Cluster Candidates with Massive Quiescent Galaxies at z ∼ 2
Galaxy clusters are crucial to understanding the role of the environment in galaxy evolution. However, due to their rarity, only a limited number of clusters have been identified at z ≳ 2. In this paper, we report a discovery of seven cluster candidates with massive quiescent galaxies at z ∼ 2 in...
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| Main Authors: | , , , , , , , , , |
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| Format: | Article |
| Language: | English |
| Published: |
IOP Publishing
2025-01-01
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| Series: | The Astrophysical Journal |
| Subjects: | |
| Online Access: | https://doi.org/10.3847/1538-4357/ada5f4 |
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| Summary: | Galaxy clusters are crucial to understanding the role of the environment in galaxy evolution. However, due to their rarity, only a limited number of clusters have been identified at z ≳ 2. In this paper, we report a discovery of seven cluster candidates with massive quiescent galaxies at z ∼ 2 in the 3.5 deg ^2 area of the XMM Large Scale Structure field, roughly doubling the known cluster sample at this frontier redshift if confirmed. We construct a photometric redshift catalog based on deep ( i ∼ 26, K _s ∼ 24) multiwavelength photometry from the u * band to the K band gathered from the Hyper Suprime-Cam Subaru Strategic Program and other collaborative/public surveys. We adopt a Gaussian kernel density estimate with two different spatial scales (10″ and 60″) to draw a density map of massive ( $\mathrm{log}({M}_{* }/{M}_{\odot })\gt 10.5$ ) and quiescent ( $\mathrm{log}(\mathrm{sSFR}\,[{\mathrm{yr}}^{-1}])\lt -10$ ) galaxies at z ∼ 2. Then, we identify seven prominent overdensities. These candidates show clear red sequences in color–magnitude diagrams ( z − H versus H ). Moreover, one of them shows an extended X-ray emission with L _X = (1.46 ± 0.35) × 10 ^44 erg s ^−1 , suggesting its virialized nature. There is no clear evidence of enhancement nor suppression of the star formation rate of the main-sequence galaxies in the clusters. We find that cluster galaxies have a higher fraction of transition population with $-10.5\lt \mathrm{log}(\mathrm{sSFR}\,[{\mathrm{yr}}^{-1}])\lt -10$ (12%) than the field (2%), which implies the ongoing star formation quenching. The quiescent fraction in the cluster candidates also exceeds that in the field. We confirm that the excess of a quiescent fraction is larger for higher-mass galaxies. This is the first statistical evidence for the mass-dependent environmental quenching at work in clusters even at z ∼ 2. |
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| ISSN: | 1538-4357 |