z ∼ 2: An Epoch of Disk Assembly
- Johns Hopkins University, 3400 North Charles St., Baltimore, MD 21218 (United States)
- Space Telescope Science Institute, 3700 San Martin Dr., Baltimore, MD 21218 (United States)
- Steward Observatory, 933 N. Cherry St., University of Arizona, Tucson, AZ 85721 (United States)
- UCO/Lick Observatory, Department of Astronomy and Astrophysics, University of California, Santa Cruz, CA 95064 (United States)
- Department of Physics, University of Connecticut, 2152 Hillside Rd. Unit 3046, Storrs, CT 06269 (United States)
- 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, Vol. 843, Issue 1; Other Information: Country of input: International Atomic Energy Agency (IAEA); ISSN 0004-637X
- Country of Publication:
- United States
- Language:
- English
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