TY - JOUR
T1 - A substantial population of massive quiescent galaxies at z ~ 4 from ZFOURGE
AU - Straatman, Caroline M S
AU - Labbé, Ivo
AU - Spitler, Lee R.
AU - Allen, Rebecca
AU - Altieri, Bruno
AU - Brammer, Gabriel B.
AU - Dickinson, Mark
AU - Van Dokkum, Pieter
AU - Inami, Hanae
AU - Glazebrook, Karl
AU - Kacprzak, Glenn G.
AU - Kawinwanichakij, Lalit
AU - Kelson, Daniel D.
AU - McCarthy, Patrick J.
AU - Mehrtens, Nicola
AU - Monson, Andy
AU - Murphy, David
AU - Papovich, Casey
AU - Persson, S. Eric
AU - Quadri, Ryan
AU - Rees, Glen
AU - Tomczak, Adam
AU - Tran, Kim Vy H
AU - Tilvi, Vithal
N1 - Copyright 2014 The American Astronomical Society. Firstly published in the Astrophysical Journal Letters, 783(1), L14, 2014, published by IOP Publishing. The original publication is available at http://www.doi.org/10.1088/2041-8205/783/1/L14. Version archived for private and non-commercial use with the permission of the author/s and according to publisher conditions. For further rights please contact the publisher.
PY - 2014/3/1
Y1 - 2014/3/1
N2 - We report the likely identification of a substantial population of massive M 1011 M 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 breaks, relatively old stellar populations, large stellar masses, and low SFRs, with a median specific SFR of 2.9 ± 1.8 × 10-11 yr-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 -5 Mpc-3 to a limit of log 10 M/M ≥ 10.6, which is 10 × and 80 × lower 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 11 M, the galaxies likely started forming stars before z = 5, with SFRs well in excess of 100 M yr-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.
AB - We report the likely identification of a substantial population of massive M 1011 M 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 breaks, relatively old stellar populations, large stellar masses, and low SFRs, with a median specific SFR of 2.9 ± 1.8 × 10-11 yr-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 -5 Mpc-3 to a limit of log 10 M/M ≥ 10.6, which is 10 × and 80 × lower 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 11 M, the galaxies likely started forming stars before z = 5, with SFRs well in excess of 100 M yr-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.
UR - http://www.scopus.com/inward/record.url?scp=84897650977&partnerID=8YFLogxK
U2 - 10.1088/2041-8205/783/1/L14
DO - 10.1088/2041-8205/783/1/L14
M3 - Article
AN - SCOPUS:84897650977
SN - 2041-8205
VL - 783
SP - 1
EP - 7
JO - Astrophysical Journal Letters
JF - Astrophysical Journal Letters
IS - 1
M1 - L14
ER -