULIRGs) at z ≈ 2 with extremely red R - [24] colors (called dust-obscured galaxies, or DOGs) which have a local maximum in their spectral energy distribution (SED) at rest-frame 1.6 μm associated with stellar emission. These sources, which we call "bump DOGs," have star formation rates (SFRs) of 400-4000 M⊙ yr-1 and have redshifts derived from mid-IR spectra which show strong polycyclic aromatic hydrocarbon emission - a sign of vigorous ongoing star formation. Using a uniform morphological analysis, we look for quantifiable differences between bump DOGs, power-law DOGs (Spitzer-selected ULIRGs with mid-IR SEDs dominated by a power law and spectral features that are more typical of obscured active galactic nuclei than starbursts), submillimeter-selected galaxies, and other less-reddened ULIRGs from the Spitzer Extragalactic First Look Survey. Bump DOGs are larger than power-law DOGs (median Petrosian radius of 8.4 ± 2.7 kpc versus 5.5 ± 2.3 kpc) and exhibit more diffuse and irregular morphologies (median M 20 of -1.08 ± 0.05 versus -1.48 ± 0.05). These trends are qualitatively consistent with expectations from simulations of major mergers in which merging systems during the peak SFR period evolve from M 20 = -1.0 to M 20 = -1.7. Less-obscured ULIRGs (i.e., non-DOGs) tend to have more regular, centrally peaked, single-object morphologies rather than diffuse and irregular morphologies. This distinction in morphologies may imply that less-obscured ULIRGs sample the merger near the end of the peak SFR period. Alternatively, it may indicate that the intense star formation in these less-obscured ULIRGs is not the result of a recent major merger. © 2011. The American Astronomical Society. All rights reserved..
• Glikman, E., Djorgovski, S. G., Stern, D., Dey, A., Jannuzi, B. T., & Lee, K. (2011). The faint end of the quasar luminosity function at z ∼ 4: Implications for ionization of the intergalactic medium and cosmic downsizing. Astrophysical Journal Letters, 728(2 PART II).
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  Abstract: We present an updated determination of the z ∼ 4 QSO luminosity function (QLF), improving the quality of the determination of the faint end of the QLF presented by Glikman et al. (2010). We have observed an additional 43 candidates from our survey sample, yielding one additional QSO at z = 4.23 and increasing the completeness of our spectroscopic follow-up to 48% for candidates brighter than R = 24 over our survey area of 3.76 deg2. We study the effect of using K-corrections to compute the rest-frame absolute magnitude at 1450 Å compared with measuring M1450 directly from the object spectra. We find a luminosity-dependent bias: template-based K-corrections overestimate the luminosity of low-luminosity QSOs, likely due to their reliance on templates derived from higher luminosity QSOs. Combining our sample with bright quasars from the Sloan Digital Sky Survey and using spectrum-based M 1450 for all the quasars, we fit a double power law to the binned QLF. Our best fit has a bright-end slope, α = 3.3 ± 0.2, and faint-end slope, β = 1.6+0.80.6. Our new data revise the faint-end slope of the QLF down to flatter values similar to those measured at z ∼ 3. The break luminosity, though poorly constrained, is at M * = -24.1+0.7-1.9, approximately 1-1.5 mag fainter than at z ∼ 3. This QLF implies that QSOs account for about half the radiation needed to ionize the intergalactic medium at these redshifts. © 2011. The American Astronomical Society.
• Graur, O., Poznanski, D., Maoz, D., Yasuda, N., Totani, T., Fukugita, M., Filippenko, A. V., Foley, R. J., Silverman, J. M., Gal-Yam, A., Horesh, A., & Jannuzi, B. T. (2011). Supernovae in the Subaru Deep Field: The rate and delay-time distribution of Type Ia supernovae out to redshift 2. Monthly Notices of the Royal Astronomical Society, 417(2), 916-940.
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  Abstract: The Type Ia supernova (SN Ia) rate, when compared to the cosmic star formation history (SFH), can be used to derive the delay-time distribution (DTD; the hypothetical SN Ia rate versus time following a brief burst of star formation) of SNe Ia, which can distinguish among progenitor models. We present the results of a supernova (SN) survey in the Subaru Deep Field (SDF). Over a period of 3 years, we have observed the SDF on four independent epochs with Suprime-Cam on the Subaru 8.2-m telescope, with two nights of exposure per epoch, in the R, i'and z' bands. We have discovered 150 SNe out to redshift z≈ 2. Using 11 photometric bands from the observer-frame far-ultraviolet to the near-infrared, we derive photometric redshifts for the SN host galaxies (for 24 we also have spectroscopic redshifts). This information is combined with the SN photometry to determine the type and redshift distribution of the SN sample. Our final sample includes 28 SNe Ia in the range 1.0 < z < 1.5 and 10 in the range 1.5 < z < 2.0. As our survey is largely insensitive to core-collapse SNe (CC SNe) at z > 1, most of the events found in this range are likely SNe Ia. Our SN Ia rate measurements are consistent with those derived from the Hubble Space Telescope (HST) Great Observatories Origins Deep Survey (GOODS) sample, but the overall uncertainty of our 1.5 < z < 2.0 measurement is a factor of 2 smaller, of 35-50per cent. Based on this sample, we find that the SN Ia rate evolution levels off at 1.0 < z < 2.0, but shows no sign of declining. Combining our SN Ia rate measurements and those from the literature, and comparing to a wide range of possible SFHs, the best-fitting DTD (with a reduced χ2= 0.7) is a power law of the form Ψ(t) ∝tβ, with index β=-1.1 ± 0.1 (statistical) ±0.17 (systematic). This result is consistent with other recent DTD measurements at various redshifts and environments, and is in agreement with a generic prediction of the double-degenerate progenitor scenario for SNe Ia. Most single-degenerate models predict different DTDs. By combining the contribution from CC SNe, based on the wide range of SFHs, with that from SNe Ia, calculated with the best-fitting DTD, we predict that the mean present-day cosmic iron abundance is in the range ZFe= (0.09-0.37)ZFe, ⊙. We further predict that the high-z SN searches now beginning with HST will discover 2-11 SNe Ia at z > 2. © 2011 The Authors Monthly Notices of the Royal Astronomical Society © 2011 RAS.
• Hickox, R. C., Myers, A. D., Brodwin, M., Alexander, D. M., Forman, W. R., Jones, C., Murray, S. S., J., M., Cool, R. J., Kochanek, C. S., Dey, A., Jannuzi, B. T., Eisenstein, D., Assef, R. J., Eisenhardt, P. R., Gorjian, V., Stern, D., Floc'H, E. L., Caldwell, N., , Goulding, A. D., et al. (2011). Clustering of obscured and unobscured quasars in the Boötes field: Placing rapidly growing black holes in the cosmic web. Astrophysical Journal, 731(2).
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  Abstract: We present the first measurement of the spatial clustering of mid-infrared-selected obscured and unobscured quasars, using a sample in the redshift range 0.7 < z < 1.8 selected from the 9 deg2 Boötes multiwavelength survey. Recently, the Spitzer Space Telescope and X-ray observations have revealed large populations of obscured quasars that have been inferred from models of the X-ray background and supermassive black hole evolution. To date, little is known about obscured quasar clustering, which allows us to measure the masses of their host dark matter halos and explore their role in the cosmic evolution of black holes and galaxies. In this study, we use a sample of 806 mid-infrared-selected quasars and ≈250,000 galaxies to calculate the projected quasar-galaxy cross-correlation function wp (R). The observed clustering yields characteristic dark matter halo masses of log(M halo [h -1 M ⊙]) = 12.7 +0.4-0.6 and 13.3+0.3-0.4 for unobscured quasars (QSO-1s) and obscured quasars (Obs-QSOs), respectively. The results for QSO-1s are in excellent agreement with previous measurements for optically selected quasars, while we conclude that the Obs-QSOs are at least as strongly clustered as the QSO-1s. We test for the effects of photometric redshift errors on the optically faint Obs-QSOs, and find that our method yields a robust lower limit on the clustering; photo-z errors may cause us to underestimate the clustering amplitude of the Obs-QSOs by at most ∼20%. We compare our results to previous studies, and speculate on physical implications of stronger clustering for obscured quasars. © 2011. The American Astronomical Society. All rights reserved.
• Lee, K., Dey, A., Reddy, N., J., M., Gonzalez, A. H., Jannuzi, B. T., Cooper, M. C., Fan, X., Bian, F., Glikman, E., Stern, D., Brodwin, M., & Cooray, A. (2011). The average physical properties and star formation histories of the UV-brightest star-forming galaxies at z ∼ 3.7. Astrophysical Journal, 733(2).
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  Abstract: We investigate the average physical properties and star formation histories (SFHs) of the most UV-luminous star-forming galaxies at z ∼ 3.7. Our results are based on the average spectral energy distributions (SEDs), constructed from stacked optical-to-infrared photometry, of a sample of the 1913 most UV-luminous star-forming galaxies found in 5.3 deg2 of the NOAO Deep Wide-Field Survey. We find that the shape of the average SED in the rest optical and infrared is fairly constant with UV luminosity, i.e., more UV-luminous galaxies are, on average, also more luminous at longer wavelengths. In the rest UV, however, the spectral slope β (≡ dlogF λ/dlogλ; measured at 0.13 μm < λrest < 0.28 μm) rises steeply with the median UV luminosity from -1.8 at L ≈ L* to -1.2 (L ≈ 4-5L*). We use population synthesis analyses to derive their average physical properties and find that (1) L UV and thus star formation rates (SFRs) scale closely with stellar mass such that more UV-luminous galaxies are also more massive, (2) the median ages indicate that the stellar populations are relatively young (200-400Myr) and show little correlation with UV luminosity, and (3) more UV-luminous galaxies are dustier than their less-luminous counterparts, such that L ≈ 4-5L* galaxies are extincted up to A(1600) = 2mag while L ≈ L* galaxies have A(1600) = 0.7-1.5mag. We argue that the average SFHs of UV-luminous galaxies are better described by models in which SFR increases with time in order to simultaneously reproduce the tight correlation between the UV-derived SFR and stellar mass and their universally young ages. We demonstrate the potential of measurements of the SFR-M * relation at multiple redshifts to discriminate between simple models of SFHs. Finally, we discuss the fate of these UV-brightest galaxies in the next 1-2Gyr and their possible connection to the most massive galaxies at z ∼ 2. © 2011. The American Astronomical Society. All rights reserved.
• Crighton, N. H., Morris, S. L., Bechtold, J., Crain, R. A., Jannuzi, B. T., Shone, A., & Theuns, T. (2010). Galaxies at a redshift of ∼0.5 around three closely spaced quasar sightlines. Monthly Notices of the Royal Astronomical Society, 402(2), 1273-1306.
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  Abstract: We examine the relationship between galaxies and the intergalactic medium at z < 1 using a group of three closely spaced background quasi-stellar objects (QSOs) with zem ≈ 1 observed with the Hubble Space Telescope. Using a new grouping algorithm, we identify groups of galaxies and absorbers across the three QSO sightlines that may be physically linked. There is an excess number of such groups compared to the number we expect from a random distribution of absorbers at a confidence level of 99.9 per cent. The same search is performed with mock spectra generated using a hydrodynamical simulation, and we find that the vast majority of such groups arise in dense regions of the simulation. We find that at z < 0.5, groups in the simulation generally trace the large-scale filamentary structure as seen in the projected 2D distribution of the H i column density in an ∼30 h-1 Mpc region. We discover a probable sub-damped Lyman α system at z = 0.557 showing strong, low-ionization metal absorption lines. Previous analyses of absorption across the three sightlines attributed these metal lines to H i. We show that even when the new line identifications are taken into account, evidence remains for planar structures with scales of ∼1 Mpc absorbing across the three sightlines. We identify a galaxy at z = 0.2272 with associated metal absorption in two sightlines, each 200 kpc away. By constraining the star formation history of the galaxy, we show that the gas causing this metal absorption may have been enriched and ejected by the galaxy during a burst of star formation 2 Gyr ago. © 2009 The Authors. Journal compilation © 2009 RAS.
• Glikman, E., Bogosavljević, M., Djorgovski, S. G., Stern, D., Dey, A., Jannuzi, B. T., & Mahabal, A. (2010). The faint end of the quasar luminosity function at z ∼ 4. Astrophysical Journal Letters, 710(2), 1498-1514.
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  Abstract: The evolution of the quasar luminosity function (QLF) is one of the basic cosmological measures providing insight into structure formation and mass assembly in the universe. We have conducted a spectroscopic survey to find faint quasars (-26.0 < M 1450 < -22.0) at redshifts z = 3.8-5.2 in order to measure the faint end of the QLF at these early times. Using available optical imaging data from portions of the NOAO Deep Wide-Field Survey and the Deep Lens Survey, we have color-selected quasar candidates in a total area of 3.76 deg2. Thirty candidates have R ≤ 23mag. We conducted spectroscopic follow-up for 28 of our candidates and found 23 QSOs, 21 of which are reported here for the first time, in the 3.74 < z < 5.06 redshift range. We estimate our survey completeness through detailed Monte Carlo simulations and derive the first measurement of the density of quasars in this magnitude and redshift interval. We find that the binned luminosity function (LF) is somewhat affected by the K-correction used to compute the rest-frame absolute magnitude at 1450 Å. Considering only our R ≤ 23 sample, the best-fit single power law (Φ L β) gives a faint-end slope β = -1.6 ± 0.2. If we consider our larger, but highly incomplete sample going 1 mag fainter, we measure a steeper faint-end slope -2 < β < -2.5. In all cases, we consistently find faint-end slopes that are steeper than expected based on measurements at z 3. We combine our sample with bright quasars from the Sloan Digital Sky Survey to derive parameters for a double-power-law LF. Our best fit finds a bright-end slope, α = -2.4 ± 0.2, and faint-end slope, β = -2.3 ± 0.2, without a well-constrained break luminosity. This is effectively a single power law, with β = -2.7 0.1. We use these results to place limits on the amount of ultraviolet radiation produced by quasars and find that quasars are able to ionize the intergalactic medium at these redshifts. © 2010. The American Astronomical Society.
• Kozlowski, S., Kochanek, C. S., Stern, D., Ashby, M. L., Assef, R. J., Bock, J. J., Borys, C., Brand, K., Brodwin, M., Brown, M. J., Cool, R., Cooray, A., Croft, S., Dey, A., Eisenhardt, P. R., Gonzalez, A., Gorjian, V., Griffith, R., Grogin, N., , Ivison, R., et al. (2010). Mid-Infrared Variability from the Spitzer Deep, Wide-Field Survey. Kozlowski et al..
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  We use the multi-epoch, mid-infrared Spitzer Deep, Wide-Field Survey toinvestigate the variability of 474,179 objects in 8.1 deg^2 of the NDWFS Bootesfield. We perform a Difference Image Analysis of the four available epochsbetween 2004 and 2008, focusing on the deeper 3.6 and 4.5 micron bands. We findthat 1.1% of the studied sample meet our standard selection criteria for beingclassed as a variable source. We require that the 3.6 and 4.5 micronlight-curves are strongly correlated (r>0.8) and that their joint varianceexceeds that for all sources with the same magnitude by 2 sigma. We thenexamine the mid-IR colors of the variable sources and match them with X-raysources from the XBootes survey, radio catalogs, 24 micron-selected AGNcandidates, and spectroscopically identified AGNs from the AGN and GalaxyEvolution Survey (AGES). Based on their mid-IR colors, most of the variablesources are AGNs (76%), with smaller contributions from stars (11%), galaxies(6%), and unclassified objects. Most of the stellar, galaxy and unclassifiedsources are false positives. For our standard selection criteria, 11-12% of themid-IR counterparts to X-ray sources, 24 micron-selected AGN candidates andspectroscopically identified AGNs show variability. Mid-IR AGN variability canbe well described by a single power-law structure function with a power-lawindex of 0.5 at both 3.6 and 4.5 microns, and an amplitude of 0.1 mag onrest-frame time scales of 2 years. The variability amplitude is higher forshorter rest-frame wavelengths and lower luminosities. (Abridged)[Journal_ref: Kozlowski et al. 2010, ApJ, 716, 530]
• Kozłowski, S., Kochanek, C. S., Stern, D., L., M., Assef, R. J., Bock, J. J., Borys, C., Brand, K., Brodwin, M., Brown, M. J., Cool, R., Cooray, A., Croft, S., Dey, A., Eisenhardt, P. R., Gonzalez, A., Gorjian, V., Griffith, R., Grogin, N., , Ivison, R., et al. (2010). Mid-infrared variability from the spitzer deep wide-field survey. Astrophysical Journal Letters, 716(1), 530-543.
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  Abstract: We use the multi-epoch, mid-infrared Spitzer Deep Wide-Field Survey to investigate the variability of objects in 8.1 deg2 of the NOAO Deep Wide Field Survey Boötes field. We perform a Difference Image Analysis of the four available epochs between 2004 and 2008, focusing on the deeper 3.6 and 4.5 μm bands. Out of 474, 179 analyzed sources, 1.1% meet our standard variability selection criteria that the two light curves are strongly correlated (r>0.8) and that their joint variance (σ12) exceeds that for all sources with the same magnitude by 2σ. We then examine the mid-IR colors of the variable sources and match them with X-ray sources from the XBoötes survey, radio catalogs, 24 μm selected active galactic nucleus (AGN) candidates, and spectroscopically identified AGNs from the AGN and Galaxy Evolution Survey (AGES). Based on their mid-IR colors, most of the variable sources are AGNs (76%), with smaller contributions from stars (11%), galaxies (6%), and unclassified objects, although most of the stellar, galaxy, and unclassified sources are false positives. For our standard selection criteria, 11%-12% of the mid-IR counterparts to X-ray sources, 24 μm AGN candidates, and spectroscopically identified AGNs show variability. The exact fractions depend on both the search depth and the selection criteria. For example, 12% of the 1131 known z>1 AGNs in the field and 14%-17% of the known AGNs with well-measured fluxes in all four Infrared Array Camera bands meet our standard selection criteria. The mid-IR AGN variability can be well described by a single power-law structure function with an index of γ ≈ 0.5 at both 3.6 and 4.5 μm, and an amplitude of S 0 ≃ 0.1 mag on rest-frame timescales of 2 yr. The variability amplitude is higher for shorter rest-frame wavelengths and lower luminosities. © 2010. The American Astronomical Society. All rights reserved.
• Kozłowski, S., Kochanek, C. S., Stern, D., Prieto, J. L., Stanek, K. Z., Thompson, T. A., Assef, R. J., Drake, A. J., Szczygieł, D., Woźniak, P., Nugent, P., Ashby, M. L., Beshore, E., Brown, M. J., Dey, A., Griffith, R., Harrison, F., Jannuzi, B. T., Larson, S., , Madsen, K., et al. (2010). SDWFS-MT-1: A self-obscured luminous supernova at z ≃ 0.2. Astrophysical Journal Letters, 722(2), 1624-1632.
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  Abstract: We report the discovery of a 6 month long mid-infrared transient, SDWFS-MT-1 (aka SN 2007va), in the Spitzer Deep, Wide-Field Survey of the NOAO Deep Wide-Field Survey Boötes field. The transient, located in a z = 0.19 low-luminosity (M[4.5] ≃-18.6 mag, L/L* ≃ 0.01) metal-poor (12 + log(O/H) ≃ 7.8) irregular galaxy, peaked at a mid-infrared absolute magnitude of M[4.5] ≃-24.2 in the 4.5 μm Spitzer/IRAC band and emitted a total energy of at least 1051 erg. The optical emission was likely fainter than the mid-infrared, although our constraints on the optical emission are poor because the transient peaked when the source was "behind" the Sun. The Spitzer data are consistent with emission by a modified blackbody with a temperature of ∼1350 K. We rule out a number of scenarios for the origin of the transient such as a Galactic star, active galactic nucleus activity, γ-ray burst, tidal disruption of a star by a black hole, and gravitational lensing. The most plausible scenario is a supernova (SN) exploding inside a massive, optically thick circumstellar medium, composed of multiple shells of previously ejected material. If the proposed scenario is correct, then a significant fraction (∼10%) of the most luminous SN may be self-enshrouded by dust not only before but also after the SN occurs. The spectral energy distribution of the progenitor of such an SN would be a slightly cooler version of η Carinae peaking at 20-30 μm. © 2010. The American Astronomical Society.
• Rujopakarn, W., Eisenstein, D. J., Rieke, G. H., Papovich, C., Cool, R. J., Moustakas, J., Jannuzi, B. T., Kochanek, C. S., Rieke, M. J., Dey, A., Eisenhardt, P., Murray, S. S., Brown, M. J., & Floc'h, E. L. (2010). The evolution of the star formation rate of galaxies at 0.0 ≤ z ≤ 1.2. Astrophysical Journal Letters, 718(2), 1171-1185.
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  Abstract: We present the 24 μm rest-frame luminosity function (LF) of star-forming galaxies in the redshift range 0.0 ≤ z ≤ 0.6 constructed from 4047 spectroscopic redshifts from the AGN and Galaxy Evolution Survey of 24 μm selected sources in the Boötes field of the NOAO Deep Wide-Field Survey. This sample provides the best available combination of large area (9 deg 2), depth, and statistically complete spectroscopic observations, allowing us to probe the evolution of the 24 μm LF of galaxies at low and intermediate redshifts while minimizing the effects of cosmic variance. In order to use the observed 24 μm luminosity as a tracer for star formation, active galactic nuclei (AGNs) that could contribute significantly at 24 μm are identified and excluded from our star-forming galaxy sample based on their mid-IR spectral energy distributions or the detection of X-ray emission. Optical emission line diagnostics are considered for AGN identification, but we find that 24 μm emission from optically selected AGNs is usually from star-forming activity and therefore should not be excluded. The evolution of the 24 μmLF of star-forming galaxies for redshifts of z ≤ 0.65 is consistent with a pure luminosity evolutionwhere the characteristic 24 μm luminosity evolves as (1 + z)3.8±0.3. We extend our evolutionary study to encompass 0.0 ≤ z ≤ 1.2 by combining our data with that of the Far-Infrared Deep Extragalactic Legacy Survey. Over this entire redshift range, the evolution of the characteristic 24 μm luminosity is described by a slightly shallower power law of (1 + z)3.4±0.2. We find a local star formation rate density of (1.09 ± 0.21) × 10-2 M⊙ yr -1 Mpc-3, and that it evolves as (1 + z) 3.5±0.2 over 0.0 ≤ z ≤ 1.2. These estimates are in good agreement with the rates using optical and UV fluxes corrected for the effects of intrinsic extinction in the observed sources. This agreement confirms that star formation at z ≲ 1.2 is robustly traced by 24 μm observations and that it largely occurs in obscured regions of galaxies. © 2010. The American Astronomical Society. All rights reserved.
• Ashby, M. L., Stern, D., Brodwin, M., Griffith, R., Eisenhardt, P., Kozlowski, S., Kochanek, C. S., Bock, J. J., Borys, C., Brand, K., Brown, M. J., Cool, R., Cooray, A., Croft, S., Dey, A., Eisenstein, D., Gonzalez, A. H., Gorjian, V., Grogin, N. A., , Ivison, R. J., et al. (2009). The Spitzer Deep, Wide-Field Survey. Astrophys.J., 701, 428-453.
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  The Spitzer Deep, Wide-Field Survey (SDWFS) is a four-epoch infrared surveyof ten square degrees in the Bootes field of the NOAO Deep Wide-Field Surveyusing the IRAC instrument on the Spitzer Space Telescope. SDWFS, a Cycle fourSpitzer Legacy project, occupies a unique position in the area-depth surveyspace defined by other Spitzer surveys. The four epochs that make up SDWFSpermit -- for the first time -- the selection of infrared-variable and highproper motion objects over a wide field on timescales of years. Because of itslarge survey volume, SDWFS is sensitive to galaxies out to z~3 with relativelylittle impact from cosmic variance for all but the richest systems. The SDWFSdatasets will thus be especially useful for characterizing galaxy evolutionbeyond z~1.5. This paper explains the SDWFS observing strategy and dataprocessing, presents the SDWFS mosaics and source catalogs, and discusses someearly scientific findings. The publicly-released, full-depth catalogs contain6.78, 5.23, 1.20, and 0.96 x 10e5 distinct sources detected to the average5-sigma, 4" diameter, aperture-corrected limits of 19.77, 18.83, 16.50, and15.82 Vega mag at 3.6, 4.5, 5.8, and 8.0 micron, respectively. The SDWFS numbercounts and color-color distribution are consistent with other, earlier Spitzersurveys. At the 6 min integration time of the SDWFS IRAC imaging, more than 50%of isolated FIRST radio sources and more than 80% of on-axis XBootes sourcesare detected out to 8.0 micron. Finally, we present the four highest propermotion IRAC-selected sources identified from the multi-epoch imaging, two ofwhich are likely field brown dwarfs of mid-T spectral class.[Journal_ref: Astrophys.J.701:428-453,2009]
• Ashby, M. L., Stern, D., Brodwin, M., Griffith, R., Eisenhardt, P., Kozłowski, S., Kochanek, C. S., Bock, J. J., Borys, C., Brand, K., Brown, M. J., Cool, R., Cooray, A., Croft, S., Dey, A., Eisenstein, D., Gonzalez, A. H., Gorjian, V., Grogin, N. A., , Ivison, R. J., et al. (2009). The spitzer deep, wide-field survey. Astrophysical Journal Letters, 701(1), 428-453.
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  Abstract: The Spitzer Deep, Wide-Field Survey (SDWFS) is a four-epoch infrared survey of 10 deg2 in the Boötes field of the NOAO Deep Wide-Field Survey using the IRAC instrument on the Spitzer Space Telescope. SDWFS, a Spitzer Cycle 4 Legacy project, occupies a unique position in the area-depth survey space defined by other Spitzer surveys. The four epochs that make up SDWFS permit - for the first time - the selection of infrared-variable and high proper motion objects over a wide field on timescales of years. Because of its large survey volume, SDWFS is sensitive to galaxies out to z ∼ 3 with relatively little impact from cosmic variance for all but the richest systems. The SDWFS data sets will thus be especially useful for characterizing galaxy evolution beyond z ∼ 1.5. This paper explains the SDWFS observing strategy and data processing, presents the SDWFS mosaics and source catalogs, and discusses some early scientific findings. The publicly released, full-depth catalogs contain 6.78, 5.23, 1.20, and 0.96 × 105 distinct sources detected to the average 5σ, 4″-diameter, aperture-corrected limits of 19.77, 18.83, 16.50, and 15.82 Vega mag at 3.6, 4.5, 5.8, and 8.0μm, respectively. The SDWFS number counts and color-color distribution are consistent with other, earlier Spitzer surveys. At the 6 minute integration time of the SDWFS IRAC imaging, >50% of isolated Faint Images of the Radio Sky at Twenty cm radio sources and >80% of on-axis XBoötes sources are detected out to 8.0μm. Finally, we present the four highest proper motion IRAC-selected sources identified from the multi-epoch imaging, two of which are likely field brown dwarfs of mid-T spectral class. © 2009. The American Astronomical Society. All rights reserved.
• Brand, K., Moustakas, J., Armus, L., Assef, R. J., Brown, M. J., Cool, R. R., Desai, V., Dey, A., Floc'H, E. L., Jannuzi, B. T., Kochanek, C. S., Melbourne, J., Papovich, C. J., & Soifer, B. T. (2009). The Origin of the 24-micron Excess in Red Galaxies. Astrophys.J., 693, 340-346.
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  Observations with the Spitzer Space Telescope have revealed a population ofred-sequence galaxies with a significant excess in their 24-micron emissioncompared to what is expected from an old stellar population. We identify 900red galaxies with 0.15
• Brand, K., Moustakas, J., Armus, L., Assef, R. J., J., M., Cool, R. R., Desai, V., Dey, A., Floc'H, E. L., Jannuzi, B. T., Kochanek, C. S., Melbourne, J., Papovich, C. J., & Soifer, B. T. (2009). The origin of the 24 μm excess in red galaxies. Astrophysical Journal, 693(1), 340-346.
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  Abstract: Observations with the Spitzer Space Telescope have revealed a population of red sequence galaxies with a significant excess in their 24 μm emission compared to what is expected from an old stellar population. We identify ∼900 red galaxies with 0.15 ≤ z ≤ 0.3 from the AGN and Galaxy Evolution Survey (AGES) selected from the NOAO Deep Wide-Field Survey Boötes field. Using Spitzer MIPS, we classify 89 (∼10%) with 24 μm infrared excess (f 24 ≥ 0.3 mJy). We determine the prevalence of active galactic nucleus (AGN) and star-formation activity in all the AGES galaxies using optical line diagnostics and mid-IR color-color criteria. Using the IRAC color-color diagram from the Spitzer Shallow Survey, we find that 64% of the 24 μm excess red galaxies are likely to have strong polycyclic aromatic hydrocarbon (PAH) emission features in the 8 μm IRAC band. This fraction is significantly larger than the 5% of red galaxies with f 24< 0.3 mJy that are estimated to have strong PAH emission, suggesting that the infrared emission is largely due to star-formation processes. Only 15% of the 24 μm excess red galaxies have optical line diagnostics characteristic of star formation (64% are classified as AGN and 21% are unclassifiable). The difference between the optical and infrared results suggests that both AGN and star-formation activity are occurring simultaneously in many of the 24 μm excess red galaxies. These results should serve as a warning to studies that exclusively use optical line diagnostics to determine the dominant emission mechanism in the infrared and other bands. We find that ∼40% of the 24 μm excess red galaxies are edge-on spiral galaxies with high optical extinctions. The remaining sources are likely to be red galaxies whose 24 μm emission comes from a combination of obscured AGN and star-formation activity. © 2009. The American Astronomical Society. All rights reserved..
• Bussmann, R. S., Dey, A., Borys, C., Desai, V., Jannuzi, B. T., Floc'H, E. L., Melbourne, J., Sheth, K., & Soifer, B. T. (2009). Infrared luminosities and dust properties of z 2 dust-obscured galaxies. Astrophysical Journal Letters, 705(1), 184-198.
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  Abstract: We present SHARC-II 350 μm imaging of twelve 24 μm bright (F 24 μm > 0.8 mJy) Dust-Obscured Galaxies (DOGs) and Combined Array for Research in Millimeter-wave Astronomy (CARMA) 1 mm imaging of a subset of two DOGs. These objects are selected from the Boötes field of the NOAO Deep Wide-Field Survey. Detections of four DOGs at 350 μm imply infrared (IR) luminosities which are consistent to within a factor of 2 of expectations based on a warm-dust spectral energy distribution (SED) scaled to the observed 24 μm flux density. The 350 μm upper limits for the 8 non-detected DOGs are consistent with both Mrk 231 and M82 (warm-dust SEDs), but exclude cold dust (Arp 220) SEDs. The two DOGs targeted at 1 mm were not detected in our CARMA observations, placing strong constraints on the dust temperature: T dust > 35-60 K. Assuming these dust properties apply to the entire sample, we find dust masses of 3 × 108M. In comparison to other dusty z 2 galaxy populations such as submillimeter galaxies (SMGs) and other Spitzer-selected high-redshift sources, this sample of DOGs has higher IR luminosities (2 × 1013 L ⊙ versus 6 × 1012 L ⊙ for the other galaxy populations) that are driven by warmer dust temperatures (>35-60 K versus 30 K) and lower inferred dust masses (3 × 108 M ⊙ versus 3 × 109 M ⊙). Wide-field Herschel and Submillimeter Common-User Bolometer Array-2 surveys should be able to detect hundreds of these power-law-dominated DOGs. We use the existing Hubble Space Telescope and Spitzer/InfraRed Array Camera data to estimate stellar masses of these sources and find that the stellar to gas mass ratio may be higher in our 24 μm bright sample of DOGs than in SMGs and other Spitzer-selected sources. Although much larger sample sizes are needed to provide a definitive conclusion, the data are consistent with an evolutionary trend in which the formation of massive galaxies at z 2 involves a submillimeter bright, cold-dust, and star-formation-dominated phase followed by a 24 μm bright, warm-dust and AGN-dominated phase. © 2009 The American Astronomical Society.
• Bussmann, R. S., Dey, A., Borys, C., Desai, V., Jannuzi, B. T., Floc'H, L. E., Melbourne, J., Sheth, K., & Soifer, B. T. (2009). Infrared Luminosities and Dust Properties of z ~ 2 Dust-Obscured Galaxies. Astrophys.J., 705, 184-198.
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  We present SHARC-II 350um imaging of twelve 24um-bright (F_24um > 0.8 mJy)Dust-Obscured Galaxies (DOGs) and CARMA 1mm imaging of a subset of 2 DOGs, allselected from the Bootes field of the NOAO Deep Wide-Field Survey. Detectionsof 4 DOGs at 350um imply IR luminosities which are consistent within a factorof 2 of expectations based on a warm dust spectral energy distribution (SED)scaled to the observed 24um flux density. The 350um upper limits for the 8non-detected DOGs are consistent with both Mrk231 and M82 (warm dust SEDs), butexclude cold dust (Arp220) SEDs. The two DOGs targeted at 1mm were not detectedin our CARMA observations, placing strong constraints on the dust temperature:T_dust > 35-60 K. Assuming these dust properties apply to the entire sample, wefind dust masses of ~3x10^8 M_sun. In comparison to other dusty z ~ 2 galaxypopulations such as sub-millimeter galaxies (SMGs) and other Spitzer-selectedhigh-redshift sources, this sample of DOGs has higher IR luminosities (2x10^13L_sun vs. 6x10^12 L_sun for the other galaxy populations), warmer dusttemperatures (>35-60 K vs. ~30 K), and lower inferred dust masses (3x10^8 M_sunvs. 3x10^9 M_sun). Herschel and SCUBA-2 surveys should be able to detecthundreds of these power-law dominated DOGs. We use HST and Spitzer/IRAC data toestimate stellar masses of these sources and find that the stellar to gas massratio may be higher in our 24um-bright sample of DOGs than in SMGs and otherSpitzer-selected sources. Although larger sample sizes are needed to provide adefinitive conclusion, the data are consistent with an evolutionary trend inwhich the formation of massive galaxies at z~2 involves a sub-millimeterbright, cold-dust and star-formation dominated phase followed by a 24um-bright,warm-dust and AGN-dominated phase.[Journal_ref: Astrophys.J.705:184-198,2009]
• Bussmann, R. S., Dey, A., Lotz, J., Armus, L., Brand, K., Brown, M. J., Desai, V., Eisenhardt, P., Higdon, J., Higdon, S., Jannuzi, B. T., Floc'H, E. L., Melbourne, J., Soifer, B. T., & Weedman, D. (2009). Hubble space telescope morphologies of z ∼ 2 dust obscured galaxies. I. Power-law sources. Astrophysical Journal, 693(1), 750-770.
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  Abstract: We present high-spatial resolution optical and near-infrared imaging obtained using the ACS, WFPC2, and NICMOS cameras aboard the Hubble Space Telescope of 31 24 μm bright z 2 Dust Obscured Galaxies (DOGs) identified in the Boötes Field of the NOAO Deep Wide-Field Survey. Although this subset of DOGs have mid-IR spectral energy distributions dominated by a power-law component suggestive of an AGN, all but one of the galaxies are spatially extended and not dominated by an unresolved component at rest-frame UV or optical wavelengths. The observed V-H and I-H colors of the extended components are 0.2-3 magnitudes redder than normal star-forming galaxies. All but one have axial ratios >0.3, making it unlikely that DOGs are composed of an edge-on star-forming disk. We model the spatially extended component of the surface brightness distributions of the DOGs with a Sérsic profile and find effective radii of 1-6 kpc. This sample of DOGs is smaller than most submillimeter galaxies (SMGs), but larger than quiescent high-redshift galaxies. Nonparametric measures (Gini and M20) of DOG morphologies suggest that these galaxies are more dynamically relaxed than local ULIRGs. We estimate lower limits to the stellar masses of DOGs based on the rest-frame optical photometry and find that these range from ∼109-1011 M. If major mergers are the progenitors of DOGs, then these observations suggest that DOGs may represent a postmerger evolutionary stage. © 2009. The American Astronomical Society. All rights reserved..
• Bussmann, R. S., Dey, A., Lotz, J., Armus, L., Brand, K., Brown, M. J., Desai, V., Eisenhardt, P., Higdon, J., Higdon, S., Jannuzi, B. T., Floc'H, L. E., Melbourne, J., Soifer, B. T., & Weedman, D. (2009). HST Morphologies of z~2 Dust Obscured Galaxies I: Power-law Sources. Astrophys.J., 693, 750-770.
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  We present high spatial resolution optical and near-infrared imaging obtainedusing the ACS, WFPC2 and NICMOS cameras aboard the Hubble Space Telescope of 3124um--bright z~2 Dust Obscured Galaxies (DOGs) identified in the Bootes Fieldof the NOAO Deep Wide-Field Survey. Although this subset of DOGs have mid-IRspectral energy distributions dominated by a power-law component suggestive ofan AGN, all but one of the galaxies are spatially extended and not dominated byan unresolved component at rest-frame UV or optical wavelengths. The observedV-H and I-H colors of the extended components are 0.2-3 magnitudes redder thannormal star-forming galaxies. All but 1 have axial ratios >0.3, making itunlikely that DOGs are composed of an edge-on star-forming disk. We model thespatially extended component of the surface brightness distributions of theDOGs with a Sersic profile and find effective radii of 1-6 kpc. This sample ofDOGs is smaller than most sub-millimeter galaxies (SMGs), but larger thanquiescent high-redshift galaxies. Non-parametric measures (Gini and M20) of DOGmorphologies suggest that these galaxies are more dynamically relaxed thanlocal ULIRGs. We estimate lower limits to the stellar masses of DOGs based onthe rest-frame optical photometry and find that these range from ~10^(9-11)M_sun. If major mergers are the progenitors of DOGs, then these observationssuggest that DOGs may represent a post-merger evolutionary stage.[Journal_ref: Astrophys.J.693:750-770,2009]
• Dai, X., Assef, R. J., Kochanek, C. S., Brodwin, M., Brown, M. J., Caldwell, N., Cool, R. J., Dey, A., Eisenhardt, P., Eisenstein, D., Gonzalez, A. H., Jannuzi, B. T., Jones, C., Murray, S. S., & Stern, D. (2009). Mid-Infrared Galaxy Luminosity Functions from the AGN and Galaxy Evolution Survey. Astrophys.J., 697, 506-521.
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  We present galaxy luminosity functions at 3.6, 4.5, 5.8, and 8.0 micronmeasured by combining photometry from the IRAC Shallow Survey with redshiftsfrom the AGN and Galaxy Evolution Survey of the NOAO Deep Wide-Field SurveyBootes field. The well-defined IRAC samples contain 3800-5800 galaxies for the3.6-8.0 micron bands with spectroscopic redshifts and z < 0.6. We obtainedrelatively complete luminosity functions in the local redshift bin of z < 0.2for all four IRAC channels that are well fit by Schechter functions. We foundsignificant evolution in the luminosity functions for all four IRAC channelsthat can be fit as an evolution in M* with redshift, \Delta M* = Qz. While wemeasured Q=1.2\pm0.4 and 1.1\pm0.4 in the 3.6 and 4.5 micron bands consistentwith the predictions from a passively evolving population, we obtainedQ=1.8\pm1.1 in the 8.0 micron band consistent with other evolving starformation rate estimates. We compared our LFs with the predictions ofsemi-analytical galaxy formation and found the best agreement at 3.6 and 4.5micron, rough agreement at 8.0 micron, and a large mismatch at 5.8 micron.These models also predicted a comparable Q value to our luminosity functions at8.0 micron, but predicted smaller values at 3.6 and 4.5 micron. We alsomeasured the luminosity functions separately for early and late-type galaxies.While the luminosity functions of late-type galaxies resemble those for thetotal population, the luminosity functions of early-type galaxies in the 3.6and 4.5 micron bands indicate deviations from the passive evolution model,especially from the measured flat luminosity density evolution. Combining ourestimates with other measurements in the literature, we found (53\pm18)% of thepresent stellar mass of early-type galaxies has been assembled at z=0.7.[Journal_ref: Astrophys.J.697:506-521,2009]
• Dai, X., Assef, R. J., Kochanek, C. S., Brodwin, M., Brown, M. J., Caldwell, N., Cool, R. J., Dey, A., Eisenhardt, P., Eisenstein, D., Gonzalez, A. H., Jannuzi, B. T., Jones, C., Murray, S. S., & Stern, D. (2009). Mid-infrared galaxy luminosity functions from the agn and galaxy evolution survey. Astrophysical Journal Letters, 697(1), 506-521.
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  Abstract: We present galaxy luminosity functions at 3.6, 4.5, 5.8, and 8.0 μm measured by combining photometry from the IRAC Shallow Survey with redshifts from the AGN and Galaxy Evolution Survey (AGES) of the NOAO Deep Wide-Field Survey Boötes field. The well defined IRAC samples contain 3800-5800 galaxies for the 3.6-8.0 μm bands with spectroscopic redshifts and z < 0.6. We obtained relatively complete luminosity functions in the local redshift bin of z < 0.2 for all four IRAC channels that are well fitted by Schechter functions. After analyzing the samples for the whole redshift range, we found significant evolution in the luminosity functions for all four IRAC channels that can be fitted as an evolution in M * with redshift, ΔM * = Qz. While we measured Q = 1.2 0.4 and 1.1 0.4 in the 3.6 and 4.5 μm bands consistent with the predictions from a passively evolving population, we obtained Q = 1.8 1.1 in the 8.0 μm band consistent with other evolving star formation rate estimates. We compared our luminosity functions with the predictions of semianalytical galaxy formation and found the best agreement at 3.6 and 4.5 μm, rough agreement at 8.0 μm, and a large mismatch at 5.8 μm. These models also predicted a comparable Q-value to our luminosity functions at 8.0 μm, but predicted smaller values at 3.6 and 4.5 μm. We also measured the luminosity functions separately for early- and late-type galaxies. While the luminosity functions of late-type galaxies resemble those for the total population, the luminosity functions of early-type galaxies in the 3.6 and 4.5 μm bands indicate deviations from the passive evolution model, especially from the measured flat luminosity density evolution. Combining our estimates with other measurements in the literature, we found 53 18% of the present stellar mass of early-type galaxies was assembled at z = 0.7. © 2009. The American Astronomical Society.
• Dawson, K. S., Aldering, G., Amanullah, R., Barbary, K., Barrientos, L. F., Brodwin, M., Connolly, N., Dey, A., Doi, M., Donahue, M., Eisenhardt, P., Ellingson, E., Faccioli, L., Fadeyev, V., Fakhouri, H. K., Fruchter, A. S., Gilbank, D. G., Gladders, M. D., Goldhaber, G., , Gonzalez, A. H., et al. (2009). An intensive hubble space telescope survey for z>1 type Ia supernovae by targeting galaxy clusters. Astronomical Journal, 138(5), 1271-1283.
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  Abstract: We present a new survey strategy to discover and study high-redshift Type Ia supernovae (SNe Ia) using the Hubble Space Telescope (HST). By targeting massive galaxy clusters at 0.9 < z < 1.5, we obtain a twofold improvement in the efficiency of finding SNe compared to an HST field survey and a factor of 3 improvement in the total yield of SN detections in relatively dust-free red-sequence galaxies. In total, sixteen SNe were discovered at z>0.95, nine of which were in galaxy clusters. This strategy provides an SN sample that can be used to decouple the effects of host-galaxy extinction and intrinsic color in high-redshift SNe, thereby reducing one of the largest systematic uncertainties in SN cosmology. © 2009 The American Astronomical Society. All rights reserved.
• Desai, V., Soifer, B. T., Dey, A., Floc'H, E. L., Armus, L., Brand, K., J., M., Brodwin, M., Jannuzi, B. T., Houck, J. R., Weedman, D. W., L., M., Gonzalez, A., Huang, J., Smith, H. A., Teplitz, H., Willner, S. P., & Melbourne, J. (2009). Strong polycyclic aromatic hydrocarbon emission from z ≈ 2 ulirgs. Astrophysical Journal Letters, 700(2), 1190-1204.
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  Abstract: Using the Infrared Spectrograph on board the Spitzer Space Telescope, we present low-resolution (64 < λ/δλ < 124), mid-infrared (20-38 μm) spectra of 23 high-redshift ULIRGs detected in the Boötes field of the NOAO Deep Wide-Field Survey. All of the sources were selected to have (1) f ν(24 μm)>0.5 mJy; (2) R - [24]>14 Vega mag; and (3) a prominent rest frame 1.6 μm stellar photospheric feature redshifted into Spitzer's 3-8 μm IRAC bands. Of these, 20 show emission from polycyclic aromatic hydrocarbons (PAHs), usually interpreted as signatures of star formation. The PAH features indicate redshifts in the range 1.5 < z < 3.0, with a mean of 〈z〉 = 1.96 and a dispersion of 0.30. Based on local templates, these sources have extremely large infrared luminosities, comparable to that of submillimeter galaxies. Our results confirm previous indications that the rest-frame 1.6 μm stellar bump can be efficiently used to select highly obscured star-forming galaxies at z 2, and that the fraction of starburst-dominated ULIRGs increases to faint 24 μm flux densities. Using local templates, we find that the observed narrow redshift distribution is due to the fact that the 24 μm detectability of PAH-rich sources peaks sharply at z = 1.9. We can analogously use observed spectral energy distributions to explain the broader redshift distribution of Spitzer-detected ULIRGs that are dominated by an active galactic nucleus (AGN). Finally, we conclude that z 2 sources with a detectable 1.6 μm stellar opacity feature lack sufficient AGN emission to veil the 7.7 μm PAH band. © 2009 The American Astronomical Society.
• Galametz, A., Stern, D., R., P., Brodwin, M., J., M., Dey, A., Gonzalez, A. H., Jannuzi, B. T., Moustakas, L. A., & Stanford, S. A. (2009). The cosmic evolution of active galactic nuclei in galaxy clusters. Astrophysical Journal Letters, 694(2), 1309-1316.
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  Abstract: We present the surface density of luminous active galactic nuclei (AGNs) associated with a uniformly selected galaxy cluster sample identified in the 8.5 deg2 Boötes field of the NOAO Deep Wide-Field Survey. The clusters are distributed over a large range of redshift (0 < z < 1.5), and we identify AGN using three different selection criteria: mid-IR color, radio luminosity, and X-ray luminosity. Relative to the field, we note a clear overdensity of the number of AGNs within 0.5 Mpc of the cluster centers at z > 0.5. The amplitude of this AGN overdensity increases with redshift. Although there are significant differences between the AGN populations probed by each selection technique, the rise in cluster AGN surface density generally increases more steeply than that of field quasars. In particular, X-ray-selected AGNs are at least 3 times more prevalent in clusters at 1 < z < 1.5 compared to clusters at 0.5 < z < 1. This effect is stronger than can be explained by the evolving median richness of our cluster sample. We thus confirm the existence of a Butcher-Oemler-type effect for AGN in galaxy clusters, with the number of AGNs in clusters increasing with redshift. © 2009. The American Astronomical Society. All rights reserved.
• Hickox, R. C., Jones, C., Forman, W. R., Murray, S. S., Kochanek, C. S., Eisenstein, D., Jannuzi, B. T., Dey, A., Brown, M. J., Stern, D., Eisenhardt, P. R., Gorjian, V., Brodwin, M., Narayan, R., Cool, R. J., Kenter, A., Caldwell, N., & Anderson, M. E. (2009). Host galaxies, clustering, Eddington ratios, and evolution of radio, X-ray, and infrared-selected AGNs. Astrophys.J., 696, 891-919.
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  We explore the connection between different classes of active galactic nuclei(AGNs) and the evolution of their host galaxies, by deriving host galaxyproperties, clustering, and Eddington ratios of AGNs selected in the radio,X-ray, and infrared. We study a sample of 585 AGNs at 0.25 < z < 0.8 usingredshifts from the AGN and Galaxy Evolution Survey (AGES) and data in the radio(WSRT 1.4 GHz), X-rays (Chandra XBootes), and mid-IR (IRAC Shallow Survey). Theradio, X-ray, and IR AGN samples show modest overlap, indicating that to theflux limits of the survey, they represent largely distinct classes of AGNs. Wederive host galaxy colors and luminosities, as well as Eddington ratios(lambda), for obscured or optically faint AGNs. We also measure the two-pointcross-correlation between AGNs and galaxies on scales of 0.3-10 h^-1 Mpc, andderive typical dark matter halo masses. We find that: (1) radio AGNs are mainlyfound in luminous red galaxies, are strongly clustered (with M_halo ~ 3x10^13h^-1 M_sun), and have very low lambda
• Hickox, R. C., Jones, C., Forman, W. R., Murray, S. S., Kochanek, C. S., Eisenstein, D., Jannuzi, B. T., Dey, A., J., M., Stern, D., Eisenhardt, P. R., Gorjian, V., Brodwin, M., Narayan, R., Cool, R. J., Kenter, A., Caldwell, N., & Anderson, M. E. (2009). Host galaxies, clustering, Eddington ratios, and evolution of radio, X-ray, and infrared-selected AGNs. Astrophysical Journal, 696(1), 891-919.
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  Abstract: We explore the connection between different classes of active galactic nuclei (AGNs) and the evolution of their host galaxies, by deriving host galaxy properties, clustering, and Eddington ratios of AGNs selected in the radio, X-ray, and infrared (IR) wavebands. We study a sample of 585 AGNs at 0.25 < z < 0.8 using redshifts from the AGN and Galaxy Evolution Survey (AGES). We select AGNs with observations in the radio at 1.4 GHz from the Westerbork Synthesis Radio Telescope, X-rays from the Chandra XBoötes Survey, and mid-IR from the Spitzer IRAC Shallow Survey. The radio, X-ray, and IR AGN samples show only modest overlap, indicating that to the flux limits of the survey, they represent largely distinct classes of AGNs. We derive host galaxy colors and luminosities, as well as Eddington ratios, for obscured or optically faint AGNs. We also measure the two-point cross-correlation between AGNs and galaxies on scales of 0.3-10 h-1 Mpc, and derive typical dark matter halo masses. We find that: (1) radio AGNs are mainly found in luminous red sequence galaxies, are strongly clustered (with Mhalo ∼ 3 × 1013 h-1 M⊙), and have very low Eddington ratios λ ≲ 10-3; (2) X-ray-selected AGNs are preferentially found in galaxies that lie in the "green valley" of color-magnitude space and are clustered similar to the typical AGES galaxies (Mhalo ∼ 1013 h-1 M⊙), with 10-3 ≲ λ ≲ 1; (3) IR AGNs reside in slightly bluer, slightly less luminous galaxies than X-ray AGNs, are weakly clustered (M halo ≲ 1012h-1 M⊙), and have λ > 10-2. We interpret these results in terms of a simple model of AGN and galaxy evolution, whereby a "quasar" phase and the growth of the stellar bulge occurs when a galaxy's dark matter halo reaches a critical mass between ∼ 1012 and 1013 M ⊙. After this event, star formation ceases and AGN accretion shifts from radiatively efficient (optical-and IR-bright) to radiatively inefficient (optically faint, radio-bright) modes. © 2009. The American Astronomical Society.
• Hovhannisyan, L. R., Mickaelian, A. M., Weedman, D. W., Floc'H, E. L., Houck, J. R., Soifer, B. T., Brand, K., Dey, A., & Jannuzi, B. T. (2009). Spitzer 24 μm excesses for bright galactic stars in botes and first look survey fields. Astronomical Journal, 138(1), 251-261.
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  Abstract: Optically bright Galactic stars (V ≲ 13 mag) having f ν(24 μm) > 1 mJy are identified in Spitzer mid-infrared surveys within 8.2 deg2 for the Boötes field of the NOAO Deep Wide-Field Survey and within 5.5 deg2 for the First Look Survey (FLS). One hundred and twenty-eight stars are identified in Boötes and 140 in the FLS, and their photometry is given. (K - [24]) colors are determined using K magnitudes from the Two Micron All Sky Survey for all stars in order to search for excess 24 μm luminosity compared to that arising from the stellar photosphere. Of the combined sample of 268 stars, 141 are of spectral types F, G, or K, and 17 of these 141 stars have 24 μm excesses with (K - [24]) > 0.2 mag. Using limits on absolute magnitude derived from proper motions, at least eight of the FGK stars with excesses are main-sequence stars, and estimates derived from the distribution of apparent magnitudes indicate that all 17 are main-sequence stars. These estimates lead to the conclusion that between 9% and 17% of the main-sequence FGK field stars in these samples have 24 μm infrared excesses. This result is statistically similar to the fraction of stars with debris disks found among previous Spitzer targeted observations of much brighter, main-sequence field stars. © 2009. The American Astronomical Society. All rights reserved..
• Hovhannisyan, L. R., Mickaelian, A. M., Weedman, D. W., Floc'H, L. E., Houck, J. R., Soifer, B. T., Brand, K., Dey, A., & Jannuzi, B. T. (2009). Spitzer 24 um Excesses for Bright Galactic Stars in Bootes and First Look Survey Fields. The Astronomical Journal, Volume, 251-261.
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  Optically bright Galactic stars (V < 13 mag) having fv(24 um) > 1 mJy areidentified in Spitzer mid-infrared surveys within 8.2 square degrees for theBootes field of the NOAO Deep Wide-Field Survey and within 5.5 square degreesfor the First Look Survey (FLS). 128 stars are identified in Bootes and 140 inthe FLS, and their photometry is given. (K-[24]) colors are determined using Kmagnitudes from the 2MASS survey for all stars in order to search for excess 24um luminosity compared to that arising from the stellar photosphere. Of thecombined sample of 268 stars, 141 are of spectral types F, G, or K, and 17 ofthese 141 stars have 24 um excesses with (K-[24]) > 0.2 mag. Using limits onabsolute magnitude derived from proper motions, at least 8 of the FGK starswith excesses are main sequence stars, and estimates derived from thedistribution of apparent magnitudes indicate that all 17 are main sequencestars. These estimates lead to the conclusion that between 9% and 17% of themain sequence FGK field stars in these samples have 24 um infrared excesses.This result is statistically similar to the fraction of stars with debris disksfound among previous Spitzer targeted observations of much brighter, mainsequence field stars.[Journal_ref: The Astronomical Journal, Volume 138, Issue 1, pp. 251-261, 07/2009]
• J., M., Moustakas, J., Caldwell, N., Palamara, D., Cool, R. J., Dey, A., Hickox, R. C., Jannuzi, B. T., Murray, S. S., & Zaritsky, D. (2009). Active galactic nuclei and the truncation of star formation in K+A galaxies. Astrophysical Journal Letters, 703(1), 150-158.
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  Abstract: We have searched for active galactic nuclei (AGNs) in K+A galaxies, using multiwavelength imaging and spectroscopy in the Boötes field of the NOAO Deep Wide-Field Survey. The K+A galaxies, which have had their star formation rapidly truncated, are selected via their strong Balmer absorption lines and weak Hα emission. Our sample consists of 24 K+A galaxies selected from 6594 0.10 < z < 0.35 galaxies brighter than I = 20 with optical spectroscopy from the AGN and Galaxy Evolution Survey. Two thirds of the K+A galaxies are likely ongoing galaxy mergers, with nearby companion galaxies or tidal tails. Galaxy mergers may be responsible for the truncation of star formation, or we are observing the aftermath of merger triggered starbursts. As expected, the optical colors of K+A galaxies largely fall between blue galaxies with ongoing star formation and red passive galaxies. However, only 1% of the galaxies with colors between the red and blue populations are K+A galaxies, and we conclude that the truncation of star formation in K+A galaxies must have been unusually abrupt (≲100 Myr). We examined the AGN content of K+A galaxies with both optical emission-line ratios (BPT diagrams) and Chandra X-ray imaging. At least half of all K+A galaxies display the optical emission-line ratios of AGNs, and a third of MR < -22 K+A galaxies host AGNs with X-ray luminosities of 1042 erg s-1. The faintest K+A galaxies do not show clear evidence for hosting AGNs, having emission-line ratios consistent with photoionization by massive stars and few X-ray detections. We speculate that two mechanisms may be responsible for the truncation of star formation in K+A galaxies, with AGN feedback only playing a role in M R ≲ -20.5 galaxies. © 2009. The American Astronomical Society. All rights reserved.
• K., M., Dey, A., & Jannuzi, B. T. (2009). The discovery of a large Lyα+He II nebula at z 1.67: A candidate low metallicity region?. Astrophysical Journal Letters, 702(1), 554-566.
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  Abstract: We have discovered a 45 kpc Lyα nebula (or Lyα "blob") at z 1.67 which exhibits strong, spatially extended He II emission and very weak C IV and C III] emission. This is the first spatially extended Lyα+He II emitter observed and the lowest redshift Lyα blob yet found. Strong Lyα and He IIλ1640 emission in the absence of metal lines has been proposed as a unique observational signature of primordial galaxy formation (e.g., from gravitational cooling radiation or Population III star formation), but no convincing examples of spatially extended Lyα+He II emitters have surfaced either in Lyα-emitting galaxy surveys at high redshifts (z > 4) or in studies of Lyα nebulae at lower redshifts. From comparisons with photoionization models, we find that the observed line ratios in this nebula are consistent with low metallicity gas (Z ≲ 10 -2-10-3 Z ȯ), but that this conclusion depends on the unknown ionization parameter of the system. The large He II equivalent width (37 10 ) and the large He II/Lyα ratio (0.12 0.04) suggest that the cloud is being illuminated by a hard ionizing continuum, either an active galactic nucleus (AGN) or very low metallicity stars, or perhaps powered by gravitational cooling radiation. Thus far there is no obvious sign of a powerful AGN in or near the system, so in order to power the nebula while remaining hidden from view even in the mid-infrared, the AGN would need to be heavily obscured. Despite the strong Lyα+He II emission, it is not yet clear what is the dominant power source for this nebula. The system therefore serves as an instructive example of how the complexities of true astrophysical sources will complicate matters when attempting to use a strong Lyα+He II signature as a unique tracer of primordial galaxy formation. © 2009 The American Astronomical Society. All rights reserved.
• Melbourne, J., Bussman, R. S., Brand, K., Desai, V., Armus, L., Dey, A., Jannuzi, B. T., Houck, J. R., Matthews, K., & Soifer, B. T. (2009). High-redshift dust obscured galaxies: A morphology-spectral energy distribution connection revealed by Keck adaptive optics. Astronomical Journal, 137(6), 4854-4866.
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  Abstract: A simple optical to mid-IR color selection, R - [24] > 14, i.e., f ν(24 μm)/fν(R) ≳ 1000, identifies highly dust obscured galaxies (DOGs) with typical redshifts of z 2 ± 0.5. Extreme mid-IR luminosities (LIR > 1012-14) suggest that DOGs are powered by a combination of active galactic nuclei (AGNs) and star formation, possibly driven by mergers. In an effort to compare their photometric properties with their rest-frame optical morphologies, we obtained high-spatial resolution (0″05-0″1) Keck Adaptive Optics K′-band images of 15 DOGs. The images reveal a wide range of morphologies, including small exponential disks (eight of 15), small ellipticals (four of 15), and unresolved sources (two of 15). One particularly diffuse source could not be classified because of low signal-to-noise ratio. We find a statistically significant correlation between galaxy concentration and mid-IR luminosity, with the most luminous DOGs exhibiting higher concentration and smaller physical size. DOGs with high concentration also tend to have spectral energy distributions (SEDs) suggestive of AGN activity. Thus, central AGN light may be biasing the morphologies of the more luminous DOGs to higher concentration. Conversely, more diffuse DOGs tend to show an SED shape suggestive of star formation. Two of 15 in the sample show multiple resolved components with separations of ∼1 kpc, circumstantial evidence for ongoing mergers. © 2009. The American Astronomical Society. All rights reserved.
• Prescott, M. K., Dey, A., & Jannuzi, B. T. (2009). The Discovery of a Large Lyman-alpha+HeII Nebula at z~1.67: A Candidate Low Metallicity Region?. Astrophys.J., 702, 554-566.
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  We have discovered a ~45 kpc Lya nebula (or Lya ``blob'') at z~1.67 whichexhibits strong, spatially-extended HeII emission and very weak CIV and CIII]emission. This is the first spatially-extended Lya+HeII emitter observed andthe lowest redshift Lya blob yet found. Strong Lya and HeII-1640 emission inthe absence of metal lines has been proposed as a unique observationalsignature of primordial galaxy formation (e.g., from gravitational coolingradiation or Population III star formation), but no convincing examples ofspatially-extended Lya+HeII emitters have surfaced either in Lya-emittinggalaxy surveys at high redshifts (z > 4) or in studies of Lya nebulae at lowerredshifts. From comparisons with photoionization models, we find that theobserved line ratios in this nebula are consistent with low metallicity gas (Z< 10^-2 - 10^-3 Z_sun), but that this conclusion depends on the unknownionization parameter of the system. The large HeII equivalent width (~37+/-10A)and the large HeII/Lya ratio (0.12+/-0.04) suggest that the cloud is beingilluminated by a hard ionizing continuum, either an AGN or very low metallicitystars, or perhaps powered by gravitational cooling radiation. Thus far there isno obvious sign of a powerful AGN in or near the system, so in order to powerthe nebula while remaining hidden from view even in the mid-infrared, the AGNwould need to be heavily obscured. Despite the strong Lya+HeII emission, it isnot yet clear what is the dominant power source for this nebula. The systemtherefore serves as an instructive example of how the complexities of trueastrophysical sources will complicate matters when attempting to use a strongLya+HeII signature as a unique tracer of primordial galaxy formation.[Journal_ref: Astrophys.J.702:554-566,2009]
• Tyler, K. D., Floc'H, E. L., Rieke, G. H., Dey, A., Desai, V., Brand, K., Borys, C., Jannuzi, B. T., Armus, L., Dole, H., Papovich, C., J., M., Blaylock, M., J., S., Higdon, J. L., Charmandaris, V., L., M., & Smith, H. A. (2009). Spitzer 70/160 μm observations of high-redshift ULIRGs and HyLIRGs in the Boötes field. Astrophysical Journal, 691(2), 1846-1853.
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  Abstract: We present new 70 and 160 μm observations of a sample of extremely red (R-[24] ≳ 15 mag), mid-infrared bright, high-redshift (1.7 ≲ z ≲ 2.8) galaxies. All targets detected in the far-infrared exhibit rising spectral energy distributions (SEDs) consistent with dust emission from obscured active galactic nuclei (AGNs) and/or star-forming regions in luminous IR galaxies (LIRGs). We find that the SEDs of the high-redshift sources are more similar to canonical AGN-dominated local ultraluminous IR galaxies (ULIRGs) with significant warm dust components than to typical local star-forming ULIRGs. The inferred IR (8-1000 μm) bolometric luminosities are found to be L bol 4 × 1012 L to3 × 1013 L (ULIRGs/hyper-luminous IR galaxies (HyLIRGs)), representing the first robust constraints on L bol for this class of object. © 2009. The American Astronomical Society. All rights reserved..
• Watson, C. R., Kochanek, C. S., Forman, W. R., Hickox, R. C., Jones, C. J., J., M., Brand, K., Dey, A., Jannuzi, B. T., Kenter, A. T., Murray, S. S., Vikhlinin, A., Eisenstein, D. J., Fazio, G. G., Green, P. J., McNamara, B. R., Rieke, M., & Shields, J. C. (2009). The star formation and nuclear accretion histories of normal galaxies in the ages survey. Astrophysical Journal, 696(2), 2206-2219.
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  Abstract: We combine IR, optical, and X-ray data from the overlapping, 9.3 deg 2 NOAO Deep Wide-Field Survey, AGN and Galaxy Evolution Survey (AGES), and XBoötes Survey to measure the X-ray evolution of 6146 normal galaxies as a function of absolute optical luminosity, redshift, and spectral type over the largely unexplored redshift range 0.1 ≲ z ≲ 0.5. Because only the closest or brightest of the galaxies are individually detected in X-rays, we use a stacking analysis to determine the mean properties of the sample. Our results suggest that X-ray emission from spectroscopically late-type galaxies is dominated by star formation, while that from early-type galaxies is dominated by a combination of hot gas and active galactic nucleus (AGN) emission. We find that the mean star formation and supermassive black hole accretion rate densities evolve like (1 + z) 31, in agreement with the trends found for samples of bright, individually detectable starburst galaxies and AGN. Our work also corroborates the results of many previous stacking analyses of faint source populations, with improved statistics. © 2009 The American Astronomical Society. All rights reserved.
• Assef, R. J., Kochanek, C. S., Brodwin, M., Brown, M. J., Caldwell, N., Cool, R. J., Eisenhardt, P., Eisenstein, D., Gonzalez, A. H., Jannuzi, B. T., Jones, C., McKenzie, E., Murray, S. S., & Stern, D. (2008). Low Resolution Spectral Templates For Galaxies From 0.2 -- 10 microns. Astrophys.J..
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  We built an optimal basis of low resolution templates for galaxies over thewavelength range from 0.2 to 10 $\mu$m using a variant of the algorithmpresented by Budavari et al. (2000). We derived them using eleven bands ofphotometry from the NDWFS, FLAMEX, zBo\"otes and IRAC Shallow surveys for 16033galaxies in the NDWFS Bo\"otes field with spectroscopic redshifts measured bythe AGN and Galaxy Evolution Survey. We also developed algorithms to accuratelydetermine photometric redshifts, K corrections and bolometric luminositiesusing these templates. Our photometric redshifts have an accuracy of$\sigma_z/(1+z) = 0.04$ when clipped to the best 95%. We used these templatesto study the spectral type distribution in the field and to estimate luminosityfunctions of galaxies as a function of redshift and spectral type. Inparticular, we note that the 5-8$\mu$m color distribution of galaxies isbimodal, much like the optical g--r colors.[Journal_ref: Astrophys.J. 676 (2008) 286]
• Assef, R. J., Kochanek, C. S., Brodwin, M., Brown, M. J., Caldwell, N., Cool, R. J., Eisenhardt, P., Eisenstein, D., Gonzalez, A. H., Jannuzi, B. T., Jones, C., McKenzie, E., Murray, S. S., & Stern, D. (2008). Low-resolution spectral templates for galaxies from 0.2 to 10 μm. Astrophysical Journal, 676(1), 286-303.
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  Abstract: We built an optimal basis of low-resolution templates for galaxies over the wavelength range from 0.2 to 10 μm using a variant of the algorithm presented by Budavari and coworkers. We derived them using 11 bands of photometry from the NDWFS, FLAMEX, zBoötes, and IRAC Shallow surveys for 16,033 galaxies in the NDWFS Bootes field with spectroscopic redshifts measured by the AGN and Galaxy Evolution Survey. We also developed algorithms to accurately determine photometric redshifts, K-corrections, and bolometric luminosities using these templates. Our photometric redshifts have an accuracy of σz/(1 + z) = 0.04 when clipped to the best 95%. We used these templates to study the spectral type distribution in the field and to estimate luminosity functions of galaxies as a function of redshift and spectral type. In particular, we note that the 5-8 μm color distribution of galaxies is bimodal, much like the optical g - r colors. © 2008. The American Astronomical Society. All rights reserved.
• Brand, K., Weedman, D. W., Desai, V., Floc'h, E. L., Armus, L., Dey, A., Houck, J. R., Jannuzi, B. T., Smith, H. A., & Soifer, B. T. (2008). Spitzer mid-infrared spectroscopy of 70 μm-selected distant luminous infrared galaxies. Astrophysical Journal, 673(1), 119-127.
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  Abstract: We present mid-infrared spectroscopy obtained with the Spitzer Space Telescope of a sample of 11 optically faint, infrared luminous galaxies selected from a Spitzer MIPS 70 μm imaging survey of the NDWFS Bootes field. These are the first Spitzer IRS spectra presented of distant 70 μm-selected sources. All the galaxies lie at redshifts 0.3 < z < 1.3 and have very large infrared luminosities of LIR ∼ (0.1-17) × 10 12 Z⊙. Seven of the galaxies exhibit strong emission features attributed to polycyclic aromatic hydrocarbons (PAHs). The average IRS spectrum of these sources is characteristic of classical starburst galaxies but with much larger infrared luminosities. The PAH luminosities of vL v(7.7 μm) ∼ (0.4-7) × 1011 L⊙ imply star formation rates of ∼40-720 M⊙ yr-1. Four of the galaxies show deep 9.7 μm silicate absorption features and no significant PAH emission features (6.2 μm equivalent widths
• Brand, K., Weedman, D. W., Desai, V., Floc'h, E. L., Armus, L., Dey, A., Houck, J. R., Jannuzi, B. T., Smith, H. A., & Soifer, B. T. (2008). Spitzer mid-infrared spectroscopy of distant X-ray luminous active galactic nuclei. Astrophysical Journal, 680(1), 119-129.
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  Abstract: We present mid-infrared spectroscopy of a sample of 16 optically faint infrared luminous galaxies obtained with the Infrared Spectrograph (IRS) on the Spitzer Space Telescope. These sources were jointly selected from Spitzer and Chandra imaging surveys in the NOAO Deep Wide-Field Survey Boötes field and were selected from their bright X-ray fluxes to host luminous AGNs. None of the spectra show significant emission from polycyclic aromatic hydrocarbons (PAHs; 6.2 μm equivalent widths
• Brodwin, M., Dey, A., Brown, M. J., Pope, A., Armus, L., Bussmann, S., Desai, V., Jannuzi, B. T., & Floc'H, E. L. (2008). Clustering of Dust-Obscured Galaxies at z ~ 2. Astrophys.J., 687.
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  We present the angular autocorrelation function of 2603 dust-obscuredgalaxies (DOGs) in the Bootes field of the NOAO Deep Wide-Field Survey. DOGsare red, obscured galaxies, defined as having R-[24] \ge 14 (F_24/F_R \ga1000). Spectroscopy indicates that they are located at 1.5 \la z \la 2.5. Wefind strong clustering, with r_0 = 7.40^{+1.27}_{-0.84} Mpc/h for the full F_24> 0.3 mJy sample. The clustering and space density of the DOGs are consistentwith those of submillimeter galaxies, suggestive of a connection between thesepopulations. We find evidence for luminosity-dependent clustering, with thecorrelation length increasing to r_0 = 12.97^{+4.26}_{-2.64} Mpc/h for brighter(F_24 > 0.6 mJy) DOGs. Bright DOGs also reside in richer environments thanfainter ones, suggesting these subsamples may not be drawn from the same parentpopulation. The clustering amplitudes imply average halo masses of log M =12.2^{+0.3}_{-0.2} Msun for the full DOG sample, rising to log M =13.0^{+0.4}_{-0.3} Msun for brighter DOGs. In a biased structure formationscenario, the full DOG sample will, on average, evolve into ~ 3 L* present-daygalaxies, whereas the most luminous DOGs may evolve into brightest clustergalaxies.[Journal_ref: Astrophys.J.687:L65-L68, 2008]
• Brodwin, M., Dey, A., Brown, M. J., Pope, A., Armus, L., Bussmann, S., Desai, V., Jannuzi, B. T., & Floc'h, E. L. (2008). Clustering of dust-obscured galaxies at z ∼ 2. Astrophysical Journal, 687(2), L65-L68.
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  Abstract: We present the angular autocorrelation function of 2603 dust-obscured galaxies (DOGs) in the Boötes field of the NOAO Deep Wide-Field Survey. DOGs are red, obscured galaxies, defined as having R - [24] ≥ 14 (F 24/FR ≥ 1000). Spectroscopy indicates that they are located at 1.5 ≲ z ≲ 2.5. We find strong clustering, with r 0 = 7.40-0.84+1.27 h-1 Mpc for the full F24 > 0.3 mJy sample. The clustering and space density of the DOGs are consistent with those of submillimeter galaxies, suggestive of a connection between these populations. We find evidence for luminosity-dependent clustering, with the correlation length increasing to r0 = 12.97-2.64+4.26 h-1 Mpc for brighter (F24 < 0.6 mJy) DOGs. Bright DOGs also reside in richer environments than fainter ones, suggesting these subsamples may not be drawn from the same parent population. The clustering amplitudes imply average halo masses of log M = 12.2-0.2+0.3 M⊙ for the full DOG sample, rising to log M = 13.0-0.3+0.4 M ⊙ for brighter DOGs. In a biased structure formation scenario, the full DOG sample will, on average, evolve into ∼3L, present-day galaxies, whereas the most luminous DOGs may evolve into brightest cluster galaxies. © 2008. The American Astronomical Society. All rights reserved.
• Brown, M. J., Zheng, Z., White, M., Dey, A., Jannuzi, B. T., Benson, A. J., Brand, K., Brodwin, M., & Croton, D. J. (2008). Red Galaxy Growth and the Halo Occupation Distribution. Astrophys.J., 682, 937-963.
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  We have traced the past 7 Gyr of red galaxy stellar mass growth within darkmatter halos. We have determined the halo occupation distribution, whichdescribes how galaxies reside within dark matter halos, using the observedluminosity function and clustering of 40,696 0.2
• Brown, M. J., Zheng, Z., White, M., Dey, A., Jannuzi, B. T., Benson, A. J., Brand, K., Brodwin, M., & Croton, D. J. (2008). Red galaxy growth and the halo occupation distribution. Astrophysical Journal, 682(2), 937-963.
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  Abstract: We have traced the past 7 Gyr of red galaxy stellar mass growth within dark matter halos. We have determined the halo occupation distribution, which describes how galaxies reside within dark matter halos, using the observed luminosity function and clustering of 40,696 0.2 < z < 1.0 red galaxies in Boötes. Half of ≃1011.9 h-1 M⊙ halos host a red central galaxy, and this fraction increases with increasing halo mass. We do not observe any evolution of the relationship between red galaxy stellar mass and host halo mass, although we expect both galaxy stellar masses and halo masses to evolve over cosmic time. We find that the stellar mass contained within the red population has doubled since z=l, with the stellar mass within red satellite galaxies tripling over this redshift range. In cluster mass halos (>1014 h-1 M⊙) most of the stellar mass resides within satellite galaxies and the intracluster light, with a minority of the stellar mass residing within central galaxies. The stellar masses of the most luminous red central galaxies are proportional to halo mass to the power of ≃0.35. We thus conclude that halo mergers do not always lead to rapid growth of central galaxies. While very massive halos often double in mass over the past 7 Gyr, the stellar masses of their central galaxies typically grow by only ≃30%. © 2008. The American Astronomical Society. All rights reserved.
• Croft, S., Breugel, W. V., J., M., Vries, W. D., Dey, A., Eisenhardt, P., Jannuzi, B., Röttgering, H., Stanford, S. A., Stern, D., & Willner, S. P. (2008). Radio-loud high-redshift protogalaxy candidates in botes. Astronomical Journal, 135(5), 1793-1802.
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  Abstract: We used the Near Infrared Camera on Keck I to obtain Ks -band images of four candidate high-redshift radio galaxies selected using optical and radio data in the NOAO Deep Wide-Field Survey in Boötes. Our targets have 1.4 GHz radio flux densities greater than 1 mJy, but are undetected in the optical to ≳24 Vega mag. Spectral energy distribution fitting suggests that three of these objects are at z > 3, with radio luminosities near the FR-I/FR-II break. The other has photometric redshift z phot = 1.2, but may in fact be at higher redshift. Two of the four objects exhibit diffuse morphologies in Ks -band, suggesting that they are still in the process of forming. © 2008. The American Astronomical Society. All rights reserved.
• Desai, V., Soieer, B. T., Dey, A., Jannuzi, B. T., Floc'h, E. L., Bian, C., Brand, K., Brown, M. J., Armus, L., Weedman, D. W., Cool, R., Stern, D., & Brodwin, M. (2008). Redshift distribution of extragalactic 24 μm sources. Astrophysical Journal, 679(2), 1204-1217.
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  Abstract: We present the redshift distribution of a complete, unbiased sample of 24 μm sources down to fv(24 μm) = 300 μJy (5 σ). The sample consists of 591 sources detected in the Boötes field of the NOAO Deep Wide-Field Survey. We have obtained optical spectroscopic redshifts for 421 sources (71%). These have a redshift distribution peaking at z ∼ 0.3, with a possible additional peak at z ∼ 0.9, and objects detected out to z = 4.5. The spectra of the remaining 170 (29%) exhibit no strong emission lines from which to determine a redshift. We develop an algorithm to estimate the redshift distribution of these sources, based on the assumption that they have emission lines but that these lines are not observable due to the limited wavelength coverage of our spectroscopic observations. The redshift distribution derived from all 591 sources exhibits an additional peak of extremely luminous (L 8-1000 μm > 3 × 1012 L⊙) objects at z ∼ 2, consisting primarily of sources without observable emission lines. We use optical line diagnostics and IRAC colors to estimate that 55% of the sources within this peak are AGN-dominated. We compare our results to published models of the evolution of infrared-luminous galaxies. The models which best reproduce our observations predict a large population of star-formation-dominated ULIRGs at z > 1.5 rather than the AGN-dominated sources we observe. © 2008. The American Astronomical Society. All rights reserved.
• Dey, A., Soifer, B. T., Desai, V., Brand, K., Floc'h, E. L., J., M., Jannuzi, B. T., Armus, L., Bussmann, S., Brodwin, M., Bian, C., Eisenhardt, P., Higdon, S. J., Weedman, D., & Willner, S. P. (2008). A significant population of very luminous dust-obscured galaxies at redshift z ∼ 2. Astrophysical Journal, 677(2), 943-956.
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  Abstract: The Spitzer Space Telescope has revealed a significant population of high-redshift (z ∼ 2) dust-obscured galaxies with large mid-infrared to ultraviolet luminosity ratios. Due to their optical faintness, these galaxies have been previously missed in traditional optical studies of the distant universe. We present a simple method for selecting this high-redshift population based solely on the ratio of the observed mid-infrared 24 μm to optical R-band flux density. We apply this method to observations of the ≈8.6 deg2 NOAO Deep Wide-Field Survey Bootes field, and uncover ≈2600 dust-obscured galaxy candidates [i.e., 0.089 arcmin-2) with 24 μm flux densities F24 μm ≥ 0.3 mJy and (R - [24]) > 14 (i.e., Fν(24 μm)/Fν(R) ≳ 1000]. These galaxies have no counterparts in the local universe. They represent 7% ± 0.6% of the 24 μm source population at F24 μm ≥ 1 mJy but increase to ≈13% ± 1% of the population at ≈0.3 mJy. These galaxies exhibit evidence of both star formation and AGN activity, with the brighter 24 μm sources being more AGN-dominated. We have measured spectroscopic redshifts for 86 of these galaxies, and find a broad redshift distribution centered at z̄ ≈ 1.99 ± 0.05. The space density of this population is ⊃DOG(F24μm ≥ 0.3 mJy) = (2.82 ± 0.05) × 10-5h703 Mpc-3, similar to that of bright submillimeter-selected galaxies at comparable redshifts. These redshifts imply large luminosities, with median νLν(8 μm) ≈ 4 × 1011 L⊙. The infrared luminosity density contributed by this relatively rare dust-obscured galaxy population is log(IRLD) ≈8.23-0.30+0.18. This is ≈60 -15+40% of that contributed by z ∼ 2 ultraluminous infrared galaxies (ULIRGs, with LIR > 1012 L ⊙); our simple selection thus identifies a significant fraction of z ∼ 2 ULIRGs. This IRLD is ≈26% ± 14% of the total contributed by all z ∼ 2 galaxies. We suggest that these dust-obscured galaxies are the progenitors of luminous (∼4L*) present-day galaxies, seen undergoing an extremely luminous, short-lived phase of both bulge and black hole growth. They may represent a brief evolutionary phase between submillimeter-selected galaxies and less obscured quasars or galaxies. © 2008. The American Astronomical Society. All rights reserved.
• Eisenhardt, P. R., Brodwin, M., Gonzalez, A. H., Stanford, A. S., Stern, D., Barmby, P., Brown, M. J., Dawson, K., Dey, A., Doi, M., Galametz, A., Jannuzi, B. T., Kochanek, C. S., Meyers, J., Morokuma, T., & Moustakas, L. A. (2008). Clusters of Galaxies in the First Half of the Universe from the IRAC Shallow Survey. Astrophys.J., 684, 905-932.
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  We have identified 335 galaxy cluster and group candidates, 106 of which areat z > 1, using a 4.5 um selected sample of objects from a 7.25 deg^2 region inthe Spitzer Infrared Array Camera (IRAC) Shallow Survey. Clusters wereidentified as 3-dimensional overdensities using a wavelet algorithm, based onphotometric redshift probability distributions derived from IRAC and NOAO DeepWide-Field Survey data. We estimate only ~10% of the detections are spurious.To date 12 of the z > 1 candidates have been confirmed spectroscopically, atredshifts from 1.06 to 1.41. Velocity dispersions of ~750 km/s for two of theseargue for total cluster masses well above 10^14 M_sun, as does the massestimated from the rest frame near infrared stellar luminosity. Although notselected to contain a red sequence, some evidence for red sequences is presentin the spectroscopically confirmed clusters, and brighter galaxies aresystematically redder than the mean galaxy color in clusters at all redshifts.The mean I - [3.6] color for cluster galaxies up to z ~ 1 is well matched by apassively evolving model in which stars are formed in a 0.1 Gyr burst startingat redshift z_f = 3. At z > 1, a wider range of formation histories is needed,but higher formation redshifts (i.e. z_f > 3) are favored for most clusters.[Journal_ref: Astrophys.J.684:905-932,2008]
• Gorjian, V., Brodwin, M., Kochanek, C. S., Murray, S., Stern, D., Brand, K., Eisenhardt, P. R., Ashby, M. L., Barmby, P., Brown, M. J., Dey, A., Forman, W., Jannuzi, B. T., Jones, C., Kenter, A. T., Pahre, M. A., Shields, J. C., Werner, M. W., & Willner, S. P. (2008). The mid-infrared properties of X-ray sources. Astrophysical Journal, 679(2), 1040-1046.
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  Abstract: We combine the results of the Spitzer IRAC Shallow Survey and the Chandra XBoötes Survey of the 8.5 deg2 Boötes field of the NOAO Deep Wide-Field Survey to produce the largest comparison of mid-IR and X-ray sources to date. The comparison is limited to sources with X-ray fluxes >8 × 10-15 ergs cm-2 s-1 in the 0.5-7.0 keV range and mid-IR sources with 3.6 μm fluxes brighter than 18.4 mag (12.3 μJy). In this most sensitive IRAC band, 85% of the 3086 X-ray sources have mid-IR counterparts at an 80% confidence level based on a Bayesian matching technique. Only 2.5%) of the sample have no IRAC counterpart at all based on visual inspection. Even for a smaller but a significantly deeper Chandra survey in the same field, the IRAC Shallow Survey recovers most of the X-ray sources. A majority (65%) of the Chandra sources detected in all four IRAC bands occupy a well-defined region of IRAC [3.6] - [4.5] versus [5.8] - [8.0] color-color space. These X-ray sources are likely infrared-luminous, unobscured type I AGNs with little mid-infrared flux contributed by the AGN host galaxy. Of the remaining Chandra sources, most are lower luminosity type I and type II AGNs whose mid-IR emission is dominated by the host galaxy, while approximately 5% are either Galactic stars or very local galaxies. © 2008. The American Astronomical Society. All rights reserved.
• Melbourne, J., Desai, V., Armus, L., Dey, A., Brand, K., Thompson, D., Soifer, B. T., Matthews, K., Jannuzi, B. T., & Houck, J. R. (2008). Morphologies of high-redshift, dust-obscured galaxies from keck laser guide star adaptive optics. Astronomical Journal, 136(3), 1110-1117.
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  Abstract: Spitzer MIPS images in the Boötes field of the NOAO Deep Wide-Field Survey have revealed a class of extremely dust-obscured galaxy (DOG) at z 2. The DOGs are defined by very red optical to mid-infrared (IR; observed-frame) colors, R - [24 μm]>14 mag, i.e. f ν(24 μm)/f ν(R)>1000. They are ultra-luminous infrared galaxies with L 8-1000 μm > 1012-1014 L, but typically have very faint optical (rest-frame UV) fluxes. We imaged three DOGs with the Keck laser guide star adaptive optics (LGSAO) system, obtaining 0.06″ resolution in the K′-band. One system was dominated by a point source, while the other two were clearly resolved. Of the resolved sources, one can be modeled as a exponential disk system. The other is consistent with a de Vaucouleurs profile typical of elliptical galaxies. The nonparametric measures of their concentration and asymmetry show the DOGs to be both compact and smooth. The AO images rule out double nuclei with separations of greater than 0.1″ (
• R., P., Brodwin, M., Gonzalez, A. H., Stanford, S. A., Stern, D., Barmby, P., J., M., Dawson, K., Arjun, D. E., Doi, M., Galametz, A., Jannuzi, B. T., Kochanek, C. S., Meyers, J., Morokuma, T., & Moustakas, L. A. (2008). Clusters of galaxies in the first half of the universe from the IRAC shallow survey. Astrophysical Journal, 684(2), 905-932.
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  Abstract: We have identified 335 galaxy cluster and group candidates, 106 of which are at z > 1, using a 4.5 μm-selected sample of objects from a 7.25 deg2 region in the Spitzer Infrared Array Camera (IRAC) Shallow Survey. Clusters were identified as three-dimensional overdensities using a wavelet algorithm, based on photometric redshift probability distributions derived from IRAC and NOAO Deep Wide-Field Survey data. We estimate only ∼10% of the detections are spurious. To date 12 of the z > 1 candidates have been confirmed spectroscopically, at redshifts from 1,06 to 1.41. Velocity dispersions of ∼750 km s-1 for two of these argue for total cluster masses well above 1014 M⊙, as does the mass estimated from the rest-frame near-infrared stellar luminosity. Although not selected to contain a red sequence, some evidence for red sequences is present in the spectroscopically confirmed clusters, and brighter galaxies are systematically redder than the mean galaxy color in clusters at all redshifts. The mean 1 - [3.6] color for cluster galaxies up to z ∼ lis well matched by a passively evolving model in which stars are formed in a 0.1 Gyr burst starting at redshift zf = 3. At z > 1, a wider range of formation histories is needed, but higher formation redshifts (i.e., Zf > 3) are favored for most clusters. © 2008. The American Astronomical Society. All rights reserved.
• Silverman, J. D., Green, P. J., Barkhouse, W. A., Kim, D. -., Kim, M., Wilkes, B. J., Cameron, R. A., Hasinger, G., Jannuzi, B. T., Smith, M. G., Smith, P. S., & Tananbaum, H. (2008). The luminosity function of X-ray-selected active galactic nuclei: Evolution of supermassive black holes at high redshift. Astrophysical Journal, 679(1), 118-139.
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  Abstract: We present a measure of the hard (2-8 keV) X-ray luminosity function (XLF) of AGNs up to z ∼ 5. At high redshifts, the wide area coverage of the Chandra Multiwavength Project is crucial to detect rare and luminous (L X > 1044 ergs s-1) AGNs. The inclusion of samples from deeper published surveys, such as the Chandra Deep Fields, allows us to span the lower LX range of the XLF. Our sample is selected from both the hard (z < 3, f2-8 kev > 6.3 × 10-16 ergs cm-2 s-1) and soft (z > 3, f0.5-2.0kev > 1.0 × 10-16 ergs cm-2 s-1) energy band detections. Within our optical magnitude limits (r′, i′ < 24), we achieve an adequate level of completeness (>50%) regarding X-ray source identification (i.e., redshift). We find that the luminosity function is similar to that found in previous X-ray surveys up to z ∼ 3 with an evolution dependent on both luminosity and redshift. At z > 3, there is a significant decline in the numbers of AGNs with an evolution rate similar to that found by studies of optically selected QSOs. Based on our XLF, we assess the resolved fraction of the cosmic X-ray background, the cumulative mass density of SMBHs, and the comparison of the mean accretion rate onto SMBHs and the star formation history of galaxies as a function of redshift. A coevolution scenario up to z ∼ 2 is plausible, although at higher redshifts the accretion rate onto SMBHs drops more rapidly. Finally, we highlight the need for better statistics of high-redshift AGNs at z ≳ 3, which is achievable with the upcoming Chandra surveys. © 2008. The American Astronomical Society. All rights reserved.
• Brand, K., Dey, A., Desai, V., Soifer, B. T., Bian, C., Armus, L., Brown, M. J., Floc'H, L. E., Higdon, S. J., Houck, J. R., Jannuzi, B. T., & Weedman, D. W. (2007). Optical Line Diagnostics of z~2 Optically Faint ULIRGs in the Spitzer Bootes Survey. Astrophys.J., 663, 204-217.
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  We present near-infrared spectroscopic observations for a sample of tenoptically faint luminous infrared galaxies (R-[24]> 14) using Keck NIRSPEC andGemini NIRI. The sample is selected from a 24 micron Spitzer MIPS imagingsurvey of the NDWFS Bootes field. We measure accurate redshifts in the range1.3 2.4-5mag. Since the narrow-line region is also extincted and the UV continuumemission from the host galaxies is extremely faint, this suggests that much ofthe obscuration is contributed by dust on large (~kpc) scales within the hostgalaxies. These sources may be examples of "host-obscured" AGN which could havespace densities comparable or greater to that of optically luminous type I AGNwith similar bolometric luminosities.[Journal_ref: Astrophys.J.663:204-217,2007]
• Brand, K., Dey, A., Desai, V., Soifer, B. T., Bian, C., Armus, L., Brown, M. J., Floc'h, E. L., Higdon, S. J., Houck, J. R., Jannuzi, B. T., & Weedman, D. W. (2007). Optical line diagnostics of z ≈ 2 optically faint ultraluminous infrared galaxies in the Spitzer bootes survey. Astrophysical Journal, 663(1 I), 204-217.
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  Abstract: We present near-infrared spectroscopic observations for a sample of 10 optically faint luminous infrared galaxies (R - [24] ≥ 14) using Keck NIRSPEC and Gemini NIRI. The sample is selected from a 24 μm Spitzer MIPS imaging survey of the NDWFS Boötes field. We measure accurate redshifts in the range 1.3 ≲ z ≲ 3.4. Based on either emission-line widths or line diagnostics, we find that all 10 galaxies harbor luminous active galactic nuclei (AGNs). Seven sources are type I AGNs, exhibiting broad (>1900 km s 1) Hα or Hβ emission lines; the remaining three are type II AGNs. Given their large mid-IR luminosities and faint optical magnitudes, we might expect these sources to be heavily extincted quasars, and therefore only visible as type II AGNs. The visibility of broad lines in 70% of the sources suggests that it is unlikely that these AGNs are being viewed through the midplane of a dusty torus. For four of the sources we constrain the Hα/Hβ Balmer decrement and estimate the extinction to the emission-line region to be large for both type I and type II AGNs, with A Hα ≳ 2.4-5 mag. Since the narrow-line region is also extincted and the UV continuum emission from the host galaxies is extremely faint, this suggests that much of the obscuration is contributed by dust on large (∼kiloparsec) scales within the host galaxies. These sources may be examples of "host-obscured" AGNs, which could have space densities comparable to or greater than that of optically luminous type I AGNs with similar bolometric luminosities. © 2007. The American Astronomical Society. All rights reserved.
• Brown, M. J., Dey, A., Jannuzi, B. T., Brand, K., Benson, A. J., Brodwin, M., Croton, D. J., & Eisenhardt, P. R. (2007). The Evolving Luminosity Function of Red Galaxies. Astrophys.J., 654, 858-877.
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  We trace the assembly history of red galaxies since z=1, by measuring theirevolving space density with the B-band luminosity function. Our sample of 39599red galaxies, selected from 6.96 square degrees of imaging from the NOAO DeepWide-Field and Spitzer IRAC Shallow surveys, is an order of magnitude larger,in size and volume, than comparable samples in the literature. We measure ahigher space density of z=0.9 red galaxies than some of the recent literature,in part because we account for the faint yet significant galaxy flux whichfalls outside of our photometric aperture. The B-band luminosity density of redgalaxies, which effectively measures the evolution of ~L* galaxies, increasesby only 36 percent from z=0 to z=1. If red galaxy stellar populations havefaded by 1.24 B-band magnitudes since z=1, the stellar mass contained withinthe red galaxy population has roughly doubled over the past 8 Gyr. This isconsistent with star-forming galaxies being transformed into ~L* red galaxiesafter a decline in their star formation rates. In contrast, the evolution of4L* red galaxies differs only slightly from a model with negligible starformation and no galaxy mergers since z=1. If this model approximates theluminosity evolution of red galaxy stellar populations, then 80 percent of thestellar mass contained within today's 4L* red galaxies was already in place atz=0.7. While red galaxy mergers have been observed, such mergers do not producerapid growth of 4L* red galaxy stellar masses between z=1 and the present day.[Journal_ref: Astrophys.J.654:858-877,2007]
• Dawson, S., Rhoads, J. E., Malhotra, S., Stern, D., Wang, J., Dey, A., Spinrad, H., & Jannuzi, B. T. (2007). A luminosity function of Lyα-emitting galaxies at z ≈ 4.5 ^1,2. Astrophysical Journal, 671(2), 1227-1240.
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  Abstract: We present a catalog of 59 z ≈ 4.5 Lyα-emitting galaxies spectroscopically confirmed in a campaign of Keck DEIMOS follow-up observations to candidates selected in the Large Area Lya (LALA) narrowband imaging survey. We targeted 97 candidates for spectroscopic follow-up; by accounting for the variety of conditions under which we performed spectroscopy, we estimate a selection reliability of ∼76%. Together with our previous sample of Keck LRIS confirmations, the 59 sources confirmed herein bring the total catalog to 73 spectroscopically confirmed z ≈ 4.5 Lyαemitting galaxies in the ≈0.7deg2 covered by the LALA imaging. As with the Keck LRIS sample, we find that a nonnegligible fraction of the confirmed Lya lines have rest-frame equivalent widths (Wγrest) that exceed the maximum predicted for normal stellar populations: 17%-31% (93% confidence) of the detected galaxies show Wγrest > 190 Å, and 12%-27% (90%) confidence) show Wγrest > 240 ÅWe construct a luminosity function of z ≈ 4.5 Lyα emission lines for comparison to Lyα luminosity functions spanning 3.1 < z < 6.6. We find no significant evidence for Lyα luminosity function evolution from z ≈ 3 to z ≈ 6. This result supports the conclusion that the intergalactic medium remains largely reionized from the local universe out to z ≈ 6.5. It is somewhat at odds with the pronounced drop in the cosmic star formation rate density recently measured between z ∼ 3 and z ∼ 6 in continuum-selected Lyman-break galaxies, and therefore potentially sheds light on the relationship between the two populations. © 2007. The American Astronomical Society. All rights reserved.
• Hickox, R. C., Jones, C., Forman, W. R., Murray, S. S., Brodwin, M., Brown, M. J., Eisenhardt, P. R., Stern, D., Kochanek, C. S., Eisenstein, D., Cool, R. J., Jannuzi, B. T., Dey, A., Brand, K., Gorjian, V., & Caldwell, N. (2007). A large population of mid-infrared selected, obscured active galaxies in the Bootes field. Astrophys.J., 1365-1387.
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  We identify a population of 640 obscured and 839 unobscured AGNs at redshifts0.7
• Hickox, R. C., Jones, C., Forman, W. R., Murray, S. S., Brodwin, M., Brown, M. J., Eisenhardt, P. R., Stern, D., Kochanek, C. S., Eisenstein, D., Cool, R. J., Jannuzi, B. T., Dey, A., Brand, K., Gorjian, V., & Caldwell, N. (2007). A large population of mid-infrared-selected, obscured active galaxies in the boötes field. Astrophysical Journal, 671(2), 1365-1387.
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  Abstract: We identify a population of 640 obscured and 839 unobscured AGNs at redshifts 0.7 < z ≲ 3 using multiwave-length observations of the 9 deg2 NOAO Deep Wide-Field Survey (NDWFS) region in Bootes. We select AGNs on the basis of Spitzer IRAC colors obtained by the IRAC Shallow Survey. Redshifts are obtained from optical spectroscopy or photometric redshift estimators. We classify the IR-selected AGNs as IRAGN 1 (unobscured) and IRAGN 2 (obscured) using a simple criterion based on the observed optical to mid-IR color, with a selection boundary of R - [4.5] = 6.1, where R and [4.5] are the Vega magnitudes in the R and IRAC 4.5 μm bands, respectively. We verify this selection using X-ray stacking analyses with data from the Chandra XBoötes survey, as well as optical photometry from NDWFS and spectroscopy from MMT/AGES. We show that (1) these sources are indeed AGNs, and (2) the optical/IR color selection separates obscured sources (with average NH ∼ 3 × 1022 cm-2 obtained from X-ray hardness ratios, and optical colors and morphologies typical of galaxies) and unobscured sources (with no X-ray absorption, and quasar colors and morphologies), with a reliability of a; 80%. The observed numbers of IRAGNs are comparable to predictions from previous X-ray, optical, and IR luminosity functions, for the given redshifts and IRAC flux limits. We observe a bimodal distribution in R - [4.5] color, suggesting that luminous IR-selected AGNs have either low or significant dust extinction, which may have implications for models of AGN obscuration. © 2007. The American Astronomical Society. All rights reserved.
• J., M., Arjun, D. E., Jannuzi, B. T., Brand, K., Benson, A. J., Brodwin, M., Croton, D. J., & Eisenharot, P. R. (2007). The evolving luminosity function of red galaxies. Astrophysical Journal, 654(2 I), 858-877.
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  Abstract: We trace the assembly history of red galaxies since z = 1 by measuring their evolving space density with the B-band luminosity function. Our sample of 39,599 red galaxies, selected from 6.96 deg2 of imaging from the NOAO Deep Wide-Field Survey and the Spitzer IRAC Shallow Survey, is an order of magnitude larger, in size and volume, than comparable samples in the literature. We measure a higher space density of z ∼ 0.9 red galaxies than some of the recent literature, in part because we account for the faint yet significant galaxy flux that falls outside of our photometric aperture. The B-band luminosity density of red galaxies, which effectively measures the evolution of ∼L* galaxies, increases by only 36% ± 13% from z = 0 to z = 1. If red galaxy stellar populations have faded by ≃ 1.24 B-band magnitudes since z = 1, the stellar mass contained within the red galaxy population has roughly doubled over the past 8 Gyr. This is consistent with star-forming galaxies being transformed into ≲L* red galaxies after a decline in their star formation rates. In contrast, the evolution of ≃4L* red galaxies differs only slightly from a model with negligible z < 1 star formation and no galaxy mergers. If this model approximates the luminosity evolution of red galaxy stellar populations, then ≃80% of the stellar mass contained within today's 4L* red galaxies was already in place at z = 0.7. While red galaxy mergers have been observed, such mergers do not produce rapid growth of 4L* red galaxy stellar masses between z = 1 and the present day. © 2007, The American Astronomical Society. All rights reserved.
• J., M., Brand, K., Dey, A., Jannuzi, B. T., Cool, R., Floc'h, E. L., Kochanek, C. S., Armus, L., Bian, C., Higdon, J., Higdon, S., Papovich, C., Rieke, G., Rieke, M., Smith, J. D., Soifer, B. T., & Weedman, D. (2007). Erratum: The 1 < z < 5 infrared luminosity function of type i quasars (Astrophysical Journal (2006) 638 (88)). Astrophysical Journal, 657(1 I), 641-.
• Poznanski, D., Maoz, D., Yasuda, N., Foley, R. J., Doi, M., Filippenko, A. V., Fukugita, M., Gal-Yam, A., Jannuzi, B. T., Morokuma, T., Oda, T., Schweiker, H., Sharon, K., Silverman, J. M., & Totani, T. (2007). Supernovae in the Subaru Deep Field: An initial sample and Type Ia rate out to redshift 1.6. Monthly Notices of the Royal Astronomical Society, 382(3), 1169-1186.
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  Abstract: Large samples of high-redshift supernovae (SNe) are potentially powerful probes of cosmic star formation, metal enrichment and SN physics. We present initial results from a new deep SN survey, based on re-imaging in the R, i′, z′ bands, of the 0.25 deg2 Subaru Deep Field (SDF), with the 8.2-m Subaru telescope and Suprime-Cam. In a single new epoch consisting of two nights of observations, we have discovered 33 candidate SNe, down to a z′-band magnitude of 26.3 (AB). We have measured the photometric redshifts of the SN host galaxies, obtained Keck spectroscopic redshifts for 17 of the host galaxies and classified the SNe using the Bayesian photometric algorithm of Poznanski et al. that relies on template matching. After correcting for biases in the classification, 55 per cent of our sample consists of Type Ia SNe and 45 per cent of core-collapse SNe. The redshift distribution of the SNe Ia reaches z ≈ 1.6, with a median of z ≈ 1.2. The core-collapse SNe reach z ≈ 1.0, with a median of z ≈ 0.5. Our SN sample is comparable to the Hubble Space Telescope/Great Observatories Origins Deep Survey (GOODS) sample in both size and redshift range. The redshift distributions of the SNe in the SDF and in GOODS are consistent, but there is a trend (which requires confirmation using a larger sample) for more high-z SNe Ia in the SDF. This trend is also apparent when comparing the SN Ia rates we derive to those based on GOODS data. Our results suggest a fairly constant rate at high redshift that could be tracking the star formation rate. Additional epochs on this field, already being obtained, will enlarge our SN sample to the hundreds, and determine whether or not there is a decline in the SN Ia rate at z ≳ 1. © 2007 The Authors. Journal compilation © 2007 RAS.
• Stern, D., Kirkpatrick, J. D., Allen, L. E., Bian, C., Blain, A., Brand, K., Brodwin, M., J., M., Cool, R., Desai, V., Dey, A., Eisenhardt, P., Gonzalez, A., Jannuzi, B. T., Menendez-Delmestre, K., Smith, H. A., Soifer, B. T., Tiede, G. P., & Wright, E. (2007). Mid-infrared selection of brown dwarfs and high-redshift quasars. Astrophysical Journal, 663(1 I), 677-685.
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  Abstract: We discuss color selection of rare objects in a wide-field multiband survey spanning from the optical to the midinfrared. Simple color criteria simultaneously identify and distinguish two of the most sought after astrophysical sources: the coolest brown dwarfs and the most distant quasars. We present spectroscopically confirmed examples of each class identified in the IRAC Shallow Survey of the Boötes field of the NOAO Deep Wide-Field Survey. IRAC J142950.8+333011 is aT4.5 brown dwarf at a distance of approximately 30-40 pc, and IRAC J142738.5+331242 is a radio-loud quasar at redshift z = 6.12. Our selection criteria identify a total of four candidates over 8 deg2 of the Boötes field. The other two candidates are both confirmed 5.5 < z < 6 quasars, previously reported by Cool et al. (2006). We discuss the implications of these discoveries and conclude that there are excellent prospects for extending such searches to cooler brown dwarfs and higher redshift quasars. © 2007. The American Astronomical Society. All rights reserved,.
• Stern, D., Kirkpatrick, J. D., Allen, L., Bian, C., Blain, A., Brand, K., Brodwin, M., Brown, M. J., Cool, R., Desai, V., Dey, A., Eisenhardt, P., Gonzalez, A., Jannuzi, B. T., Menendez-Delmestre, K., Smith, H. A., Soifer, B. T., Tiede, G. P., & Wright, E. (2007). Mid-Infrared Selection of Brown Dwarfs and High-Redshift Quasars. Astrophys.J., 663, 677-685.
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  We discuss color selection of rare objects in a wide-field, multiband surveyspanning from the optical to the mid-infrared. Simple color criteriasimultaneously identify and distinguish two of the most sought afterastrophysical sources: the coolest brown dwarfs and the most distant quasars.We present spectroscopically-confirmed examples of each class identified in theIRAC Shallow Survey of the Bootes field of the NOAO Deep Wide-Field Survey. ISSJ142950.9+333012 is a T4.5 brown dwarf at a distance of approximately 42 pc,and ISS J142738.5+331242 is a radio-loud quasar at redshift z=6.12. Ourselection criteria identify a total of four candidates over 8 square degrees ofthe Bootes field. The other two candidates are both confirmed 5.5
• White, M., Zheng, Z., Brown, M. J., Dey, A., & Jannuzi, B. T. (2007). Evidence for merging or disruption of red galaxies from the evolution of their clustering. Astrophys.J., 655.
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  The formation and evolution of massive red galaxies form a crucial test oftheories of galaxy formation based on hierarchical assembly. In this letter weuse observations of the clustering of luminous red galaxies from the Bootesfield and N-body simulations to argue that about 1/3 of the most luminoussatellite galaxies appear to undergo merging or disruption within massive halosbetween z~0.9 and z~0.5.[Journal_ref: Astrophys.J.655:L69-L72,2007]
• White, M., Zheng, Z., J., M., Arjun, D., & Jannuzi, B. T. (2007). Evidence for merging or disruption of red galaxies from the evolution of their clustering. Astrophysical Journal, 655(2 II), L69-L72.
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  Abstract: The formation and evolution of massive red galaxies form a crucial test of theories of galaxy formation based on hierarchical assembly. In this Letter we use observations of the clustering of luminous red galaxies from the Boötes field and N-body simulations to argue that about 1/3 of the most luminous satellite galaxies appear to undergo merging or disruption within massive halos between z ≃ 0.9 and 0.5. © 2007. The American Astronomical Society. All rights reserved.
• Wilman, R. J., Morris, S. L., Jannuzi, B. T., Dave, R., & Shone, A. M. (2007). The association between gas and galaxies II: The 2-point correlation function. Mon.Not.Roy.Astron.Soc., 375, 735-744.
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  We measure the 2-point correlation function, xi(AG), between galaxies andquasar absorption line systems at z1E17 cm^-2. For CIV absorbers, the peakstrength of xi(AG) is comparable to that of HI absorbers with N(HI)>1E16.5cm^-2. We do not reproduce the differences reported by Chen et al. between 1-Dxi(AG) measurements using galaxy sub-samples of different spectral types, butthe full impact of systematic differences in our samples is hard to quantify.We compare the observations with smoothed particle hydrodynamical (SPH)simulations and discover that in the observations xi(AG) is more concentratedto the smallest separations than in the simulations. The latter also display a`finger of god' elongation of xi(AG) along the LOS in redshift space, which isabsent from our data, but similar to that found by Ryan-Weber for thecross-correlation of quasar absorbers and HI-emission-selected galaxies. Thephysical origin of these `fingers of god' is unclear and we highlight severalpossible areas for further investigation.[Journal_ref: Mon.Not.Roy.Astron.Soc.375:735-744,2007]
• Wilman, R. J., Morris, S. L., Jannuzi, B. T., Davé, R., & Shone, A. M. (2007). The association between gas and galaxies - II. The two-point correlation function. Monthly Notices of the Royal Astronomical Society, 375(2), 735-744.
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  Abstract: We measure the two-point correlation function, ξAG, between galaxies and quasar absorption-line systems at z < 1, using the data set of Morris & Jannuzi on 16 lines-of-sight (LOS) with ultraviolet (UV) spectroscopy and galaxy multi-object spectroscopy (Paper I). The measurements are made in 2D redshift space out to π = 20 h-1 Mpc (comoving) along the LOS and out to σ = 2 h-1 Mpc projected; as a function of H I column density in the range NHI = 1013-10 19 cm-2, also for CIV absorption systems, and as a function of galaxy spectral type. This extends the absorber-galaxy pair analysis of Paper I. We find that the amplitude of the peak in ξAG at the smallest separations increases slowly as the lower limit on N HI is increased from 1013 to 1016 cm -2, and then jumps sharply (albeit with substantial uncertainties) for NHI > 1017 cm-2. For C IV absorbers, the peak strength of ξ AG is roughly comparable to that of Hi absorbers with NHI > 1016.5 cm-2, consistent with the finding that the C IV absorbers are associated with strong H I absorbers. We do not reproduce the differences reported by Chen et al. between 1D ξAG measurements using galaxy subsamples of different spectral types. However, the full impact on the measurements of systematic differences in our samples is hard to quantify. We compare the observations with smoothed particle hydrodynamical (SPH) simulations and discover that in the observations ξAG is more concentrated to the smallest separations than in the simulations. The latter also display a 'finger of god' elongation of ξAG along the LOS in redshift space, which is absent from our data, but similar to that found by Ryan-Weber for the cross-correlation of quasar absorbers and H I-emission-selected galaxies. The physical origin of these 'fingers of god' is unclear, and we thus highlight several possible areas for further investigation. © 2007 RAS.
• Barkhouse, W. A., Green, P. J., Vikhlinin, A., Kim, D. -., Perley, D., Cameron, R., Silverman, J., Mossman, A., Burenin, R., Jannuzi, B. T., Kim, M., Smith, M. G., Smith, R. C., Tananbaum, H., & Wilkes, B. J. (2006). ChaMP Serendipitous Galaxy Cluster Survey. Astrophys.J., 955-976.
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  We present a survey of serendipitous extended X-ray sources and opticalcluster candidates from the Chandra Multi-wavelength Project (ChaMP). Our maingoal is to make an unbiased comparison of X-ray and optical cluster detectionmethods. In 130 archival Chandra pointings covering 13 square degrees, we use awavelet decomposition technique to detect 55 extended sources, of which 6 arenearby single galaxies. Our X-ray cluster catalog reaches a typical flux limitof about ~10^-14 erg s^-1 cm^-2, with a median cluster core radius of 21arcsec. For 56 of the 130 X-ray fields, we use the ChaMP's deep NOAO/4m MOSAICg, r, and i imaging to independently detect cluster candidates using a Voronoitessellation and percolation (VTP) method. Red-sequence filtering decreases thegalaxy fore/background contamination and provides photometric redshifts toz~0.7. From the overlapping 6.1 square degree X-ray/optical imaging, we find115 optical clusters (of which 11% are in the X-ray catalog) and 28 X-rayclusters (of which 46% are in the optical VTP catalog). The median redshift ofthe 13 X-ray/optical clusters is 0.41, and their median X-ray luminosity (0.5-2keV) is L_X=(2.65\pm0.19)x10^43 ergs s^-1. The clusters in our sample that areonly detected in our optical data are poorer on average (~4sigma) than theX-ray/optically matched clusters, which may partially explain the difference inthe detection fractions.[Journal_ref: Astrophys.J. 645 (2006) 955-976]
• Barkhouse, W. A., Green, P. J., Vikhlinin, A., Kim, D. -., Perley, D., Cameron, R., Silverman, J., Mossman, A., Burenin, R., Jannuzi, B. T., Kim, M., Smith, M. G., Smith, R. C., Tananbaum, H., & Wilkes, B. J. (2006). ChaMP serendipitous galaxy cluster survey. Astrophysical Journal Letters, 645(2 I), 955-976.
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  Abstract: We present a survey of serendipitous extended X-ray sources and optical cluster candidates from the Chandra Multiwavelength Project (ChaMP). Our main goal is to make an unbiased comparison of X-ray and optical cluster detection methods. In 130 archival Chandra pointings covering 13 deg2, we use a wavelet decomposition technique to detect 55 extended sources, of which 6 are nearby single galaxies. Our X-ray cluster catalog reaches a typical flux limit of about ∼10-14 ergs cm-2 s-1, with a median cluster core radius of 21′. For 56 of the 130 X-ray fields, we use the ChaMP's deep NOAO 4 m MOSAIC g′, r′, and i′ imaging to independently detect cluster candidates using a Voronoi tessellation and percolation (VTP) method. Red-sequence filtering decreases the galaxy fore- and background contamination and provides photometric redshifts to z ∼ 0.7. From the overlapping 6.1 deg2 X-ray/optical imaging, we find 115 optical clusters (of which 11% are in the X-ray catalog) and 28 X-ray clusters (of which 46% are in the optical VTP catalog). The median redshift of the 13 X-ray/optical clusters is 0.41, and their median X-ray luminosity (0.5-2 keV) is LX = (2.65 ± 0.19) × 1043 ergs s -1. The clusters in our sample that are only detected in our optical data are poorer on average (∼4 σ) than the X-ray/optically matched clusters, which may partially explain the difference in the detection fractions. © 2006. The American Astronomical Society. All rights reserved.
• Borys, C., Blain, A. W., Dey, A., Floc'h, E. L., Jannuzi, B. T., Barnard, V., Bian, C., Brodwin, M., Menéndez-Delmestre, K., Thompson, D., Brand, K., Brown, M. J., Dowell, C. D., Eisenhardt, P., Farrah, D., Frayer, D. T., Higdon, J., Higdon, S., Phillips, T., , Soifer, B. T., et al. (2006). MIPS J142824.0+352619: A hyperluminous starburst galaxy at z = 1.325. Astrophysical Journal Letters, 636(1 I), 134-139.
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  Abstract: Using the SHARC-II camera at the Caltech Submillimeter Observatory to obtain 350 μm images of sources detected with the MIPS instrument on Spitzer, we have discovered a remarkable object at z = 1.325 ± 0.002 with an apparent far-infrared luminosity of 3.2(±0.7) × 1013 L⊙. Unlike other z > 1 sources of comparable luminosity selected from mid-IR surveys, MIPS J142824.0+352619 lacks any trace of AGN activity, and is likely a luminous analog of galaxies selected locally by IRAS, or at high redshift in the submillimeter. This source appears to be lensed by a foreground elliptical galaxy at z = 1.034, although the amplification is likely modest (≲10). We argue that the contribution to the observed optical/near-IR emission from the foreground galaxy is small, and hence are able to present the rest-frame UV through radio spectral energy distribution of this galaxy. Due to its unusually high luminosity, MIPS J142824.0+352619 presents a unique chance to study a high-redshift dusty starburst galaxy in great detail. © 2006. The American Astronomical Society. All rights reserved.
• Brand, K., Brown, M. J., Dey, A., Jannuzi, B. T., Kochanek, C. S., Kenter, A. T., Fabricant, D., Fazio, G. G., Forman, W. R., Green, P. J., Jones, C. J., McNamara, B. R., Murray, S. S., Najita, J. R., Rieke, M., Shields, J. C., & Vikhlinin, A. (2006). The Chandra XBootes Survey - III: Optical and Near-IR Counterparts. Astrophys.J., 641, 140-157.
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  The XBootes Survey is a 5-ks Chandra survey of the Bootes Field of the NOAODeep Wide-Field Survey (NDWFS). This survey is unique in that it is the largest(9.3 deg^2), contiguous region imaged in X-ray with complementary deep opticaland near-IR observations. We present a catalog of the optical counterparts tothe 3,213 X-ray point sources detected in the XBootes survey. Using a Bayesianidentification scheme, we successfully identified optical counterparts for 98%of the X-ray point sources. The optical colors suggest that the opticallydetected galaxies are a combination of z10). These objects are likely high redshiftand/or dust obscured AGN. These sources have generally harder X-ray spectrathan sources with 0.1
• Brand, K., Dey, A., Weedman, D., Desai, V., Floc'H, E., Jannuzi, B. T., Soifer, B. T., Brown, M. J., Eisenhardt, P., Gorjian, V., Papovich, C., Smith, H. A., Willner, S. P., & Cool, R. J. (2006). The active galactic nuclei contribution to the mid-infrared emission of luminous infrared galaxies. Astrophysical Journal Letters, 644(1), 143-147.
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  Abstract: We determine the contribution of AGN to the mid-IR emission of luminous infrared galaxies (LIRGs) at z > 0.6 by measuring the mid-IR dust continuum slope of 20,039 mid-IR sources. The 24 μm sources are selected from a Spitzer MIPS survey of the NOAO Deep Wide-Field Survey Boötes field and have corresponding 8 μm data from the IRAC Shallow Survey. There is a clear bimodal distribution in the 24 to 8 μm flux ratio. The X-ray-detected sources fall within the peak corresponding to a flat spectrum in vf v, implying that it is populated by AGN-dominated LIRGs, whereas the peak corresponding to a higher 24 to 8 μm flux ratio is likely due to LIRGs whose IR emission is powered by starbursts. The 24 μm emission is increasingly dominated by AGN at higher 24 μm flux densities (f 24): the AGN fraction of the z > 0.6 sources increases from 9% at f24 ≈ 0.35 mJy to 74% ±20% at f24 ≈ 3 mJy, in good agreement with model predictions. Deep 24 μm, small-area surveys, like GOODS, will be strongly dominated by starburst galaxies. AGN are responsible for ∼3%-7% of the total 24 μm background. © 2006. The American Astronomical Society. All rights reserved.
• Brand, K., Dey, A., Weedman, D., Desai, V., Floc'H, L. E., Jannuzi, B. T., Soifer, B. T., Brown, M. J., Eisenhardt, P., Gorjian, V., Papovich, C., Smith, H. A., Willner, S. P., & Cool, R. J. (2006). The AGN Contribution to the Mid-IR Emission of Luminous Infrared Galaxies. Astrophys.J., 143-147.
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  We determine the contribution of AGN to the mid-IR emission of luminousinfrared galaxies (LIRGs) at z>0.6 by measuring the mid-IR dust continuum slopeof 20,039 mid-IR sources. The 24 micron sources are selected from aSpitzer/MIPS survey of the NOAO Deep Wide-Field Survey Bo\"otes field and havecorresponding 8 micron data from the IRAC Shallow Survey. There is a clearbimodal distribution in the 24 micron to 8 micron flux ratio. The X-raydetected sources fall within the peak corresponding to a flat spectrum innufnu, implying that it is populated by AGN-dominated LIRGs, whereas the peakcorresponding to a higher 24 micron to 8 micron flux ratio is likely due toLIRGs whose infrared emission is powered by starbursts. The 24 micron emissionis increasingly dominated by AGN at higher 24 micron flux densities (f_24): theAGN fraction of the z>0.6 sources increases from ~9% at f_24 ~ 0.35 mJy to74+/-20% at f_24 ~ 3 mJy in good agreement with model predictions. Deep 24micron, small area surveys, like GOODS, will be strongly dominated by starburstgalaxies. AGN are responsible for ~ 3-7% of the total 24 micron background.[Journal_ref: Astrophys.J. 644 (2006) 143-147]
• Brand, K., J., M., Dey, A., Jannuzi, B. T., Kochanek, C. S., Kenter, A. T., Fabricant, D., Fazio, G. G., Forman, W. R., Green, P. J., Jones, C. J., McNamara, B. R., Murray, S. S., Najita, J. R., Rieke, M., Shields, J. C., & Vikhlinin, A. (2006). The Chandra XBoötes survey. III. Optical and near-infrared counterparts. Astrophysical Journal Letters, 641(1 I), 140-157.
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  Abstract: The XBoötes Survey is a 5 ks Chandra survey of the Boötes Field of the NOAO Deep Wide-Field Survey (NDWFS). This survey is unique in that it is the largest (9.3 deg2) contiguous region imaged in X-ray with complementary deep optical and near-infrared (near-IR) observations. We present a catalog of the optical counterparts to the 3213 X-ray point sources detected in the XBoötes survey. Using a Bayesian identification scheme, we successfully identified optical counterparts for 98% of the X-ray point sources. The optical colors suggest that the optically detected galaxies are a combination of z < 1 massive early-type galaxies and bluer star-forming galaxies whose optical AGN emission is faint or obscured, whereas the majority of the optically detected point sources are likely quasars over a large redshift range. Our large-area, X-ray-bright, optically deep survey enables us to select a large sub-sample of sources (773) with high X-ray-to-optical flux ratios (fx/fo > 10). These objects are likely high-redshift and/or dust-obscured AGNs. These sources have generally harder X-ray spectra than sources with 0.1 < fx/fo < 10. Of the 73 X-ray sources with no optical counterpart in the NDWFS catalog, 47 are truly optically blank down to R ∼ 25.5 (the average 50% completeness limit of the NDWFS R-band catalogs). These sources are also likely to be high-redshift and/or dust-obscured AGNs. © 2006. The American Astronomical Society. All rights reserved.
• Brodwin, M., Brown, M. J., Ashby, M. L., Bian, C., Brand, K., Dey, A., Eisenhardt, P. R., Eisenstein, D. J., Gonzalez, A. H., Huang, J. -., Jannuzi, B. T., Kochanek, C. S., McKenzie, E., Murray, S. S., Pahre, M. A., Smith, H. A., Soifer, B. T., Stanford, S. A., Stern, D., & Elston, R. J. (2006). Photometric redshifts in the IRAC shallow survey. Astrophysical Journal Letters, 651(2 I), 791-803.
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  Abstract: Accurate photometric redshifts are calculated for nearly 200,000 galaxies to a 4.5 μm flux limit of ∼13 μJy in the 8.5 deg2 Spitzer IRAC Shallow Survey. Using a hybrid photometric redshift algorithm incorporating both neural net and template-fitting techniques, calibrated with over 15,000 spectroscopic redshifts, a redshift accuracy of σ = 0.06(1 + z) is achieved for 95% of galaxies at 0 < z < 1.5. The accuracy is σ = 0.12(1 + z) for 95% of active galactic nuclei (AGNs) at 0 < z < 3. Redshift probability functions, central to several ongoing studies of the galaxy population, are computed for the full sample. We demonstrate that these functions accurately represent the true redshift probability density, allowing the calculation of valid confidence intervals for all objects. These probability functions have already been used to successfully identify a population of Spitzer-selected high-redshift (z > 1) galaxy clusters. We present one such spectroscopically confirmed cluster at 〈z〉 = 1.24, ISCS J1434.5+3427. Finally, we present a measurement of the 4.5 μm-selected galaxy redshift distribution. © 2006. The American Astronomical Society. All rights reserved.
• Brodwin, M., Brown, M. J., Ashby, M. L., Bian, C., Brand, K., Dey, A., Eisenhardt, P. R., Eisenstein, D. J., Gonzalez, A. H., Huang, J. -., Jannuzi, B. T., Kochanek, C. S., McKenzie, E., Pahre, M. A., Smith, H. A., Soifer, B. T., Stanford, S. A., Stern, D., & Elston, R. J. (2006). Photometric Redshifts in the IRAC Shallow Survey. Astrophys.J., 651, 791-803.
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  Accurate photometric redshifts are calculated for nearly 200,000 galaxies toa 4.5 micron flux limit of ~13 uJy in the 8.5 deg^2 Spitzer/IRAC Shallowsurvey. Using a hybrid photometric redshift algorithm incorporating bothneural-net and template-fitting techniques, calibrated with over 15,000spectroscopic redshifts, a redshift accuracy of \sigma = 0.06(1+z) is achievedfor 95% of galaxies at 0
• Brown, M. J., Brand, K., Dey, A., Jannuzi, B. T., Cool, R., Floc'H, E. L., Kochanek, C. S., Armus, L., Bian, C., Higdon, J., Higdon, S., Papovich, C., Rieke, G., Rieke, M., Smith, J. D., Soifer, B. T., & Weedman, D. (2006). The 1Astrophys.J., 638:88-99,2006; Erratum-ibid.657, 88-99.
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  We determine the rest-frame 8 micron luminosity function of type I quasarsover the redshift range 1
• Cool, R. J., Kochanek, C. S., Eisenstein, D. J., Stern, D., Brand, K., Brown, M. J., Arjun, D. E., Eisenhardt, P. R., Xiaohui, F. A., Gonzalez, A. H., Green, R. F., Jannuzi, B. T., Mckenzie, E. H., Rieke, G. H., Rieke, M., Soifer, B. T., Spinrad, H., & Elston, R. J. (2006). The discovery of three new z > 5 quasars in the AGN and Galaxy Evolution Survey. Astronomical Journal, 132(2), 823-830.
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  Abstract: We present the discovery of three z > 5 quasars in the AGN and Galaxy Evolution Survey spectroscopic observations of the NOAO Deep Wide-Field Survey (NDWFS) Bootes Field. These quasars were selected as part of a larger Spitzer mid-infrared quasar sample, with no selection based on optical colors. The highest redshift object, NDWFS J142516.3+325409, at z = 5.85, is the lowest luminosity z > 5.8 quasar currently known. We compare mid-infrared techniques for identifying z > 5 quasars to more traditional optical techniques and show that mid-infrared colors allow for the selection of high-redshift quasars even at redshifts at which quasars lie near the optical stellar locus and at z > 7, where optical selection is impossible. Using the superb multiwavelength coverage available in the NDWFS Bootes field, we construct the spectral energy distributions (SEDs) of high-redshift quasars from observed B w band to 24 μm (rest-frame 600 Å-3.7μm). We show that the three high-redshift quasars have quite similar SEDs, and the rest-frame composite SED of low-redshift quasars from the literature shows little evolution compared to our high-redshift objects. We compare the number of z > 5 quasars we have discovered to the expected number from published quasar luminosity functions. While analyses of the quasar luminosity function are tenuous based on only three objects, we find that a relatively steep luminosity function with ψ ∝ L -3.2 provides the best agreement with the number of high-redshift quasars discovered in our survey. © 2006. The American Astronomical Society. All rights reserved.
• Cool, R. J., Kochanek, C. S., Eisenstein, D. J., Stern, D., Brand, K., Brown, M. J., Dey, A., Eisenhardt, P. R., Fan, X., Gonzalez, A. H., Green, R. F., Jannuzi, B. T., McKenzie, E. H., Rieke, G. H., Rieke, M., Soifer, B. T., Spinrad, H., & Elston, R. J. (2006). The Discovery of Three New z>5 Quasars in the AGN and Galaxy Evolution Survey. Astron.J., 132, 823-830.
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  We present the discovery of three z>5 quasars in the AGN and Galaxy EvolutionSurvey (AGES) spectroscopic observations of the NOAO Deep Wide-Field Survey(NDWFS) Bootes Field. These quasars were selected as part of a larger Spitzermid-infrared quasar sample with no selection based on optical colors. Thehighest redshift object, NDWFS J142516.3+325409, z=5.85, is thelowest-luminosity z>5.8 quasar currently known. We compare mid-infraredtechniques for identifying z>5 quasars to more traditional optical techniquesand show that mid-infrared colors allow for selection of high-redshift quasarseven at redshifts where quasars lie near the optical stellar locus and at z>7where optical selection is impossible. Using the superb multi-wavelengthcoverage available in the NDWFS Bootes field, we construct the spectral energydistributions (SEDs) of high-redshift quasars from observed Bw-band to 24microns (rest-frame 600 Angstroms - 3.7 microns). We show that the threehigh-redshift quasars have quite similar SEDs, and the rest-frame composite SEDof low-redshift quasars from the literature shows little evolution compared toour high-redshift objects. We compare the number of z>5 quasars we havediscovered to the expected number from published quasar luminosity functions.While analyses of the quasar luminosity function are tenuous based on onlythree objects, we find that a relatively steep luminosity function with PsiL^(-3.2) provides the best agreement with the number of high-redshift quasarsdiscovered in our survey.[Journal_ref: Astron.J.132:823-830,2006]
• Desai, V., Armus, L., Soifer, B. T., Weedman, D. W., Higdon, S., Bian, C., Borys, C., Spoon, H. W., Charmandaris, V., Brand, K., Brown, M. J., Dey, A., Higdon, J., Houck, J., Jannuzi, B. T., Floc'H, L. E., Ashby, M. L., & Smith, H. A. (2006). IRS spectra of two ultraluminous infrared galaxies at z=1.3. Astrophys.J., 641, 133-139.
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  We present low-resolution (64 < R < 124) mid-infrared (8--38 micron)Spitzer/IRS spectra of two z~1.3 ultraluminous infrared galaxies (LFIR~10^13)discovered in a Spitzer/MIPS survey of the Bootes field of the NOAO DeepWide-Field Survey (NDWFS). MIPS J142824.0+352619 is a bright 160 micron sourcewith a large infrared-to-optical flux density ratio and a possible lensingamplification of 20) galaxies in the NDWFS. Its mid-infrared spectrum lacksemission features, but the broad 9.7 micron silicate absorption band placesthis source at z~1.3. Given this redshift, SST24 J142827.19+354127.71 has amongthe largest rest-frame 5 micron luminosities known. The similarity of its SEDto those of known AGN-dominated ULIRGs and its lack of either PAH features orlarge amounts of cool dust indicate that the powerful mid-infrared emission isdominated by an active nucleus rather than a starburst. Our results illustratethe power of the IRS in identifying massive galaxies in the ``redshift desert''and in discerning their power sources. Because they are bright, MIPSJ142824.0+352619 (pending future observations to constrain its lensingamplification) and SST24 J142827.19+354127.71 are useful z>1 templates of ahigh luminosity starburst and AGN, respectively.[Journal_ref: Astrophys.J.641:133-139,2006]
• Desai, V., Armus, L., Soifer, B. T., Weedman, D. W., Higdon, S., Bian, C., Borys, C., Spoon, H. W., Charmandaris, V., Brand, K., Brown, M. J., Dey, A., Higdon, J., Houck, J., Jannuzi, B. T., Floc'h, E. L., Ashby, M. L., & Smith, H. A. (2006). IRS spectra of two ultraluminous infrared galaxies at z = 1.3. Astrophysical Journal Letters, 641(1 I), 133-139.
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  Abstract: We present low-resolution (64 < R < 124) mid-infrared (8-38 μm) spectra of two z ≈ 1.3 ultraluminous infrared galaxies (ULIRGs) with L 8-1000 μm ≈ 1013 L⊙. The spectra were taken with the Infrared Spectrograph (IRS) on board the Spitzer Space Telescope. Both objects were discovered in the NOAO Deep Wide-Field Survey (NDWFS) Bootes field. MIPS J142824.0+352619 is a bright 160 μm source with a large infrared-to-optical flux density ratio. Previous authors provided evidence for a foreground lens and estimated an amplification of ≲10, although this factor is currently poorly constrained. The 6.2, 7.7, 11.3, and 12.8 μm polycyclic aromatic hydrocarbon (PAH) emission bands in its IRS spectrum indicate a redshift of z ≈ 1.3. The large equivalent width of the 6.2 μm PAH feature indicates that at least 50% of the mid-infrared energy is generated in a starburst, an interpretation supported by a large [Ne II]/[Ne III] ratio and a low upper limit on the X-ray luminosity. SST24 J142827.19+354127.71 has the brightest 24 μm flux (10.55 mJy) among optically faint (R > 20) galaxies in the NDWFS. Its mid-infrared spectrum lacks emission features, but the broad 9.7 μm silicate absorption band places this source at z ≈ 1.3. Optical spectroscopy confirms a redshift of z = 1.293 ± 0.001. Given this redshift, SST24 J142827.19+354127.71 has among the largest rest-frame 5 μm luminosities known. The similarity of its SED to those of known AGN-dominated ULIRGs and its lack of either PAH features or large amounts of cool dust indicate that the mid-infrared emission is dominated by an AGN rather than a starburst. © 2006. The American Astronomical Society. All rights reserved.
• Elston, R. J., Gonzalez, A. H., McKenzie, E., Brodwin, M., Brown, M. J., Cardona, G., Dey, A., Dickinson, M., Eisenhardt, P. R., Jannuzi, B. T., Lin, Y., Mohr, J. J., Raines, N. S., Stanford, S. A., & Stern, D. (2006). The FLAMINGOS Extragalactic Survey. Astrophys.J., 639, 816-826.
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  Using the Florida Multi-object Imaging Near-IR grism ObservationalSpectrometer (FLAMINGOS), we have conducted the FLAMINGOS Extragalactic Survey(FLAMEX), a deep imaging survey covering 7.1 square degrees within the 18.6 sq.deg NOAO Deep Wide-Field Survey (NDWFS) regions. FLAMEX is the first deep,wide-area near-infrared survey to image in both the J and Ks filters, and islarger than any previous NIR surveys of comparable depth. The intent of FLAMEXis to facilitate the study of galaxy and galaxy cluster evolution at 1
• Elston, R. J., Gonzalez, A. H., Mckenzie, E., Brown, M., J., M., Cardona, G., Dey, A., Dickinson, M., Eisenhardt, P. R., Jannuzi, B. T., Lin, Y., Mohr, J. J., Raines, S. N., Stanford, S. A., & Stern, D. (2006). The flamingos extragalactic survey. Astrophysical Journal Letters, 639(2 I), 816-826.
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  Abstract: Using the Florida Multi-object Imaging Near-IR Grism Observational Spectrometer (FLAMINGOS), we have conducted the FLAMINGOS Extragalactic Survey (FLAMEX), a deep imaging survey covering 7.1 deg2 within the 18.6 deg2 NOAO Deep Wide-Field Survey (NDWFS) regions. FLAMEX is the first deep, wide-area, nearinfrared survey to image in both the J and Ks filters, and is larger than any previous NIR survey of comparable depth. The intent of FLAMEX is to facilitate the study of galaxy and galaxy cluster evolution at 1 < z < 2 by providing rest-frame optical photometry for the massive galaxy population at this epoch. This effort is designed to yield a public data set that complements and augments the suite of existing surveys in the NDWFS fields. We present an overview of FLAMEX and initial results based on ∼ 150,000 Ks-selected sources in the Bootes field. We describe the observations and reductions, quantify the data quality, and verify that the number counts are consistent with results from previous surveys. Finally, we comment on the utility of this sample for detailed study of the ERO population, and present one of the first spectroscopically confirmed z > 1 galaxy clusters detected using the joint FLAMEX, NDWFS, and Spitzer IRAC Shallow Survey data sets. © 2006. The American Astronomical Society. All rights reserved.
• J., M., Brand, K., Dey, A., Jannuzi, B. T., Cool, R., Floc'h, E. L., Kochanek, C. S., Armus, L., Bian, C., Higdon, J., Higdon, S., Papovich, C., Rieke, G., Rieke, M., Smith, J. D., Soifer, B. T., & Weedman, D. (2006). The 1 < z < 5 infrared luminosity function of type I quasars. Astrophysical Journal Letters, 638(1 I), 88-99.
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  Abstract: We determine the rest-frame 8 μm luminosity function of type I quasars over the redshift range 1 < z < 5. Our sample consists of 292 24 μm sources brighter than 1 mJy selected from 7.17 deg2 of the Spitzer Space Telescope MIPS survey of the NOAO Deep Wide-Field Survey Bootes field. The AGN and Galaxy Evolution Survey (AGES) has measured redshifts for 270 of the R < 21.7 sources, and we estimate that the contamination of the remaining 22 sources by stars and galaxies is low. We are able to select quasars missed by ultraviolet excess quasar surveys, including reddened type I quasars and 2.2 < z < 3.0 quasars with optical colors similar to main-sequence stars. We find that reddened type I quasars comprise ∼20% of the type I quasar population. Nonetheless, the shape, normalization, and evolution of the rest-frame 8 μm luminosity function are comparable to those of quasars selected from optical surveys. The 8 μm luminosity function of type I quasars is well approximated by a power law with index -2.75 ± 0.14. We directly measure the peak of the quasar space density to be at z = 2.6 ± 0.3. © 2006. The American Astronomical Society. All rights reserved.
• Kollmeier, J. A., Onken, C. A., Kochanek, C. S., Gould, A., Weinberg, D. H., Dietrich, M., Cool, R., Dey, A., Eisenstein, D. J., Jannuzi, B. T., Floc'H, E. L., & Stern, D. (2006). Black Hole Masses and Eddington Ratios at 0.3Astrophys.J., 648, 128-139.
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  We study the distribution of Eddington luminosity ratios, L_bol/L_edd, ofactive galactic nuclei (AGNs) discovered in the AGN and Galaxy Evolution Survey(AGES). We combine H-beta, MgII, and CIV line widths with continuumluminosities to estimate black hole (BH) masses in 407 AGNs, covering theredshift range z~0.3-4 and the bolometric luminosity range L_bol~10^45-10^47erg/s. The sample consists of X-ray or mid-infrared (24 micron) point sourceswith optical magnitude R
• Kollmeier, J. A., Unken, C. A., Kochanek, C. S., Gould, A., Weinberg, D. H., Dietrich, M., Cool, R., Arjun, D. E., Eisenstein, D. J., Jannuzi, B. T., Floc'H, E. L., & Stern, D. (2006). Black hole masses and eddington ratios at 0.3 < z < 4. Astrophysical Journal Letters, 648(1 I), 128-139.
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  Abstract: We study the distribution of Eddington luminosity ratios, L boj/LEdd, of active galactic nuclei (AGNs) discovered in the AGN and Galaxy Evolution Survey (AGES). We combine Hβ, Mg II, and C IV line widths with continuum luminosities to estimate black hole (BH) masses in 407 AGNs, covering the redshift range z ∼ 0.3-4 and the bolometric luminosity range Lbol ∼ 1045-1047 ergs s-1. The sample consists of X-ray or mid-infrared (24 μm) point sources with optical magnitude R ≤ 21.5 mag and optical emission-line spectra characteristic of AGNs. For the range of luminosity and redshift probed by AGES, the distribution of estimated Eddington ratios is well described as log-normal, with a peak at Z-bol/LEdd ≃ 1/4 and a dispersion of 0.3 dex. Since additional sources of scatter are minimal, this dispersion must account for contributions from the scatter between estimated and true BH mass and the scatter between estimated and true bolometric luminosity. Therefore, we conclude that (1) neither of these sources of error can contribute more than ∼0.3 dex rms, and (2) the true Eddington ratios of optically luminous AGNs are even more sharply peaked. Because the mass estimation errors must be smaller than ∼0.3 dex, we can also investigate the distribution of Eddington ratios at fixed BH mass. We show for the first time that the distribution of Eddington ratios at fixed BH mass is peaked, and that the dearth of AGNs at a factor of ∼ 10 below Eddington is real and not an artifact of sample selection. These results provide strong evidence that supermassive BHs gain most of their mass while radiating close to the Eddington limit, and they suggest that the fueling rates in luminous AGNs are ultimately determined by BH self-regulation of the accretion flow rather than galactic-scale dynamical disturbances. © 2006. The American Astronomical Society. All rights reserved.
• Morris, S. L., & Jannuzi, B. T. (2006). The association between gas and galaxies -I. CFHT spectroscopy and pair analysis. Monthly Notices of the Royal Astronomical Society, 367(3), 1261-1281.
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  Abstract: We investigate the relative distribution of the gaseous contents of the Universe (as traced by a sample of Lyα absorbers), and the luminous baryonic matter (as traced by a redshift survey of galaxies in the same volume searched for Lyα absorbers), along 16 lines of sight (LOS) between redshifts 0 and 1. Our galaxy redshift survey was made with the multi-object spectrograph on the Canada-France-Hawaii Telescope and, when combined with galaxies from the literature in the same LOS, gives us a galaxy sample of 636 objects. By combining this with an absorption-line sample of 406 absorbing systems drawn from published works, we are able to study the relationship between gas and galaxies over the latter half of the age of the Universe. A correlation between absorbers and galaxies is detected out to separation of 1.5 Mpc. This correlation is weaker than the galaxy-galaxy correlation. There is also some evidence that the absorbing systems seen in C IV are more closely related to galaxies, although this correlation could be with column density rather than metallicity. The above results are all consistent with the absorbing gas and the galaxies coexisting in dark matter filaments and knots as predicted by current models where the column density of the absorbing gas is correlated with the underlying matter density. © 2006 RAS.
• Morris, S. L., & Jannuzi, B. T. (2006). The association between gas and galaxies I: CFHT spectroscopy and pair analysis. Mon.Not.Roy.Astron.Soc., 1261-1281.
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  We investigate the relative distribution of the gaseous contents of theUniverse (as traced by a sample of Lyman alpha (lya) absorbers), and theluminous baryonic matter (as traced by a redshift survey of galaxies in thesame volume searched for lya absorbers), along 16 lines-of-sight (LOS) betweenredshifts 0 and 1. Our galaxy redshift survey was made with the Multi-ObjectSpectrograph (MOS) on Canada-France-Hawaii Telescope (CFHT) and, when combinedwith galaxies from the literature in the same LOS, gives us a galaxy sample of636 objects. By combining this with an absorption line sample of 406 absorbingsystems drawn from published works, we are able to study the relationshipbetween gas and galaxies over the latter half of the age of the Universe. Acorrelation between absorbers and galaxies is detected out to separation of 1.5Mpc. This correlation is weaker than the galaxy-galaxy correlation. There isalso some evidence that the absorbing systems seen in CIV are more closelyrelated to galaxies, although this correlation could be with column densityrather than metallicity. The above results are all consistent with theabsorbing gas and the galaxies co-existing in dark matter filaments and knotsas predicted by current models, where the column density of the absorbing gasis correlated with the underlying matter density.[Journal_ref: Mon.Not.Roy.Astron.Soc. 367 (2006) 1261-1281]
• Weedman, D. W., Soifer, B. T., Hao, L., Higdon, J. L., Higdon, S. J., Houck, J. R., Floc'h, E. L., Brown, M. J., Dey, A., Jannuzi, B. T., Rieke, M., Desai, V., Bian, C., Thompson, D., Armus, L., Teplitz, H., Eisenhardt, P., & Willner, S. P. (2006). Spitzer IRS spectra of optically faint infrared sources with weak spectral features. Astrophysical Journal Letters, 651(1 I), 101-112.
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  Abstract: Spectra have been obtained with the low-resolution modules of the Infrared Spectrograph (IRS) on the Spitzer Space Telescope (Spitzer) for 58 sources having fν(24 μm) > 0.75 mJy. Sources were chosen from a survey of 8.2 deg2 within the NOAO Deep Wide-Field Survey region in Boötes (NDWFS) using the Multiband Imaging Photometer (MIPS) on Spitzer. Most sources are optically very faint (I > 24 mag). Redshifts have previously been determined for 34 sources, based primarily on the presence of a deep 9.7 μm silicate absorption feature, with a median z of 2.2. Spectra are presented for the remaining 24 sources for which we were previously unable to determine a confident redshift because the IRS spectra show no strong features. Optical photometry from the NDWFS and infrared photometry with MIPS and the Infrared Array Camera on Spitzer (IRAC) are given, with K photometry from the Keck I telescope for some objects. The sources without strong spectral features have overall spectral energy distributions (SEDs) and distributions among optical and infrared fluxes that are similar to those for the sources with strong absorption features. Nine of the 24 sources are found to have feasible redshift determinations based on fits of a weak silicate absorption feature. Results confirm that the "1 mJy" population of 24 μm Spitzer sources that are optically faint is dominated by dusty sources with spectroscopic indicators of an obscured AGN rather than a starburst. There remain 14 of the 58 sources observed in Boötes for which no redshift could be estimated, and 5 of these sources are invisible at all optical wavelengths. © 2006. The American Astronomical Society. All rights reserved.
• Weedman, D. W., Soifer, B. T., Hao, L., Higdon, J. L., Higdon, S. J., Houck, J. R., LeFloc'h, E., Brown, M. J., Dey, A., Jannuzi, B. T., Rieke, M., Desai, V., Bian, C., Thompson, D., Armus, L., Teplitz, H., Eisenhardt, P., & Willner, S. P. (2006). Spitzer IRS Spectra of Optically Faint Infrared Sources with Weak Spectral Features. Astrophys.J., 651, 101-112.
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  Spectra have been obtained with the low-resolution modules of the InfraredSpectrograph (IRS) on the Spitzer Space Telescope (Spitzer) for 58 sourceshaving f$_{\nu}$(24 micron) > 0.75 mJy. Sources were chosen from a survey of8.2 deg$^{2}$ within the NOAO Deep Wide-Field Survey region in Bootes (NDWFS)using the Multiband Imaging Photometer (MIPS) on the Spitzer Space Telescope.Most sources are optically very faint (I > 24mag). Redshifts have previouslybeen determined for 34 sources, based primarily on the presence of a deep 9.7micron silicate absorption feature, with a median z of 2.2. Spectra arepresented for the remaining 24 sources for which we were previously unable todetermine a confident redshift because the IRS spectra show no strong features.Optical photometry from the NDWFS and infrared photometry with MIPS and theInfrared Array Camera on the Spitzer Space Telescope (IRAC) are given, with Kphotometry from the Keck I telescope for some objects. The sources withoutstrong spectral features have overall spectral energy distributions (SEDs) anddistributions among optical and infrared fluxes which are similar to those forthe sources with strong absorption features. Nine of the 24 sources are foundto have feasible redshift determinations based on fits of a weak silicateabsorption feature. Results confirm that the "1 mJy" population of 24 micronSpitzer sources which are optically faint is dominated by dusty sources withspectroscopic indicators of an obscured AGN rather than a starburst. Thereremain 14 of the 58 sources observed in Bootes for which no redshift could beestimated, and 5 of these sources are invisible at all optical wavelengths.[Journal_ref: Astrophys.J.651:101-112,2006]
• Appleton, P. N., Fadda, D. T., Marleau, F. R., Frayer, D. T., Helou, G., Condon, J. J., Choi, P. I., Yan, L., Lacy, M., Wilson, G., Armus, L., Chapman, S. C., Fang, F., Heinrichson, I., Im, M., Jannuzi, B. T., Storrie-Lombardi, L., Shupe, D., Soifer, B. T., , Squires, G., et al. (2005). Erratum: The far- and mid-infrared/radio correlations in the Spitzer extragalactic first look survey (Astrophysical Journal Supplement Series (2004) 154 (147)). Astrophysical Journal, Supplement Series, 156(1), 111-.
• Borys, C., Barnard, V., Bian, C., Blain, A. W., Brown, M. J., Dey, A., Dowell, C. D., Frayer, D. T., Higdon, J., Higdon, S., Jannuzi, B., Fl'och, E. L., Soifer, B. T., & Phillips, T. G. (2005). Discovery of hyperluminous infrared galaxies using spitzer and sharc-II. European Space Agency, (Special Publication) ESA SP, 275-276.
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  Abstract: We have used observations taken as part of the Bootes Spitzer GTO program to pre-select high redshift luminous star-forming galaxy candidates. Subsequent ground-based sub-millimeter imaging using SHARC-II at the Caltech Submillimeter Observatory detected several objects, including one particularly exotic one: An extremely bright infrared galaxy with an apparent luminosity in excess of 10 13.5L ⊙. It has a spectral energy distribution similar to that of Arp 220, though appears to be at a much higher redshift. Although lensing is one possible explanation, this object has helped refine the selection method, and hints at a way to pre-select similar objects using Mid-IR silicate absorption features. galaxy evolution; galaxy formation; starburst galaxies.
• Borys, C., Blain, A. W., Dey, A., Floc'H, L. E., Jannuzi, B. T., Barnard, V., Bian, C., Brodwin, M., Men'Endez-Delmestre, K., Thompson, D., Brand, K., Brown, M. J., Dowell, C. D., Eisenhardt, P., Farrah, D., Frayer, D. T., Higdon, J., Higdon, S., Phillips, T., , Soifer, B. T., et al. (2005). MIPS J142824.0+352619: A Hyperluminous Starburst Galaxy at z=1.325. Astrophys.J., 636, 134-139.
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  Using the SHARC-II camera at the Caltech Submillimeter Observatory to obtain350 micron images of sources detected with the MIPS instrument on Spitzer, wehave discovered a remarkable object at z=1.325+/-0.002 with an apparentFar-Infrared luminosity of 3.2(+/-0.7) x 10^13 Lsun. Unlike other z>1 sourcesof comparable luminosity selected from mid-IR surveys, MIPS J142824.0+352619lacks any trace of AGN activity, and is likely a luminous analog of galaxiesselected locally by IRAS, or at high redshift in the submillimeter. This sourceappears to be lensed by a foreground elliptical galaxy at z=1.034, although theamplification is likely modest (~10). We argue that the contribution to theobserved optical/Near-IR emission from the foreground galaxy is small, andhence are able to present the rest-frame UV through radio Spectral EnergyDistribution of this galaxy. Due to its unusually high luminosity, MIPSJ142824.0+352619 presents a unique chance to study a high redshift dustystarburst galaxy in great detail.[Journal_ref: Astrophys.J.636:134-139,2005]
• Brand, K., Dey, A., Brown, M. J., Watson, C. R., Jannuzi, B. T., Najita, J. R., Kochanek, C. S., Shields, J. C., Fazio, G. G., Forman, W. R., Green, P. J., Jones, C. J., Kenter, A. T., McNamara, B. R., Murray, S. S., Rieke, M., & Vikhlinin, A. (2005). Tracing the Nuclear Accretion History of the Red Galaxy Population. Astrophys.J., 723-732.
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  We investigate the evolution of the hard X-ray luminosity of the red galaxypopulation using a large sample of 3316 red galaxies selected over a wide rangein redshift (0.3
• Brand, K., Dey, A., J., M., Watson, C. R., Jannuzi, B. T., Najita, J. R., Kochanek, C. S., Shields, J. C., Fazio, G. G., Forman, W. R., Green, P. J., Jones, C. J., Kenter, A. T., McNamara, B. R., Murray, S. S., Rieke, M., & Vikhlinin, A. (2005). Tracing the nuclear accretion history of the red galaxy population. Astrophysical Journal Letters, 626(2 I), 723-732.
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  Abstract: We investigate the evolution of the hard X-ray luminosity of the red galaxy population using a large sample of 3316 red galaxies selected over a wide range in redshift (0.3 < z < 0.9) from a 1.4 deg2 region in the Boǒ̈tes field of the NOAO Deep Wide-Field Survey (NDWFS). The red galaxies are early-type, bulge-dominated galaxies and are selected to have the same evolution-corrected, absolute A-band magnitude distribution as a function of redshift to ensure that we are tracing the evolution in the X-ray properties of a comparable optical population. Using a stacking analysis of 5 ks Chandra/ACIS observations within this field to study the X-ray emission from these red galaxies in three redshift bins, we find that the mean X-ray luminosity increases as a function of redshift. The large mean X-ray luminosity and the hardness of the mean X-ray spectrum suggest that the X-ray emission is largely dominated by active galactic nuclei (AGNs) rather than stellar sources. The hardness ratio can be reproduced by either an absorbed (NH ≈ 2 × 1022 cm-2) Γ = 1.7 power-law source, consistent with that of a population of moderately obscured Seyfert-like AGNs, or an unabsorbed Γ = 0.7 source, suggesting a radiatively inefficient accretion flow (e.g., an advection-dominated accretion flow). We also find that the emission from this sample of red galaxies constitutes at least 5% of the hard X-ray background. These results suggest a global decline in the mean AGN activity of normal early-type galaxies from z ∼ 1 to the present, which indicates that we are witnessing the tailing off of the accretion activity onto supermassive black holes in early-type galaxies since the quasar epoch. © 2005. The American Astronomical Society. All rights reserved.
• Brown, M. J., Jannuzi, B. T., Dey, A., & Tiede, G. P. (2005). The Clustering of Extragalactic Extremely Red Objects. Astrophys.J..
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  We have measured the angular and spatial clustering of 671 K5Extremely Red Objects (EROs) from a 0.98 square degree sub-region of the NOAODeep Wide-Field Survey (NDWFS). Our study covers nearly 5 times the area andhas twice the sample size of any previous ERO clustering study. The wide fieldof view and BwRIK passbands of the NDWFS allow us to place improved constraintson the clustering of z=1 EROs. We find the angular clustering of EROs isslightly weaker than in previous measurements, and w(1')=0.25+/-0.05 forK
• Dey, A., Bian, C., Soifer, B. T., Brand, K., Brown, M. J., Chaffee, F. H., LeFloc'h, E., Hill, G., Houck, J. R., Jannuzi, B. T., Rieke, M., Weedman, D., Brodwin, M., & Eisenhardt, P. (2005). Discovery of a Large ~200 kpc Gaseous Nebula at z=2.7 with the Spitzer Space Telescope. Astrophys.J., 654-666.
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  We report the discovery of a very large, spatially extended Ly alpha-emitting nebula at z=2.656 associated with a luminous mid-infrared source. Thebright mid-infrared source (F(24um)=0.86 mJy) was first detected inobservations made using the Spitzer Space Telescope. Existing broad-bandimaging data from the NOAO Deep Wide-Field Survey revealed the mid-infraredsource to be associated with a diffuse, spatially extended, optical counterpartin the Bw band. Spectroscopy and further imaging of this target reveals thatthe optical source is an almost purely line-emitting nebula with little, ifany, detectable diffuse continuum emission. The Lya nebula has a luminosity ofL[Lya] ~ 1.7e44 erg/s and an extent of at least 20 arcsec (160 kpc). Itscentral ~8 arcsec shows an ordered, monotonic velocity profile; interpreted asrotation, this region encloses a mass M = 6e12 Msun. Several sources lie withinthe nebula. The central region of the nebula shows narrow (~365 km/s) emissionlines of CIV and HeII. The mid-infrared source is a compact object lying withinthe nebula, but offset from the center by a projected distance of ~2.5 arcsec(20 kpc), and likely to be an enshrouded AGN. A young star-forming galaxy liesnear the northern end of the nebula. We suggest that the nebula is a site ofrecent multiple galaxy and AGN formation, with the spatial distribution ofgalaxies within the nebula perhaps tracking the formation history of thesystem.[Journal_ref: Astrophys.J. 629 (2005) 654-666]
• Dey, A., Bian, C., Soifer, B. T., Brand, K., J., M., Chaffee, F. H., Floc'h, E. L., Hill, G., Houck, J. R., Jannuzi, B. T., Rieke, M., Weedman, D., Brodwin, M., & Eisenhardt, P. (2005). Discovery of a large ∼200 kpc gaseous nebula at z ≈ 2.7 with the Spitzer Space Telescope. Astrophysical Journal Letters, 629(2 I), 654-666.
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  Abstract: We report the discovery of a very large, spatially extended Lyα-emitting nebula at z = 2.656 associated with a luminous mid-infrared source. The bright mid-infrared source (F24μm = 0.86 mJy) was first detected in observations made using the Spitzer Space Telescope. Existing broadband imaging data from the NOAO Deep Wide-Field Survey revealed the mid-infrared source to be associated with a diffuse, spatially extended, optical counterpart in the BW band. Spectroscopy and further imaging of this target reveals that the optical source is an almost purely line-emitting nebula with little, if any, detectable diffuse continuum emission. The Lyα nebula has a luminosity of LLyα ≈ 1.7 × 1044 ergs s-1 and an extent of at least 20″ (160 kpc). Its central ≈8″ shows an ordered, monotonic velocity profile; interpreted as rotation, this region encloses a mass M ≈ 6 × 1012 M⊙. Several sources lie within the nebula. The central region of the nebula shows narrow (≈365 km s-1) emission lines of C IV and He II. The midinfrared source is a compact object lying within the nebula but offset from the center by a projected distance of ≈2″.5 (20 kpc), and likely to be an enshrouded AGN. Ayoung star-forming galaxy lies near the northern end of the nebula. We suggest that the nebula is a site of recent multiple galaxy and AGN formation, with the spatial distribution of galaxies within the nebula perhaps tracking the formation history of the system. © 2005. The American Astronomical Society. All rights reserved.
• Higdon, J. L., Higdon, S. J., Weedman, D. W., Houck, J. R., Floc'H, L. E., Brown, M. J., Dey, A., Jannuzi, B. T., Soifer, B. T., & Rieke, M. J. (2005). Spitzer Observations of Optically "Invisible" Radio and X-Ray Sources: High Redshift AGN. Astrophys.J., 58-69.
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  We have combined a survey at 24 microns to 0.3 mJy with the Multiband ImagingPhotometer (MIPS) on the Spitzer Space Telescope, a 20 cm A-array VLA surveycovering 0.5 deg^2, and an existing 172 ks Chandra X-Ray Observatory exposureto investigate the nature of optically faint radio and X-ray sources in theNOAO Deep Wide-Field Survey (NDWFS) in Bootes. We find little overlap betweenthe radio and infrared selected populations: only 9% of the infrared sourcesare detected in the radio and only 33% of the radio sources are detected in theinfrared. Thirty-six (10%) of the 377 compact radio sources lack opticalcounterparts in the NDWFS Bw, R, & I images. We refer to these objects asoptically invisible radio sources (OIRS). Only four of the thirty-one OIRSsobserved with MIPS are detected at 24 microns. Comparisons of the radio andinfrared properties of the OIRSs with various galaxy spectral energydistributions demonstrate that most of these sources are powered by AGN ratherthan starbursts. Similarly, eleven X-ray sources observed by both MIPS and theVLA are classified as optically invisible X-ray sources (OIXS). None aredetected at 24 microns or 20 cm. All seven OIXSs detected in Chandra's 0.5-2keV band have infrared to X-ray flux ratios consistent with their luminositybeing dominated by an unobscured AGN. From these results we conclude that boththe optically invisible radio and X-ray source populations are primarily AGN,relatively unaffected by dust and most likely at z > 1. No OIRSs are detectedin X-ray emission and no OIXSs are detected at 20 cm. However, given the widerange in radio and X-ray properties of known AGN and the size of our samples,this lack of overlap does not necessarily imply AGN source populations.[Journal_ref: Astrophys.J. 626 (2005) 58-69]
• Higdon, J. L., Higdon, S. J., Weedman, D. W., Houck, J. R., Floc'h, E. L., Brown, M. J., Dey, A., Jannuzi, B. T., Soifer, B. T., & Rieke, M. J. (2005). Spitzer observations of optically "invisible" radio and X-ray sources: High-redshift active galactic nuclei. Astrophysical Journal Letters, 626(1 I), 58-69.
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  Abstract: We have combined a survey at 24 μm to 0.3 mJy with the Multiband Imaging Photometer (MIPS) on the Spitzer Space Telescope, a 20 cm A-configuration Very Large Array (VLA) survey covering 0.5 deg2, and an existing 172 ks Chandra X-Ray Observatory exposure to investigate the nature of optically faint radio and X-ray sources in the NOAO Deep Wide-Field Survey (NDWFS) in the Bootes field. A catalog of 392 radio sources is defined with optical identifications or magnitude limits. We find little overlap between the radio- and infrared-selected populations: only 9% of the infrared sources are detected in the radio, and only 33% of the radio sources are detected in the infrared. Thirty-six (10%) of the 377 compact radio sources lack optical counterparts in the NDWFS BW, R, and I images. We refer to these objects as optically invisible radio sources (OIRSs). Only four (13%) of the 31 OIRSs observed with MIPS are detected at 24 μm. Comparisons of the radio and infrared properties of the OIRSs with various galaxy spectral energy distributions demonstrate that most of these sources are powered by active galactic nuclei (AGNs) rather than starbursts. Similarly, 11 X-ray sources observed by both MIPS and the VLA are classified as optically invisible X-ray sources (OIXSs). None is detected at 24 μm or 20 cm. All seven OIXSs detected in Chandra's 0.5-2 keV band have infrared to X-ray flux ratios consistent with their luminosity being dominated by an unobscured AGN. From these results we conclude that both the optically invisible radio and X-ray source populations are primarily AGNs, relatively unaffected by dust, and most likely at z > 1. No OIRSs are detected in X-ray emission, and no OIXSs are detected at 20 cm. However, given the wide range in radio and X-ray properties of known AGNs and the size of our samples, this lack of overlap does not necessarily imply different AGN source populations. © 2005. The American Astronomical Society. All rights reserved.
• Houck, J. R., Soifer, B. T., Weedman, D., Higdon, S. J., Higdon, J. L., Herter, T., Brown, M. J., Dey, A., Jannuzi, B. T., Floc'H, L. E., Rieke, M., Armus, L., Charmandaris, V., Brandl, B. R., & Tepliitz, H. I. (2005). Spectroscopic Redshifts to z > 2 for Optically Obscured Sources Discovered with the Spitzer Space Telescope. Astrophys.J., 622.
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  We have surveyed a field covering 9.0 degrees^2 within the NOAO DeepWide-Field Survey region in Bootes with the Multiband Imaging Photometer on theSpitzer Space Telescope (SST) to a limiting 24 um flux density of 0.3 mJy.Thirty one sources from this survey with F(24um) > 0.75 mJy which are opticallyvery faint (R > 24.5 mag) have been observed with the low-resolution modules ofthe Infrared Spectrograph on SST. Redshifts derived primarily from strongsilicate absorption features are reported here for 17 of these sources; 10 ofthese are optically invisible (R > 26 mag), with no counterpart in B_W, R, orI. The observed redshifts for 16 sources are 1.7 < z < 2.8. These represent anewly discovered population of highly obscured sources at high redshift withextreme infrared to optical ratios. Using IRS spectra of local galaxies astemplates, we find that a majority of the sources have mid-infrared spectralshapes most similar to ultraluminous infrared galaxies powered primarily byAGN. Assuming the same templates also apply at longer wavelengths, bolometricluminosities exceed 10^13 L(solar).[Journal_ref: Astrophys.J.622:L105-L108,2005]
• Houck, J. R., Soifer, B. T., Weedman, D., Higdon, S. J., Higdon, J. L., Herter, T., Brown, M. J., Dey, A., Jannuzi, B. T., Floc'h, E., Rieke, M., Armus, L., Charmandaris, V., Brandl, B. R., & Teplitz, H. I. (2005). Spectroscopic redshifts to z > 2 for optically obscured sources discovered with the spitzer space telescope. Astrophysical Journal Letters, 622(2 II), L105-L108.
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  Abstract: We have surveyed a field covering 9.0 deg2 within the NOAO Deep Wide-Field Survey region in Bootes with the Multiband Imaging Photometer on the Spitzer Space Telescope (SST) to a limiting 24 μm flux density of 0.3 mJy. Thirty-one sources from this survey with F24μm > 0.75 mJy that are optically very faint (R ≳ 24.5 mag) have been observed with the low-resolution modules of the Infrared Spectrograph on SST (IRS). Redshifts derived primarily from strong silicate absorption features are reported here for 17 of these sources; 10 of these are optically invisible (R ≳ 26 mag), with no counterpart in BW, R, or I. The observed redshifts for 16 sources are 1.7 < z < 2.8. These represent a newly discovered population of highly obscured sources at high redshift with extreme infrared-to-optical ratios. Using IRS spectra of local galaxies as templates, we find that a majority of the sources have mid-infrared spectral shapes most similar to ultraluminous infrared galaxies powered primarily by active galactic nuclei. Assuming that the same templates also apply at longer wavelengths, bolometric luminosities exceed 1013 L⊙. © 2005. The American Astronomical Society. All rights reserved.
• J., M., Jannuzi, B. T., Dey, A., & Tiede, G. P. (2005). The clustering of extragalactic extremely red objects. Astrophysical Journal Letters, 621(1 I), 41-52.
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  Abstract: We have measured the angular and spatial clustering of 671 K < 18.40, R - K > 5 extremely red objects (EROs) from a 0.98 deg2 subregion of the NOAO Deep Wide-Field Survey (NDWFS). Our study covers nearly 5 times the area and has twice the sample size of any previous ERO clustering study. The wide field of view and BWRIK passbands of the NDWFS allow us to place improved constraints on the clustering of z ∼ 1 EROs. We find that the angular clustering of EROs is slightly weaker than in previous measurements, and ω(1′) = 0.25 ± 0.05 for K < 18.40 EROs. We find no significant correlation of ERO spatial clustering with redshift, apparent color, or absolute magnitude, although given the uncertainties, such correlations remain plausible. We find that the spatial clustering of K < 18.40, R - K > 5 EROs is well approximated by a power law, with r0 = 9.7 ± 1.1 h-1 Mpc in comoving coordinates. This is comparable to the clustering of ∼4L* early-type galaxies at z < 1 and is consistent with the brightest EROs being the progenitors of the most massive elliptical galaxies. There is evidence of the angular clustering of EROs decreasing with increasing apparent magnitude, when NDWFS measurements of ERO clustering are combined with those from the literature. Unless the redshift distribution of K≳20 EROs is very broad, the spatial clustering of EROs decreases from r0 = 9.7 ± 1.1 A-1 Mpc for K < 18.40 to r0 ∼ 7.5 A-1 Mpc for K≳20 EROs. © 2005. The American Astronomical Society. All rights reserved.
• Kaspi, S., Maoz, D., Netzer, H., Peterson, B. M., Vestergaard, M., & Jannuzi, B. T. (2005). The Relationship Between Luminosity and Broad-Line Region Size in Active Galactic Nuclei. Astrophys.J., 61-71.
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  We reinvestigate the relationship between the characteristic broad-lineregion size (R_blr) and the Balmer emission-line, X-ray, UV, and opticalcontinuum luminosities. Our study makes use of the best availabledeterminations of R_blr for a large number of active galactic nuclei (AGNs)from Peterson et al. Using their determinations of R_blr for a large sample ofAGNs and two different regression methods, we investigate the robustness of ourcorrelation results as a function of data sub-sample and regression technique.Though small systematic differences were found depending on the method ofanalysis, our results are generally consistent. Assuming a power-law relationR_blr \propto L^\alpha, we find the mean best-fitting \alpha is about0.67+/-0.05 for the optical continuum and the broad H\beta luminosity, about0.56+/-0.05 for the UV continuum luminosity, and about 0.70+/-0.14 for theX-ray luminosity. We also find an intrinsic scatter of about 40% in theserelations. The disagreement of our results with the theoretical expected slopeof 0.5 indicates that the simple assumption of all AGNs having on average sameionization parameter, BLR density, column density, and ionizing spectral energydistribution, is not valid and there is likely some evolution of a few of thesecharacteristics along the luminosity scale.[Journal_ref: Astrophys.J. 629 (2005) 61-71]
• Kaspi, S., Maoz, D., Netzer, H., Peterson, B. M., Vestergaard, M., & Jannuzi, B. T. (2005). The relationship between luminosity and broad-line region size in active galactic nuclei. Astrophysical Journal Letters, 629(1 I), 61-71.
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  Abstract: We reinvestigate the relationship between the characteristic broad-line region size (RBLR) and the Balmer emission-line, X-ray, UV, and optical continuum luminosities. Our study makes use of the best available determinations of RBLR for a large number of active galactic nuclei (AGNs) from Peterson et al. Using their determinations of RBLR for a large sample of AGNs and two different regression methods, we investigate the robustness of our correlation results as a function of data subsample and regression technique. Although small systematic differences were found depending on the method of analysis, our results are generally consistent. Assuming a power-law relation RBLR ∝ Lα, we find that the mean best-fitting α is about 0.67 ± 0.05 for the optical continuum and the broad Hβ luminosity, about 0.56 ± 0.05 for the UV continuum luminosity, and about 0.70 ± 0.14 for the X-ray luminosity. We also find an intrinsic scatter of ∼40% in these relations. The disagreement of our results with the theoretical expected slope of 0.5 indicates that the simple assumption of all AGNs having on average the same ionization parameter, BLR density, column density, and ionizing spectral energy distribution is not valid and there is likely some evolution of a few of these characteristics along the luminosity scale. © 2005. The American Astronomical Society. All rights reserved.
• Kenter, A., Murray, S. S., Forman, W. R., Jones, C., Green, P., Kochanek, C. S., Vikhlinin, A., Fabricant, D., Fazio, G., Brand, K., J., M., Dey, A., Jannuzi, B. T., Najita, J., McNamara, B., Shields, J., & Rieke, M. (2005). XBootes: An X-ray survey of the NDWFS Bootes field. II. The X-ray source catalog. Astrophysical Journal, Supplement Series, 161(1), 9-20.
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  Abstract: We present results from a Chandra survey of the 9 deg 2 Bootes field of the NOAO Deep Wide-Field Survey (NDWFS). This XBootes survey consists of 126 separate contiguous ACIS-I observations each of approximately 5000 s in duration. These unique Chandra observations allow us to search for large-scale structure and to calculate X-ray source statistics over a wide, contiguous field of view with arcsecond angular resolution and uniform coverage. Optical spectroscopic follow-up observations and the rich NDWFS data set will allow us to identify and classify these X-ray-selected sources. Using wavelet decomposition, we detect 4642 point sources with n ≥ 2 counts. In order to keep our detections ∼99% reliable, we limit our list to sources with n ≥ 4 counts. For a 5000 s observation and assuming a canonical unabsorbed active galactic nucleus (AGN) type X-ray spectrum, a 4 count on-axis source corresponds to a flux of 4.7 × 10 -15 ergs cm -2 s -1 in the soft (0.5-2 keV) band, 1.5 × 10 -14 ergs cm -2 s -1 in the hard (2-7 keV) band, and 7.8 × 10 -15 ergs cm -2 s -1 in the full (0.5-7 keV) band. The full 0.5-7 keV band n ≥ 4 count list has 3293 point sources. In addition to the point sources, 43 extended sources have been detected, consistent with the depth of these observations and the number counts of clusters. We present here the X-ray catalog for the XBootes survey, including source positions, X-ray fluxes, hardness ratios, and their uncertainties. We calculate and present the differential number of sources per flux density interval, N(S), for the point sources. In the soft (0.5-2 keV) band, N(S) is well fitted by a broken power law with slope of 2.60 -0.12+0.11 at bright fluxes and 1.74 -0.22+0.28 for faint fluxes. The hard source N(S) is well described by a single power law with an index of -2.93 -0.09+0.09. © 2005. The American Astronomical Society. All rights reserved.
• Murray, S. S., Kenter, A., Forman, W. R., Jones, C., Green, P. J., Kochanek, C. S., Vikhlinin, A., Fabricant, D., Fazio, G., Brand, K., J., M., Dey, A., Jannuzi, B. T., Najita, J., Mcnamara, B., Shields, J., & Rieke, M. (2005). XBootes: An X-ray survey of the NDWFS Bootes field. I. Overview and initial results. Astrophysical Journal, Supplement Series, 161(1), 1-8.
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  Abstract: We obtained a 5 ks deep Chandra X-ray Observatory ACIS-I map of the 9.3 deg 2 Bootes field of the NOAO Deep Wide-Field Survey. Here we describe the data acquisition and analysis strategies leading to a catalog of 4642 (3293) point sources with 2 or more (4 or more) counts, corresponding to a limiting flux of roughly 4(8) × 10 -15 ergs cm -2 s -1 in the 0.5-7 keV band. These Chandra XBootes data are unique in that they constitute the widest contiguous X-ray field yet observed to such a faint flux limit. Because of the extraordinarily low background of the ACIS, we expect only 14% (0.7%) of the sources to be spurious. We also detected 43 extended sources in this survey. The distribution of the point sources among the 126 pointings (ACIS-I has a 16′ × 16′ field of view) is consistent with Poisson fluctuations about the mean of 36.8 sources per pointing. While a smoothed image of the point source distribution is clumpy, there is no statistically significant evidence of large-scale filamentary structure. We do find however, that for θ > 1′, the angular correlation function of these sources is consistent with previous measurements, following a power law in angle with slope ∼-0.7. In a 1.4 deg 2 sample of the survey, approximately 87% of the sources with 4 or more counts have an optical counterpart to R ∼ 26 mag. As part of a larger program of optical spectroscopy of the NDWFS Bootes area, spectra have been obtained for ∼900 of the X-ray sources, most of which are quasars or active galactic nuclei. © 2005. The American Astronomical Society. All rights reserved.
• Silverman, J. D., Green, P. J., Barkhouse, W. A., Cameron, R. A., Foltz, C., Jannuzi, B. T., Kim, D. -., Kim, M., Mossman, A., Tananbaum, H., Wilkes, B. J., Smith, M. G., Smith, R. C., & Smith, P. S. (2005). Co-moving space density of X-ray-selected Active Galactic Nuclei. Astrophys.J., 630-637.
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  For measurement of the AGN luminosity function and its evolution, X-rayselection samples all types of AGN and provides reduced obscuration bias incomparison with UV-excess or optical surveys. The apparent decline inoptically-selected quasars above z~3 may be strongly affected by such a bias.The Chandra Multiwavelength Project (ChaMP) is characterizing serendipitouslydetected X-ray sources in a large number of fields with archival Chandraimaging. We present a preliminary measure of the co-moving space density usinga sample of 311 AGN found in 23 ChaMP fields (~1.8 deg^2) supplemented with 57X-ray bright AGN from the CDF-N and CDF-S. Within our X-ray flux (f(0.3-8.0keV) > 4x10^-15 erg cm^-2 s^-1) and optical magnitude (r' < 22.5) limits, oursample includes 14 broad emission line AGN at z > 3. Using this X-ray selectedsample, we detect a turnover in the co-moving space density of luminous type 1AGN (log Lx > 44.5; units erg s^-1; measured in the 0.3-8.0 keV band andcorrected for Galactic absorption) at z > 2.5. Our X-ray sample is the first toshow a behavior similar to the well established evolution of the optical quasarluminosity function. A larger sample of high redshift AGN and with a greaterfraction of identified sources, either spectroscopic or photometric, at faintoptical magnitudes (r' > 22.5) are required to remove the remaining uncertaintyin our measure of the X-ray luminosity function. We confirm that for z < 1,lower luminosity AGN (log Lx < 44.5) are more prevalent by more than an orderof magnitude than those with high luminosity. We have combined the Chandrasample with AGN from the ROSAT surveys to present a measure of the spacedensity of luminous type 1 AGN in the soft X-ray band (0.5-2.0 keV) whichconfirms the broad band turnover described above.[Journal_ref: Astrophys.J. 624 (2005) 630-637]
• Silverman, J. D., Green, P. J., Barkhouse, W. A., Cameron, R. A., Foltz, C., Jannuzi, B. T., Kim, D. -., Kim, M., Mossman, A., Tananbaum, H., Wilkes, B. J., Smith, M. G., Smith, R. C., & Smith, P. S. (2005). Comoving space density of X-ray-selected active galactic nuclei. Astrophysical Journal Letters, 624(2 I), 630-637.
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  Abstract: For measurement of the active galactic nucleus (AGN) luminosity function and its evolution, X-ray selection samples all types of AGNs and provides reduced obscuration bias in comparison with UV excess or optical surveys. The apparent decline in optically selected quasars above z ∼ 3 may be strongly affected by such a bias. The Chandra Multiwavelength Project (CHAMP) is characterizing serendipitously detected X-ray sources in a large number of fields with archival Chandra imaging. We present a preliminary measure of the comoving space density using a sample of 311 AGNs found in 23 CHAMP fields (∼1.8 deg2) supplemented with 57 X-ray-bright AGNs from the Chandra Deep Field-North and Chandra Deep Field-South. Within our X-ray flux (f0.3-8.0keV > 4 × 10-15 ergs cm-2 s-1) and optical magnitude (r′ < 22.5) limits, our sample includes 14 broad emission-line AGNs at z > 3. Using this X-ray-selected sample, we detect a turnover in the comoving space density of luminous type 1 AGNs (log LX > 44.5 ergs s-1, measured in the 0.3-8.0 keV band and corrected for Galactic absorption) at z > 2.5. Our X-ray sample is the first to show a behavior similar to the well-established evolution of the optical quasar luminosity function. A larger sample of high-redshift AGNs and with a greater fraction of identified sources, either spectroscopic or photometric, at faint optical magnitudes (r′ > 22.5) are required to remove the remaining uncertainty in our measure of the X-ray luminosity function, particularly given the possibility that AGNs might be more easily obscured optically at high redshift. We confirm that for z < 1, lower luminosity AGNs (log LX < 44.5) are more prevalent by more than an order of magnitude than those with high luminosity. We have combined the Chandra sample with AGNs from the ROSAT surveys to present a measure of the space density of luminous type 1 AGNs in the soft X-ray band (0.5-2.0 keV) that confirms the broadband turnover described above. © 2005. The American Astronomical Society. All rights reserved.
• Silverman, J. D., Green, P. J., Barkhouse, W. A., Kim, D. -., Aldcroft, T. L., Cameron, R. A., Wilkes, B. J., Mossman, A., Ghosh, H., Tananbaum, H., Smith, M. G., Smith, R. C., Smith, P. S., Foltz, C., Wik, D., & Jannuzi, B. T. (2005). Hard X-ray-emitting active galactic nuclei selected by the Chandra multiwavelength project. Astrophysical Journal Letters, 618(1 I), 123-138.
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  Abstract: We present X-ray and optical analysis of 188 active galactic nuclei (AGN) identified from 497 hard X-ray (f2.0-8.0 kev > 2.7 × 10 -15 ergs cm-2 s-1) sources in 20 Chandra fields (1.5 deg2) forming part of the Chandra Multiwavelength Project. These medium depth X-ray observations enable us to detect a representative subset of those sources responsible for the bulk of the 2-8 keV cosmic X-ray background. Brighter than our optical spectroscopic limit, we achieve a reasonable degree of completeness (77% of X-ray sources with counterparts r′ < 22.5 have been classified): broad emission-line AGNs (62%), narrow emission-line galaxies (24%), absorption line galaxies (7%), stars (5%), or clusters (2%). We find that most X-ray unabsorbed AGNs (NH < 1022 cm-2) have optical properties characterized by broad emission lines and blue colors, similar to optically selected quasars from the Sloan Digital Sky Survey but with a slightly broader color distribution. However, we also find a significant population of redder (g′ - i′ < 1.0) AGNs with broad optical emission lines. Most of the X-ray-absorbed AGNs (1022 cm-2 < NH < 1024 cm-2) are associated with narrow emission-line galaxies, with red optical colors characteristically dominated by luminous, early-type galaxy hosts rather than from dust reddening of an AGN. We also find a number of atypical AGNs; for instance, several luminous AGNs show both strong X-ray absorption (NH >; 1022 cm-2) and broad emission lines. Overall, we find that 81% of X-ray-selected AGNs can be easily interpreted in the context of current AGN unification models. Most of the deviations seem to be due to an optical contribution from the host galaxies of the low-luminosity AGNs.
• Stanford, S. A., Eisenhardt, P. R., Brodwin, M., Gonzalez, A. H., Stern, D., Jannuzi, B. T., Dey, A., J., M., Mckenzie, E., & Elston, R. (2005). An IR-selected galaxy cluster at z = 1.41. Astrophysical Journal Letters, 634(2 II), L129-L132.
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  Abstract: We report the discovery of a galaxy cluster at z = 1.41. ISCS J143809+341419 was found in the Spitzer/IRAC Shallow Survey of the Bootes field in the NOAO Deep Wide-Field Survey carried out using IRAC. The cluster candidate was initially identified as a high-density region of objects with photometric redshifts in the range 1.3 < z < 1.5. Optical spectroscopy of a limited number of objects in the region shows that five galaxies within an ∼120″ diameter region lie at z = 1.41 ± 0.01. Most of these member galaxies have broadband colors consistent with the expected spectral energy distribution of a passively evolving elliptical galaxy formed at high redshift. The redshift of ISCS J143809+341419 is the highest currently known for a spectroscopically confirmed cluster of galaxies. © 2005. The American Astronomical Society. All rights reserved.
• Stern, D., Eisenhardt, P., Gorjian, V., Kochanek, C. S., Caldwell, N., Eisenstein, D., Brodwin, M., Brown, M. J., Cool, R., Dey, A., Green, P., Jannuzi, B. T., Murray, S. S., Pahre, M. A., & Willner, S. P. (2005). Mid-Infrared Selection of Active Galaxies. Astrophys.J., 631, 163-168.
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  Mid-infrared photometry provides a robust technique for identifying activegalaxies. While the ultraviolet to mid-infrared continuum of normal galaxies isdominated by the composite stellar black body curve and peaks at approximately1.6 microns, the ultraviolet to mid-infrared continuum of active galaxies isdominated by a power law. Consequently, with sufficient wavelength baseline,one can easily distinguish AGN from stellar populations. Mirroring the tendencyof AGN to be bluer than galaxies in the ultraviolet, where galaxies (and stars)sample the blue, rising portion of stellar spectra, AGN tend to be redder thangalaxies in the mid-infrared, where galaxies sample the red, falling portion ofthe stellar spectra. We report on Spitzer Space Telescope mid-infrared colors,derived from the IRAC Shallow Survey, of nearly 10,000 spectroscopicallyidentified sources from the AGN and Galaxy Evolution Survey. Based on thisspectroscopic sample, we find that simple mid-infrared color criteria provideremarkably robust separation of active galaxies from normal galaxies andGalactic stars, with over 80% completeness and less than 20% contamination.Considering only broad-lined AGN, these mid-infrared color criteria identifyover 90% of spectroscopically identified quasars and Seyfert 1s. Applying thesecolor criteria to the full imaging data set, we discuss the implied surfacedensity of AGN and find evidence for a large population of optically obscuredactive galaxies.[Journal_ref: Astrophys.J.631:163-168,2005]
• Stern, D., Eisenhardt, P., Gorjian, V., Kochanek, C. S., Caldwell, N., Eisenstein, D., Brodwin, M., J., M., Cool, R., Dey, A., Green, P., Jannuzi, B. T., Murray, S. S., Pahre, M. A., & Willner, S. P. (2005). Mid-infrared selection of active galaxies. Astrophysical Journal Letters, 631(1 I), 163-168.
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  Abstract: Mid-infrared photometry provides a robust technique for identifying active galaxies. While the ultraviolet to mid-infrared (λ ≲ 5 μm) continuum of stellar populations is dominated by the composite blackbody curve and peaks at approximately 1.6 μm, the ultraviolet to mid-infrared continuum of active galactic nuclei (AGNs) is dominated by a power law. Consequently, with a sufficient wavelength baseline, one can easily distinguish AGNs from stellar populations. Mirroring the tendency of AGNs to be bluer than galaxies in the ultraviolet, where galaxies (and stars) sample the blue, rising portion of stellar spectra, AGNs tend to be redder than galaxies in the mid-infrared, where galaxies sample the red, falling portion of the stellar spectra. We report on Spitzer Space Telescope mid-infrared colors, derived from the IRAC Shallow Survey, of nearly 10,000 spectroscopically identified sources from the AGN and Galaxy Evolution Survey. On the basis of this spectroscopic sample, we find that simple mid-infrared color criteria provide remarkably robust separation of active galaxies from normal galaxies and Galactic stars, with over 80% completeness and less than 20% contamination. Considering only broad-lined AGNs, these mid-infrared color criteria identify over 90% of spectroscopically identified quasars and Seyfert 1 galaxies. Applying these color criteria to the full imaging data set, we discuss the implied surface density of AGNs and find evidence for a large population of optically obscured active galaxies. © 2005. The American Astronomical Society. All rights reserved.
• Appleton, P. N., Fadda, D. T., Marleau, F. R., Frayer, D. T., Helou, G., Condon, J. J., Choi, P. I., Yan, L., Lacy, M., Wilson, G., Armus, L., Chapman, S. C., Fang, F., Heinrichson, I., Im, M., Jannuzi, B. T., Storrie-Lombardi, L., Shupe, D., Soifer, B. T., , Squires, G., et al. (2004). The far- and mid-infrared/radio correlations in the Spitzer extragalactic first look survey. Astrophysical Journal, Supplement Series, 154(1), 147-150.
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  Abstract: Using the Spitzer Space Telescope and the Very Large Array (VLA), we present the first direct evidence that the well-known far-infrared/radio correlation is valid to cosmologically significant redshift. We also confirm, with improved statistics compared with previous surveys, a similar result for the mid-IR/radio correlation. We explore the dependence of monochromatic q 24 and q70 on z. The results were obtained by matching Spitzer sources at 24 and 70 μm with VLA 1.4 GHz microjansky radio sources obtained for the Spitzer First Look Survey (FLS). Spectroscopic redshifts have been obtained for over 500 matched IR/radio sources using observations at WIYN and Keck, and archival Sloan Digital Sky Survey (SDSS) data extending out to z > 2. We find that 924 shows significantly more dispersion than q70. By comparing the observed fluxes at 70, 24, and 4.5 μm with a library of SED templates, we find that the larger dispersion in q24 is predictable in terms of systematic variations in spectral energy distribution (SED) shape throughout the population. Although the models are not able to encompass the full range of observed behavior (both the presence of either extremely flat or extremely steep IR SEDs), the fitting parameters were used to "k-correct" the higher z galaxies, which resulted in a reduced scatter in q. For comparison, we also corrected these data using the SED for M82. The results for 24 and 70 μm provide strong consistent evidence for the universality of the mid- and far-IR/radio correlations out to redshifts of at least z = 1.
• Bechtold, J., & Jannuzi, B. T. (2004).

  Obituary: Richard Joseph Elston, 1960-2004

  . Bulletin of the American Astronomical Society, 36(5), 1671-1672.
• Dawson, S., Rhoads, J. E., Malhotra, S., Stern, D., Dey, A., Spinrad, H., Jannuzi, B. T., Wang, J., & Landes, E. (2004). Spectroscopic Properties of the z=4.5 Lyman-alpha Emitters. Astrophys.J., 707-717.
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  We present Keck/LRIS optical spectra of 17 Lya-emitting galaxies and oneLyman break galaxy at z=4.5 discovered in the Large Area Lyman Alpha (LALA)survey. The survey has identified a sample of ~350 candidate Lya-emittinggalaxies at z=4.5 in a search volume of 1.5 x 10^6 comoving Mpc^3. We targeted25 candidates for spectroscopy; hence, the 18 confirmations presented hereinsuggest a selection reliability of 72%. The large equivalent widths (medianW(rest)~80 A) but narrow physical widths (v < 500 km/s) of the Lya emissionlines, along with the lack of accompanying high-ionization state emissionlines, suggest that these galaxies are young systems powered by star formationrather than by AGN activity. Theoretical models of galaxy formation in theprimordial Universe suggest that a small fraction of Lya-emitting galaxies atz=4.5 may still be nascent, metal-free objects. Indeed, we find with 90%confidence that 3 to 5 of the confirmed sources show W(rest) > 240 A, exceedingthe maximum Lya equivalent width predicted for normal stellar populations.Nonetheless, we find no evidence for HeII 1640 emission in either individual orcomposite spectra, indicating that though these galaxies are young, they arenot truly primitive, Population III objects.[Journal_ref: Astrophys.J. 617 (2004) 707-717]
• Dawson, S., Rhoads, J. E., Malhotra, S., Stern, D., Dey, A., Spinrad, H., Jannuzi, B. T., Wang, J., & Landes, E. (2004). Spectroscopic properties of the z ≈ 4.5 Lyα emitters. Astrophysical Journal Letters, 617(2 I), 707-717.
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  Abstract: We present Keck Low Resolution Imaging Spectrometer optical spectra of 17 Lyα-emitting galaxies and one Lyman break galaxy at z ≈ 4.5 discovered in the Large Area Lyman Alpha survey. The survey has identified a sample of ∼350 candidate Lyα-emitting galaxies at z ≈ 4.5 in a search volume of 1.5 × 106 comoving Mpc3. We targeted 25 candidates for spectroscopy; hence, the 18 confirmations presented herein suggest a selection reliability of 72%. The large equivalent widths (median Wλrest ≈ 80 Å) but narrow physical widths (Δv < 500 km s-1) of the Lyα emission lines, along with the lack of accompanying high-ionization state emission lines, suggest that these galaxies are young systems powered by star formation rather than by active galactic nucleus activity. Theoretical models of galaxy formation in the primordial universe suggest that a small fraction of Lyα-emitting galaxies at z ≈ 4.5 may still be nascent, metal-free objects. Indeed, we find with 90% confidence that three to five of the confirmed sources show W λrest > 240 Å, exceeding the maximum Lyα equivalent width predicted for normal stellar populations. Nonetheless, we find no evidence for He II λ1640 emission in either individual or composite spectra, indicating that although these galaxies are young, they are not truly primitive, Population III objects.
• Eisenhardt, P. R., Stern, D., Brodwin, M., Fazio, G. G., Rieke, G. H., Rieke, M. J., Werner, M. W., Wright, E. L., Allen, L. E., Arendt, R. G., Ashby, M. L., Barmby, P., Forrest, W. J., Hora, J. L., Huang, J. -., Huchra, J., Pahre, M. A., Pipher, J. E., Reach, W. T., , Smith, H. A., et al. (2004). Infrared array camera (IRAC) shallow survey. Astrophysical Journal, Supplement Series, 154(1), 48-53.
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  Abstract: The Infrared Array Camera (IRAC) shallow survey covers 8.5 deg2 in the NOAO Deep Wide-Field Survey in Boötes with three or more 30 s exposures per position. An overview of the survey design, reduction, calibration, star-galaxy separation, and initial results is provided. The survey includes ≈370,000, 280,000, 38,000, and 34,000 sources brighter than the 5 σ limits of 6.4, 8.8, 51, and 50 μJy at 3.6, 4.5, 5.8, and 8 μm, respectively, including some with unusual spectral energy distributions.
• Fadda, D., Jannuzi, B. T., Ford, A., & Siorrie-Lombardi, L. J. (2004). The spitzer space telescope first-look survey: KPNO mosaic-1 R-band images and source catalogs. Astronomical Journal, 128(1 1783), 1-15.
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  Abstract: We present R-band images covering more than 11 square degrees of sky that were obtained in preparation for the Spitzer Space Telescope First-Look Survey (FLS). The FLS was designed to characterize the mid-infrared sky at depths 2 orders of magnitude deeper than previous surveys. The extragalactic component is the first cosmological survey done with Spitzer. Source catalogs extracted from the R-band images are also presented. The R-band images were obtained using the Mosaic-1 camera on the 4 m Mayall Telescope of the Kitt Peak National Observatory. Two relatively large regions of the sky were observed to modest depth: the main FLS extragalactic field (17 h18 m00 s, +59°30′00″.0 [J2000]; l = 88°.3, b = +34°.9) and the ELAIS-N1 field (16 h10 m01 s, +54°30′36″.0; l = 84°.2, b = +44°.9). While both these fields were in early plans for the FLS, only a single deep-pointing test observation was made at the ELAIS-N1 location. The larger Legacy program SWIRE will include this region among its surveyed areas. The data products of our KPNO imaging (images and object catalogs) are made available to the community through the World Wide Web (via the Spitzer Science Center and NOAO Science Archive). The overall quality of the images is high. The measured positions of sources detected in the images have rms uncertainties in their absolute positions on the order of 0″.35 with possible systematic offsets on the order of 0″.1, depending on the reference frame of comparison. The relative astrometric accuracy is much better than 1/10 of an arcsecond. Typical delivered image quality in the images is 1″.1 full width at half-maximum. The images are relatively deep, since they reach a median 5 σ depth limiting magnitude of R = 25.5 (Vega) as measured within a 1.35 FWHM aperture, for which the signal-to-noise ratio (S/N) is maximal. Catalogs have been extracted with SExtractor, using thresholds in area and flux for which the number of false detections is below 1% at R = 25. Only sources with S/N > 3 have been retained in the final catalogs. Comparing the galaxy number counts from our images with those of deeper R-band surveys, we estimate that our observations are 50% complete at R = 24.5. These limits in depth are sufficient to identify a substantial fraction of the infrared sources that will be detected by Spitzer.
• Green, P. J., Silverman, J. D., Cameron, R. A., Kim, D. -., Wilkes, B. J., Barkhouse, W. A., LaCluyze, A., Morris, D., Mossman, A., Ghosh, H., Grimes, J. P., Jannuzi, B. T., Tananbaum, H., Aldcroft, T. L., & Collaboration, T. C. (2004). The Chandra Multiwavelength Project: Optical Followup of Serendipitous Chandra Sources. Astrophys.J.Suppl., 150, 43-71.
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  We present followup optical g', r', and i', imaging and spectroscopy ofserendipitous X-ray sources detected in 6 archival Chandra, images included inthe Chandra, Multiwavelength Project (ChaMP). Of the 486 X-ray sources detectedbetween 3e-16 and 2e-13 (with a median flux of 3e-15 erg cm-2 s-1, we findoptical counterparts for 377 (78%), or 335 (68%) counting only uniquecounterparts. We present spectroscopic classifications for 125 objects,representing 75% of sources with r3.5. We identify28 sources (22%) as galaxies that show narrow emission lines, while 22 (18%)are absorption line galaxies. Eight galaxies lacking broad line emission haveX-ray luminosities that require they host an AGN (logL_X>43). Half of thesehave hard X-ray emission suggesting that high gas columns obscure both theX-ray continuum and the broad emission line regions. We find objects in oursample that show signs of X-ray or optical absorption, or both, but with nostrong evidence that these properties are coupled. ChaMP's deep X-ray andoptical imaging enable multiband selection of small and/or high-redshift groupsand clusters. In these 6 fields we have discovered 3 new clusters of galaxies,two with z>0.4, and one with photometric evidence that it is at a similarredshift.[Journal_ref: Astrophys.J.Suppl.150:43-71,2004]
• Green, P. J., Silverman, J. D., Cameron, R. A., Kim, D. -., Wilkes, B. J., Barkhouse, W. A., LaCluyzé, A., Morris, D., Mossman, A., Ghosh, H., Grimes, J. P., Jannuzi, B. T., Tananbaum, H., Aldcroft, T. L., Baldwin, J. A., Chaffee, F. H., Dey, A., Dosaj, A., Evans, N. R., , Fan, X., et al. (2004). The Chandra multiwavelength project: Optical follow-up of serendipitous Chandra sources. Astrophysical Journal, Supplement Series, 150(1), 43-71.
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  Abstract: We present follow-up optical g′, r′, and i′ imaging and spectroscopy of serendipitous X-ray sources detected in six archival Chandra images included in the Chandra Multiwavelength Project (ChaMP). Of the 486 X-ray sources detected between 3 × 10-16 and 2 × 10 -13 (with a median flux of 3 × 10-15) ergs cm -2 s-1, we find optical counterparts for 377 (78%), or 335 (68%) counting only unique counterparts. We present spectroscopic classifications for 125 objects, representing 75% of sources with r* < 21 optical counterparts (63% to r* = 22). Of all classified objects, 63 (50%) are broad-line active galactic nuclei (AGNs), which tend to be blue in (g*-r*) colors. X-ray information efficiently segregates these quasars from stars, which otherwise strongly overlap in these SDSS colors until z > 3.5. We identify 28 sources (22%) as galaxies that show narrow emission lines, while 22 (18%) are absorption line galaxies. Eight galaxies lacking broad-line emission have X-ray luminosities that require they host an AGN (log Lx > 43). Half of these have hard X-ray emission suggesting that high gas columns obscure both the X-ray continuum and the broad emission line regions. We find objects in our sample that show signs of X-ray or optical absorption, or both, but with no strong evidence that these properties are coupled. ChaMP's deep X-ray and optical imaging enable multiband selection of small and/or high-redshift groups and clusters. In these six fields we have discovered three new clusters of galaxies, two with z > 0.4, and one with photometric evidence for a similar redshift.
• Murray, S. S., Forman, W. R., Jones, C. F., Kenter, A., Green, P., Fabricant, D., Fazio, G., Jannuzi, B., Dey, A., Najita, J., Brown, M., Brand, K., Shields, J., McNamara, B., Rieke, M., & Kochanek, C. (2004). X-ray 3 dimensional survey in the NDWFS Bootes field: Large area Chandra shallow X-ray survey -I. Proceedings of SPIE - The International Society for Optical Engineering, 5488(PART 1), 242-250.
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  Abstract: In March and April 2003, the Chandra X-ray Observatory carried out a series of 126 short observations (5 ksec each) covering a continuous area of the Boötes constellation to construct a large area shallow X-ray survey. These observations were carried out as collaboration of Guest Observer (C. Jones PI) and Guaranteed Time Observer (S. Murray PI) programs. We present here, in Paper I, an initial analysis of the survey data and the source detection process, showing the sky coverage, exposure map, and some of the collective properties of the resulting catalog of sources. The Boötes area was selected to overlap a well studied region where optical, and radio data, to sufficient depth, have already been obtained making the identification of candidate counterparts straight forward. In 5 ksec, we reach a limiting flux of ∼ 10 -3 cts -1 (corresponding to ∼ 10 -14 erg cm -2 s -1 0.5 - 7.0 keV). We examine the spatial distribution of the sources in this ̃9.3 square degree survey region using several techniques to search for evidence of cosmic variance in the X-ray source density on scales as small as the ACIS-I field of view (̃16×16 arc minutes). With follow up optical spectroscopy using the MMT/Hectospec, we can obtain spectroscopic redshifts for about 1/3 - 1./2 of the X-ray sources, which can be used to look for evidence of large scale structures traced by AGN associated with the cosmic web.
• Rhoads, J. E., Chun, X. u., Dawson, S., Dey, A., Malhotra, S., Wang, J., Jannuzi, B. T., Spinrad, H., & Stern, D. (2004). A luminous Lyα-emitting galaxy at redshift z = 6.535: Discovery and spectroscopic confirmation. Astrophysical Journal Letters, 611(1 I), 59-67.
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  Abstract: We present a redshift z = 6.535 galaxy discovered by its Lyα emission in a 9180 Å narrowband image from the Large Area Lyman Alpha survey. The Lyα line luminosity (1.1 × 1043 ergs s-1) is among the largest known for star-forming galaxies at z ≈ 6.5. The line shows the distinct asymmetry that is characteristic of high-redshift Lyα. The 2 σ lower bound on the observer-frame equivalent width is greater than 530 Å. This is hard to reconcile with a neutral intergalactic medium (IGM) unless the Lyα line is intrinsically strong and is emitted from its host galaxy with an intrinsic Doppler shift of several hundred km s-1. If the IGM is ionized, it corresponds to a rest-frame equivalent width greater than 40 Å after correcting for Lyα forest absorption. We also present a complete spectroscopic follow-up of the remaining candidates with line flux greater than 2 × 10-17 ergs cm-2 s-1 in our 1200 arcmin2 narrowband image. These include another galaxy with a strong emission line at 9136 Å and no detected continuum flux, which, however, is most likely an [O III] λ5007 source at z = 0.824, on the basis of a weak detection of the [O III] λ4959 line.
• Rhoads, J. E., Xu, C., Dawson, S., Dey, A., Malhotra, S., Wang, J., Jannuzi, B. T., Spinrad, H., & Stern, D. (2004). A Luminous Lyman-alpha Emitting Galaxy at Redshift z=6.535: Discovery and Spectroscopic Confirmation. Astrophys.J., 611, 59-67.
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  We present a redshift z=6.535 galaxy discovered by its Lyman alpha emissionin a 9180A narrowband image from the Large Area Lyman Alpha (LALA) survey. TheLy-a line luminosity (1.1e43 erg/s) is among the largest known for star forminggalaxies at z=6.5. The line shows the distinct asymmetry that is characteristicof high-redshift Ly-a. The 2 sigma lower bound on the observer-frame equivalentwidth is > 530A. This is hard to reconcile with a neutral intergalactic mediumunless the Ly-a line is intrinsically strong and is emitted from its hostgalaxy with an intrinsic Doppler shift of several hundred km/s. If the IGM isionized, it corresponds to a rest frame equivalent width > 40A after correctingfor Ly-a forest absorption. We also present complete spectroscopic followup of the remaining candidateswith line flux > 2e-17 erg/cm2/s in our 1200 square arcminute narrowband image.These include another galaxy with a strong emission line at 9136A and nodetected continuum flux, which however is most likely an [OIII] source atz=0.824 based on a weak detection of the [OIII] 4959A line.[Journal_ref: Astrophys.J.611:59-67,2004]
• Silverman, J., Green, P., Barkhouse, W., Kim, D., Aldcroft, T., Cameron, R., Wilkes, B., Mossman, A., Ghosh, H., Tananbaum, H., Smith, M., Smith, R., Smith, P., Foltz, C., Wik, D., & Jannuzi, B. (2004). Hard X-ray emitting Active Galactic Nuclei selected by the Chandra Multi-wavelength Project. Astrophys.J., 618, 123-138.
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  We present X-ray and optical analysis of 188 AGN identified from 497 hardX-ray (f (2.0-8.0 keV) > 2.7x10^-15 erg cm^-2 s^-1) sources in 20 Chandrafields (1.5 deg^2) forming part of the Chandra Multi-wavelength Project. Thesemedium depth X-ray observations enable us to detect a representative subset ofthose sources responsible for the bulk of the 2-8 keV Cosmic X-ray Background.Brighter than our optical spectroscopic limit, we achieve a reasonable degreeof completeness (77% of X-ray sources with counter-parts r'< 22.5 have beenclassified): broad emission line AGN (62%), narrow emission line galaxies(24%), absorption line galaxies (7%), stars (5%) or clusters (2%). We find thatmost X-ray unabsorbed AGN (NH1.0) AGN with broad optical emission lines. Most of the X-rayabsorbed AGN (10^22
• Wang, J. X., Malhotra, S., Rhoads, J. E., Brown, M. J., Dey, A., Heckman, T. M., Jannuzi, B. T., Norman, C. A., Tiede, G. P., & Tozzi, P. (2004). The 172 ks Chandra exposure of the LALA Bootes field: X-ray source catalog. Astronomical Journal, 127(1 1777), 213-229.
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  Abstract: We present an analysis of a deep, 172 ks Chandra observation of the Large Area Lyman Alpha survey (LALA) Bootes field, obtained with the Advanced CCD Imaging Spectrometer (ACIS-I) on board the Chandra X-Ray Observatory. This is one of the deepest Chandra images of the extragalactic sky; only the 2 Ms Chandra Deep Field North (CDF-N) and 1 Ms Chandra Deep Field South (CDF-S) are substantially deeper. In this paper we present the X-ray source catalog obtained from this image, along with an analysis of source counts and optical identifications. The X-ray image is composed of two individual observations obtained in 2002 and reaches 0.5-2.0 and 2.0-10.0 keV flux limits of 1.5 × 10 -16 and 1.0 × 10 -15 ergs cm -2 s -1, respectively, for point sources near the aim point. A total of 168 X-ray sources were detected: 160 in the 0.5-7.0 keV band, 132 in the 0.5-2.0 keV band, and 111 in the 2.0-7,0 keV band. The X-ray source counts were derived and compared with those from other Chandra deep surveys; the hard X-ray source density of the LALA Bootes field is 33% higher than that of CDF-S at the flux level of 2.0 × 10 -15 ergs cm -2 s -1, confirming the field-to-field variances of the hard-band source counts reported by previous studies. The deep exposure resolves ≳72% of the 2.0-10.0 keV X-ray background. Our primary optical data are R-band imaging from the NOAO Deep Wide-Field Survey (NDWFS), with a limiting magnitude of R = 25.7 (Vega, 3 σ, and 4″ diameter aperture). We have found optical counterparts for 152 of the 168 Chandra sources (90%); 144 of these are detected in the R-band image, and eight have optical counterparts in other bands (either B W, V, I, or z′). Among the R-band nondetected sources, not more than 11 of them can possibly be at z > 5, based on the hardness ratios of their X-ray emission and nondetections in bluer bands (B W V). The majority (∼76%) of the X-ray sources are found to have log(f X/f R) within 0.0 ± 1; these are believed to be AGNs. Most of the X-ray-faint/optically bright sources [log(f X/f R) < -1.0] are optically extended; these are low-z normal galaxies or low-luminosity AGNs. There is also a population of sources that are X-ray overluminous for their optical magnitudes [log(f X/f R) > 1.0], which are harder in X-ray and are probably obscured AGNs.
• Brown, M. J., Dey, A., Jannuzi, B. T., Lauer, T. R., Tiede, G. P., & Mikles, V. J. (2003). Red Galaxy Clustering in the NOAO Deep Wide-Field Survey. Astrophys.J., 225-238.
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  We have measured the clustering of z1000 galaxies to be selected as a function ofspectral type, absolute magnitude, and photometric redshift. Spectral synthesismodels can be used to predict the colors and luminosities of a galaxypopulation as a function of redshift. We have used PEGASE2 models, withexponentially declining star formation rates, to estimate the observed colorsand luminosity evolution of galaxies and to connect, as an evolutionarysequence, related populations of galaxies at different redshifts. A red galaxysample, with present-day rest-frame Vega colors of Bw-R>1.44, was chosen toallow comparisons with the 2dF Galaxy Redshift Survey and Sloan Digital SkySurvey. We find the spatial clustering of red galaxies to be a strong functionof luminosity, with r0 increasing from 4.4+/-0.4 Mpc/h at M_R=-20 to 11.2+/-1.0Mpc/h at M_R=-22. Clustering evolution measurements using samples where therest-frame selection criteria vary with redshift, including all deepsingle-band magnitude limited samples, are biased due to the correlation ofclustering with rest-frame color and luminosity. The clustering of M_R=-21,Bw-R>1.44 galaxies exhibits no significant evolution over the redshift rangeobserved with r0= 6.3+/-0.5 Mpc/h in comoving coordinates. This is consistentwith recent LCDM models where the bias of L* galaxies undergoes rapid evolutionand r0 evolves very slowly at z
• Brown, M. J., Dey, A., Jannuzi, B. T., Lauer, T. R., Tiede, G. P., & Mikles, V. J. (2003). Red galaxy clustering in the NOAO deep wide-field survey. Astrophysical Journal Letters, 597(1 I), 225-238.
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  Abstract: We have measured the clustering of 0.30 < z < 0.90 red galaxies and constrained models of the evolution of large-scale structure using the initial 1.2 deg2 data release of the NOAO Deep Wide-Field Survey (NDWFS). The area and BwRI passbands of the NDWFS allow samples of ≳103 galaxies to be selected as a function of spectral type, absolute magnitude, and photometric redshift. Spectral synthesis models can be used to predict the colors and luminosities of a galaxy population as a function of redshift. We have used PEGASE2 models, with exponentially declining star formation rates, to estimate the observed colors and luminosity evolution of galaxies and to connect, as an evolutionary sequence, related populations of galaxies at different redshifts. A red galaxy sample, with present-day rest-frame Vega colors of Bw-R > 1.44, was chosen to allow comparisons with the 2dF Galaxy Redshift Survey and Sloan Digital Sky Survey. We find the spatial clustering of red galaxies to be a strong function of luminosity, with r0 increasing from 4.4 ±0.4 h-1 Mpc at MR - 5 log h ≈-20.0 to 11.2 ±1.0 h-1 Mpc at MR - 5 log h ≈-22.0. Clustering evolution measurements using samples where the rest-frame selection criteria vary with redshift, including all deep single-band magnitude limited samples, are biased because of the correlation of clustering with rest-frame color and luminosity. The clustering of -21.5 < MR - 5 log h < -20.5, Bw-R > 1.44 galaxies exhibits no significant evolution over the redshift range observed with r 0 = 6.3 ±0.5 h-1 Mpc in comoving coordinates. This is consistent with recent ACDM, models in which the bias of L* galaxies undergoes rapid evolution and r0 evolves very slowly at z < 2.
• Green, P. J., Cameron, R., Ghosh, H., Grimes, J., Kim, D., Morris, D., Mossman, A., Silverman, J., Wilkes, B., Baldwin, J., Jannuzi, B., Harnden, R., Kashyap, V., LaCluyzé, A., Maksym, P., Schlegel, E., Tananbaum, H., Vikhlinin, A., Smith, C., & Smith, M. (2003). The Chandra multi-wavelength project (ChaMP): Results and prospects. Astronomische Nachrichten, 324(1-2), 93-96.
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  Abstract: The cosmic diffuse X-ray background radiation has been almost completely resolved into point sources by Chandra and XMM. However, the nature and evolution of those sources are just beginning to be investigated. The answers are key to our understanding of the inter-relationship over cosmic time of (a) the formation and growth of black holes, (b) star formation, and (c) hierarchical structure formation. This requires multiwavelength followup of Chandra sources over a large area. The Chandra Multiwavelength Project (ChaMP) is a serendipitous survey of the X-ray sky, covering about 14 deg2 of sky in the X-ray flux range of -13 to -16 (log 0.5-2 keV flux, cgs) and will include about 8000 sources, 70% of which are expected to be active galactic nuclei (AGN). Using Chandra archival data, we span flux limits between those reached by previous satellites and those of the deepest small-area Chandra and XMM surveys, allowing study of larger samples of rare objects like luminous absorbed AGN, groups and clusters of galaxies, and their spatial correlations. Optical imaging and spectroscopy of the ChaMP fields are underway at a variety of telescopes using Sloan g′, r′, and i′ filters to a flux limit matched to the X-ray such that about 75% of the X-ray sources will be optically identified. We also plan for radio and near-IR observations of subsets of the ChaMP sample to expand our multi-wavelength coverage and increase the fraction of sources identified.
• Matheson, T., Garnavich, P. M., Stanek, K. Z., Bersier, D., Holland, S. T., Krisciunas, K., Caldwell, N., Berlind, P., Bloom, J. S., Bolte, M., Bonanos, A. Z., Brown, M. J., Brown, W. R., Calkins, M. L., Challis, P., Chornock, R., Echevarria, L., Eisenstein, D. J., Everett, M. E., , Filippenko, A. V., et al. (2003). Photometry and spectroscopy of GRB 030329 and its associated supernova 2003dh: The first two months. Astrophysical Journal Letters, 599(1 I), 394-407.
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  Abstract: We present extensive optical and infrared photometry of the afterglow of gamma-ray burst (GRB) 030329 and its associated supernova (SN) 2003dh over the first two months after detection (2003 March 30-May 29 UT). Optical spectroscopy from a variety of telescopes is shown and, when combined with the photometry, allows an unambiguous separation between the afterglow and SN contributions. The optical afterglow of the GRB is initially a power-law continuum but shows significant color variations during the first week that are unrelated to the presence of an SN. The early afterglow light curve also shows deviations from the typical power-law decay. An SN spectrum is first detectable ∼7 days after the burst and dominates the light after ∼11 days. The spectral evolution and the light curve are shown to closely resemble those of SN 1998bw, a peculiar Type Ic SN associated with GRB 980425, and the time of the SN explosion is close to the observed time of the GRB. It is now clear that at least some GRBs arise from core-collapse SNe.
• Rhoads, J. E., Dey, A., Malhotra, S., Stern, D., Spinrad, H., Jannuzi, B. T., Dawson, S., Brown, M. J., & Landes, E. (2003). Spectroscopic confirmation of three redshift z ≈ 5.7 Lyα emitters from the Large-Area Lyman Alpha survey. Astronomical Journal, 125(3 1767), 1006-1013.
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  Abstract: Narrowband searches for Lyα emission are an efficient way of identifying star-forming galaxies at high redshifts. We present Keck Telescope spectra confirming redshifts z ≈ 5.7 for three objects discovered in the Large-Area Lyman Alpha (LALA) survey at Kitt Peak National Observatory. All three spectra show strong, narrow emission lines with the asymmetric profile that is characteristically produced in high-redshift Lyα emitters by preferential H I absorption in the blue wing of the line. These objects are undetected in deep BW, V, R, and λ ≈ 6600 Å narrowband images from the NOAO Deep Wide-Field Survey and from LALA, as expected from Lyman break and Lyα forest absorption at redshift z ≈ 5.7. All three objects show large equivalent widths ( ≳ 150 Å in the rest frame), suggesting at least one of the following: a top-heavy initial mass function, very low stellar metallicity, or the presence of an active nucleus. We consider the case for an active nucleus to be weak in all three objects due to the limited width of the Lyα emission line (less than 500 km s -1) and the absence of any other indicator of quasar activity. The three confirmed high-redshift objects were among four spectroscopically observed targets drawn from the sample of 18 candidates presented by Rhoads & Malhotra. Thus, these spectra support the Lyα emitter population statistics from our earlier photometric study, which imply little evolution in number density from z = 5.7 to 4.5 and provide strong evidence that the reionization redshift is zr > 5.7.
• Sabra, B. M., Hamann, F., Jannuzi, B. T., George, I. M., & Shields, J. C. (2003). The Nature of the UV/X-Ray Absorber in PG 2302+029. Astrophys.J., 66-72.
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  We present Chandra X-ray observations of the radio-quiet QSO PG 2302+029.This quasar has a rare system of ultra-high velocity (-56,000 km/s) UVabsorption lines that form in an outflow from the active nucleus (Jannuzi etal. 2003). The Chandra data indicate that soft X-ray absorption is alsopresent. We perform a joint UV and X-ray analysis, using photoionizationcalculations, to detemine the nature of the absorbing gas. The UV and X-raydatasets were not obtained simultaneously. Nonetheless, our analysis suggeststhat the X-ray absorption occurs at high velocities in the same general regionas the UV absorber. There are not enough constraints to rule out multi-zonemodels. In fact, the distinct broad and narrow UV line profiles clearlyindicate that multiple zones are present. Our preferred estimates of theionization and total column density in the X-ray absorber (log U=1.6,N_H=10^22.4 cm^-2) over predict the O VI 1032, 1038 absorption unless the X-rayabsorber is also outflowing at ~56,000 km/s, but they over predict the Ne VIII770, 780 absorption at all velocities. If we assume that the X-ray absorbinggas is outflowing at the same velocity of the UV-absorbing wind and that thewind is radiatively accelerated, then the outflow must be launched at a radiusof < 10^15 cm from the central continuum source. The smallness of this radiuscasts doubts on the assumption of radiative acceleration.[Journal_ref: Astrophys.J. 590 (2003) 66-72]
• Sabra, B. M., Hamann, F., Jannuzi, B. T., George, I. M., & Shields, J. C. (2003). The nature of the ultraviolet/X-ray absorber in PG 2302+029. Astrophysical Journal Letters, 590(1 I), 66-72.
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  Abstract: We present Chandra X-ray observations of the radio-quiet QSO PG 2302+029. This quasar has a rare system of ultra-high-velocity (-56,000 km s-1) UV absorption lines that form in an outflow from the active nucleus. The Chandra data indicate that soft X-ray absorption is also present. We perform a joint UV and X-ray analysis, using photoionization calculations, to determine the nature of the absorbing gas. The UV and X-ray data sets were not obtained simultaneously. Nonetheless, our analysis suggests that the X-ray absorption occurs at high velocities in the same general region as the UV absorber. There are not enough constraints to rule out multizone models. In fact, the distinct broad and narrow UV line profiles clearly indicate that multiple zones are present. Our preferred estimates of the ionization and total column density in the X-ray absorber (log U = 1.6, NH = 1022.4 cm -2) overpredict the O VI λλ1032, 1038 absorption unless the X-ray absorber is also outflowing at ∼56,000 km s-1, but they overpredict the Ne VIII λλ770, 780 absorption at all velocities. If we assume that the X-ray-absorbing gas is outflowing at the same velocity as the UV-absorbing wind and that the wind is radiatively accelerated, then the outflow must be launched at a radius of ≤1015 cm from the central continuum source. The smallness of this radius casts doubts on the assumption of radiative acceleration.
• Green, P. J., Kochanek, C., Siemiginowska, A., Kim, D., Markevitch, M., Silverman, J., Dosaj, A., Jannuzi, B. T., & Smith, C. (2002). Chandra observations of the QSO pair Q2345+007: Binary or massive dark lens?. Astrophysical Journal Letters, 571(2 I), 721-732.
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  Abstract: The components of the wide (7″.3) separation quasar pair Q2345+007A, B (z = 2.15) have the most strikingly similar optical spectra seen to date (Steidel & Sargent) yet no detected lensing mass, making this system the best candidate known for a massive (∼1014 M⊙) dark matter lens system. Here we present results from a 65 ks Chandra observation designed to investigate whether it is a binary quasar or a gravitational lens. We find no X-ray evidence for a lensing cluster to a (0.5-2 keV) flux limit of 2 × 10-15 ergs cm-2 s -1, which is consistent with lensing only for a reduced baryon fraction. Using the Chandra X-ray observations of the quasars themselves, together with new and published optical measurements, we use the observed emission properties of the quasars for further tests between the lens and binary hypotheses. Assuming similar line-of-sight absorption to the images, we find that their X-ray continuum slopes are inconsistent (ΓA = 2.30-0.30+0.36 and ΓB = 0.83 -0.44+0.49) as are their X-ray-to-optical flux ratios. The probability that B suffers intrinsic absorption sufficient to account for these spectral differences is negligible. We present new optical evidence that the flux ratio of the pair is variable, so the time delay in a lens scenario could cause some of the discrepancies. However, adequately large variations in overall spectral energy distribution are rare in individual QSOs. All new evidence here weighs strongly toward the binary interpretation. Q2345+007 thus may represent the highest redshift example known of an interaction-triggered but as-yet unmerged luminous active galactic nucleus.
• Silverman, J. D., Green, P. J., Kim, D., Wilkes, B. J., Cameron, R. A., Morris, D., Dosaj, A., Smith, C., Infante, L., Smith, P. S., Jannuzi, B. T., & Mathur, S. (2002). Discovery of a z = 4.93, X-ray-selected quasar by the Chandra Multiwavelength Project (ChaMP). Astrophysical Journal Letters, 569(1 II), L1-L4.
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  Abstract: We present X-ray and optical observations of CXOMP J213945.0-234655, a high-redshift (z = 4.93) quasar discovered through the Chandra Multiwavelength Project (ChaMP). This object is the most distant X-ray-selected quasar published, with a rest-frame X-ray luminosity of Lx = 5.9 × 1044 ergs s-1 (measured in the 0.3-2.5 keV band and corrected for Galactic absorption). CXOMP J213945.0-234655 is a g′ dropout object (>26.2), with r′ = 22.87 and i′ = 21.36. The rest-frame X-ray-to-optical flux ratio is similar to quasars at lower redshifts and slightly X-ray bright relative to z >4 optically selected quasars observed with Chandra. The ChaMP is beginning to acquire significant numbers of high-redshift quasars to investigate the X-ray luminosity function out to z ∼5.
• Kulkarni, V. P., Hill, J. M., Schneider, G., Weymann, R. J., Storrie-Lombardi, L. J., Rieke, M. J., Thompson, R. I., & Jannuzi, B. T. (2001). A search for the damped Lyα absorber at z = 1.86 toward QSO 1244+3443 with NICMOS. Astrophysical Journal Letters, 551(1 PART 1), 37-47.
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  Abstract: We have carried out a high-resolution imaging search for the galaxy associated with the damped Lyα absorber (DLA) at z = 1.859 toward the zem = 2.48 quasar QSO 1244+3443, using the Hubble Space Telescope (HST) and the near-infrared camera and multiobject spectrometer (NICMOS). Images were obtained in the broad filter F160W and the narrow filter F187N with camera 2 on NICMOS with the goal of detecting the rest-frame optical continuum and the Hα line emission from the DLA. After pointspread function (PSF) subtraction, two weak features are seen at projected separations of 0″.16-0″.24 from the quasar. Parts of these features may be associated with the DLA, although we cannot completely rule out that they could be artifacts of the PSF. If associated with the DLA, the objects would be ≈1-2 h-170 kpc in size with integrated flux densities of 2.5 and 3.3 μJy in the F160W filter, implying luminosities at λcentral = 5600 Å in the DLA rest frame of 4.4-5.9 × 109 h-270 L⊙ at z = 1.86, for q0 = 0.5. However, no significant Hα line emission is seen from these objects, suggesting low star formation rates (SFRs). Our 3 σ upper limit on the SFR in the DLA is 1.3 h-270 M⊙ yr-1 for q0 = 0.5 (2.4 h-270 M⊙ yr-1 for q0 = 0.1). This together with our earlier result for LBQS 1210 + 1731 mark a significant improvement over previous constraints on the star formation rates of DLAs. Dust within the DLA could extinguish Hα emission, but this would require the dust content in the DLA to be much higher than that inferred from previous DLA observations. A combination of low star formation rate and some dust extinction is likely to be responsible for the lack of Hα emission. Alternatively, the objects, if real, may be associated with the host galaxy of the quasar rather than with the DLA. In any case, our observations suggest that the DLA is not a large bright protodisk, but a compact object or a low surface brightness galaxy. If the two features are PSF artifacts or associated with the quasar host, then the constraints on the size and luminosity of the DLA are even more severe.
• Churchill, C. W., Mellon, R. R., Charlton, J. C., Jannuzi, B. T., Kirhakos, S., Steidel, C. C., & Schneider, D. P. (2000). Low and High Ionization Absorption Properties of Mg II Absorption-Selected Galaxies at Intermediate Redshifts. I. General Properties. Astrophys.J.Suppl., 91-120.
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  We present extensive metal-line absorption properties for 45 absorptionsystems that were selected by their Mg II absorption at redshifts between 0.4and 1.4. For each system the properties of several chemical species aredetermined, including a wide range of ionization conditions. In the optical,the absorption systems have been observed at ~6 km/s resolution withHIRES/Keck, which covered Mg II, several Fe II transitions, Mg I, and in somecases (depending upon redshift), Ca II, Ti II, Mn II, and Al III. Ultraviolet,lower resolution (~230 km/s) Faint Object Spectrograph data (1600 - 3275 Ang)were obtained from the Hubble Space Telescope archive. These spectra covered AlII, Al III, Si II, Si III, Si IV, C II, C III, C IV, N V, O VI, and severalLyman series transitions, with coverage dependent upon the absorption systemredshift. From these data, we infer that Mg II absorbing galaxies atintermediate redshifts have multiphase gaseous structures.[Journal_ref: Astrophys.J.Suppl. 130 (2000) 91-120]
• Churchill, C. W., Mellon, R. R., Charlton, J. C., Jannuzi, B. T., Kirhakos, S., Steidel, C. C., & Schneider, D. P. (2000). Low- and high-ionization absorption properties of Mg II absorption-selected galaxies at intermediate redshifts. I. General properties. Astrophysical Journal, Supplement Series, 130(1), 91-119.
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  Abstract: We present extensive metal-line absorption properties for 45 absorption systems that were selected by their Mg II absorption at redshifts between 0.4 and 1.4. For each system the properties of several chemical species are determined, including a wide range of ionization conditions. In the optical, the absorption systems have been observed at ∼6 km s-1 resolution with HIRES/Keck, which covered Mg II, several Fe II transitions, Mg I, and in some cases (depending upon redshift) Ca II, Ti II, Mn II, and Al III. Ultraviolet, lower resolution (∼230 km s-1) Faint Object Spectrograph data (1600-3275 Å) were obtained from the Hubble Space Telescope archive. These spectra covered Al II, Al III, Si II, Si III, Si IV, C II, C III, C IV, N V, O VI, and several Lyman series transitions, with coverage dependent upon the absorption system redshift. From these data, we infer that Mg II-absorbing galaxies at intermediate redshifts have multiphase gaseous structures.
• Churchill, C. W., Mellon, R. R., Charlton, J. C., Jannuzi, B. T., Kirhakos, S., Steidel, C. C., & Schneider, D. P. (2000). Low- and high-ionization absorption properties of Mg II absorption-selected galaxies at intermediate redshifts. II. Taxonomy, kinematics, and galaxies. Astrophysical Journal Letters, 543(2 PART 1), 577-598.
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  Abstract: We examine a sample of 4:5 Mg II absorption-selected systems over the redshift range 0.4-1.4 in order to better understand the range of physical conditions present in the interstellar and halo gas associated with intermediate redshift galaxies. Mg II and Fe II absorption profiles were observed at a resolution of ≃6 km s-1 with HIRES/Keck. Lyα and C IV data were measured in FOS spectra obtained from the Hubble Space Telescope archive (resolution ≃230 km s-1). We perform a multivariate analysis of Wr(Mg II), Wr(Fe II), Wr(C IV), and Wr(Lyα) (rest-frame equivalent widths) and the Mg II kinematic spread. There is a large range of high-to low-ionization properties and kinematics in intermediate-redshift absorbers, that we find can be organized into five categories: "classic," "C IV-deficient," "single/weak," "double," and "damped Lyα/H I-rich." These categories arise, in part, because there is a strong connection between low-ionization kinematics and the location of an absorber on the Wr(C IV)-Wr(Mg II) plane. Using photoionization modeling, we infer that in most absorbers a significant fraction of the C IV arises in a phase separate from that giving rise to the Mg II. We show that many of the C IV profiles are resolved in the FOS spectra because of the velocity structure in the C IV gas. For 16 systems, the galaxy MK, MB, B - K, and impact parameters are measured. We compare the available absorption-line properties (taken from Paper I) to the galaxy properties but find no significant (greater than 3 σ) correlations, although several suggestive trends are apparent. We compare the locations of our intermediate redshift absorbers on the Wr(C IV)-Wr(Mg II) plane with those of lower and higher redshift data taken from the literature and find evidence for evolution that is connected with the Mg II kinematics seen in HIRES/ Keck profiles of Mg II at z > 1.4. We discuss the potential of using the above categorizations of absorbers to understand the evolution in the underlying physical processes giving rise to the gas and governing its ionization phases and kinematics. We also discuss how the observed absorbing gas evolution has interesting parallels with scenarios of galaxy evolution in which mergers and the accretion of "protogalactic clumps" govern the gas physics and provide reservoirs for elevated star formation rates at high redshift. At intermediate and lower redshifts, the galaxy gaseous components and star formation rates may become interdependent and self-regulatory such that, at z ≤ 1, the kinematics and balance of high-and low-ionization gas may be related to the presence of star-forming regions in the host galaxy.
• Kaspi, S., Smith, P. S., Netzer, H., Maoz, D., Jannuzi, B. T., & Giveon, U. (2000). Reverberation Measurements for 17 Quasars and the Size-Mass-Luminosity Relations in Active Galactic Nuclei. Astrophys.J..
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  (abridged) We have spectrophotometrically monitored a well-defined sample of28 Palomar-Green quasars in order to obtain measurements of their BLRs and toinvestigate the relationships between quasar luminosity, central black holemass, and broad emission line region (BLR) size in active galactic nuclei(AGN). Spectrophotometry was obtained every 1-4 months for 7.5 years, yielding20-70 observing epochs per object. Both the continuum and emission line fluxesof all of the quasars were observed to change during the duration of theobserving program. Seventeen of the 28 objects were observed with adequatesampling to search for correlated variations between the Balmer emission linesand the continuum flux. For each of these 17 objects, a significant correlationwas observed, with the Balmer line variations lagging those of the continuum by\~100 days (rest frame). Our work increases the available luminosity range forstudying the size-mass-luminosity relations in AGN by two orders of magnitudeand doubles the number of objects suitable for such studies. Combining ourresults with comparable published data available for Seyfert 1 galaxies, wefind the BLR size scales with the rest-frame 5100 A luminosity asL^{0.70+-0.03}. This determination of the scaling of the size of the BLR as afunction of luminosity is significantly different from those previouslypublished, and suggests that the effective ionization parameter in AGN may be adecreasing function of luminosity. We are also able to constrain, subject toour assumption that gravity dominates the motions of the BLR gas, the scalingrelationship between the mass of the central black holes and the luminosity inAGN: M \propto L^{0.5+-0.1}. This is inconsistent with all AGN having opticalluminosity that is a constant fraction of the Eddington luminosity.[Journal_ref: Astrophys.J. 533 (2000) 631]
• Kaspi, S., Smith, P. S., Netzer, H., Maoz, D., Jannuzi, B. T., & Giveon, U. (2000). Reverberation measurements for 17 quasars and the size-mass-luminosity relations in active galactic nuclei. Astrophysical Journal Letters, 533(2 PART 1), 631-649.
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  Abstract: Correlated variations in the line and continuum emission from active galactic nuclei (AGNs) can be used to determine the size and geometry of the broad emission-line regions (BLRs). We have spectrophotometrically monitored a well-defined sample of 28 Palomar-Green quasars in order to obtain measurements of their BLRs and to investigate the relationships between quasar luminosity, central black hole mass, and BLR size in AGNs. Spectrophotometry was obtained every 1-4 months for 7.5 yr, yielding 20-70 observing epochs per object. Both the continuum and emission-line fluxes of all of the quasars were observed to change during the duration of the observing program. Seventeen of the 28 objects were observed with adequate sampling (≳ 20 independent observing epochs) to search for correlated variations between the Balmer emission lines and the continuum flux. For each of these 17 objects, a significant correlation was observed, with the Balmer-line variations lagging those of the continuum by ∼ 100 days (rest frame). Our work increases the available luminosity range for studying the size-mass-luminosity relations in AGNs by 2 orders of magnitude and doubles the number of objects suitable for such studies. Combining our results with comparable published data available for Seyfert 1 galaxies, we find the BLR size scales with the rest-frame 5100 Å luminosity as L0.70±0.03. This determination of the scaling of the size of the BLR as a function of luminosity is significantly different from those previously published and suggests that the effective ionization parameter in AGNs may be a decreasing function of luminosity. We are also able to constrain, subject to our assumption that gravity dominates the motions of the BLR gas, the scaling relationship between the mass of the central black holes and the luminosity in AGNs. We find that the central mass scales with 5100 Å luminosity as M ∝ L0.5±0.1. This is inconsistent with all AGNs having optical luminosity that is a constant fraction of the Eddington luminosity.
• Kulkarni, V. P., Hill, J. M., Schneider, G., Weymann, R. J., Storrie-Lombardi, L., Rieke, M. J., Thompson, R. I., & Jannuzi, B. T. (2000). Nicmos imaging of the damped lyx absorber at z-1, 89 toward LBQS 1210 + 1731: Contraints on size and star formation rate. Astrophysical Journal Letters, 536(1 PART 1), 36-61.
• Rhoads, J. E., Malhotra, S., Dey, A., Stern, D., Spinrad, H., & Jannuzi, B. (2000). First Results from the Large Area Lyman Alpha Survey. Astrophysical Journal Letters, v..
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  We report on a new survey for z=4.5 Lyman alpha sources, the Large Area LymanAlpha (LALA) survey. Our survey achieves an unprecedented combination of volumeand sensitivity by using narrow-band filters on the new 8192x8192 pixel CCDMosaic Camera at the 4 meter Mayall telescope of Kitt Peak NationalObservatory. Well-detected sources with flux and equivalent width matching known highredshift Lyman alpha galaxies (i.e., observed equivalent width above 80Angstroms and line+continuum flux between 2.6e-17 and 5.2e-17 erg/cm^2/sec inan 80 Angstrom filter) have an observed surface density corresponding to 11000+- 700 per square degree per unit redshift at z=4.5. Spatial variation in thissurface density is apparent on comparison between counts in 6561 and 6730Angstrom filters. Early spectroscopic followup results from the Keck telescope included threesources meeting our criteria for good Lyman alpha candidates. Of these, one isconfirmed as a z=4.52 source, while another remains consistent with eitherz=4.55 or z=0.81. We infer that 30 to 50% of our good candidates are bona fideLyman alpha emitters, implying a net density of about 4000 Lyman alpha galaxiesper square degree per unit redshift.[Journal_ref: Astrophysical Journal Letters, v. 545, p. L85 (2000)]
• Rhoads, J. E., Malhotra, S., Dey, A., Stern, D., Spinrad, H., & Jannuzi, B. T. (2000). First results from the Large-Area Lyman Alpha survey. Astrophysical Journal Letters, 545(2 PART 2), L85-L88.
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  Abstract: We report on a new survey for z ≈ 4.5 Lyα sources, the Large-Area Lyman Alpha (LALA) survey. Our survey achieves an unprecedented combination of volume and sensitivity by using narrowband filters on the new 8192 2 pixel CCD Mosaic camera at the 4 m Mayall telescope of Kitt Peak National Observatory. Well-detected sources with flux and equivalent width matching previously known high-redshift Lyα galaxies (i.e., observed equivalent width EW > 80 Å; 2.6 × 10-17 ergs cm-2 s-1 < line + continuum flux < 5.2 × 10-17 ergs cm-2 s-1, and a small uncertainty on the equivalent width, δEW < EW/4) have an observed surface density corresponding to 11,000 ± 700 deg-2 per unit redshift at z = 4.5. Variations in this surface density are apparent on comparison between counts in 6561 ± 40 and 6730 ± 40 Å filters. Early spectroscopic followup results from the Keck telescope included three sources meeting our criteria for good Lyα candidates. Of these, one is confirmed as a z = 4.52 source, another remains consistent with either z = 4.55 or z = 0.81, and the third is an [O III] λ5007 emitter at z = 0.34. These pilot spectroscopic results suggest that approximately one-third of our good candidates are bona fide Lyα emitters, implying a net density of ∼4000 Lyα emitters per square degree per unit redshift.
• Savage, B. D., Wakker, B., Jannuzi, B. T., Bahcall, J. N., Bergeron, J., Boksenberg, A., Hartig, G. F., Kirhakos, S., Murphy, E. M., Sargent, W. L., Schneider, D. P., Turnshek, D., & Wolfe, A. M. (2000). The Hubble Space Telescope Quasar Absorption Line Key Project. XV. Milky Way absorption lines. Astrophysical Journal, Supplement Series, 129(2), 563-610.
• Churchill, C. W., Mellon, R. R., Charlton, J. C., Jannuzi, B. T., Kirhakos, S., Steidel, C. C., & Schneider, D. P. (1999). The C IV absorption-Mg II kinematics connection in 〉z〈 ∼ 0.7 galaxies. Astrophysical Journal Letters, 519(1 PART 2), L43-L46.
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  Abstract: We have examined Faint Object Spectrograph data from the Hubble Space Telescope archive for C IV λλ1548, 1550 absorption associated with 40 Mg II λλ2796, 2803 absorption-selected galaxies at 0.4 ≤ z ≤ 1.4. We report a strong correlation between Mg II kinematics, measured in ∼6 km s-1 resolution HIRES/Keck spectra, and Wr(1548); this implies a physical connection between the processes that produce "outlying velocity" Mg II clouds and high-ionization galactic/halo gas. We found no trend in ionization condition Wr(1548)/Wr(2796) with galaxy-QSO line-of-sight separation for 13 systems with confirmed associated galaxies, suggesting no obvious ionization gradient with galactocentric distance in these intermediate-red shift galaxies. We find tentative evidence (2 σ) that Wr(1548)/Wr(2796) is anticorrelated with galaxy B-K color; if further data corroborate this trend, in view of the strong C IV-Mg II kinematics correlation, it could imply a connection between stellar populations, star formation episodes, and the kinematics and ionization conditions of halo gas at z ∼ 1.
• McNamara, B. R., Jannuzi, B. T., Sarazin, C. L., Elston, R., & Wise, M. (1999). An alignment effect in FR I radio galaxies: U-band polarimetry of the Abell 2597 cluster central galaxy. Astrophysical Journal Letters, 518(1 PART 1), 167-176.
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  Abstract: We have obtained U-band polarimetry of the spatially extended blue optical continuum associated with the FR I radio source PKS 2322-122, located in the Abell 2597 cluster central galaxy. We find a 3 σ upper limit to the degree of optical continuum polarization of less than 6%. The accuracy of the measurement is limited primarily by our ability to measure the amount of diluting galactic starlight. This limit is inconsistent with the blue continuum being primarily scattered light or synchrotron radiation. We can therefore exclude models that attribute the blue continuum to scattered light from an active nucleus that is hidden from direct view. Our result does not support the unification paradigm for BL Lac objects and FR I radio sources. Essentially all of the data pertaining to the blue continuum along the radio source - the "blue lobes" - indicate that they are regions of recent star formation. The spatial coincidence between the blue lobes and disturbances in the radio source suggests that star formation may have been induced by an interaction between the radio source and the cool (less than 104 K) surrounding gas. This result, in addition to the results of a similar study of the A1795 cluster central galaxy, shows that under the appropriate conditions FR I radio sources may be capable of inducing significant episodes of star formation in elliptical galaxies. We compare the rest-frame U-band polarized luminosities and 1.4 GHz radio powers of A2597 and A1795 to those for several high-redshift radio galaxies exhibiting the alignment effect. We find that if the polarized luminosities of radio galaxies scale in proportion to their radio luminosities, we would not have detected a polarized signal in either A2597 or A1795. We suggest that the strength of the active galactic nucleus is the fundamental property distinguishing some powerful high-redshift radio galaxies exhibiting the alignment effect from the lower power FR I radio galaxies in cooling flows that exhibit the blue lobe phenomenon. While both FR I and FR II radio sources seem to be capable of triggering star formation, FR I radio sources seem to be incapable of producing a large enough polarized luminosity to contribute significantly to the aligned continuum radiation.
• Simpson, C., Eisenhardt, P., Armus, L., Chokshi, A., Dickinson, M., Djorgovski, S. G., Elston, R., Jannuzi, B. T., McCarthy, P. J., Pahre, M. A., & Soifer, B. T. (1999). Young stars and nonstellar emission in the aligned radio galaxy 3C 256. Astrophysical Journal Letters, 525(2 PART 1), 659-672.
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  Abstract: We present ground-based images of the z = 1.824 radio galaxy 3C 256 in the standard BVRIJHK filters and an interference filter centered at 8800 Å, a Hubble Space Telescope image in a filter dominated by Lyα emission (F336W), and spectra covering rest-frame wavelengths from Lyα to [O III] λ5007. Together with published polarimetry observations, we use these to decompose the overall spectral energy distribution into nebular continuum emission, scattered quasar light, and stellar emission. The nebular continuum and scattered light together comprise half (one-third) of the V-band (K-band) light within a 4″ aperture and are responsible for the strong alignment between the optical/near-infrared light and the radio emission. The stellar emission is dominated by a population estimated to be 100-200 Myr old (assuming a Salpeter IMF) and formed in a short burst with a peak star formation rate of 1-4 × 103 M⊙ yr-1. The total stellar mass is estimated to be no more than 2 × 1011 M⊙, which is far less than other luminous radio galaxies at similar redshifts, and suggests that 3C 256 will undergo further star formation or mergers.
• Jannuzi, B. T., Bahcall, J. N., Bergeron, J., Boksenberg, A., Hartig, G. F., Kirhakos, S., Sargent, W. L., Savage, B. D., Schneider, D. P., Turnshek, D. A., Weymann, R. J., & Wolfe, A. M. (1998). The Hubble Space Telescope Quasar Absorption Line Key Project XIII. A Census of Absorption Line Systems at Low Redshift. Astrophys.J.Suppl..
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  We present a catalogue of absorption lines obtained from the analysis of theultra-violet spectra of 66 quasars. The data were acquired with the FaintObject Spectrograph of the HST as part of the Quasar Absorption Line Survey, aKey Project for the first four cycles of HST observations. This is the third ofa series of catalogues of absorption lines produced from the survey andincreases the number of quasars whose higher resolution (R=1300) spectra wehave published from 17 to 83. The general properties and execution of thesurvey are reviewed, including descriptions of the final sample of observedobjects and the algorithmic processes used to construct the catalogue. Thedetection of a single damped Ly-a system in a path length of Delta_z=49 yieldsan observed number of damped systems per unit redshift of(dN/dz)_{damp}(z=0.58)=0.020 with 95% confidence boundaries of 0.001 to 0.096systems per unit redshift. We include notes on our analysis of each of theobserved quasars and the absorption systems detected in each spectrum. Someespecially interesting systems include low redshift Ly-a absorbers suitable forextensive follow-up observations (in the spectra of TON28 and PG1216+069),possibly physically associated pairs of extensive metal line absorption systems(e.g., in the spectrum of PG0117+213), and systems known to be associated withgalaxies (e.g., in the spectrum of 3C232).[Journal_ref: Astrophys.J.Suppl. 118 (1998) 1]
• Jannuzi, B. T., Bahcall, J. N., Bergeron, J., Boksenberg, A., Hartig, G. F., Kirhakos, S., Sargent, W. L., Savage, B. D., Schneider, D. P., Turnshek, D. A., Weymann, R. J., & Wolfe, A. M. (1998). The Hubble Space Telescope Quasar absorption line key project. XIII. A census of absorption-line systems at low redshift. Astrophysical Journal, Supplement Series, 118(1), 1-125.
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  Abstract: We present a catalog of absorption lines obtained from the analysis of the ultraviolet spectra of 66 quasars. The data were acquired with the Faint Object Spectrograph of the Hubble Space Telescope (HST) as part of the Quasar Absorption Line Survey, a Key Project for the first four cycles of HST observations. This is the third of a series of catalogs of absorption lines produced from the survey and increases the number of quasars whose higher resolution (R = 1300) spectra we have published from 17 to 83. The general properties and execution of the survey are reviewed, including descriptions of the final sample of observed objects and the algorithmic processes used to construct the catalog. This database is suitable for a wide variety of studies of gaseous systems in the nearby universe. This third catalog includes 2594 absorption lines and brings the total number of absorption lines in the combined catalog to 3238. The third catalog has 878 identified Lyα lines, 27 extensive metal line systems (detected absorption lines from four or more metal ions), 88 C IV systems, and 34 O VI systems. The combined catalog contains the following numbers of extragalactic absorption lines: 1129 Lyα lines, 107 C IV systems, 41 O VI systems, 16 Lyman limit systems, and one damped Lyα system (in the spectrum of PG 0935 + 416). In addition, there are 25 pairs of identified Lyα lines that are candidate C IV doublets. Of the 122 identified C IV and candidate C IV systems in the completely identified sample of absorption lines, 24 ± 5 are expected to be chance coincidences of other lines (based upon Monte Carlo simulations). The detection of a single damped Lyα system in a path length of Δz = 49 yields an observed number of damped systems per unit redshift of (dN/dz)damp(z = 0.58) = 0.020 with 95% confidence boundaries of 0.001-0.096 systems per unit redshift. We include notes on our analysis of each of the observed quasars and the absorption systems detected in each spectrum. Some especially interesting systems include low-redshift Lyα absorbers suitable for extensive follow-up observations (e.g., in the spectra of TON 28 and PG 1216+069), possibly physically associated pairs of extensive metal line absorption systems (e.g., in the spectrum of PG 0117+213), and systems known to be associated with galaxies (e.g., in the spectrum of 3C 232). The spectra of five broad absorption line (BAL) quasars (UM 425, PG 1254+047, PG 1411+442, PG 1700+518, and PG 2112+059) can be found in this third catalog, bringing the total number of BAL quasars in the combined catalog to six (including PG 0043+039).
• Weymann, R. J., Jannuzi, B. T., Limin, L. u., Bahcall, J. N., Bergeron, J., Boksenberg, A., Hartig, G. F., Kirhakos, S., Sargent, W. L., Savage, B. D., Schneider, D. P., Turnshek, D. A., & Wolfe, A. M. (1998). The hubble space telescope quasar absorption line key project. XIV. The evolution of Lyα absorption lines in the redshift interval z = 0-1.5¹. Astrophysical Journal Letters, 506(1 PART I), 1-18.
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  Abstract: We present the results of an analysis of the rate of evolution of the Lyα absorption lines in the redshift interval 0.0 to ∼ 1.5 based upon a sample of 987 Lyα absorption lines identified in the spectra of 63 QSOs obtained with the Faint Object Spectrograph (FOS) of the Hitbble Space Telescope (HST). These spectra were obtained as part of the QSO Absorption Line Survey, an HST Key Project during the first four years of observations with the telescope. Fits to the evolution of the number of absorbers per unit redshift (dN/dz) of the form dN/dz = A × (1 + z)γ continue to yield values of γ in the range 0.1-0.3, decidedly flatter than results from ground-based data pertaining to the redshift range z > 1.7. These results are consistent with our previous results based on a much smaller sample of lines, but the uncertainties in the fit have been greatly reduced. The combination of the HST and ground-based data suggest a marked transition in the rate of evolution of the Lyα lines at a redshift of about 1.7. The 19 Lyα lines from an additional higher redshift QSO from our sample for which tentative line identifications are available (UM 18; zem = 1.89) support the suggestion of a rapid increase at around this redshift. We derive the cumulative distribution of the full sample of Lyα lines and show that the distribution in redshift can indeed be well represented by a power law of the form (1 + z)γ. For this same sample, the distribution of equivalent widths of the Lyα absorbers above a rest equivalent width of 0.1 Åis fit quite well by an exponential. Comparing samples of Lyα lines, one set of which has redshifts the same as, or very near to, the redshifts of ions from heavy elements and another set in which no ions from heavy elements have been identified, we find that the Lyα systems with heavy element detections have a much steeper slope than the high rest equivalent width portion of the Lyman-only sample. We argue that this result is not likely to be due to either line misidentification or incomplete spectral coverage. Considering the insensitivity of the equivalent width to large changes in the column density for saturated lines, we suggest that this result is probably attributable to rapid evolution of the very highest column density systems, rather than real differences in metallicity. We find evidence that the rate of evolution increases with increasing equivalent width. We compare our results for the variation of line density with redshift to recent numerical simulations of Lyα absorbers, in particular, to those of Riediger, Petitjean, & Mucket, which extend to zero redshift. We find fairly good agreement between these simulations and our results, though the rapid evolution we find in the Lyα systems containing heavy element ions is not predicted in their models. We speculate that these heavy element-containing Lyα systems involve those clouds closely associated with galaxies, whose column densities are too high and whose sizes are too small to be included in the Riediger et al. simulations. Our results for Lyα lines at the high end of our equivalent width distribution are compatible with the recent analysis of the absorber-galaxy correlation by Chen et al. For the weaker lines, however, our results suggest that whatever association exists between absorbers and galaxies is different from that for the stronger lines. We conclude with some suggestions for further observations. © 1998. The American Astronomical Society. All rights reserved.
• Weymann, R. J., Jannuzi, B. T., Lu, L., Bahcall, J. N., Bergeron, J., Boksenberg, A., Hartig, G. F., Kirhakos, S., Sargent, W. L., Savage, B. D., Schneider, D. P., Turnshek, D. A., & Wolfe, A. M. (1998). The HST Quasar Absorption Line Key Project. XIV. The Evolution of Ly-alpha Absorption Lines in the Redshift Interval 0 to 1.5. ApJ,.
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  We present an analysis of the evolution of the Ly alpha absorption lines inthe redshift interval 0.0 to \sim 1.5 based upon a sample of 987 linesidentified in the spectra of 63 QSOs obtained with the Faint ObjectSpectrograph on the Hubble Space Telescope. Fits to the number of absorbers perunit redshift dN/dz = A \times (1+z)^\gamma yield values of \gamma in the range0.1 to 0.3, decidedly flatter than results from groundbased data pertaining tothe redshift range z > 1.7. The combination of the space and groundbased datasuggest a marked transition in the rate of evolution of the Ly alpha lines at aredshift of about 1.7. The distribution in redshift is well represented by apower law and the distribution of equivalent widths above a rest equivalentwidth of 0.1 \AA is fit well by an exponential. The sample of Ly alpha systemswhich has ions from heavy elements has a much larger value of \gamma than asample of lines of comparable strength without heavy elements. We argue thatthis is not likely due to either line misidentification or incomplete spectralcoverage and suggest that it is due to rapid evolution of the very highestcolumn density systems, rather than differences in metallicity. We also findevidence that the rate of evolution increases with increasing equivalent width.We compare our results for the variation of line density with redshift torecent numerical simulations of Ly alpha absorbers, and find fairly goodagreement. Our results for the stronger Ly alpha lines in our sample arecompatible with the recent analysis of the absorber--galaxy correlation by Chenet al. 1998 but for the weaker lines our results suggest that the associationbetween absorbers and galaxies is different from that for the stronger lines.[Journal_ref: ApJ, 506 (1998) 1]
• Jannuzi, B. T., Yanny, B., & Impey, C. (1997). Hubble space telescope imaging of the host galaxies of three x-ray-selected BL lacertae objects. Astrophysical Journal Letters, 491(1 PART I), 146-152.
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  Abstract: Hubble Space Telescope (HST) WFPC-2 I-band (F814W) images of three X-ray-selected BL Lacertae objects (MS 1221.8+2452, MS 1407.9 + 5954, and MS 2143.4 + 0704) reveal that each of these BL Lac objects is well centered in an extended nebulosity that is consistent in brightness and morphology with light from an elliptical galaxy at their previously reported redshifts. Each of the detected host galaxies have radial surface-brightness profiles that are well fitted by a de Vaucouleurs law with effective radii of between 3 and 12 kpc (H0 = 50 km s-1 Mpc-1, q0 = 0). The absolute magnitudes of the host galaxies fall in the range of luminosities determined for other BL Lacertae object host galaxies, - 24.7 < M; < -23.5. In addition to allowing the measurement of the host galaxy magnitudes and radial surface brightness profiles, the HST images allow a search for substructure in the host galaxies and for the presence of close companion galaxies at spatial resolutions not yet achievable from the ground. While no evidence was found for any "bars" or spiral arms, "boxy" isophotes are present in the host galaxy of at least one of the three objects observed as part of this study (MS 2143.4+0704). The apparent magnitudes and image properties of the companions of the BL Lac objects are cataloged as part of this work. The three BL Lac objects appear to occur in diverse environments, from relative isolation (MS 1221.8+2452) to, possibly, a rich group of galaxies (MS 1407.9 + 5954). © 1997. The American Astronomical Society. All rights reserved.
• Jannuzi, B. T., Yanny, B., & Impey, C. (1997). Imaging of the Host Galaxies of Three X-Ray Selected BL Lacertae Objects. Astrophys.J., 491.
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  Hubble Space Telescope (HST) WFPC-2 I-band (F814W) images of three X-rayselected BL Lacertae objects (MS1221.8+2452, MS1407.9+5954, & MS2143.4+0704)reveal that each of these BL Lac objects is well-centered in an extendednebulosity that is consistent in brightness and morphology with being lightfrom an elliptical galaxy at the previously reported redshifts of these BL Lacobjects. Each of the detected host galaxies have radial surface brightnessprofiles that are well fit by a DeVaucouleurs' law with effective radii ofbetween 3 to 12 kpc (H_0=50 km s^{-1} Mpc^{-1}, q_0 = 0). The absolutemagnitudes of the host galaxies fall in the range -24.7 < M_I < -23.5, in therange of luminosities determined for other BL Lacertae object host galaxies. Inaddition to allowing the measurement of the host galaxy magnitudes and radialsurface brightness profiles, the HST images allow a search for substructure inthe host galaxies and the presence of close companion galaxies at spatialresolutions not yet achievable from the ground. While no evidence was found forany ``bars'' or spiral arms, ``boxy'' isophotes are present in the host galaxyof at least one of the three objects observed as part of this study(MS2143.4+0704). The apparent magnitudes and image properties of the companionsof the BL Lac objects are catalogued as part of this work. The three BL Lacsappear to occur in diverse environments, from being fairly isolated(MS1221.8+2452) to possibly being a member of a rich group of galaxies(MS1407.9+5954).[Journal_ref: Astrophys.J.491:146,1997]
• Laor, A., Jannuzi, B. T., Green, R. F., & Boroson, T. A. (1997). The ultraviolet properties of the narrow-line quasar I Zw 1. Astrophysical Journal Letters, 489(2 PART I), 656-671.
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  Abstract: I Zwicky 1 (I Zw 1) is the prototype narrow-line quasar. Its narrow-line profiles minimize blending effects and thus allow a significantly more accurate study of individual quasar emission lines. We report here the results of our study of the 1150-3250 Å emission of I Zw 1 using a high signal-to-noise (50-120) spectrum obtained with the Faint Object Spectrograph of the Bubble Space Telescope. The UV spectrum of I Zw 1 is very rich in emission lines, with essentially no wavelength range free of emission-line features. The following main new results are obtained: 1. The Mg II λ2798 doublet is partially resolved, and the measured doublet ratio is 1.2/1. This ratio verifies theoretical predictions that the Mg II λ2798 line is thermalized in the broad-line region (BLR). 2. The AI HI λ1857 doublet is clearly resolved, with a thermalized doublet ratio of 1.25/1. The line optical depth provides an upper limit to the clouds' distance from the ionizing source that is consistent with the "standard" BLR radius. 3. A weak associated UV absorption system is detected in N v (possibly also in C IV and Lyα as well), suggesting an outflow with a velocity of ∼1870 km s-1 and velocity dispersion of ≲300 km s-1. 4. Lines from ions of increasing ionization level show increasing excess blue-wing flux and an increasing line peak velocity shift, reaching a maximum blueshift of ∼2000 km s-1 for He II λ1640. This may indicate an outflowing component in the BLR, where the ionization level increases with velocity and which is visible only in the approaching direction. The highest velocity part of this outflow may produce the associated UV absorption system. 5. The small C III] λ1909 equivalent width and the small C III] λ1909/Lyα and C III] λ1909/Si III] λ1892 flux ratios indicate a typical BLR density of ne ∼ 1011 cm-3, i.e., about an order of magnitude larger than that implied by C III] λ1909 in most quasars. A BLR component with a density ne ≳ 1011 cm-3 is implied by the EW and doublet ratio of the Al III λ1857 doublet. 6. Prominent Fe II UV 191 emission is seen, together with weaker line emission at 1294 Å and 1871 Å. These three features have been proposed by Johansson & Jordan as evidence for significant Lyα pumping of the 8-10 eV levels of Fe II. 7. Significant Fe III emission is present. The Fe III UV 34 and UV 48 multiplets are clearly resolved, and Fe in UV 1, UV 47, UV 50, and UV 68 may also be present. The implications of significant Fe III emission for the conditions in the BLR need to be explored. 8. Very weak [C III] λ1907 and [Si III] λ1883 emission may be present, suggesting a narrow-lineregion component with ne ∼ 5 × 105 cm-3. The rich UV emission spectrum of I Zw 1 should serve as a useful "template" for the identification of weak features in other active galactic nuclei and as a useful benchmark for photoionization models, in particular, for models of the complex Fe II emission spectrum. © 1997. The American Astronomical Society. All rights reserved.
• Tran, H. D., Filippenko, A. V., Schmidt, G. D., Bjorkman, K. S., Jannuzi, B. T., & Smith, P. S. (1997). Probing the geometry and circumstellar environment of SN 1993J in M81. Publications of the Astronomical Society of the Pacific, 109(735), 489-503.
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  Abstract: We have monitored the polarized radiation of the Type IIb SN 1993 J in M81 over a period of 41 days, starting from 7 days after the explosion on 1993 March 27.5 (UT). Our data show clear evidence that the intrinsic continuum polarization of SN 1993J evolved from being essentially negligible on April 3-4, to a peak value of ∼1% in late April 1993, and started to decline by the middle of May. The polarized flux spectrum in late April strongly resembled spectra of Type Ib supernovae, with prominent He I lines but redshifted ∼3380 km s-1 relative to the total flux spectrum. These data are consistent with models of Höflich; they suggest that the polarization was most likely produced by either an asymmetric helium core configuration of material and/or flux, or scattering from an asymmetric circumstellar distribution of dusty material. A combination of electron and dust scattering, as well as a clumpy or stratified distribution of the emitting gas, are possible as the polarization mechanism of the continuum and emission lines. The latter interpretation is supported by the fact that 1-2 months after the explosion, the observed rotations of polarization position angle across prominent line features remain even after correction for effects of interstellar polarization. This indicates that emission lines of He I, Fe II, [O I], and H are all intrinsically polarized at position angles different from that of the continuum, with the non-Balmer lines generally being most highly polarized. If the supernova had an oblate geometry, our data are consistent with a small viewing angle (i.e., more or less equator-on), although the degree of asphericity that gave rise to the polarization at early times is probably smaller (minor to major axis ratio ≳0.7) than has been previously suggested.
• Yanny, B., Jannuzi, B. T., & Impey, C. (1997). HST Imaging of the BL Lacertae Object OJ 287. Astrophys.J., 484.
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  Hubble Space Telescope WFPC-2 I-band (F814W) images of the BL Lacertae objectOJ 287 and the surrounding field are presented. We find evidence of associatedextended nebulosity near OJ 287, as well as a small nebulosity to the West,which may be spatially coincident with the position of previously observedradio emission. The brightness of a host galaxy is difficult to determine dueto the brightness of the active nucleus, but it lies in the range -21.5 > M_R >-23.1 (H_0 = 100 km s^{-1} Mpc^{-1}, q_0 = 0). No evidence is seen for thepreviously reported optical ``jet'' at position angle 220 degrees to a surfacebrightness limit of I = 24.3 mag arcsec^{-2}. There are several resolved andunresolved objects within 17'' of OJ~287 in the field to limits of I=25 (pointsource 5\sigma detections). The magnitudes and relative positions of theseobjects are reported. An offset in the centroid position between the OJ 287point source and the underlying nebulosity reported by Wurtz, Stocke and Yee isconfirmed and measured to be about 0.4 (1.2h^{-1} kpc at the redshift ofOJ~287). This offset is tentatively interpreted as evidence for recent mergeractivity rather than a sign of gravitational microlensing.[Journal_ref: Astrophys.J.484:L113-L116,1997]
• Yanny, B., Jannuzi, B. T., & Impey, C. (1997). Hubble Space Telescope imaging of the BL lacertae object OJ 287. Astrophysical Journal Letters, 484(2 PART II), L113-L116.
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  Abstract: Hubble Space Telescope WFPC-2 I-band (F814W) images of the BL Lacertae object OJ 287 and the surrounding field are presented. We find evidence of associated extended nebulosity near OJ 287, as well as a small nebulosity to the west, which may be spatially coincident with the position of previously observed radio emission. The brightness of a host galaxy is difficult to determine because of the brightness of the active nucleus, but it lies in the range -21.5 > MR > -23.1 (H0 = 100 km s-1 Mpc-1, q0 = 0). No evidence is seen for the previously reported optical "jet" at position angle 220° to a surface brightness limit of I = 24.3 mag arcsec-2. There are several resolved and unresolved objects within 17″ of OJ 287 in the field to limits of / = 25 (point source 5 σ detections). The magnitudes and relative positions of these objects are reported. An offset in the centroid position between the OJ 287 point source and the underlying nebulosity reported by Wurtz, Stocke, and Yee is confirmed and measured to be about 0″.4 (1.2 h-1 kpc at the redshift of OJ 287). This offset is tentatively interpreted as evidence for recent merger activity rather than as a sign of gravitational microlensing. © 1997. The American Astronomical Society. All rights reserved.
• Bahcall, J. N., Bergeron, J., Boksenberg, A., Hartig, G. F., Jannuzi, B. T., Kirhakos, S., Sargent, W. L., Savage, B. D., Schneider, D. P., Turnshek, D. A., Weymann, R. J., & Wolfe, A. M. (1996). The HST Quasar Absorption Line Key Project VII. Absorption Systems at $z_{\rm abs} \leq 1.3$. Astrophys.J., 19-49.
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  We present evidence that clumps of \lya lines are physically associated withabout half of the extensive metal-line systems (absorption systems with four ormore observed metal-line species) found in this paper, demonstrate that allfour \lylimit systems discussed here correspond to extensive metal-lineabsorption systems, and present an extraordinary pair of extensive metal-lineabsorption systems within 2000~km/s of each other at $z~=~0.95$ that areprobably an early manifestation of large scale structure. These results areobtained using ultraviolet spectra, taken with the higher-resolution gratingsof the Faint Object Spectrograph of the Hubble Space Telescope, for fourquasars with emission-line redshifts between 1.0 and 1.3. We also determine theevolution of \lya absorption lines at redshifts less than 1.3 by combining theresults for 13 smaller redshift quasars discussed in Paper I of this serieswith the 4 moderate redshift quasars analyzed in the present paper. For $z_{\rmabs}~\leq~1.3$, the density of \lya lines with equivalent widths greater than0.24~\AA\ is adequately fit by $\left(dN/dz\right) =\left(dN/dz\right)_0\cdot(1 + z)^\gamma$ with $(dN/dz)_0 = 24.3 \pm 6.6$ \lya lines per unitredshift, and $\gamma = 0.58 \pm 0.50$ (1-$\sigma$ uncertainties). This rate ofevolution at low redshifts is less than the evolutionary rate inferred fromseveral different ground-based data samples that pertain to high redshifts. Theobserved gaseous structures at redshifts of $0.5$ to $1.0$ with velocitydispersions of $6 \times 10^2$ \kms to $1.4 \times 10^3$ \kms (or velocityspans of $1.2 \times 10^3$ \kms to $3 \times 10^3$ \kms) constitute aconstraint on cosmological models of structure formation.[Journal_ref: Astrophys.J. 457 (1996) 19-49]
• Bahcall, J. N., Bergeron, J., Boksenberg, A., Hartig, G. F., Jannuzi, B. T., Klrhakos, S., Sargent, W. L., Savage, B. D., Schneider, D. P., Turnshek, D. A., Weymann, R. J., & Wolfe, A. M. (1996). The hubble space telescope quasar absorption line key project. VII. Absorption systems at z_abs ≤ 1.3. Astrophysical Journal Letters, 457(1 PART I), 19-49.
• Jannuzi, B. T., Hartig, G. F., Kirhakos, S., Sargent, W. L., Turnshek, D. A., Weymann, R. J., Bahcall, J. N., Bergeron, J., Boksenberg, A., Savage, B. D., Schneider, D. P., & Wolfe, A. M. (1996). The HST Quasar Absorption Line Key Project XII. The Unusual Absorption Line System in the Spectrum of PG 2302+029 ---Ejected or Intervening?. Astrophys.J..
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  We report the discovery of a high-ionization broad absorption line system ata redshift of z_abs=0.695 in the spectrum of the z_em=1.052 radio-quiet quasarPG 2302+039. Broad absorption with FWHM from 3,000 to 5,000 km/s is detectedfrom C IV, N V, and O VI in HST Faint Object Spectrograph spectra of thequasar. A narrow line system (FWHM approximately 250 km/s) at z_abs=0.7016 isresolved from the broad blend and includes absorption by Ly-alpha and the C IV,N V, and O VI doublets. No absorption by low-ionization metal species (e.g. SiII and Mg II) is detected in the HST or ground-based spectra for either thebroad or the narrow system. The centroids of the broad system lines aredisplaced by approximately 56,000 km/s to the blue of the quasar's broademission lines. The reddest extent of the broad line absorption is more than50,000 km/s from the quasar. The properties of this system are unprecedentedwhether it is an intervening or an ejected system.[Journal_ref: Astrophys.J. 470 (1996) L11-L14]
• Jannuzi, B. T., Hartig, G. F., Kirhakos, S., Sargent, W. L., Turnshek, D. A., Weymann, R. J., Bahcall, J. N., Bergeron, J., Boksenberg, A., Savage, B. D., Schneider, D. P., & Wolfe, A. M. (1996). The Hubble Space Telescope quasar absorption line key project: The unusual absorption-line system in the spectrum of PG 2302+029 - Ejected or intervening?. Astrophysical Journal Letters, 470(1 PART II), L11-L14.
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  Abstract: We report the discovery of a high-ionization broad absorption line system at a redshift of zabs = 0.695 in the spectrum of the zem = 1.052 radio-quiet quasar PG 2302+029. Broad absorption with FWHM from 3000 to 5000 km s-1 is detected from C IV, N V, and O VI in Hubble Space Telescope (HST) Faint Object Spectrograph spectra of the quasar. A narrow-line system (FWHM ∼ 250 km s-1) at zabs = 0.7016 is resolved from the broad blend and includes absorption by Lyα and the C IV, N V, and O VI doublets. No absorption by low-ionization metal species (e.g., Si II and Mg II) is detected in the HST or ground-based spectra for either the broad or the narrow system. The centroids of the broad system lines are displaced by ∼56,000 km s-1 to the blue of the quasar's broad emission lines. The reddest extent of the broad-line absorption is more than 50,000 km s-1 from the quasar. The properties of this system are unprecedented, whether it is an intervening or an ejected system. © 1996. The American Astronomical Society. All rights reserved.
• Kaspi, S., Smith, P. S., Maoz, D., Netzer, H., & Jannuzi, B. T. (1996). Measurement of the Broad Line Region Size in Two Bright Quasars. Astrophys.J..
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  We present 4 years of spectrophotometric monitoring data for two radio-quietquasars, PG 0804+762 and PG 0953+414, with typical sampling intervals ofseveral months. Both sources show continuum and emission line variations. Thevariations of the H$\beta$ line follow those of the continuum with a time lag,as derived from a cross-correlation analysis, of 93$\pm$30 days for PG 0804+762and 111$\pm$55 days for PG 0953+414. This is the first reliable measurement ofsuch a lag in active galactic nuclei with luminosity $L>10^{45}$ erg s$^{-1}$.The broad line region (BLR) size that is implied is almost an order ofmagnitude larger than that measured in several Seyfert 1 galaxies and isconsistent with the hypothesis that the BLR size grows as $L^{0.5}$.[Journal_ref: Astrophys.J. 471 (1996) L75]
• Kaspi, S., Smith, P. S., Maoz, D., Netzer, H., & Jannuzi, B. T. (1996). Measurement of the broad-line region size in two bright quasars. Astrophysical Journal Letters, 471(2 PART II), L75-L78.
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  Abstract: We present 4 years of spectrophotometric monitoring data for two radio-quiet quasars, PG 0804+762 and PG 0953+414, with typical sampling intervals of several months. Both sources show continuum and emission-line variations. The variations of the Hβ line follow those of the continuum with a time lag, as derived from a cross-correlation analysis, of 93 ± 30 days for PG 0804+762 and 111 ± 55 days for PG 0953+414. This is the first reliable measurement of such a lag in active galactic nuclei with luminosity L > 1045 ergs s-1. The broad-line region (BLR) size that is implied is almost an order of magnitude larger than that measured in several Seyfert 1 galaxies and is consistent with the hypothesis that the BLR size grows as L0.5. © 1996. The American Astronomical Society. All rights reserved.
• McNamara, B. R., Jannuzi, B. T., Elston, R., Sarazin, C. L., & Wise, M. (1996). U-band polarimetry of the radio-aligned optical continuum in the abell 1795 cluster central galaxy. Astrophysical Journal Letters, 469(1 PART I), 66-72.
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  Abstract: We have obtained U-band polarimetry of the lobes of blue optical continuum located along the z = 0.063 F-R I radio source in the Abell 1795 cluster central galaxy. We find an upper limit to the degree of polarization of the light emitted from the lobes of less than 7%. The accuracy of this measurement is limited by the presence of diluting background starlight. This limit is inconsistent with the lobes being scattered light that originated in an obscured, anisotropically radiating nucleus, unless the radiation is beamed and is viewed at an angle ≲22° to the line of sight, which is unlikely. The absence of a polarized signal and detailed correspondence between the radio lobes and optical lobes is inconsistent with synchrotron light. The blue optical lobes are probably regions of recent star formation. If a burst of star formation were triggered by the expanding radio lobes, the age of the burst population should be ∼107 yr. Then, the star formation rate in both lobes, assuming the local IMF, is ∼20 M⊙ yr-1, and the stellar mass of the lobes is ∼108 M⊙. The material fueling the star formation and the radio source may have originated from the cooling flow or accretion from one or more gaseous cluster galaxies. © 1996. The American Astronomical Society. All rights reserved.
• Mcnamara, B. R., Wise, M., Sarazin, C. L., Jannuzi, B. T., & Elston, R. (1996). Optical structure in the abell 1795 cluster central galaxy: Evidence for stripping and deflection of radio jets. Astrophysical Journal Letters, 466(1 PART II), L9-L12.
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  Abstract: We have obtained a deep U-band image of the central ∼100 kpc of the Abell 1795 cluster central galaxy. This image shows several faint (μu ∼ 23-24 mag arcsec-2), thin structures, of unknown origin, that extend between 20 and 70 kpc into the galaxy's halo. Some are located along filaments of nebular line emission. Two structures, detected in the ground-based U-band image and in V and R images obtained with the WFPC2 on the Hubble Space Telescope (HST), extend toward faint, disturbed galaxies. The structures may be stripped stellar and gaseous debris from several sub-L* galaxies that are interacting with the central dominant galaxy. The lobes of blue optical continuum found earlier along the galaxy's radio lobes are resolved into bright knots on the HST images. The knots are probably composed of young stars. A dust lane lies along the edges of the radio jets and along the edge of the northern radio lobe. The dust and associated cold, dense gas may have deflected the radio jets and may have become entrained along the radio jets and lobes. The images strengthen recent arguments for radio-triggered star formation in A1795, and they raise the possibility that some of the accreted gas may have been stripped from neighboring galaxies. © 1996. The American Astronomical Society. All rights reserved.
• Sarajedini, V. L., Green, R. F., & Jannuzi, B. T. (1996). Requirements for investigating the connection between Lyman-α absorption clouds and the large-scale distribution of galaxies. Astrophysical Journal Letters, 457(2 PART I), 542-550.
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  Abstract: We model the requirements on observational data that would allow an accurate determination of the degree of association between Lyman-α absorbers and peaks in the redshift distribution of galaxies (large-scale structures like clusters of galaxies). We compare simulated distributions of low-redshift Lyman-α absorption systems, constrained to be consistent with the distribution observed with HST, with the large-scale distribution of galaxies determined from pencil-beam redshift surveys. We estimate the amount of observational data required from catalogs of Lyman-α absorbers and galaxies to allow a statistically significant test of the association of absorbers with large-scale structures of galaxies. We find that for each line of sight observed for Lyα absorption lines (assuming that the entire redshift range out to z ≃ 0.4 is observable), redshifts must be obtained for at least ∼18 galaxies brighter than MB = -18 and having redshifts between 0.2 and 0.4. Based on the redshift surveys used in this study, a search radius of ∼ 10′ from the quasar line of sight is required. This will ensure that all peaks in the galaxy redshift distribution are represented by at least one galaxy in the observed sample. If Lyman-α absorbers are intrinsically uncorrelated with galaxies, we find that about eight lines of sight must be observed to show that the distributions are different at the 95% confidence level. However, if a fraction of the Lyman-α absorbers are distributed with the peaks in the galaxy distribution, ∼38 lines of sight must be mapped for the distribution of both Lyman-α absorbers and galaxies in order to determine the fraction of absorbers distributed with the peaks of the galaxy distribution to an accuracy of 10%. © 1996. The American Astronomical Society. All rights reserved.
• Jannuzi, B. T., Elston, R., Schmidt, G. D., Smith, P. S., & Stockman, H. S. (1995). Detection of extended polarized ultraviolet radiation from the z = 1.82 radio galaxy 3C 256. Astrophysical Journal Letters, 454(2 PART 2), L111-L115.
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  Abstract: We have detected spatially extended linear polarized UV emission from the high-redshift radio galaxy 3C 256 (z = 1.82). A spatially integrated (7″.8 diameter aperture) measurement of the degree of polarization of the V-band (rest frame 0.19 μm) emission yields a value of 16.4% (±2.2%) with a position angle of 42°.4 (±3°.9), orthogonal to the position angle on the sky of the major axis of the extended emission. The peak emission measured with a 3″.6 diameter circular aperture is 11.7% (±1.5%) polarized with a position angle of 42°.4 (±3°.6). An image of the polarized flux is presented, clearly displaying that the polarized flux is extended and present over the entire extent of the object. While it has been suggested that the UV continuum of 3C 256 might be due to star formation (see paper by Elston) or a protogalaxy (see paper by Eisenhardt & Dickinson) based on its extremely blue spectral energy distribution and similar morphology at UV and visible wavelengths, we are unable to reconcile the observed high degree of polarization with such a model. While the detection of polarized emission from HZRGs has been shown to be a common phenomena, 3C 256 is only the third object for which a measurement of the extended polarized UV emission has been presented. These data lend additional support to the suggestion first made by di Serego Alighieri and collaborators that the "alignment effect," the tendency for the extended UV continuum radiation and line emission from HZRGs to be aligned with the major axis of the extended radio emission, is in large part due to scattering of anisotropic nuclear emission.
• Laor, A., Bahcall, J. N., Jannuzi, B. T., Schneider, D. P., & Green, R. F. (1995). The ultraviolet emission properties of 13 quasars. Astrophysical Journal, Supplement Series, 99(1), 1-26.
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  Abstract: We analyze the ultraviolet (UV) emission properties of a sample of 13 quasars studied with the Hubble Space Telescope (HST). The quasars redshifts are in the range 0.165 ≤ z ≤ 2.06, and their absolute magnitudes are in the range -30.1 ≤ Mv ≤ -24.4. The data were obtained with the Faint Object Spectrograph and have a spectral resolution of ∼ 1300 and a signal-to-noise ratio S/N ∼ 20 per resolution element. We include in the analysis optical spectra covering Hβ and the narrow [O III] λλ4959, 5007 doublet for 7 of the 13 quasars. We find that the profile of the O VI + Lyβ blend can be reproduced well using a "symmetric Lyα" template. The remarkable similarity of the Lyα and O VI profiles rules out significant line emission from a high-velocity and high ionization level component inner to the broad line region (the very broad line region, VBLR), suggested in a number of earlier studies of active galactic nuclei. The Hβ line profile is in most cases different from the Lyα and C IV profiles, which indicates that Hβ and the bulk of the UV lines are not produced by the same distribution of clouds in the broad line region (BLR). The following previously unobserved emission features were found in our spectra: (1) λ ∼ 832 Å, most likely O II λ833 + O III λλ833, 835 emission. (2) λ ∼ 1070 Å, most likely an Fe II multiplet. (3) λ ∼ 1175 Å, probably due to C III*. Possible implications of these features are briefly mentioned. The narrow [O III]-like components in both Lyα and C III] are generally significantly weaker than expected based on the observed [O III] λ5007 flux. This result is consistent with the 1993 finding of Wills et al. and implies that the narrow line region (NLR) in quasars produces weaker UV/optical emission line ratios compared with the NLR in Seyfert 2 galaxies. A study of a combined sample of 18 quasars observed with HST (including Paper I) suggests that the equivalent widths of all lines, excluding N V, decreases with increasing continuum luminosity. The slopes of the EW versus luminosity relations for the different lines do not clearly favor explanations which invoke either a decrease in ionization parameter, or softening of the ionizing continuum, with increasing luminosity, as the single physical mechanism producing this effect. We verify with our larger sample the conclusions of Paper I concerning the presence of N III λ991, C III λ977, and Lyβ, the similarity of the C IV λ1549 and Lyα profiles, and the generally small velocity shifts of the broad line peaks relative to the peak of [O III] λ5007. In particular, we find a very small average shift for O VI (120 ± 270 km s-1 relative to Lyα), which does not support the suggestion made in earlier studies that the line peak velocity shift increases systematically with ionization level. The software developed for the line profile fitting and template deblending is available upon request. © 1995. The American Astronomical Society. All rights reserved.
• Stengler-Larrea, E. A., Boksenberg, A., Steidel, C. C., Sargent, W. L., Bahcall, J. N., Bergeron, J., Hartig, G. F., Jannuzi, B. T., Kirhakos, S., Savage, B. D., Schneider, D. P., Turnshek, D. A., & Weymann, R. J. (1995). The Hubble Space Telescope quasar absorption line key project. V. Redshift evolution of Lyman limit absorption in the spectra of a large sample of quasars. Astrophysical Journal Letters, 444(1), 64-70.
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  Abstract: Using a sample of 119 QSOs, containing objects we have selected having previously available high quality ground-based and IUE spectral observations, together with Hubble Space Telescope (HST) observations of 26 QSOs from Bahcall et al. (1993, 1995) and Impey et al. (1995) and new optical observations of 41 objects by Steidel & Sargent (1995), we study the redshift evolution of Lyman limit absorption systems (LLSs; τ > 1.0) over the redshift range 0.32 ≤ zLLS < 4.11. The HST observations significantly improve the determination of the low redshift (0.4 < zLLS < 1.4) distribution. We find the effect which may have been responsible for the apparent strong evolution at zLLS > 2.5 found by Lanzetta (1991), which led him to consider a broken, not single, power law as a better description of the redshift distribution of LLSs. After removing objects which may bias our sample, leaving a total of 169 QSOs, we find the distribution is well described by a single power law, and obtain for the number density as a function of redshift the form N(z) = N0(1 + z)γ with γ = 1.50 ± 0.39 and N0 = 0.25-0.10+0.17, consistent with a constant comoving density of absorbers in a Friedmann universe with q0 = 0 but indicating evolution if q0 = 1/2.
• Bergeron, J., Petitjean, P., Sargent, W. L., Bahcall, J. N., Boksenberg, A., Hartig, G. F., Jannuzi, B. T., Kirhakos, S., Savage, B. D., Schneider, D. P., Turnshek, D. A., Weymann, R. J., & Wolfe, A. M. (1994). The Hubble space telescope quasar absorption line key project. VI. Properties of the metal-rich systems. Astrophysical Journal Letters, 436(1), 33-43.
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  Abstract: We present an analysis of the properties of a sample of 18 metal-rich, low-redshift zabs ≪ zem absorbers seen in low- and medium-resolution spectra obtained for the Quasar Absorption Line Key Project with the Hubble Space Telescope Faint Object Spectrograph. For most of the C IV and Lyman-limit systems, observations in the optical wavelength range of the expected associated Mg II absorption are available. As at high redshift (z ∼ 2), there are two subclasses of absorbers which are characterized by the presence or absence of Mg II absorption. However, some low-redshift Mg II and Fe II absorptions originate from regions optically thin to UV ionizing photons and thus, at low redshift, the low-ionization systems do not always trace high opacities, as is the case at high redshift. This implies that the mean ionization state of metal-rich, optically thin absorbing clouds falls with decreasing redshift, which is consistent with the hypothesis that the gas is photoionized by the metagalactic UV background radiation field. Two main constraints are derived from the analysis of the Lyman-limit sample, assuming photoionization models are valid. First, a low opacity to ionizing photons (τLL ≲ 1), as observed for several Mg II-Fe II systems at z ∼ 0.5, sets limits on the ionization level of hydrogen, thus on the total hydrogen column density and the heavy element abundances, [Z/H] ∼ -0.5 to -0.3. Second, the dimensions of individual Mg II clouds are smaller than at high redshift by a factor 3-10. At z ≳ 0.6, the O VI absorption doublet is detected in four of the five zabs ≪ zem systems for which the O VI wavelength range has been observed, whereas the associated N V doublet is detected in only two cases. This suggests that the presence of a high-ionization O VI phase is a general property of z ∼ 0.6-1 absorption systems, as is also probably the case at high redshift. These O VI absorbers can be ionized by the UV metagalactic field if their density is low, nH ≲ 3 × 10-4 cm-3. The O VI phase would then be a homogeneous region of large extent, r ≳ 50 kpc. A detailed photoionization model of the zabs = 0.791 absorber toward PKS 2145 + 06 confirms the properties derived from the Mg II, C IV, O VI, and Lyman-limit samples. The galaxy causing this extensive metal-line absorption system has been identified, and its possible contribution to the UV ionizing flux does not substantially modify the value of the derived parameters. The heavy element abundances are about half the solar values. The O VI region has a density about 20 times lower than the Mg II clouds and a size of ∼ 70 kpc. Alternatively, the high-ionization phase could be collisionally ionized and trace gas associated with a possible group of galaxies at the absorber redshift.
• Espey, B. R., Turnshek, D. A., Lee, L., Bergeron, J., Boksenberg, A., Hartig, G. F., Jannuzi, B. T., Sargent, W. L., Savage, B. D., Schneider, D. P., Weymann, R. J., & Wolfe, A. M. (1994). The HST quasar absorption line key project. IX. An emission-line study of PG 2251+113. Astrophysical Journal Letters, 434(2), 484-492.
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  Abstract: We present HST and quasi-simultaneous ground-based observations of the z = 0.3252 QSO PG 2251+113. We find a correlation between line widths and the critical density for de-excitation of the forbidden emission lines observed in this object. We can show that this correlation also applies to the semiforbidden and possibly also the permitted lines which arise in the broad emission-line region. While this result was predicted from statistical studies, it has never previously been shown to hold in detail in any individual object. This relationship between the narrow and broad emission-line regions may help constrain dynamical models of both regions. We examine the implications of this result for a simple radial infall model of the emitting gas developed to explain the origin of narrow-line profiles.
• Jannuzi, B. T., Elston, R., Schmidt, G. D., Smith, P. S., & Stockman, H. S. (1994). The Hidden Nuclear Spectrum of the Luminous IRAS Source FSC10214$+$4724. Astrophys.J..
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  Optical spectropolarimetry of the luminous IRAS source FSC10214$+$4724(z$=2.286$) reveals that the strong (\twid17\%) linear polarization detected byLawrence \etal\/ is shared by both the narrow UV emission lines and theunderlying continuum. This observation and the brightness of the source ruleout synchrotron emission and dichroic extinction by dust as the polarizingmechanism, leaving scattering as the only plausible cause of the polarizedemission. The narrowness of the lines requires that the scatterers be dustgrains or cool ($
• Jannuzi, B. T., Elston, R., Schmidt, G. D., Smith, P. S., & Stockman, H. S. (1994). The hidden nuclear spectrum of the luminous IRAS source FSC 10214+4724. Astrophysical Journal Letters, 429(2 PART 2), L49-L52.
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  Abstract: Optical spectropolarimetry of the luminous IRAS source FSC 10214+4724 (z = 2.286) reveals that the strong (∼17%) linear polarization detected by Lawrence et al. is shared by both the narrow UV emission lines and the underlying continuum. This observation and the brightness of the source rule out synchrotron emission and dichroic extinction by dust as the polarizing mechanism, leaving scattering as the only plausible cause of the polarized emission. The narrowness of the lines requires that the scatterers be dust grains or cool (below 1.6 × 104 K) electrons. We can recover the spectrum that is incident on the scattering medium provided we make some reasonable assumptions regarding the source geometry. The scattered UV spectrum has a power-law index α of -1.2 ± 0.6 (Fv ∝ vα), steeper than would be expected from a young burst of star formation but similar to that of many AGNs.
• Jannuzi, B. T., Smith, P. S., & Elston, R. (1994). The optical polarization properties of X-ray-selected BL Lacertae objects. Astrophysical Journal Letters, 428(1), 130-142.
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  Abstract: We discuss the optical polarization properties of X-ray-selected BL Lacertae objects (XSBLs) as determined from 3 yr of monitoring the polarization of 37 BL Lac objects and candidates. The observed objects include a complete X-ray flux limited sample drawn from the Einstein Extended Medium Sensitivity Survey (EMSS). We find that the majority of the XSBLs classified solely on the appearance of their optical spectra are true members of the class of BL Lacertae objects since they possess intrinsically polarized and variable continua. The duty cycle of polarized emission (fraction of time spent with the degree of polarization greater than 4%) from XSBLs is 44%. The maximum observed percent polarizations are of order 10%, considerably below the maximum values observed for radio-selected BL Lacertae objects and blazars (30%-40%). While XSBLs have variable polarized emission, the majority (≈85%) have preferred polarization position angles on timescales at least as long as 3 yr. This reflects stability in the geometry of the region emitting the linearly polarized optical emission. We describe the spectral dependence of the degree of polarization and discuss some of the possible mechanisms producing the observed characteristics. While dilution of the polarized emission by the host galaxy starlight is certainly present in some objects, we demonstrate that the average polarization properties of XSBLs derived from our observations are not drastically affected by this effect. While the confirmed BL Lac objects are shown to be photometric variables, the objects in our monitored sample did not display the larger than 1 mag variations generally used to characterize the optical variability of radio-selected BL Lacertae objects or blazars in general.
• Laor, A., Bahcall, J. N., Jannuzi, B. T., Schneider, D. P., Green, R. F., & Hartig, G. F. (1994). The Ultraviolet Emission Properties of Five Low-Redshift Active Galactic Nuclei at High Signal to Noise and Spectral Resolution. Astrophys.J., 110-125.
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  We analyze the ultraviolet (UV) emission line and continuum properties offive low-redshift active galactic nuclei (four luminous quasars:PKS~0405$-$123, H1821+643, PG~0953+414, and 3C273, and one bright Seyfert 1galaxy: Mrk~205). The HST spectra have higher signal-to-noise ratios (typically$\sim 60$ per resolution element) and spectral resolution ($R = 1300$) than allpreviously- published UV spectra used to study the emission characteristics ofactive galactic nuclei. We include in the analysis ground-based optical spectracovering \hb\ and the narrow [O III] $\lambda\lambda$4959,5007 doublet. Thefollowing new results are obtained: \lyb/\lya=0.03$-$0.12 for the four quasars,which is the first accurate measurement of the long-predicted \lyb\ intensityin QSOs. The cores of \lya\ and C~IV are symmetric to an accuracy of betterthan 2.5% within about 2000 km s$^{-1}$ of the line peak. This high degree ofsymmetry of \lya\ argues against models in which the broad line cloud velocityfield has a significant radial component. The observed smoothness of the \lya\and C~IV line profiles requires at least $\sim 10^4$ individual clouds if bulkvelocity is the only line-broadening mechanism. The overall similarity of the\lya\ and C IV $\lambda$1549 profiles rules out models for the broad lineregion (BLR) with a radial distribution of virialized....[Journal_ref: Astrophys.J. 420 (1994) 110-125]
• Laor, A., Bahcall, J. N., Jannuzi, B. T., Schneider, D. P., Green, R. F., & Hartig, G. F. (1994). The ultraviolet emission properties of five low-redshift active galactic nuclei at high signal-to-noise ratio and spectral resolution. Astrophysical Journal Letters, 420(1), 110-135.
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  Abstract: We analyze the ultraviolet (UV) emission line and continuum properties of five low-redshift active galactic nuclei (four luminous quasars: PKS 0405-123, H1821+643, PG 0953+414, and 3C 273, and one bright Seyfert 1 galaxy: Mrk 205). The HST spectra have higher signal-to-noise ratios (typically ∼60 per resolution element) and spectral resolution (R = 1300) than all previously published UV spectra used to study the emission characteristics of active galactic nuclei. We include in the analysis ground-based optical spectra covering Hβ and the narrow [O III] λλ4959, 5007 doublet. The following new results are obtained: Lyβ/Lyα = 0.03-0.12 for the four quasars, which is the first accurate measurement of the long-predicted Lyβ intensity in QSOs. The cores of Lyα and C IV are symmetric to an accuracy of better than 2.5% within about 2000 km s-1 of the line peak. This high degree of symmetry of Lyα argues against models in which the broad line cloud velocity field has a significant radial component. The observed smoothness of the Lyα and C IV line profiles requires at least ∼ 104 individual clouds if bulk velocity is the only line-broadening mechanism. The overall similarity of the Lyα and C IV λ1549 profiles rules out models for the broad-line region (BLR) with a radial distribution of virialized clouds having an ionization parameter U ∝ Radius-1. The measured high values of O VI λ1034/Lyα and low values of C III λ977/O VI γ1034 imply a BLR component with U ∼ 1. The excess red-wing flux in O VI relative to Lyα suggests the presence of an inner, high-velocity, optically thin component with U > 1 in the BLR. The N v/Lyα ratio is 0.135 ± 0.01 for the four quasars, which may be an indication of higher than solar N abundance and metallicity. The maximum contribution of a narrow ([O III]-like) component is about 3%-6% of the total broad-line flux; this limit is generally highest for C III]. This result constrains the covering factor of the narrow line region or indicates the presence of dust. An unresolved component having full width at half-maximum less than 230 km s-1 typically contributes less than 0.5% of the observed broad lines flux. The HST data permit the first relatively accurate measurements of the Lyγ, C III λ977, S VI λλ933, 945, and the N III λ991 emission lines, as well as the measurement of a number of other weak or strongly blended lines at λ > 1216 Å. In agreement with observations of high-redshift quasars, the peaks of Lyα, C IV, and C III] are blueshifted by ∼ 200 km s-1 relative to [O III] λ5007, while He II λ1640 is shifted by about 500 km s-1. The low ionization lines, Mg II, Hβ, and O I λ1304, are in most cases only marginally shifted to the red.
• Maoz, D., Smith, P. S., Jannuzi, B. T., Kaspi, S., & Netzer, H. (1994). How fast do quasar emission lines vary? First results from a program to monitor the Balmer lines of the Palomar-Green Quasars. Astrophysical Journal Letters, 421(1), 34-45.
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  Abstract: We have monitored spectrophotometrically a subsample (28) of the Palomar-Green Bright Quasar Sample for 2 years in order to test for correlations between continuum and emission-line variations and to determine the timescales relevant to mapping the broad-line regions of high-luminosity AGNs. Half of the quasars showed optical continuum variations with amplitudes in the range 20-75%. The rise and fall time for the continuum variations is typically 0.5-2 years. In most of the objects with continuum variations, we detect correlated variations in the broad Hα and Hβ emission lines. The amplitude of the line variations is usually 2-4 times smaller than the optical continuum fluctuations. We present light curves and analyze spectra for six of the variable quasars with 1000-10,000 Å luminosity in the range of 0.3-4 × 1045 ergs s-1. In four of these objects the lines respond to the continuum variations with a lag that is smaller than or comparable to our typical sampling interval (a few months). Although continued monitoring is required to confirm these results and increase their accuracy, the present evidence indicates that quasars with the above luminosities have broad-line regions smaller than about 1 lt-yr. Two of the quasars monitored show no detectable line variations despite relatively large-amplitude continuum changes. This could be a stronger manifestation of the low-amplitude line-response phenomenon we observe in the other quasars.
• Smith, P. S., Schmidt, G. D., Jannuzi, B. T., & Elston, R. (1994). The synchrotron continuum of the highly polarized quasar PKS 1546+027. Astrophysical Journal Letters, 426(2), 535-541.
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  Abstract: The wavelength dependence of optical linear polarization of the highly polarized quasar (HPQ) PKS 1546+027 is investigated for the first time. Both spectropolarimeiry and broad-band filter polarimetry are presented for a period when the object was undergoing a strong outburst in flux and polarization. The rapid polarization variations observed argues that an optically thin synchrotron-emitting region, similar in polarization properties to BL Lacertae objects and optically violent variable (OVV) quasars, is the major source of polarized flux from this object. The continuum polarization increases dramatically with wavelength and is about twice as high at 8000 Å than at 4000 Å. Spectropolarimetry reveals that the emission-line flux from PKS 1546+027 dilutes the continuum polarization and is probably unpolarized. There is no evidence for any variation in polarization position angle with wavelength. The polarized flux spectrum is well-represented by a steep power law with a spectral index of -2.2, supporting the view that the polarized flux has a nonthermal origin. The observed polarization properties of PKS 1546+027 are consistent with a model that has been proposed to explain the optical to ultraviolet continua of several OVVs. In this model the optical to near-UV spectral flux distribution is a combination of light from a polarized synchrotron component plus an unpolarized component with spectral properties typical of low-polarization quasars.
• Turnshek, D. A., Espey, B. R., Kopko Jr., M., Rauch, M., Weymann, R. J., Jannuzi, B. T., Boksenberg, A., Bergeron, J., Hartig, G. F., Sargent, W. L., Savage, B. D., Schneider, D. P., & Wolfe, A. M. (1994). The HST quasar absorption line key project. IV. HST faint object spectrograph and ground-based observations of the unusual low-redshift broad absorption-line quasi-stellar object PG 0043 + 039. Astrophysical Journal Letters, 428(1), 93-112.
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  Abstract: HST FOS observations have shown that the spectrum of the low-redshift (zem ≃ 0.384) QSO PG 0043 + 039 exhibits weak broad absorption lines (BALs). The BALs were discovered during the course of UV spectrophotometry made for the HST Quasar Absorption Line Key Project. The HST data are analyzed along with ground-based optical and IUE spectrophotometry. The object is found to have a number of atypical properties relative to normal non-BAL QSOs. For example, the object is one of the strongest Fe II emitters known, narrow-line [O III] and [O II] emission is not detected, and the C IV broad emission line is exceedingly weak. The observed continuum is atypical in the sense that it is much weaker than that of a normal optically selected QSO at rest wavelengths ≲ 2200 Å. Intrinsic reddening of E(B - V) ≃ 0.11 mag by dust similar to that found in the SMC at the redshift of PG 0043 + 039 conservatively accounts for the observed continuum shape moderately well. These observed characteristics are typical of low-ionization BAL QSOs, but convincing evidence for BALs due to low-ionization transitions of Mg II, Al III, Al II, or C II does not exist. Therefore, this object may be a misaligned BAL QSO having many of the characteristics of low-ionization BAL QSOs with the sight line passing through a putative dusty region, but evidently missing clouds of high enough column density to produce observable low-ionization BALs. If the intrinsic dust-extinction model is correct, the observations suggest that the dust is not confined to the presumably higher density, low-ionization BAL clouds, but that it has drifted to nearby high-ionization BAL regions. We also consider other possible mechanisms for producing the shape of the continuous energy distribution which cannot be ruled out. We compare the Fe II emission in PG 0043+039 with that in another Key Project QSO, NGC 2841-UB 3, which has optical Fe II emission comparable in strength to that in PG 0043 + 039, but has anomalously weak UV Fe II emission. In addition, from an analysis of UV and optical spectrophotometric data at 5 epochs over ∼ 11 yr, there is tentative evidence that PG 0043+039 has varied in brightness by as much as 1.1 mag during this time interval. Two different interpretations of PG 0043 + 039 and the low-ionization BAL QSOs are considered: One is that the low-ionization BAL QSOs comprise a distinct population of QSOs that have large BAL region covering factor, no appreciable narrow emission-line region, and other atypical properties. An alternative possibility is that PG 0043 + 039 has a small BAL region covering factor, which is consistent with previously proposed models for most BAL QSOs, but that nonspherical geometries coupled with mechanisms for anisotropic emission give rise to aspect-angle dependent QSO spectral properties, such as weak narrow-line [O III] emission. While the actual value of the BAL region covering factor in PG 0043 + 039 and low-ionization BAL QSOs is unclear, given the absence of a specific model which would give rise to anisotropic continuum or line emission of the type required, the evidence presented here would seem to indicate that the BAL region covering factor in a subclass of QSOs is larger than resonance line scattering models generally indicate. Various model scenarios for explaining the weak narrow-line [O III] emission are considered, but there is no definitive explanation.
• Bahcall, J. N., Bergeron, J., Boksenberg, A., Hartig, G. F., Jannuzi, B. T., Kirhakos, S., Sargent, W. L., Savage, B. D., Schneider, D. P., Turnshek, D. A., Weymann, R. J., & Wolfe, A. M. (1993). The Hubble Space Telescope quasar absorption line key project. I. First observational results, including Lyman-alpha and Lyman-limit systems. Astrophysical Journal, Supplement Series, 87(1), 1-43.
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  Abstract: We present spectra for a total of 37 quasars with small and moderate redshifts; the quasars were observed with the Faint Object Spectrograph of the Hubble Space Telescope. The spectra are obtained either at a resolution of R = 1300 (hereafter "higher resolution") or a resolution of R = 180 (hereafter "lower resolution"). We report new higher resolution measurements of the absorption lines in the ultraviolet spectra of 11 quasars with emission-line redshifts that lie between 0.3 and 1.0. Improved reductions are provided for higher resolution observations of two additional small-redshift quasars observed as part of the Guaranteed Time observational program. These observations cover all or part of the wavelength range 1180-3270 Å in the observed frame. In addition, we present lower dispersion spectra (R = 180, wavelength range 1150-2430 Å) obtained for 24 objects with redshifts between 0.5 and 1.4. Calibrated spectra and continuum fits are shown for each object. A well-defined sample of absorption lines was constructed algorithmically from all of the higher resolution data; the detection limit is expressed in terms of a limiting equivalent width as a function of wavelength. A total of 358 lines are selected by the software in the higher resolution spectra. Time-dependent flat-field features represent the most serious and difficult-to-quantify source of systematic errors. The identifications of interstellar and of extragalactic lines were made in the higher resolution spectra with the aid of software that utilizes the detection limit as a function of wavelength and the known atomic properties of cosmologically abundant ions. A total of 104 extragalactic Lyα systems are identified, of which nine are found at the same redshifts as metal-line systems. The absorption lines that are not identified Galactic interstellar features or extragalactic metal lines are not uniformly distributed; their line density is more than 10 times larger within (rather than outside) the region accessible to extragalactic hydrogen absorption, providing statistical support for the identifications of Lyα systems. The local number density of Lyα systems with rest equivalent widths larger than 0.32 Å and without detected metal lines is (dN/dz)0 ≈ 15.1 ± 2 Lyα systems per unit redshift, if the local Lyα systems are members of the same population as the previously observed large-redshift Lyα lines (i.e., the evolutionary parameter is fixed at γ = 0.75, and the assumed exponential distribution of equivalent widths is characterized by W* = 0.32 Å). If γ and W* are allowed to vary, then (dN/dz)0 ≈ 17.7 ± 4.3 Lyα systems per unit redshift with γ = 0.30 ± 0.62 and W* = 0.22 ± 0.02 Å. The two-point correlation function of the velocity splittings does not show statistically significant evidence of clumping. A sample at least 3 times larger than the one analyzed in this paper would be required to test the hypothesis that Lyα absorption systems observed at small redshifts are clustered like galaxies. The spectra of 29 quasars have been searched algorithmically for the existence of Lyman-limit systems. A total of 10 Lyman-limit systems with an optical depth greater than 0.4 were identified. The number density of such systems at redshifts between 0.4 and 1.4 in our sample is (dN/dz)LLS = 0.8(1 + z)0.5 for a nonevolving population in a q0 = 0.5 universe and (dN/dz)LLS = 0.3(1 + z)2.4 if they evolve as rapidly as Lyα clouds observed at large redshifts. A search for damped Lyα lines revealed only one candidate line, in the spectrum of PKS 2251 + 11, among the spectra of the 36 quasars that were studied. The paucity of damped Lyα lines at small and moderate redshifts shows that the number density of damped absorption systems decreases with decreasing redshift. Of the observed lines, 44% are identified with Galactic interstellar features, 47% with extragalactic absorption systems, and 9% are unidentified. Eleven extragalactic C IV doublets are detected. The incidence of C IV absorption per unit redshift at 〈z〉 ≃ 0.3 and with Wrest(λ1548) ≥ 0.3 Å is dN/dz = 0.9 ± 0.4, significantly lower than the value found at higher redshifts. No obvious correlation is found between radio power of the quasars and the seven occurrences of associated absorption. Three individual absorption systems are of special interest: a broad absorption line system in the spectrum of PG 0043+039; a strong, apparently broad high-excitation associated absorption system in 3C 351; and a rich, high-excitation intervening metal-line system in PKS 2145+06 which has 16 identified lines.
• Bahcall, J. N., Jannuzi, B. T., Schneider, D. P., & Hartig, G. F. (1993). The ultraviolet absorption spectrum of the quasar PKS 0405-12 and the local density of lyman-alpha absorption systems. Astrophysical Journal Letters, 405(2), 491-497.
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  Abstract: A sample of 32 absorption lines has been identified in the ultraviolet spectrum of the z = 0.57 quasar PKS 0405 - 12 The observations were obtained using three R = 1300 gratings of the Faint Object Spectrograph of the Hubble Space Telescope. The data cover the wavelength range 1190-3260 Å. The sample was constructed by requiring that all included lines have a measured equivalent width greater than the wavelength-dependent 3 σ detection limit for unresolved lines. Sixteen of the absorption features are due to Galactic interstellar lines. There are 10 extragalactic Lyα absorption lines in the complete sample, all with observed equivalent widths greater than or equal to 0.40 Å; three of the Lyα lines have Lyβ counterparts. The number of Lyα lines observed in the spectrum of PKS 0405 - 12 is within 1 σ of the number predicted on the basis of previous HST observations of 3C 273 and of H1821 + 643. Combining the HST observations of 3C 273, H1821 + 643, and PKS 0405 - 12, we estimate the local number density of Lyα systems with rest equivalent widths larger than 0.32 Å to be dN/dz(Wrest ≥ 0.32 Å) ≈ 15 ± 4 Lyα lines per unit redshift. Ground-based images reveal a rich field of galaxies in the direction of PKS 0405 - 12, including many galaxies with the brightnesses and sizes expected if they belong to a cluster associated with the quasar The quasar spectrum does not show any evidence for absorption at the redshift of the emission lines, indicating a covering factor of less than unity for the halos of galaxies in the cluster around PKS 0405 - 12.
• Fleming, T. A., Green, R. F., Jannuzi, B. T., Liebert, J., Smith, P. S., & Fink, H. (1993). Three new BL Lacertae objects in the Palomar-Green Survey. Astronomical Journal, 106(5), 1729-1733.
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  Abstract: We have identified three BL Lacertae objects in the Palomar-Green Survey which were previously misclassified as DC white dwarfs, namely PG 1246 + 586, PG 1424 + 240, and PG 1437 + 398. Our reclassification is based on the detection of these objects as x-ray sources in the ROSAT all-sky survey and upon our subsequent detection of intrinsic linearly polarized and variable optical emission from these sources. As a result of the ROSAT survey, the number of identified BL Lac objects in the Palomar-Green catalog of UV excess objects has been doubled. Corrected optical positions are presented for PG 1246 + 586 and PG 1437 + 398.
• Gorkom, J. V., Bahcall, J. N., Jannuzi, B. T., & Schneider, D. P. (1993). A very large array search for emission from H I associated with nearby Lyman α absorbers. Astronomical Journal, 106(6), 2213-2217.
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  Abstract: We present a sensitive VLA search for H I emission from the vicinity of the Lyman α clouds in the Virgo Cluster, which were recently discovered with HST in absorption toward the nearest quasar 3C273. We searched an area of 40 by 40 arcmin centered on 3C273, covering a velocity range from 840 to 1840 km s-1. The bandpass was self-calibrated on 3C273 leading to a spectral dynamic range of better than 105 to 1. No H I was detected. The rms noise in the final images corresponds to a 3σ column density sensitivity of 2.8×1019 cm-2 on scales of a few kpc. Small H I clouds could have been detected down to a few times 106 script M sign ⊙. Our failure to detect H I in emission at the higher column densities sets a lower limit to the radius of the Lyman α clouds of 3.9 kpc, assuming a spherical geometry.
• Jannuzi, B. T., Green, R. F., & French, H. (1993). An optical polarization survey for BL Lacertae objects and highly polarized quasars. Astrophysical Journal Letters, 404(1), 100-111.
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  Abstract: We present the results of an extensive optical survey for highly polarized objects. The survey is complete to a B magnitude of 20 and covers 560 square degrees. We did not find any confirmed BL Lac objects, highly polarized quasars, or blazars, but we are able to constrain the surface density of the various populations of linearly polarized objects. Our constraints on the numbers of a population of polarized objects are a function of the duty cycle and the degree of polarization of the objects being constrained. We rule out the presence of an abundant population of radio-quiet BL Lacertae objects.
• Jannuzi, B. T., Smith, P. S., & Elston, R. (1993). Optical polarimetry and photometry of x-ray selected BL lacertae objects. Astrophysical Journal, Supplement Series, 85(2), 265-291.
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  Abstract: We present the data from 3 years of monitoring the optical polarization and apparent brightness of 37 X-ray selected BL Lacertae objects. The monitored objects include a complete sample drawn from the Einstein Extended Medium Sensitivity Survey (EMSS). We confirm the BL Lac identifications for 15 of these 22 objects. We include descriptions of the objects and samples in our monitoring program and of the existing complete samples of BL Lac objects, highly polarized quasars, optically violent variable quasars, and blazars. The data are analyzed and implications discussed in Jannuzi, Smith, and Elston (Paper II).
• Jannuzi, B. T., Smith, P. S., & Elston, R. (1993). The Optical Polarization Properties of X-ray Selected BL Lacertae Objects. Astrophys.J.Suppl., 265-291.
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  We discuss the optical polarization properties of X-ray selected BL Lacertaeobjects (XSBLs) as determined from three years of monitoring 37 BL Lac objectsand candidates. The observed objects include a complete X-ray flux limitedsample drawn from the EMS Survey. The majority of the XSBLs classi- fied solelyon the appearance of their spectra are members of the class of BL~Lacs sincethey possess intrinsically polarized and variable continua. The duty cycle ofpolarized emission from XSBLs is 40\%. The majority of XSBLs ($\approx 85$\%)have preferred polarization position angles on time scales as long as threeyears. This reflects stability in the geometry of the region emitting thepolarized optical emission. We discuss the observed spectral dependence of thedegree of polarization and some of the possible mechanisms for producing theobserved characteristics. While dilution of the polarized emission by the hostgalaxy starlight is present in some objects, we demon- strate that the averagepolarization properties derived from our observations are not drasticallyaffected by this effect. The objects in our monitored sample did not displaythe larger than one magnitude variations generally used to characterize theoptical variability of blazars in general.[Journal_ref: Astrophys.J.Suppl. 85 (1993) 265-291]
• Savage, B. D., Limin, L. u., Bahcall, J. N., Bergeron, J., Boksenberg, A., Hartig, G. F., Jannuzi, B. T., Kirhakos, S., Lockman, F. J., Sargent, W. L., Schneider, D. P., Turnshek, D., Weymann, R. J., & Wolfe, A. M. (1993). The Hubble Space Telescope Quasar Absorption Line Key Project. III. First observational results on Milky Way gas. Astrophysical Journal Letters, 413(1), 116-136.
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  Abstract: We report on absorption by Milky Way disk and halo gas seen in Quasar Absorption Line Key Project measurements of 15 quasars obtained with the Faint Object Spectrograph (FOS) of the Hubble Space Telescope (HST). The measurements extend from 1150 to 3270 Å for four objects and from 1600 to 3270 Å for 11 objects and have a velocity resolution (FWHM) of 220-240 km s-1 and signal-to-noise ratio of typically 25 per resolution element. The data processing techniques are presented in Key Project Papers I and II. Milky Way absorption lines comprise 44% of all absorption lines found in the first group of 13 Key Project spectra. The Milky Way lines observed in the highest quality data for 3C 273 and H1821+643 include lines from H I, C II, C II*, C IV, O I, N I, Mg I, Mg II, Al II, Al III, Si II, Si IV, Si IV, S II, Mn II, Fe II, and Zn II. Strong singly ionized metal lines of Fe II λλ2600.17 and 2586.65 and Mg II λλ2796.35 and 2803.53 are detected in all the spectra. High-quality H I 21 cm emission spectra are used to make small adjustments to the FOS wavelength scale to bring the UV data onto an LSR velocity system. The strong metal lines of Fe II and Mg II permit a sensitive search for metal-line analogs to the high-velocity clouds seen in H I 21 cm emission. Toward three quasars we detect resolved, very high negative velocity (v < -250 km s-1) metal-line absorption. Toward four quasars we detect blended high negative velocity absorption (-250 km s-1 < v < -100 km s-1). Therefore, seven of 15 sight lines observed in this limited sample exhibit high-velocity or very high velocity metal-line absorption. Lower limits to the Mg-to-H abundance ratio of 0.059, 0.12, and 0.32 times the solar abundance are obtained for the three detections of very high velocity Mg II absorption toward PKS 2251+11, PG 0043+039, and 3C 454.3, respectively. However, cloud clumping may influence this result, since the H I reference column density from 21 cm emission measurements is obtained with a 21′ beam. The sight line to PG 1259+593 reveals absorptions in the lines of Mg II, Fe II, C II, and Si II which are in part due to absorption in high-velocity cloud Complex C III. Two sight lines (H1821+643 and 3C 351) which extend through the warped outer Galaxy exhibit strong absorption by singly ionized metals (C II, Si II, Fe II, Mg II) and highly ionized gas (C IV) at velocities corresponding to absorption in the outer Galaxy. Combining our measurements of C IV with data from the literature, we derive a Galactic C IV exponential scale height of 4.9 kpc and a midplane density of 7.1 × 10-9 atoms cm-3. However, the C IV distribution is so patchy that the measurements are found to be equally well fitted by a spherical halo model with a Galactocentric exponential scale length of 6.9 kpc. A comparison of absorption in high-redshift damped Lyα systems with the absorption produced by the Milky Way shows that an appreciable fraction of the damped Lyα absorption-line systems have mixed ionization absorption-line characteristics roughly similar to that found for six sight lines through the Milky Way disk and halo. Since the low-ionization lines are highly saturated, this similarity does not imply similar abundances in the neutral and weakly ionized gas but instead probably suggests a similarity in the kinematical behavior of the different absorbing media.
• Schneider, D. P., Hartig, G. F., Jannuzi, B. T., Kirhakos, S., Saxe, D. H., Weymann, R. J., Bahcall, J. N., Bergeron, J., Boksenberg, A., Sargent, W. L., Savage, B. D., Turnshek, D. A., & Wolfe, A. M. (1993). The Hubble Space Telescope quasar absorption line key project. II. Data calibration and absorption-line selection. Astrophysical Journal, Supplement Series, 87(1), 45-62.
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  Abstract: We present the observational and data processing aspects of the Hubble Space Telescope Quasar Absorption Line Key Project. Topics discussed include the observational technique, calibration of the data, software that simulates the data, the automated procedure used to identify and characterize the absorption features, and the determination of the sensitivity limits of the survey.
• Spinrad, H., Filippenko, A. V., Yee, H. K., Ellingson, E., Blades, J. C., Bahcall, J. N., Jannuzi, B. T., Bechtold, J., & Dobrzycki, A. (1993). Hydrogen and metal absorption lines in PKS 0405 - 123 from the halos of low redshift galaxies. Astronomical Journal, 106(1), 1-5.
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  Abstract: Hubble Space Telescope ultraviolet spectra and ground-based optical spectra of the bright quasar PKS 0405 - 123 are used to identify two absorption-line systems probably produced by the halos of foreground galaxies. The quasar lies in a rich galaxy field. Loose groups of galaxies are present in the field at 〈z1〉 =0.1669 and 〈z2〉 =0.3519. Ly α, C IV λ1549, and probably Mg II λ2798 resonance lines are detected in an absorption system at z=0.1670. An absorption system consisting of only Ly α is observed at z=0.3516. We cannot be completely certain which foreground galaxy is responsible for the metal line absorption system at z1. A likely candidate is a large, luminous, early-type spiral 40″ (projected distance 78h-1 kpc) to the east of the quasar. However, the origin of the z1 system could possibly be a small, undetected galaxy more precisely aligned along our line of sight to PKS 0405 - 123, or a very faint galaxy whose redshift has not yet been measured.
• Bahcall, J. N., Hartig, G. F., Jannuzi, B. T., Maoz, D., & Schneider, D. P. (1992). Faint object spectrograph observations of the large-redshift gravitational lens candidate 1208+1011. Astrophysical Journal Letters, 400(2 PART 2), L51-L54.
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  Abstract: We report HST spectroscopic observations of the z = 3.8 gravitational lens candidate 1208+1011. Lowdispersion (R = 200) Faint Object Spectrograph data, covering the wavelength range 3700-7800 Å, were obtained for each of the two components (V ≈ 18.3 and 19.8 mag) and for a comparison (blank) field; the fainter component and the blank field are both separated by 0″.47 from the brighter image. The spectra of both components possess strong Lyα/N V and O VI/Lyβ emission lines at a redshift of 3.8 as well as a number of similar absorption features. Both components have a ratio of the equivalent widths of the O VI complex to the Lyα complex much larger than the typical value seen in large-redshift quasars. There are small differences in the measured profiles of the Lyα and O VI/Lyβ emission lines of the images. These differences could be caused by absorption along different paths to a single lensed object, by unequal imaging of extended emissions, by systematic measuring errors, or by intrinsic differences in two nearly identical neighboring quasars.
• Bahcall, J. N., Jannuzi, B. T., Schneider, D. P., Hartig, G. F., & Green, R. F. (1992). The ultraviolet absorption spectrum of the Quasar H1821 + 643 (z = 0.297). Astrophysical Journal Letters, 397(1), 68-80.
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  Abstract: We report measurements of the absorption lines in the ultraviolet spectrum of the nearby luminous quasar H1821 + 643 (z = 0.297). The results were obtained using high-resolution observations with the faint object spectrograph of the Hubble Space Telescope. A total of 51 absorption lines and a number of emission features were detected between 1190 and 3260 Å. A complete sample of 38 absorption lines was constructed with the detection limit defined in terms of a limiting equivalent width as a function of wavelength. The identifications with interstellar and with extra-galactic lines were made with the aid of software that utilizes the limiting detection sensitivity as a function of wavelength and the known atomic properties of cosmologically abundant ions. The majority of the absorption features are Galactic interstellar lines. The interstellar absorption lines and the quasar emission lines present in the spectrum of H1821 + 643 are similar to the lines observed in other small-redshift quasars. There are five strong extragalactic Lyα absorption lines in the spectrum of H1821 + 643, all with observed equivalent widths greater than 0.45 Å. Combining the HST observations of 3C 273 and H1821 + 643, we estimate the local number density of Lyα systems with rest equivalent widths larger than 0.32 Å to be (dN/dz)0 ≈ 13 ± 5 Lyα lines per unit redshift. Some of the Lyα systems with redshifts significantly different from the quasar appear to be associated with galaxies or with clusters of galaxies. Two of the Lyα lines have the same redshift within cΔz = 400 km s-1 as that of an emission-line galaxy located at a projected separation from the quasar of approximately 90 kpc (H0 = 100 km s-1 Mpc-1). This system at z = 0.226 is part of a triplet of Lyα lines that have a total redshift separation of cz = ± 450 km s-1. There is also statistical evidence that some of the Lyα systems are clumped more than would be expected if they were distributed randomly along the line of sight to H1821 + 643. Many of the Lyα systems observed at small redshifts may be associated with large hydrogen halos of galaxies or groups and clusters of galaxies. One of the Lyα systems in H1821 + 643 occurs at an absorption redshift approximately equal to the emission-line redshift of the quasar and is accompanied by absorption from the C IV and O VI doublets; this is an example of what has been called associated absorption. zabs ≈ zem, for large-redshift quasars. No lines from low-ionization ions are detected in this system. The observations of H1821 + 643 fail to confirm previous suggestions that associated absorption is correlated with strong radio emission (H1821 + 643 is radio-quiet) or with low optical luminosity (H1821 + 643 is comparable in luminosity to 3C 273). The observations are consistent with two previously proposed conjectures, that associated absorption is produced in clusters of galaxies containing the quasars or that the absorption is produced in the gas associated with the quasars.
• Bahcall, J. N., Jannuzi, B. T., Schneider, D. P., Hartig, G. F., & Jenkins, E. B. (1992). The near-ultraviolet spectrum of Markarian 205. Astrophysical Journal Letters, 398(2), 495-500.
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  Abstract: We report measurements of the absorption and of the emission lines between 1600 and 3200 Å in the spectrum of the nearby AGN Markarian 205 (z = 0.071), which lies at a projected distance of 3 kpc (H0 = 100 km S-1) from the nucleus of the nearby barred spiral galaxy, NGC 4319 (z = 0.0047). The results were obtained using high-resolution (R = 1300) observations with the Faint Object Spectrograph of the Hubble Space Telescope. A total of 15 absorption lines, 13 of which are produced by Galactic gas, and four AGN emission lines are detected. Two of the absorption lines, the Mg II resonant doublet, are produced by gas in the intervening galaxy NGC 4319. This is the first detection of absorption due to intervening gas in this famous quasar-galaxy pair.
• Stocke, J. T., Wurtz, R., Wang, Q., Elston, R., & Jannuzi, B. T. (1992). The BL Lacertae object PKS 1413+135: Is it within or behind a spiral galaxy?. Astrophysical Journal Letters, 400(1 PART 2), L17-L20.
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  Abstract: New observations of the very red quasar or BL Lac object PKS 1413+135 are presented. Optical imaging and spectroscopy confirm the claim that the host galaxy to this BL Lac is a spiral, and H-band imaging shows the point source centered in the galaxy to within 0″.1 A reanalysis of Einstein X-ray data finds evidence for an extremely large column density in this source of n(H) ≥ 2 × 1022 cm2. The Av ≥ 30 mag suggested by this n(H) can produce the unusual near-IR exponential decline in the spectrum of PKS 1413+135, at variance with previous interpretations. While the astrometric evidence supports the hypothesis that PKS 1413+135 is the very unusual case of a BL Lac object in a spiral galaxy, a highly extincted nuclear source would produce other observable features in this galaxy that are not observed: narrow emission-line region and large thermal IR flux. Their absence argues for this source being background to the spiral.
• Bahcall, J. N., Jannuzi, B. T., Schneider, D. P., Hartig, G. F., Bohlin, R., & Junkkarinen, V. (1991). The ultraviolet absorption spectrum of 3C 273. Astrophysical Journal Letters, 377(1 PART II), L5-L8.
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  Abstract: We identify six Lyα absorption systems with equivalent widths greater than 0.2 Å in the ultraviolet spectrum of the nearby quasar 3C 273, more than expected on the basis of extrapolations of the observed number of Lyα clouds seen at large redshifts. Two Lyα lines appear to be produced by gas in the Virgo Cluster or by the halos of galaxies associated with the Virgo Cluster. We also detect all the interstellar absorption lines that are expected on the basis of abundance, atomic physics, and ionization considerations. © 1991. The American Astronomical Society. All rights reserved.
• Jannuzi, B. T., & Elston, R. (1991). Detection of polarized ultraviolet emission from the high-redshift radio galaxy 3C 265. Astrophysical Journal Letters, 366(2 PART 2), L69-L72.
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  Abstract: We have detected significant polarization of the UV emission from the high-redshift radio galaxy 3C 265. The nucleus is 9.2% (±2.2%) and 8.4% (±2.1%) polarized at B and R, respectively. The position angle of the electric field of the observed radiation is perpendicular to the axis of the radio emission and to the major axis of the UV emission of the galaxy in both passbands. The observed high level of polarization suggests that a substantial fraction of the UV emission is either scattered or produced by a nonthermal source. For 3C 265, we can place an upper limit of 13% (2 σ) for the polarization of the integrated extended emission.
• Smith, P. S., Jannuzi, B. T., & Elston, R. (1991). UBVRI photometry of stars in the fields of X-ray selected BL Lacertae objects. Astrophysical Journal, Supplement Series, 77(1), 67-73.
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  Abstract: We present UBVRI photometry of stars in the fields of 38 X-ray selected BL Lacertae objects, two X-ray selected AGNs, and one X-ray binary system (possibly a cataclysmic variable). These stars are suitable for use as photometric comparison stars for optical monitoring programs involving these X-ray selected objects. A total of 166 observations of 87 stars were made on seven photometric nights. At least two stars were observed in every field. UBVRI measurements of three stars were made in the fields of MS 0950.9+4929, MS 1552.1+2020, and H2154-304. Four stars were measured in the field of H1426+428. Finding charts for all of these objects are included in this paper.

Proceedings Publications

• Alberts, S., Pope, A., Brodwin, M., Atlee, D. W., Lin, Y., Chary, R., Dey, A., Eisenhardt, P. R., Gettings, D., Gonzalez, A. H., Jannuzi, B., Mancone, C., Moustakas, J., Snyder, G. F., Stanford, S. A., Stern, D., Weiner, B. J., & Zeimann, G. (2014, jan). How Environment Affects Star Formation: Tracing Activity in High Redshift Galaxy Clusters. In American Astronomical Society Meeting Abstracts, 223, #130.02.
• Green, R. F., Allen, L., Alvarez Del Castillo, E. M., Brocious, D. K., Corbally, C. J., Davis, D. R., Falco, E. E., Gabor, P., Hall, J. C., Jannuzi, B., Larson, S. M., Mighell, K. J., Nance, C., Shankland, P. D., Walker, C. E., Williams, G., & Zaritsky, D. F. (2014, jan). Progress in Dark Sky Protection in Southern Arizona. In American Astronomical Society Meeting Abstracts, 223, #413.05.
• Hall, J. C., Shankland, P. D., Green, R. F., & Jannuzi, B. (2014, jan). Recent Local and State Action in Arizona to Maintain Sky Quality. In American Astronomical Society Meeting Abstracts, 223, #413.06.
• Palamara, D. P., Brown, M. J., Jannuzi, B., White, M., Norberg, P., Team, G., & Team, N. (2014, jan). How do galaxies populate dark matter halos across cosmic time?. In American Astronomical Society Meeting Abstracts, 223, #231.06.
• Jannuzi, B. (2013, jun). Panel Discussion: WIYN Observatory: Partnerships. In American Astronomical Society Meeting Abstracts, 222, #204.02.
• Lee, K., Alberts, S., Atlee, D. W., Dey, A., Pope, A., Jannuzi, B., Reddy, N. A., & Brown, M. J. (2013, jan). Herschel Detection of Dust Emission from UV-Luminous Star-Forming Galaxies at 3.3 ltz lt4.3. In American Astronomical Society Meeting Abstracts, 221, #129.07.
• Finkelstein, K. D., Finkelstein, S. L., Tilvi, V., Malhotra, S., Rhoads, J. E., Grogin, N. A., Pirzkal, N., Dey, A., Jannuzi, B. T., Mobasher, B., Pakzad, S., & Wang, J. (2012, may). Stellar Population Properties of z=4.5 and z=5.7 Lyman Alpha Emitters based on Spitzer Observations. In American Astronomical Society Meeting Abstracts #220, 220, #429.04.
• Finkelstein, K. D., Malhotra, S., Rhoads, J. E., Finkelstein, S. L., Tilvi, V., Grogin, N. A., Pirzkal, N., Dey, A., Jannuzi, B. T., Mobasher, B., Pakzad, S., & Wang, J. (2012, jan). Probing the Rest-Frame Optical Continuum of z=4.5 Lyman Alpha Emitters with Spitzer. In American Astronomical Society Meeting Abstracts #219, 219, #340.07.
• Krug, H. B., Veilleux, S., Tilvi, V., Malhotra, S., Rhoads, J., Hibon, P., Swaters, R., Probst, R., Dey, A., Dickinson, M., & Jannuzi, B. (2012, jan). Searching for High-redshift Ly$ alpha$ Emitters in the COSMOS Field with NEWFIRM. In American Astronomical Society Meeting Abstracts #219, 219, #129.02.
• Shipley, H. V., Papovich, C., Dey, A., Jannuzi, B., Rieke, G., & Weiner, B. (2012, jan). Spitzer Infrared Spectrograph Observations of Infrared-Luminous Galaxies at Moderate Redshift: Diagnostics of AGN and Star Formation. In American Astronomical Society Meeting Abstracts #219, 219, #246.17.

Poster Presentations

• Males, J. R., Christensen, E., Jannuzi, B. T., Alfred, D., Connors, T., Rascon, M., Pearce, E. C., Kim, D. W., Oh, C. J., Martin, H., Peyton, K., Assenmacher, W., Teran, J., Neff, D., Davidson, W., Angel, R., & Kingley, J. (2018, June). An inexpensive turnkey 6.5-m observatory with customizing options. Ground-based and Airborne Telescopes VII, part of SPIE Astronomical Telescopes + Instrumentation. Austin TX: SPIE.
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  A turnkey 6.5-m observatory has been developed for broad science applications with predefined performance specifications that can be verified on sky. This observatory can be delivered within five years at a fixed price. By combining academia and industrial partners with extensive experience and enormous investments in infrastructure it is possible to produce a highly valued optimized observatory with cost and schedule certainty. The challenge for scientists now becomes developing the science and instruments and not the observatory.