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

By C. Straatman, I. Labbé, Lee R. Spitler, R. Allen, B. Altieri, G. Brammer, Mark Dickinson, P. V. van Dokkum, H. Inami, Karl Glazebrook and 14 more. 2013

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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 Å 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 log10M/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 × 1011 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.

Subfields: Astronomy and Astrophysics, Instrumentation

View Paper: https://www.semanticscholar.org/paper/e8431055ccdf71e1ba7e203913db12c22e2892fd

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Citations in the corpus

Near infrared spectroscopy and star-formation histories of 3 ≤ z ≤ 4 quiescent galaxies (2018, methodology): “…Hill et al. 2016; Glazebrook et al. 2017), and that their number density has been rising continuously until the present day (e.g., Faber et al. 2007; Ilbert et al. 2010; Brammer et al. 2011; Muzzin et al. 2013; Ilbert et al. 2013; Stefanon et al. 2013; Tomczak et al. 2014; Straatman et al. 2014).”
Inferring the star formation histories of massive quiescent galaxies with bagpipes: evidence for multiple quenching mechanisms (2017, background): “…† Scottish Universities Physics Alliance observed to display across at least the 10 − 11 billion years since redshift, z = 2 − 3 (e.g. Strateva et al. 2001; Bell et al. 2004; Faber et al. 2007; Williams et al. 2009; Brammer et al. 2009; Whitaker et al. 2011, 2013; Straatman et al. 2014, 2016).”
Introducing the Illustris Project: the evolution of galaxy populations across cosmic time (2014, background): “7 Note however that there is also indirect evidence for extreme star formation that is obscured at z 5 (Straatman et al. 2014).”
The galaxy stellar mass function at 3.5 ≤z ≤ 7.5 in the CANDELS/UDS, GOODS-South, and HUDF fields (2015, result): “While the existence of passively evolved galaxies at z = 4 has also been shown recently by Straatman et al. (2014) using the ZFOURGE data set and deep Herschel observations, in agreement with early results by Fontana et al. (2009) in the GOODS-South field, we show here that they do contribute…”