z ∼ 2: An Epoch of Disk Assembly

Journal Article · Sat Jul 01 04:00:00 EDT 2017 · Astrophysical Journal

DOI:https://doi.org/10.3847/1538-4357/AA740C· OSTI ID:22876048

Simons, Raymond C.; Heckman, Timothy M.; Vega, Alexander de la ^[1]; Kassin, Susan A.; Snyder, Gregory F. ^[2]; Weiner, Benjamin J. ^[3]; Faber, Sandra M.; Koo, David C. ^[4]; Trump, Jonathan R. ^[5]; Pacifici, Camilla ^[6]

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1. Johns Hopkins University, 3400 North Charles St., Baltimore, MD 21218 (United States)
2. Space Telescope Science Institute, 3700 San Martin Dr., Baltimore, MD 21218 (United States)
3. Steward Observatory, 933 N. Cherry St., University of Arizona, Tucson, AZ 85721 (United States)
4. UCO/Lick Observatory, Department of Astronomy and Astrophysics, University of California, Santa Cruz, CA 95064 (United States)
5. Department of Physics, University of Connecticut, 2152 Hillside Rd. Unit 3046, Storrs, CT 06269 (United States)
6. Goddard Space Flight Center, Code 665, Greenbelt, MD (United States)

We explore the evolution of the internal gas kinematics of star-forming galaxies from the peak of cosmic star formation at z∼2 to today. Measurements of galaxy rotation velocity V {sub rot}, which quantify ordered motions, and gas velocity dispersion σ{sub g}, which quantify disordered motions, are adopted from the DEEP2 and SIGMA surveys. This sample covers a continuous baseline in redshift over 0.1 < z < 2.5, spanning 10 Gyr. At low redshift, nearly all sufficiently massive star-forming galaxies are rotationally supported (V{sub rot}>σ{sub g}). By z = 2, 50% and 70% of galaxies are rotationally supported at low (10{sup 9}--10{sup 10} M{sub ⊙}) and high (10{sup 10}--10{sup 11} M{sub ⊙}) stellar mass, respectively. For V{sub rot} > 3 σ{sub g}, the percentage drops below 35% for all masses. From z = 2 to now, galaxies exhibit remarkably smooth kinematic evolution on average. All galaxies tend toward rotational support with time, and higher-mass systems reach it earlier. This is largely due to a mass-independent decline in σ{sub g} by a factor of 3 since z = 2. Over the same time period, V {sub rot} increases by a factor of 1.5 in low-mass systems but does not evolve at high mass. These trends in V {sub rot} and σ{sub g} are at a fixed stellar mass and therefore should not be interpreted as evolutionary tracks for galaxy populations. When populations are linked in time via abundance matching, σ{sub g} declines as before and V {sub rot} strongly increases with time for all galaxy populations, enhancing the evolution in V{sub rot}/σ{sub g}. These results indicate that z=2 is a period of disk assembly, during which strong rotational support is only just beginning to emerge.

• OSTI ID: 22876048
• Journal Information: Astrophysical Journal, Journal Name: Astrophysical Journal Journal Issue: 1 Vol. 843; ISSN ASJOAB; ISSN 0004-637X
• Country of Publication: United States
• Language: English

Related Subjects

79 ASTRONOMY AND ASTROPHYSICS
ABUNDANCE
DISPERSIONS
GALACTIC EVOLUTION
GALAXIES
MASS
RED SHIFT
ROTATION
STARS
VELOCITY