Quantified diffuse light in compact groups of galaxies

TL;DR

This study investigates the distribution and fraction of intra-group light (IGL) in 36 Hickson compact galaxy groups using deep optical observations, revealing correlations with group morphology and luminosity, and comparing IGL profiles to dark matter simulations.

Contribution

It provides the first detailed analysis of IGL distribution in a sizable sample of compact groups, linking IGL properties to group dynamics and dark matter profiles.

Findings

IGL brightness correlates with the fraction of early-type galaxies.

The IGL profile has a Sersic index around 0.5-1, similar to dark matter halo profiles.

IGL brightness depends on the total luminosity of the group.

Abstract

The vast majority of stars in galaxy groups are contained within their constituent galaxies. Some small fraction of stars is expected, however, to follow the global dark matter potential of the group. In compact groups, interactions between the galaxies should be frequent. This leads to a more intensive material stripping from the group members, which finally forms an intra-group light component (IGL). Therefore, the distribution of the IGL should be related to the distribution of the total mass in the compact group and its dynamical status. In this study we consider the distribution and fraction of the IGL in a sample of 36 Hickson compact groups (HCGs). We use deep observations of these compact groups (down to surface brightness $\sim 28$ mag\,arcsec$^{-2}$ in the $r$ band) obtained with the WISE $28$-inch telescope. For five HCGs with a bright symmetric IGL component, we carry out multicomponent photometric decomposition to simultaneously fit the galaxy profiles and the IGL. For the remaining groups, we only fit the profiles of their constituent galaxies. We find that the mean surface brightness of the IGL correlates with the mean morphology of the group: it becomes brighter in the groups with a larger fraction of early-type galaxies. On the other hand, the IGL brightness depends on the total luminosity of the group. The IGL profile tends to have a S\'ersic index $n\sim0.5-1$, which is generally consistent with the mass density profile of dark matter haloes in compact groups obtained from cosmological simulations.