CANDELS+3D-HST: Compact SFGs at z ∼ 2-3, the progenitors of the first quiescent galaxies
- UCO/Lick Observatory and Department of Astronomy and Astrophysics, University of California, Santa Cruz, CA 95064 (United States)
- Universidad Complutense de Madrid, F. CC. Físicas, 28040 Madrid (Spain)
- Yonsei University Observatory, Yonsei University, Seoul 120-749 (Korea, Republic of)
- Pennsylvania State University, University Park, PA 16802 (United States)
- Max-Planck-Institut für extraterrestrische Physik, Postfach 1312, Giessenbachstr., D-85741 Garching (Germany)
- Department of Astronomy, University of Michigan, Ann Arbor, MI 48109 (United States)
- Racah Institute of Physics, The Hebrew University, Jerusalem 91904 (Israel)
- Santa Cruz Institute for Particle Physics, University of California, Santa Cruz, CA 95064 (United States)
- Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218 (United States)
- Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States)
- Kapteyn Astronomical Institute, University of Groningen, P.O. Box 800, 9700 AV Groningen (Netherlands)
- Departamento de Física Teórica, Universidad Autónoma de Madrid, 28049 Madrid (Spain)
- Centre for Astrophysics and Supercomputing, Swinburne University of Technology, PO Box 218, Hawthorn, VIC 3122 (Australia)
- Astronomy Department, University of Massachusetts, 710 North Pleasant Street, Amherst, MA 01003 (United States)
We analyze the star-forming and structural properties of 45 massive (log(M/M{sub ☉}) >10) compact star-forming galaxies (SFGs) at 2 < z < 3 to explore whether they are progenitors of compact quiescent galaxies at z ∼ 2. The optical/NIR and far-IR Spitzer/Herschel colors indicate that most compact SFGs are heavily obscured. Nearly half (47%) host an X-ray-bright active galactic nucleus (AGN). In contrast, only about 10% of other massive galaxies at that time host AGNs. Compact SFGs have centrally concentrated light profiles and spheroidal morphologies similar to quiescent galaxies and are thus strikingly different from other SFGs, which typically are disk-like and sometimes clumpy or irregular. Most compact SFGs lie either within the star formation rate (SFR)-mass main sequence (65%) or below it (30%), on the expected evolutionary path toward quiescent galaxies. These results show conclusively that galaxies become more compact before they lose their gas and dust, quenching star formation. Using extensive HST photometry from CANDELS and grism spectroscopy from the 3D-HST survey, we model their stellar populations with either exponentially declining (τ) star formation histories (SFHs) or physically motivated SFHs drawn from semianalytic models (SAMs). SAMs predict longer formation timescales and older ages ∼2 Gyr, which are nearly twice as old as the estimates of the τ models. Both models yield good spectral energy distribution fits, indicating that the systematic uncertainty in the age due to degeneracies in the SFH is of that order of magnitude. However, SAM SFHs better match the observed slope and zero point of the SFR-mass main sequence. Contrary to expectations, some low-mass compact SFGs (log(M/M{sub ☉}) =10-10.6) have younger ages but lower specific SFRs than that of more massive galaxies, suggesting that the low-mass galaxies reach the red sequence faster. If the progenitors of compact SFGs are extended SFGs, state-of-the-art SAMs show that mergers and disk instabilities (DIs) are both able to shrink galaxies, but DIs are more frequent (60% versus 40%) and form more concentrated galaxies. We confirm this result via high-resolution hydrodynamic simulations.
- OSTI ID:
- 22365374
- Journal Information:
- Astrophysical Journal, Vol. 791, 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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