Activity in Galactic Nuclei of Compact Group Galaxies in the Local Universe

TL;DR

This study investigates nuclear activity in galaxies within local compact groups, revealing that their AGN fraction is moderate and not the highest among environments, likely due to limited gas supply despite frequent interactions.

Contribution

It provides the first comprehensive comparison of AGN fractions in compact groups versus clusters and fields using SDSS data and emission-line diagnostics.

Findings

AGN fraction in compact groups is 17-42%.

AGN activity is not strongly correlated with galaxy density.

Lack of mid-infrared AGN detections suggests limited gas supply.

Abstract

We study the nuclear activity of galaxies in local compact groups. We use a spectroscopic sample of 238 galaxies in 58 compact groups from the Sloan Digital Sky Survey data release 7 to estimate the fraction of AGN-host galaxies in compact groups, and to compare it with those in cluster and field regions. We use emission-line ratio diagrams to identify AGN-host galaxies, and find that the AGN fraction of compact group galaxies is 17-42% depending on the AGN classification method. The AGN fraction in compact groups is not the highest among the galaxy environments. This trend remains even if we use several subsamples segregated by galaxy morphology and optical luminosity. The AGN fraction for early-type galaxies decreases with increasing galaxy number density, but the fraction for late-type galaxies changes little. We find no mid-infrared detected AGN-host galaxies in our sample of compact groups using Wide-field Infrared Survey Explorer data. These results suggest that the nuclear activity of compact group galaxies (mostly early types) is not strong because of lack of gas supply even though they may experience frequent galaxy-galaxy interactions and mergers that could trigger nuclear activity.