Date: 11/9/2023
Cosmic Vine: A z=3.44 Large-Scale Structure Hosting Massive Quiescent Galaxies
JWST color-composed image of the Cosmic Vine (Red: F356W+F410W+F444W; Green: F200W+F277W; Blue: F115W+F150W). Left: The large scale structure. Sources with 3.435 < zspec < 3.455 are marked with green circles. White contours show the overdensity of 3.2 < zphot < 3.7 sources in step of 2, 4 and 6s levels. Right: 10'' × 10'' images centered on two massive galaxies in the Cosmic Vine. Galaxies with zspec are highlighted with green arrows, and candidate members with 3.3 < zphot < 3.6 are marked with cyan arrows.
Abstract: We report the discovery of a large-scale structure at z=3.44 revealed by JWST data in the EGS field. This structure, dubbed "Cosmic Vine", consists of 20 galaxies with spectroscopic redshifts at 3.4370%). Comparisons with simulations suggest that the Cosmic Vine would form a cluster with halo mass >10^14 Msun at z=0, and the two massive galaxies are likely forming the brightest cluster galaxies (BCGs). The results unambiguously reveal that massive quiescent galaxies can form in growing large-scale structures at z>3, thus disfavoring the environmental quenching mechanisms that require a virialized cluster core. Instead, as suggested by the interacting and bulge-dominated morphologies, the two galaxies are likely quenched by merger-triggered starburst or AGN feedback before falling into a cluster core. Moreover, we found that the observed specific star formation rates of massive quiescent galaxies in z>3 dense environments are two orders of magnitude lower than that of the BCGs in the TNG300 simulation. This discrepancy potentially poses a challenge to the models of massive cluster galaxy formation. Future studies comparing a large sample with dedicated cluster simulations are required to solve the problem.
