分类： 天文学 >> 天文学 提交时间： 2023-02-19
Shuowen Jin
Nikolaj B. Sillassen
Georgios E. Magdis
Aswin P. Vijayan
Gabriel B. Brammer
Vasily Kokorev
John R. Weaver
Raphael Gobat
Clara Giménez-Arteaga
Francesco Valentino
Malte Brinch
Carlos Gómez-Guijarro
Marko Shuntov
Sune Toft
Thomas R. Greve
David Blanquez Sese
摘要： We report the discovery of a compact group of galaxies, CGG-z5, at z~5.2 in the EGS field covered by the JWST/CEERS survey. CGG-z5 was selected as the highest overdensity of galaxies at z>2 in recent JWST public surveys and it consists of six candidate members lying within a projected area of $1.5''\times3''$ (10$\times$20~kpc$^2$). All group members are HST/F435W and HST/F606W dropouts while securely detected in the JWST/NIRCam bands, yielding a narrow range of robust photometric redshifts $5.011$) at z~1. This implies that CGG-z5 could be a "proto-massive galaxy" captured during a short-lived phase of massive galaxy formation.
分类： 天文学 >> 天文学 提交时间： 2023-02-19
Malte Brinch
Thomas R. Greve
John R. Weaver
Gabriel Brammer
Olivier Ilbert
Marko Shuntov
Shuowen Jin
Daizhong Liu
Clara Giménez-Arteaga
Caitlin M. Casey
Iary Davidson
Seiji Fujimoto
Anton M. Koekemoer
Vasily Kokorev
Georgios Magdis
H. J. McCracken
Conor J. R. McPartland
Bahram Mobasher
David B. Sanders
Sune Toft
摘要： We conduct a systematic search for protocluster candidates at $z \geq 6$ in the COSMOS field using the recently released COSMOS2020 source catalog. We select galaxies using a number of selection criteria to obtain a sample of galaxies that have a high probability of being inside a given redshift bin. We then apply overdensity analysis to the bins using two density estimators, a Weighted Adaptive Kernel Estimator and a Weighted Voronoi Tessellation Estimator. We have found 15 significant ($>4\sigma$) candidate galaxy overdensities across the redshift range $6\le z\le7.7$. The majority of the galaxies appear to be on the galaxy main sequence at their respective epochs. We use multiple stellar-mass-to-halo-mass conversion methods to obtain a range of dark matter halo mass estimates for the overdensities in the range of $\sim10^{11-13}\,M_{\rm \odot}$, at the respective redshifts of the overdensities. The number and the masses of the halos associated with our protocluster candidates are consistent with what is expected from the area of a COSMOS-like survey in a standard $\Lambda$CDM cosmology. Through comparison with simulation, we expect that all the overdensities at $z\simeq6$ will evolve into a Virgo-/Coma-like clusters at present (i.e., with masses $\sim 10^{14}-10^{15}\,M_{\rm \odot}$). Compared to other overdensities identified at $z \geq 6$ via narrow-band selection techniques, the overdensities presented appear to have $\sim10\times$ higher stellar masses and star-formation rates. We compare the evolution in the total star-formation rate and stellar mass content of the protocluster candidates across the redshift range $6\le z\le7.7$ and find agreement with the total average star-formation rate from simulations.
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