A Targeted Survey for HI Clouds in Galaxy Groups

Abstract

Five galaxy groups with properties similar to those of the Local Group have been surveyed for HI clouds with the Arecibo Telescope. In total 300 pointings have been observed on grids of approximately 2.5 x 1.5 Mpc centred on the groups. The 4.5 sigma detection limit on the minimal detectable HI masses is approximately 7 x 10^6 M_sun (H_0=65). All detections could be attributed to optical galaxies; no significant detections of HI clouds have been made. This null result leads to the conclusion that the total HI mass of intragroup clouds must be less than 10 per cent of the total HI mass of galaxy groups and less than 0.05 per cent of the dynamical mass. The recent hypothesis that Galactic high velocity clouds are Local Group satellite galaxies is highly inconsistent with these observations.