The role of small-scale environments in the quenching of massive galaxies at $1<z<5$

TL;DR

This study confirms the association of a high-redshift galaxy group with a massive quiescent galaxy and shows that environmental factors like overdensities significantly influence galaxy quenching at $1<z<5$.

Contribution

It provides spectroscopic confirmation of a galaxy group at $z=4.53$ linked to a quiescent galaxy and statistically demonstrates the impact of small-scale overdensities on galaxy quenching.

Findings

A galaxy group at $z=4.53$ associated with a quiescent galaxy was spectroscopically confirmed.

Higher fraction of quiescent galaxies found in group or cluster environments at $1<z<5$.

Environmental quenching mechanisms like mergers are more prevalent in overdense regions at high redshift.

Abstract

Massive quiescent galaxies (QGs) at high redshifts are likely progenitors of massive elliptical galaxies in the local Universe. Recent observations, such as the discovery of QGs in overdensity (galaxy groups and proto-clusters) at high redshifts, have highlighted the importance of the relationship between star formation activity in galaxies and the surrounding environment. We spectroscopically confirm a galaxy group associated with a massive QG at $z_\mathrm{spec}=4.53$ from the Lyman break feature using Subaru/FOCAS. This group consists of at least three star-forming galaxies within 150 pkpc of the QG, which suggests the importance of physical association with other galaxies for galaxy quenching. In order to understand the role of the surrounding environment, we also perform a statistical analysis to characterize the typical environment of QGs at high redshifts. By selecting QGs using the SFR-based selection in the COSMOS field, we find that the fraction of QGs is higher in group or cluster-like environment at $1<z_\mathrm{phot}<5$. This means some of the processes that regulate galaxy quenching occurs more frequently in the overdensity regions. In particular, the elevated fraction of QGs within small-scale overdensities ($<100\mathrm{-}300$ pkpc) at $z>2$ demonstrates that environmental quenching (primarily driven by galaxy mergers and interactions) plays a major role in the formation and evolution of massive QGs at high redshifts.