Abstract
Abstract We report a massive quiescent galaxy at z spec = 3.0922 − 0.004 + 0.008 spectroscopically confirmed at a protocluster in the SSA22 field by detecting the Balmer and Ca ii absorption features with the multi-object spectrometer for infrared exploration on the Keck I telescope. This is the most distant quiescent galaxy confirmed in a protocluster to date. We fit the optical to mid-infrared photometry and spectrum simultaneously with spectral energy distribution (SED) models of parametric and nonparametric star formation histories (SFHs). Both models fit the observed SED well and confirm that this object is a massive quiescent galaxy with a stellar mass of log ( M ⋆ / M ⊙ ) = 11.26 − 0.04 + 0.03 and 11.54 − 0.00 + 0.03 , and a star formation rate of SFR/M ⊙ yr−1 < 0.3 and = 0.01 − 0.01 + 0.03 for parametric and nonparametric models, respectively. The SFH from the former modeling is described as an instantaneous starburst whereas that of the latter modeling is longer-lived, but both models agree with a sudden quenching of the star formation at ∼0.6 Gyr ago. This massive quiescent galaxy is confirmed in an extremely dense group of galaxies predicted as a progenitor of a brightest cluster galaxy formed via multiple mergers in cosmological numerical simulations. We discover three new plausible [O iii]λ5007 emitters at 3.0791 ≤ z spec ≤ 3.0833 serendipitously detected around the target. Two of them just between the target and its nearest massive galaxy are possible evidence of their interactions. They suggest the future great size and stellar mass evolution of this massive quiescent galaxy via mergers.
Highlights
Deep multiwavelength imaging surveys have uncovered wide variations in galaxy populations at high redshift
We reduced the data using a standard procedure, but the flux is calibrated to our previous Ks-band image taken with multi-object infrared camera and spectrograph (MOIRCS) (Kubo et al 2013), which is calibrated to the UKIRT Infrared Deep Sky Survey (UKIDSS)
We confirm a massive quiescent galaxy at the core of a protocluster at z = 3.09 in the SSA22 field. This is the most distant quiescent galaxy confirmed with Balmer absorption features in a protocluster to date, and a securely selected giant elliptical/brightest cluster galaxy (BCG) progenitor
Summary
Deep multiwavelength imaging surveys have uncovered wide variations in galaxy populations at high redshift. We have studied a protocluster at z = 3.09 in the SSA22 field (Steidel et al 1998), which is known as one of the most significant structures at high redshift This structure was first identified by the overdensity of optically selected galaxies (Steidel et al 1998; Hayashino et al 2004; Matsuda et al 2005; Yamada et al 2012) and in later studies, was further characterized with the overdensity of active galactic nuclei (AGNs) selected in X-ray (Lehmer et al 2009a, 2009b), SMGs (Tamura et al 2009; Umehata et al 2014, 2015, 2017, 2018), and dusty starburst and passively evolving galaxies selected photometrically based on the deep NIR imaging (Kubo et al 2013).
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