Searching for the Intra-Group Medium in Loose Groups of Galaxies

Abstract

We have conducted a study with the VLA, DRAO Synthesis Telscope, and the FUSE satellite to search for the intra-group medium in two loose groups of galaxies: GH 144 and GH 158. No HI was detected near the background AGN in GH 158, however two previously unknown dwarf galaxies were detected in GH 144. Lyman-alpha, -beta, CIII and NV absorption was detected in GH 144 by FUSE. Using this data and previously published data we found that the virial mass of GH 144 is 2x10^12 M(sun). Of this 8% lies in the individual group galaxies, and less than 8% is in the dense neutral intra-group medium. From our absorption line data we constrain the diffuse IGM to have a volume density greater than log n = -5.2 in a layer less than 22 kpc thick assuming a metallicity of 0.4 solar. While these values are uncertain, it is unlikely that this diffuse gas contributes a significant fraction of the group mass. Given the depth of the absorbing material and its separation from the nearest galaxies, it seems most likely it originates from a small-clump in the IGM, perhaps an ionized high-velocity cloud. (abridged)