HI Deficiency in X-ray Bright Groups

Abstract

Denser environments do influence the evolution of neutral gas in galaxies as demonstrated by the studies of galaxies in clusters. In them, ram-pressure stripping seems the important mechanism responsible for the gas evolution. However, not all the gas evolution in cluster galaxies may be due to their present environment. Redshift surveys indicate that a large fraction of galaxies occur in small groups [2, 4, 5]. These groups possibly merge to form subclusters which in turn may combine to form clusters. Various evidences suggest that the gas evolution in such “sub-clusters” may be important. Lower velocity dispersion among galaxies in groups enhance tidal interactions, which can affect their gas content, morphology and possibly star formation rate. However, the cold gas evolution in groups is an idea relatively unexplored. Therefore, we carried out two observational studies of H i content of galaxies in groups, with the view to study the effect of the hot IGM, on the H i content of the spiral galaxies. Here, we summarise the results of these studies: (a) comparative study of the H i content of galaxies in groups with and without hot intra-group medium (IGM), (b) H i imaging of some of the galaxies from X-ray bright groups.