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Title: A SUBSTANTIAL POPULATION OF MASSIVE QUIESCENT GALAXIES AT z ∼ 4 FROM ZFOURGE

We report the likely identification of a substantial population of massive M ∼ 10{sup 11} M {sub ☉} galaxies at z ∼ 4 with suppressed star formation rates (SFRs), selected on rest-frame optical to near-IR colors from the FourStar Galaxy Evolution Survey (ZFOURGE). The observed spectral energy distributions show pronounced breaks, sampled by a set of near-IR medium-bandwidth filters, resulting in tightly constrained photometric redshifts. Fitting stellar population models suggests large Balmer/4000 Å breaks, relatively old stellar populations, large stellar masses, and low SFRs, with a median specific SFR of 2.9 ± 1.8 × 10{sup –11} yr{sup –1}. Ultradeep Herschel/PACS 100 μm, 160 μm and Spitzer/MIPS 24 μm data reveal no dust-obscured SFR activity for 15/19(79%) galaxies. Two far-IR detected galaxies are obscured QSOs. Stacking the far-IR undetected galaxies yields no detection, consistent with the spectral energy distribution fit, indicating independently that the average specific SFR is at least 10 × smaller than that of typical star-forming galaxies at z ∼ 4. Assuming all far-IR undetected galaxies are indeed quiescent, the volume density is 1.8 ± 0.7 × 10{sup –5} Mpc{sup –3} to a limit of log{sub 10} M/M {sub ☉} ≥ 10.6, which is 10 × and 80 × lowermore » than at z = 2 and z = 0.1. They comprise a remarkably high fraction (∼35%) of z ∼ 4 massive galaxies, suggesting that suppression of star formation was efficient even at very high redshift. Given the average stellar age of 0.8 Gyr and stellar mass of 0.8 × 10{sup 11} M {sub ☉}, the galaxies likely started forming stars before z = 5, with SFRs well in excess of 100 M {sub ☉} yr{sup –1}, far exceeding that of similarly abundant UV-bright galaxies at z ≥ 4. This suggests that most of the star formation in the progenitors of quiescent z ∼ 4 galaxies was obscured by dust.« less
Authors:
;  [1] ;  [2] ; ; ;  [3] ;  [4] ;  [5] ; ;  [6] ;  [7] ; ; ;  [8] ; ; ; ; ; ;  [9] more »; « less
  1. Leiden Observatory, Leiden University, P.O. Box 9513, 2300 RA Leiden (Netherlands)
  2. Department of Physics and Astronomy, Faculty of Sciences, Macquarie University, Sydney, NSW 2109 (Australia)
  3. Centre for Astrophysics and Supercomputing, Swinburne University, Hawthorn, VIC 3122 (Australia)
  4. European Space Astronomy Centre (ESAC)/ESA, Villanueva de la Cañada, 28691, Madrid (Spain)
  5. European Southern Observatory, Alonso de Córdova 3107, Casilla 19001, Vitacura, Santiago (Chile)
  6. National Optical Astronomy Observatory, Tucson, AZ (United States)
  7. Department of Astronomy, Yale University, New Haven, CT 06520 (United States)
  8. George P. and Cynthia W. Mitchell Institute for Fundamental Physics and Astronomy, Department of Physics and Astronomy, Texas A and M University, College Station, TX 77843 (United States)
  9. Carnegie Observatories, Pasadena, CA 91101 (United States)
Publication Date:
OSTI Identifier:
22363943
Resource Type:
Journal Article
Resource Relation:
Journal Name: Astrophysical Journal Letters; Journal Volume: 783; Journal Issue: 1; Other Information: Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; COLOR; COSMIC DUST; COSMOLOGY; DENSITY; DETECTION; ENERGY SPECTRA; FILTERS; GALACTIC EVOLUTION; GALAXIES; MASS; RED SHIFT; STARS; ULTRAVIOLET RADIATION