Accelerated structural evolution of galaxies in a starbursting cluster at z=2.51

TL;DR

This study reveals that galaxies in a starbursting cluster at z=2.51 are structurally smaller and exhibit different color gradients compared to field galaxies, indicating early environmental effects on galaxy evolution.

Contribution

It provides new insights into how environment influences galaxy structure and stellar populations during the peak formation epoch at high redshift.

Findings

High-mass cluster SFGs are smaller and older with steep negative color gradients.

Low-mass cluster SFGs include compact galaxies with positive color gradients.

Environmental effects like tidal and ram pressure stripping are evident in low-mass galaxies.

Abstract

Structural properties of cluster galaxies during their peak formation epoch, $z \sim 2-4$ provide key information on whether and how environment affects galaxy formation and evolution. Based on deep HST/WFC3 imaging towards the z=2.51 cluster, J1001, we explore environmental effects on the structure, color gradients, and stellar populations of a statistical sample of cluster SFGs. We find that the cluster SFGs are on average smaller than their field counterparts. This difference is most pronounced at the high-mass end ($M_{\star} > 10^{10.5} M_{\odot}$) with nearly all of them lying below the mass-size relation of field galaxies. The high-mass cluster SFGs are also generally old with a steep negative color gradient, indicating an early formation time likely associated with strong dissipative collapse. For low-mass cluster SFGs, we unveil a population of compact galaxies with steep positive color gradients that are not seen in the field. This suggests that the low-mass compact cluster SFGs may have already experienced strong environmental effects, e.g., tidal/ram pressure stripping, in this young cluster. These results provide evidence on the environmental effects at work in the earliest formed clusters with different roles in the formation of low and high-mass galaxies.