Caitlin M. Casey

I am an observational astronomer specializing in extragalactic astrophysics. I search for the most massive galaxies that push the boundaries of what is possible to form in our Universe. Galaxies at the extremes often have unusual characteristics -- they're unusually bright, have extraordinary star-formation efficiences, and contain the most massive supermassive black holes of their era. There are several ways to find such massive systems using different observational tracers; my expertise lies in finding these galaxies from the optical/near-infrared through radio wavelengths.

The Distant Universe

I am PI of both the COSMOS-Web Survey (the largest JWST Cycle 1 program) and the COSMOS Survey along with Prof. Jeyhan Kartaltepe at RIT. COSMOS-Web is a 0.6deg^2 NIRCam imaging program, with 0.2deg^2 MIRI imaging collected in parallel, with the goal of revealing the sources of cosmic reionization. Data were obtained from January 2023 through May of 2024.

Listen to me explain the exciting JWST science we'll do on the Vox Unexplainable Podcast, or read about it on Vox here and here. I've also enjoyed talking about JWST on NPR's All Things Considered, NPR's 1A Program, the Marketplace Make Me Smart Podcast, the Texas Standard (NPR program for state of Texas), and been profiled by the Texas Monthly and Austin Monthly magazines.

The Obscured Universe

Instrumental limitations have restricted galaxy evolution resesarch to optical and near-infrared wavelengths for several decades, biasing our view of the distant Universe to unobscured starlight. Thanks to innovative millimeter-wave technology of the past few years, our window to galaxies’ dust and gas content has dramatically improved. Both play an essential role in the growth of galaxies within large-scale cosmic web. I have expertise at both optical/near-infrared and submillimeter through radio wavelengths, and I use multiwavelength observations to interpret gas and dust tracers from the local Universe back to the first galaxies 13 billion years ago. These tracers have indicated much of what we have learned from galaxies’ starlight is biased and potentially inaccurate. In addition, I use these unique dust and gas tracers to learn about the collapse of large scale structure within the first few billion years after the Big Bang.

Watch my Newton Lacy Pierce Prize Lecture on The Obscured Early Universe at the 233rd AAS Meeting HERE.

Watch my plenary lecture at the 230th AAS Meeting on The Universe's Most Extreme Star-Forming Galaxies HERE.

Focus & Goals

The immediate aims of my research group are to address the following questions:

• do massive galaxies reionize the universe?
• are the first massive galaxies highly clustered? how do they evolve toward z=0?
• are early massive galaxies super-efficient star formers?
• do early supermassive black holes lead or lag behind the growth of their host galaxies?
• are massive galaxy clusters built up in periods of rapid filamentary collapse, or steady increased growth?
• are the first galaxies in the Universe dust-free?
• how does early Universe dust production pathways differ from those observable in the local Universe?
• are galaxy mergers an important catalyst for the build-up of stellar mass in the Universe?

Research Group Members

Please visit our group page to learn more about each member and their work!

Publications from the Group (updated summer 2024)

• Akins et al. (2025b) ApJ submitted
  Tentative Detection of neutral gas in a Little Red Dot at z=4.46ADS Link
  
• McKinney et al. (2025b) ApJ submitted
  Modeing Galaxies in the Early Universe with Supernovae Dust AttenuationADS Link
  
• Akins et al. (2025a) ApJ 980, 29
  Strong Rest-frame UV Emission Lines in a "Little Red Dot" Active Galactic Nucleus at z=7: Early Supermassive Black Hole Growth alongside Compact Massive Star Formation?ADS Link
  
• McKinney et al. (2025) ApJ 979, 229
  SCUBADive. 1. JWST+ALMA Analysis of 289 Submillimeter Galaxies in COSMOS-WebADS Link
  
• Cooper et al. (2025) ApJ accepted
  RUBIES: JWST/NIRSpec resolves evolutionary phases of dusty star-forming galaxies at z~2ADS Link
  
• Long et al. (2024) ApJ submitted
  The Extended Mapping Obscuration to Reionization with ALMA (Ex-MORA) Survey: 5sigma Source Catalog and Redshift DistributionADS Link
  
• Casey et al. (2024b) ApJ 975, 4
  Dust in Little Red DotsADS Link
  
• Akins et al. (2024) ApJ submitted
  COSMOS-Web: The over-abundance and physical nature of ``little red dots'' -- Implications for early galaxy and SMBH assemblyADS Link
  
• Gentile et al. (2024) ApJ 973, 2
  Not-so-little Red Dots: Two Massive and Dusty Starbursts at z~5-7 Pushing the Limits of Star Formation Discovered by JWST in the COSMOS-Web SurveyADS Link
  
• Cooper et al. (2023) ApJ 970, 50
  The Web Epoch of Reionization Lya Survey (WERLS). 1. MOSFIRE Spectroscopy of z~7-8 Lya Emitters.ADS Link
  
• Franco et al. (2024) ApJ 973, 23
  Unveiling the Distant Universe: Characterizing z>9 Galaxies in the First Epoch of COSMOS-WebADS Link
  
• Long et al. (2024) ApJ 970, 68
  Efficient NIRCam Selection of Quiescent Galaxies at 3ADS Link
  
• Casey et al. (2024) ApJ 965, 98
  COSMOS-Web: Intrinsically Luminous z>10 Galaxy Candidates Test Early Stellar Mass AssemblyADS Link
  
• McKinney et al. (2023) ApJ 956, 72
  A Near-infrared-faint, Far-infrared-luminous Dusty Galaxy at z~5 in COSMOS-WebADS Link
  
• Akins et al. (2023) ApJ 956, 61
  Two massive, compact, and dust-obscured candidate z~8 galaxies discovered by JWSTADS Link
  
• Fujimoto et al. (2023) ApJ 955, 130
  ALMA FIR View of Ultra-high-redshift Galaxy Candidates at z~11-17: Blue Monsters or Low-z Red Interlopers?ADS Link
  
• Magee et al. (2023) RNAAS 7, 110
  Rotation Curve Measurement of Dark Matter Content of a z~0.5 GalaxyADS Link
  
• Long et al. (2023) ApJ 953, 11
  Missing Giants: Predictions on Dust-Obscured Galaxy Stellar Mass Assembly Throughout Cosmic Time, ADS Link
  
• Champagne et al. (2023) ApJ 952, 99
  A Mixture of LBG Overdensities in the Fields of Three 6ADS Link
  
• McKinney et al. (2023) ApJ 946, 39
  Broad Emission Lines in Optical Spectra of Hot, Dust-obscured Galaxies Can Contribute Significantly to JWST/NIRCam Photometry, ADS Link
  
• Casey et al. (2023) ApJ 954, 31
  The COSMOS-Web Survey: An Overview of the JWST Cosmic Origins Survey, ADS Link
  
• Zavala et al. (2022b) ApJ 943, 9
  A dusty starburst masquerading as an ultra-high redshift galaxy in JWST CEERS Observations, ADS Link
• Zavala et al. (2022a) ApJ 933, 242
  Probing Cold Gas in a Massive, Compact Star-forming Galaxy at z=6, ADS Link
• Drew & Casey (2022) ApJ 930, 142
  No Redshift Evolution of Galaxies’ Dust Temperatures Seen from 0 < z < 2, ADS Link
• Cooper et al. (2022) ApJ 930, 32
  Searching Far and Long. I. Pilot ALMA 2mm Follow-up of Bright Dusty Galaxies as a Redshift Filter, ADS Link
• Manning et al. (2022) ApJ 925, 23
  Characterization of Two 2mm detected Optically Obscured Dusty Star-forming Galaxies, ADS Link
• Casey et al. (2021) ApJ 923, 215
  Mapping Obscuration to Reionization with ALMA (MORA): 2 mm Efficiently Selects the Highest-Redshift Obscured Galaxies, ADS Link
• Champagne et al. (2021) ApJ 913, 110
  Comprehensive Gas Characterization of the z=2.5 Protocluster: A Cluster Core Caught in the Beginning of Virialization?, ADS Link
• Burnham et al. (2021) ApJ 910, 89
  The Physical Drivers of the Luminosity-weighted Dust Temperatures in High-Redshift Galaxies, ADS Link
• Zavala et al. (2021) ApJ 909, 165
  The Evolution of the IR Luminosity Function and Dust-obscured Star Formation over the Past 13 Billion Years, ADS Link
• Premnath, Spilker, Casey & Gurwell (2020) RNAAS 4, 173
  Evidence for a Buried AGN in an Extremely Bright Dusty Galaxy at z = 2, IOP Link
• Casey (2020) ApJ 900, 68
  Far-Infrared Photometric Redshifts: A New Approach to a Highly Uncertain Enterprise, ADS Link
• Manning et al. (2020) MNRAS 495, 1724
  SuperCLASS - II. Photometric redshifts and characteristics of spatially resolved μJy radio sources, ADS Link
• Drew et al. (2020) ApJ 892, 104
  Three Dusty Star-forming Galaxies at z~1.5, ADS Link
• Zavala et al. (2019) ApJ 887, 183
  On the Gas Content, Star Formation Efficiency, and Environmental Quenching of Massive Galaxies in Protoclusters at z~2.0-2.5, ADS Link
• Casey et al. (2019) ApJ 887, 55
  Physical Characterization of an Unlensed, Dusty Star-forming Galaxy at z=5.85, ADS Link
• Urias, Zavala & Casey (2020) RNAAS, 3, 140
  Characterizing a Dusty Star-forming Galaxy at z~3, IOP Link
• Casey et al. (2019) Bulletin of the AAS, 51 212 (arxiv/1903.05634)
  Taking Census of Massive, Star-Forming Galaxies formed <1Gyr After the Big Bang, ADS Link
• Wicker & Casey (2019) RNAAS, 3, 83
  Constraining Multiplicity and Clustering Using Empirical Models of the (Sub)Millimeter Sky, IOP Link
• Schechter & Casey (2018) RNAAS 2, 4
  Examining the Gas Outflow for a Typical Dusty Star-forming Galaxy at z=2, IOP Link
• Zavala et al. (2018) ApJ in press
  Constraining the volume density of Dusty Star-Forming Galaxies through the first 3mm Number Counts from ALMA, ADS Link
• Drew et al. (2018) ApJ in press
  Evidence of a Flat Outer Rotation Curve in a Starbursting Disk Galaxy at z=1.6, ADS Link
• Champagne et al. (2018) ApJ 867, 153
  No Evidence for Millimeter Continuum Source Overdensities in the Environments of z>6 Quasars, ADS Link
• Casey et al. (2018b) ApJ 862, 78
  An Analysis of ALMA Deep Fields and the Perceived Dearth of High-z Galaxies, ADS Link
• Casey et al. (2018a) ApJ 862, 77
  The Brightest Galaxies in the Dark Ages: Galaxies' Dust Continuum Emission During the Reionization Era, ADS Link
• Casey et al. (2017) ApJ 840, 101
  Near-Infrared MOSFIRE Spectra of Dusty Star-Forming Galaxies at z<4, ADS Link
• Hung et al. (2016) ApJ 826, 130
  Large-Scale Structure around a z=2.1 Cluster, ADS Link
• Casey (2016) ApJ 824, 36
  The Ubiquity of Coeval Starbursts in Massive Galaxy Cluster Progenitors, ADS Link
• Casey et al. (2015) ApJL 808, 33
  A Massive, Distant Protocluster at z=2.47 Caught in a Phase of Rapid Formation?, ADS Link

Caitlin Casey's First Authored Publications from postdoc years and before:

• Casey et al. (2014) ApJ 796, 95
  Are Dusty Galaxies Blue? Insights on UV Attenuation from Dust-selected Galaxies, ADS Link
• Casey, Narayanan & Cooray (2014) Physics Reports 541, 45
  Dusty Star-Forming Galaxies at High Redshift, ADS Link
• Casey et al. (2013) MNRAS 436, 1919
  Characterization of SCUBA-2 450um and 850um selected galaxies in the COSMOS field, ADS Link
• Casey et al. (2012c) ApJ 761, 139
  A Population of z>2 Far-infrared Herschel-SPIRE-selected Starbursts, ADS Link
• Casey et al. (2012b) ApJ 761, 140
  A Redshift Survey of Herschel Far-infrared Selected Starbursts and Implications for Obscured Star Formation, ADS Link
• Casey (2012) MNRAS 425, 3094
  Far-infrared spectral energy distribution fitting for galaxies near and far, ADS Link
• Casey et al. (2011b) MNRAS 415, 2723
  Molecular gas in submillimetre-faint, star-forming ultraluminous galaxies at z>1, ADS Link
• Casey et al. (2011a) MNRAS 411, 2739
  Spectroscopic characterization of 250um-selected hyper-luminous star-forming galaxies, ADS Link
• Casey et al. (2009c) MNRAS 400, 670
  A search for neutral carbon towards two z=4.05 submillimetre galaxies, GN20 and GN20.2, ADS Link
• Casey et al. (2009b) MNRAS 399, 121
  Confirming a population of hot-dust dominated, star-forming, ultraluminous infrared galaxies at high-redshift, ADS Link
• Casey et al. (2009a) MNRAS 395, 1249
  Constraining star formation and AGN in z~2 massive galaxies using high-resolution MERLIN radio observations, ADS Link
• Casey et al. (2008b) ApJS 177, 131
  Optical Selection of Faint Active Galactic Nuclei in the COSMOS Field, ADS Link
• Casey et al. (2008a) AJ 136, 181
  PC 1643+4631A, B: the Lyman-alpha Forest at the Edge of Coherence, ADS Link