The Obscured Universe

Caitlin Casey's Research Page

I am an observational astronomer specializing in dust-obscured star-formation and gas-enrichment of galaxies across cosmic time. 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, it is now possible to probe galaxies’ dust and gas directly, both playing 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:
  • are galaxy mergers an important catalyst for the build-up of stellar mass in the Universe?
  • are massive galaxies predominantly built through catastrophic galaxy mergers, or isolated processes?
  • 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 will current and future deep dust and gas surveys in the high-redshift Universe change our existing picture of galaxy evolution, as developed from predominantly optical and near-infrared observations?

Research Group Members

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

Starbursting Galaxies

Though hundreds of times more rare than "Milky Way" type galaxies, the Universe's most massive, intense starbursts may be the key to unlocking the physics of star formation and the relationship between galaxies and their environment in large scale structure. Physics is pushed to its limits in these systems: they experience incredibly dense star formation throughout their disturbed disks on short timescles, ~100 million years or less.  Recent improvements in radio/ millimeter/ submillimeter technology has hinted that they are the dominating population for cosmic star-formation in the Universe's infancy.  Yet, we know almost nothing about them compared to galaxies easily detected in the optical with the Hubble Space Telescope.  My research group aims at detecting and characterize obscured starbursts in the early Universe, using them interpret galaxy formation and evolution, and relate them to the familiar galaxies we see in our local neighborhood.

The assembly history of galaxy clusters

Numerical simulations of massive galaxy cluster formation show that the Universe's most massive clusters, and the galaxies living in those clusters, assemble rapidly at early times. While more than 20 protoclusters -- or pre-virialized clusters -- have been discovered at z>2, the observational evidence for such rapid growth is weak. My group is working on characterizing the growth of such large structures by inference from their constituant galaxies' characteristics. For example, a cluster containing an abundance of rare starbursts is most likely undergoing an unusual burst phase of growth, marked by the collision or collapse of intergalactic filaments. By combining the work of large dark energy surveys, like HETDEX, with wide field of view submillimeter bolometer maps, we will be able to characterize the structural growth of clusters and the galaxies in them.

Cold Gas in the Early Universe

Cold molecular gas is the most fundamental building block for star formation, yet is poorly constrained observationally in distant galaxies in comparison to these same galaxies' stellar populations. Understanding the process of galaxy formation and evolution requires we take census of the gas which builds stars and not just the stars themselves; this gas tells a rich story of how galaxies are born, fed from the Intergalactic Medium (IGM), recycle material to mature, and eventually die in a complex mix of quenching and feedback mechanisms. The diversity of galaxies in the early Universe hint that the process of growth from primoridal gas clouds is complex and should be a top observational priority for next generation facilities. I am leading a team which is making key predictions for the observations of gas in the distant Universe from the next generation Very Large Array (ngVLA).

Publications from the Group

  • Schechter & Casey (2018) RNAAS 2, 4
    Examining the Gas Outflow for a Typical Dusty Star-forming Galaxy at z=2IOP 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 before joining UT Austin:
  • 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