Groups and Protocluster Candidates in the CLAUDS and HSC-SSP Joint Deep Surveys

Abstract

Using the extended halo-based group finder developed by Yang et al., which is able to deal with galaxies via spectroscopic and photometric redshifts simultaneously, we construct galaxy group and candidate protocluster catalogs in a wide redshift range (0 < z < 6) from the joint CFHT Large Area U-band Deep Survey and Hyper Suprime-Cam Subaru Strategic Program deep data set. Based on a selection of 5,607,052 galaxies with i-band magnitude m i < 26 and a sky coverage of 34.41 deg2, we identify a total of 2,232,134 groups, of which 402,947 groups have at least three member galaxies. We have visually checked and discussed the general properties of these richest groups at redshift z > 2.0. By checking the galaxy number distributions within a 5–7 h −1Mpc projected separation and a redshift difference Δz ≤ 0.1 around those richest groups at redshift z > 2, we identify lists of 761, 343, and 43 protocluster candidates in the redshift bins 2 ≤ z < 3, 3 ≤ z < 4, and z ≥ 4, respectively. In general, these catalogs of galaxy groups and protocluster candidates will provide useful environmental information in probing galaxy evolution along cosmic time.

Environmental Dependence of the Mass–Metallicity Relation in Cosmological Hydrodynamical Simulations

“…Both simulations also predict that the scatter in the stellar mass-halo mass relation correlates with the gas-phase metallicity, in the sense that galaxies in more massive halos are more metal-poor (see Cui et al 2021;Zhang et al 2022b;Wang et al 2023, for correlation with other galaxy properties). This prediction can be tested in our local universe and high z using the galaxy group catalog (Yang & Mo 2008;Yang et al 2021;Li et al 2022a). In addition, the observational measurements of the gas-phase metallicity difference between protocluster and field galaxies can be further improved with the coming high-z spectroscopic galaxy surveys (Takada et al 2014;Maiolino et al 2020;Wang et al 2021).…”

The JWST Advanced Deep Extragalactic Survey: Discovery of an Extreme Galaxy Overdensity at z = 5.4 with JWST/NIRCam in GOODS-S

“…The two halo mass estimates derived in Section 3.3 are given by the turquoise triangles. For comparison, groups and protoclusters at z < 6 from Li et al (2022) are given in grayscale, while protoclusters at z > 6 from Brinch et al (2023) are given by the gray points. The magenta shaded region shows the expected halo mass evolution of a Coma-like cluster (Chiang et al 2013).…”

“…The two halo mass estimates derived here in Section 3 are given by the turquoise triangles, where the triangles indicate that these are likely underestimates of the true halo mass. Groups and protoclusters at z < 6 from Li et al (2022) are given in grayscale, while protocluster candidates in the COSMOS field at z > 6 from Brinch et al (2023) are given by the gray points for comparison, both selected based on photometric redshifts, with dark matter halo mass estimates that assume the same stellar-to-halo abundance matching relation used here. The magenta shaded region shows the expected halo mass evolution of a Coma-like cluster (Chiang et al 2013) assuming a smooth evolution at z > 6.…”

“…However, these processes make it difficult to ascertain important evidence (e.g., both the initial relative positions and velocities of the constituent galaxies) related to the early formation and evolution of the most massive gravitationally bound structures. For this reason, searching for protoclusters in the early Universe offers our best chance of understanding the initial formation and subsequent evolution of galaxy clusters today (e.g., Li et al 2022;Brinch et al 2023;Morishita et al 2023).…”