Kinematic downsizing at z ∼ 2

Journal Article · Mon Oct 10 04:00:00 EDT 2016 · Astrophysical Journal

DOI:https://doi.org/10.3847/0004-637X/830/1/14· OSTI ID:22868623

Simons, Raymond C.; Heckman, Timothy M. ^[1]; Kassin, Susan A.; Koekemoer, Anton ^[2]; Trump, Jonathan R. ^[3]; Weiner, Benjamin J. ^[4]; Barro, Guillermo ^[5]; Koo, David C.; Guo, Yicheng ^[6]; Pacifici, Camilla ^[7]

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1. Johns Hopkins University, Baltimore, MD 21218 (United States)
2. Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218 (United States)
3. Department of Astronomy and Astrophysics and Institute for Gravitation and the Cosmos, 525 Davey Lab, The Pennsylvania State University, University Park, PA 16802 (United States)
4. Steward Observatory, 933 N. Cherry St, University of Arizona, Tucson, AZ 85721 (United States)
5. Department of Astronomy, University of California Berkeley, 501 Campbell Hall, Berkeley, CA 94720 (United States)
6. UCO/Lick Observatory, Department of Astronomy and Astrophysics, University of California, Santa Cruz, CA 95064 (United States)
7. Astrophysics Science Division, Goddard Space Flight Center, Code 665, Greenbelt, MD 20771 (United States)

We present results from a survey of the internal kinematics of 49 star-forming galaxies at z∼2 in the CANDELS fields with the Keck/MOSFIRE spectrograph, Survey in the near-Infrared of Galaxies with Multiple position Angles (SIGMA). Kinematics (rotation velocity V {sub rot} and gas velocity dispersion σ{sub g}) are measured from nebular emission lines which trace the hot ionized gas surrounding star-forming regions. We find that by z∼2, massive star-forming galaxies (log M{sub ∗}/M{sub ⊙}≳10.2) have assembled primitive disks: their kinematics are dominated by rotation, they are consistent with a marginally stable disk model, and they form a Tully–Fisher relation. These massive galaxies have values of V{sub rot}/σ{sub g} that are factors of 2–5 lower than local well-ordered galaxies at similar masses. Such results are consistent with findings by other studies. We find that low-mass galaxies (log M{sub ∗}/M{sub ⊙}≲10.2) at this epoch are still in the early stages of disk assembly: their kinematics are often dominated by gas velocity dispersion and they fall from the Tully–Fisher relation to significantly low values of V {sub rot}. This “kinematic downsizing” implies that the process(es) responsible for disrupting disks at z∼2 have a stronger effect and/or are more active in low-mass systems. In conclusion, we find that the period of rapid stellar mass growth at z∼2 is coincident with the nascent assembly of low-mass disks and the assembly and settling of high-mass disks.

• OSTI ID: 22868623
• Journal Information: Astrophysical Journal, Journal Name: Astrophysical Journal Journal Issue: 1 Vol. 830; ISSN ASJOAB; ISSN 0004-637X
• Country of Publication: United States
• Language: English

Related Subjects

79 ASTRONOMY AND ASTROPHYSICS
DISPERSIONS
EMISSION
GALACTIC EVOLUTION
GALAXIES
MASS
ROTATION
STARS
VELOCITY