The Massive Ancient Galaxies at z > 3 NEar-infrared (MAGAZ3NE) Survey: Confirmation of Extremely Rapid Star Formation and Quenching Timescales for Massive Galaxies in the Early Universe*

Abstract

We present near-infrared spectroscopic confirmations of a sample of 16 photometrically selected galaxies with stellar masses ( )>11 at redshift z>3 from the XMM-VIDEO and COSMOS-UltraVISTA fields using Keck/MOSFIRE as part of the Massive Ancient Galaxies At z > 3 NEar-infrared (MAGAZ3NE) survey. Eight of the ultramassive galaxies (UMGs) have specific star formation rates (sSFR)<0.03 Gyr −1 , with negligible emission lines. Another seven UMGs show emission lines consistent with active galactic nuclei and/or star formation, while only one UMG has sSFR>1 Gyr −1 . Model star formation histories of these galaxies describe systems that formed the majority of their stars in vigorous bursts of several hundred megayear duration around < < z 4 6 during which hundreds to thousands of solar masses were formed per year. These formation ages of <1 Gyr prior to observation are consistent with ages derived from measurements of D n (4000) and EW 0 (Hδ). Rapid quenching followed these bursty star-forming periods, generally occurring less than 350Myr before observation, resulting in post-starburst SEDs and spectra for half the sample. The rapid formation timescales are consistent with the extreme star formation rates observed in < < z 4 7 dusty starbursts observed with ALMA, suggesting that such dusty galaxies are progenitors of these UMGs. While such formation histories have been suggested in previous studies, the large sample introduced here presents the most compelling evidence yet that vigorous star formation followed by rapid quenching is almost certainly the norm for high-mass galaxies in the early universe. The UMGs presented here were selected to be brighter than K s =21.7, raising the intriguing possibility that even (fainter) older quiescent UMGs could exist at this epoch.Unified Astronomy Thesaurus concepts: Galaxy evolution (594); High-redshift galaxies (734); Quenched galaxies (2016)

The GOGREEN survey: dependence of galaxy properties on halo mass at z &gt; 1 and implications for environmental quenching

“…This is additionally compatible with recent high redshift work showing that quiescent galaxies exist at redshifts as high as e.g. z ∼ 3−5 (Forrest et al 2020;Valentino et al 2020).…”

An Ancient Massive Quiescent Galaxy Found in a Gas-rich z ∼ 3 Group

“…Such studies usually leave out galaxies similar to Galaxy-D that are expected to have an older (>1 Gyr) stellar population, due to preferential selection of brighter targets. Forrest et al (2020b) show that galaxies with such ages would be considerably less bright (by ∼1-2 mag) in near-IR (NIR), compared to PSBs. For example, in comparison to Galaxy-D, the Valentino et al (2020) andD'Eugenio et al (2020b) samples in the Ks band are on average brighter by 1.7 and 2.4 mag, respectively.…”

“…This form of rapid quenching has been extensively proposed to explain populations of QGs at z ∼ 3-4 (e.g., Schreiber et al 2018b;D'Eugenio et al 2020aD'Eugenio et al , 2020bForrest et al 2020aForrest et al , 2020bValentino et al 2020). However, these are usually found to be PSBs, with t 50 < 0.8 Gyr (Figure 5).…”

“…Hydrodynamical simulations and semianalytical models have found it difficult to reproduce massive (10 11 M * ) quiescent galaxies (QGs) beyond z  3 (Steinhardt et al 2016;Schreiber et al 2018b;Cecchi et al 2019), while observations have been pushing the redshift boundary by detecting such systems at z ∼ 3-4 (Gobat et al 2012;Glazebrook et al 2017;Schreiber et al 2018a;D'Eugenio et al 2020a;Forrest et al 2020aForrest et al , 2020bSaracco et al 2020;Valentino et al 2020). Most of the systems so far observed belong to a population of recently quenched "poststarburst" (PSB) galaxies with their last star formation episode occurring over the last <0.8 Gyr.…”

“…Most of the systems so far observed belong to a population of recently quenched "poststarburst" (PSB) galaxies with their last star formation episode occurring over the last <0.8 Gyr. However, we might still be missing a fraction of older (1 Gyr) QGs (D'Eugenio et al 2020b;Forrest et al 2020b). Moreover, there has not been any insight on the influence of the environment over such galaxies, as most of those studied are field objects.…”