Research on the Intra-Group Light in the HCG 95 Group.

Abstract

The Intra-Group/Cluster Light (IGL/ICL) can be used to study the dynamical evolution of galaxy groups and clusters. Hickson Compact Groups (HCGs) have a high density and a low velocity dispersion, providing a unique environment to study galaxies merger and properties of interacting galaxies. It is also a promising target for the study of IGL. The g and r band deep imaging data of HCG 95 were obtained with Chinese Near Object Survey Telescope (CNEOST). The IGL fraction in HCG 95 is measured with model fitting using GALFIT, giving an IGL fraction (defined by the ratio between the IGL luminosity and the group total luminosity) of 3.55% $\pm$ 0.38% and 3.78% $\pm$ 0.59% in the g and r band, respectively. When applying the surface brightness threshold method, the IGL fraction is 1.9%–10% and 1.5%–10% in the g an r band, respectively. The color of the IGL ($g-r=0.78\pm 0.37$) is similar to that of the HCG 95A and HCG 95C in the group ($g-r=0.82-0.85$), suggesting that it is composed by an old population. It is showed that the IGL in the group may be from the stripped material of interaction between HCG 95A and HCG 95C, with little recent accretion. Combined with the IGL fraction measurements from literatures, we find that the IGL fraction shows no clear correlation with the total mass of groups. A positive correlation is found between the IGL fraction and the early-type galaxies fraction of groups, suggesting that the IGL fraction is linked to the evolutionary stage of a group.