The Fastest Galaxy Evolution in an Unbiased Compact Group Sample with WISE

TL;DR

This study reveals that galaxy evolution in compact groups is faster than in clusters, with MIR properties indicating more rapid changes influenced by both internal and external environments.

Contribution

It provides the first comprehensive analysis of MIR properties of galaxies in a large, unbiased sample of compact groups, highlighting environmental effects on galaxy evolution.

Findings

Compact group galaxies have bluer MIR colors than cluster galaxies.

Late-type members in compact groups are bluer than those in clusters.

Galaxy evolution proceeds faster in compact groups than in cluster centers.

Abstract

We study the mid-infrared (MIR) properties of galaxies in compact groups and their environmental dependence using the \textit{Wide-field Infrared Survey Explorer (WISE)} data. We use a volume-limited sample of 670 compact groups and their 2175 member galaxies with $M_r< -19.77$ and $0.01<z<0.0741$, drawn from \citet{sohn+16}, which were identified using a friends-of-friends algorithm. Among the 2175 galaxies, 1541 galaxies are detected at \textit{WISE} 12 $\micron$ with a signal-to-noise ratio greater than 3. Among the 1541 galaxies, 433 AGN-host galaxies are identified by using both optical and MIR classification scheme. Using the remaining 1108 non-AGN galaxies, we find that the MIR $[3.4]-[12]$ colors of compact group early-type galaxies are on average bluer than those of cluster early-type galaxies. When compact groups have both early- and late-type member galaxies, the MIR colors of the late-type members in those compact groups are bluer than the MIR colors of cluster late-type galaxies. As compact groups are located in denser regions, they tend to have larger early-type galaxy fractions and bluer MIR color galaxies. These trends are also seen for neighboring galaxies around compact groups. However, compact group member galaxies always have larger early-type galaxy fractions and bluer MIR colors than their neighboring galaxies. Our findings suggest that the properties of compact group galaxies depend on both internal and external environments of compact groups, and that galaxy evolution is faster in compact groups than in the central regions of clusters.