A Massive Quiescent Galaxy in a Group Environment at z = 4.53
Galaxy groups
QB460-466
Quenched galaxies
Galaxy quenching
Galaxy evolution
Astrophysics of Galaxies (astro-ph.GA)
High-redshift galaxies
FOS: Physical sciences
Astrophysics
Galaxy environments
Astrophysics - Astrophysics of Galaxies
DOI:
10.3847/1538-4357/ad1ff1
Publication Date:
2024-02-28T09:17:55Z
AUTHORS (13)
ABSTRACT
Abstract
We report on the spectroscopic confirmation of a massive quiescent galaxy at z
spec = 4.53 in the COSMOS field. The object was first identified as a galaxy with suppressed star formation at z
phot ∼ 4.65 from the COSMOS2020 catalog. The follow-up spectroscopy with Keck/MOSFIRE in the K band reveals faint [O ii] emission and the Balmer break, indicative of evolved stellar populations. We fit the spectral energy distribution using photometry and a spectrum to infer physical properties. The obtained stellar mass is high (M
* ∼ 1010.8
M
⊙) and the current star formation rate is more than 1 dex below that of main-sequence galaxies at z = 4.5. Its star formation history suggests that this galaxy experienced rapid quenching from z ∼ 5. The galaxy is among the youngest quiescent galaxies confirmed so far at z
spec > 3 with z
form ∼ 5.2 (200 Myr ago), which is the epoch when 50% of the total stellar mass was formed. A unique aspect of the galaxy is that it is in an extremely dense region; there are four massive star-forming galaxies at 4.4 < z
phot < 4.7 located within 150 physical kpc from the galaxy. Interestingly, three of them have virial radii that strongly overlap with that of the central quiescent galaxy (∼70 kpc), suggesting that the overdensity region is likely the highest-redshift candidate of a dense group with a spectroscopically confirmed quiescent galaxy at the center. The group provides us with a unique opportunity to gain insights into the role of the group environment in quenching at z ∼ 5, which corresponds to the formation epoch of massive elliptical galaxies in the local Universe.
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