A mid-IR study of Hickson Compact Groups I : Probing the Effects of Environment in Galaxy Interactions

TL;DR

This study investigates the infrared properties of Hickson Compact Groups using mid-infrared imaging to understand environmental effects on galaxy interactions and evolution, revealing differences based on group dynamical age.

Contribution

It provides a detailed analysis of mid-infrared properties of HCGs, comparing them with isolated and interacting galaxies, and explores the impact of group dynamical age on galaxy characteristics.

Findings

No significant difference in star formation rates between HCGs and isolated/interacting galaxies.

Old groups host late-type galaxies with slightly lower specific star formation rates.

Diffuse cold dust is present in the intergalactic medium of several old groups.

Abstract

Hickson Compact Groups (HCGs) are among the densest galaxy environments of the local universe. To examine the effects of the environment on the infrared properties of these systems, we present an analysis of Spitzer and ISO mid-infrared imaging as well as deep ground based near-infrared imaging of 14 HCGs containing a total of 69 galaxies. Based on mid-infrared color diagnostics we identify the galaxies which appear to host an active nucleus, while using a suite of templates, we fit the complete infrared spectral energy distribution for each group member. We compare our estimates of galaxy mass, star formation rate, total infrared luminosities, and specific star formation rates (sSFR) for our HCG sample, to samples of isolated galaxies and interacting pairs and find that overall there is no discernible difference among them. However, HCGs which can be considered as dynamically "old", host late-type galaxies with a slightly lower sSFR than the one found in dynamically "young" groups. This could be attributed to multiple past interactions among the galaxies in old groups, that have led to the build up of their stellar mass. It is also consistent with our prediction for the presence of diffuse cold dust in the intergalactic medium of 9 of the dynamically "old" groups.