Forming compact massive galaxies
- Department of Astronomy, Yale University, New Haven, CT 06511 (United States)
- Leiden Observatory, Leiden University, 2300-RA Leiden (Netherlands)
- Space Telescope Science Institute, Baltimore, MD 21218 (United States)
- Max-Planck-Institut für Extraterrestrische Physik, Giessenbachstrasse, D-85748 Garching (Germany)
- South African Astronomical Observatory, P.O. Box 9, Observatory, Cape Town 7935 (South Africa)
- Astrophysics Science Division, Goddard Space Center, Greenbelt, MD 20771 (United States)
- Max Planck Institute for Astronomy (MPIA), Königstuhl 17, D-69117 Heidelberg (Germany)
- Steward Observatory, University of Arizona, 933 North Cherry Avenue, Tucson, AZ 85721 (United States)
- UCO/Lick Observatory, University of California, Santa Cruz, CA 95064 (United States)
- Department of Astronomy, University of California, Berkeley, CA 94720 (United States)
In this paper we study a key phase in the formation of massive galaxies: the transition of star-forming galaxies into massive (M{sub stars} ∼ 10{sup 11}M{sub ⊙}), compact (r{sub e} ∼ 1 kpc) quiescent galaxies, which takes place from z ∼ 3 to z ∼ 1.5. We use HST grism redshifts and extensive photometry in all five 3D-HST/CANDELS fields, more than doubling the area used previously for such studies, and combine these data with Keck MOSFIRE and NIRSPEC spectroscopy. We first confirm that a population of massive, compact, star-forming galaxies exists at z ≳ 2, using K-band spectroscopy of 25 of these objects at 2.0 < z < 2.5. They have a median [N ii]/Hα ratio of 0.6, are highly obscured with SFR(tot)/SFR(Hα) ∼10, and have a large range of observed line widths. We infer from the kinematics and spatial distribution of Hα that the galaxies have rotating disks of ionized gas that are a factor of ∼2 more extended than the stellar distribution. By combining measurements of individual galaxies, we find that the kinematics are consistent with a nearly Keplerian fall-off from V{sub rot} ∼ 500 km s{sup −1} at 1 kpc to V{sub rot} ∼ 250 km s{sup −1} at 7 kpc, and that the total mass out to this radius is dominated by the dense stellar component. Next, we study the size and mass evolution of the progenitors of compact massive galaxies. Even though individual galaxies may have had complex histories with periods of compaction and mergers, we show that the population of progenitors likely followed a simple inside-out growth track in the size–mass plane of Δlogr{sub e}∼0.3ΔlogM{sub stars}. This mode of growth gradually increases the stellar mass within a fixed physical radius, and galaxies quench when they reach a stellar density or velocity dispersion threshold. As shown in other studies, the mode of growth changes after quenching, as dry mergers take the galaxies on a relatively steep track in the size–mass plane.
- OSTI ID:
- 22882458
- Journal Information:
- Astrophysical Journal, Vol. 813, Issue 1; Other Information: Country of input: International Atomic Energy Agency (IAEA); Since 2009, the country of publication for this journal is the UK.; ISSN 0004-637X
- Country of Publication:
- United Kingdom
- Language:
- English
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