The Origin of Intergalactic Light in Compact Groups of Galaxies

Mark J Henriksen

doi:10.3390/universe7080303

Abstract

We investigate the origin of intergalactic light (IGL) in close groups of galaxies. IGL is hypothesized to be the byproduct of interaction and merger within compact groups. Comparing the X-ray point source population in our sample of compact groups that have intergalactic light with compact groups without IGL, we find marginal evidence for a small increase in ultra-luminous X-ray sources (ULXs). There is also a significant bias towards lower luminosity high mass X-ray binaries (HMXRBs). We interpret this as an indication that groups with visible IGL represent a later evolutionary phase than other compact groups. They have galaxies characterized by quenching of star formation (lower star formation rate (SFR) inferred from lower HMXRB luminosity) after stellar material has been removed from the galaxies into the intergalactic medium, which is the source of the IGL. We conclude that the presence of an increased fraction of ULXs is due to past interaction and mergers within groups that have IGL.

Highlights

Compact Groups (CGs) of Galaxies are small and relatively isolated aggregates with mean separations on the order of a component galaxy diameter
We found a greater number of low luminosity high mass X-ray binaries (HMXRBs) compared with typical compact groups
We have characterized the X-ray point sources that are co-spatial with galaxies in compact groups known to have diffuse intergalactic light

Summary

Introduction

Compact Groups (CGs) of Galaxies are small and relatively isolated aggregates with mean separations on the order of a component galaxy diameter. Giant ellipticals with high X-ray luminosity are hypothesized to be the endpoint of galaxy mergers that occur primarily within groups. The group X-ray emission would be retained as a bright halo around a giant elliptical galaxy.

Results

Conclusion