The Ages, Metallicities, and Element Abundance Ratios of Massive Quenched Galaxies at z ≍ 1.6

Journal
Date Issued
2015
Author(s)
Onodera, M.
•
Carollo, C. M.
•
Renzini, A.
•
Cappellari, M.
•
Mancini, C.
•
Arimoto, N.
•
Daddi, E.
•
Gobat, R.
•
•
Tacchella, S.
•
Yamada, Y.
DOI
Abstract
We investigate the stellar population properties of a sample of 24 massive quenched galaxies at 1.25< zspec< 2.09 identified in the COSMOS field with our Subaru/Multi-object Infrared Camera and Spectrograph near-IR spectroscopic observations. Tracing the stellar population properties as close to their major formation epoch as possible, we try to put constraints on the star formation history, post-quenching evolution, and possible progenitor star-forming populations for such massive quenched galaxies. By using a set of Lick absorption line indices on a rest-frame optical composite spectrum, the average age, metallicity [Z/H], and α-to-iron element abundance ratio [α/Fe] are derived as log(age/Gyr)=0.04-0.08+0.10, [Z/H]=0.24-0.14+0.20, and [α /Fe]=0.31-0.12+0.12, respectively. If our sample of quenched galaxies at < z≥1.6 is evolved passively to z = 0, their stellar population properties will align in excellent agreement with local counterparts at similar stellar velocity dispersions, which qualifies them as progenitors of local massive early-type galaxies. Redshift evolution of stellar population ages in quenched galaxies combined with low redshift measurements from the literature suggests a formation redshift of zf∼ 2.3, around which the bulk of stars in these galaxies have been formed. The measured [α/Fe] value indicates a star formation timescale of ≲ 1 Gyr, which can be translated into a specific star formation rate of ≃ 1 Gyr-1 prior to quenching. Based on these findings, we discuss identifying possible progenitor star-forming galaxies at z≃ 2.3. We identify normal star-forming galaxies, i.e., those on the star-forming main sequence, followed by a rapid quenching event, as likely precursors of the quenched galaxies at < z≥1.6 presented here.

Based on data collected at the Subaru telescope, which is operated by the National Astronomical Observatory of Japan. (Proposal IDs: S09A-043, S10A-058, and S11A-075.)

Volume
808
Issue
2
Start page
161
Uri
Url
Issn Identifier
0004-637X
Ads BibCode
2015ApJ...808..161O
Rights
open.access
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