A targeted survey for H I clouds in galaxy groups

Five galaxy groups with properties similar to those of the Local Group have been surveyed for H i clouds with the Arecibo Telescope. In total 300 pointings have been observed on grids of approximately 2.5×1.5 Mpc2 centred on the groups. The 4.5σ detection limit on the minimal detectable H i masses is approximately 7×106 M⊙(H0=65 km s−1 Mpc−1). All detections could be attributed to optical galaxies; no significant detections of H i clouds have been made. This null result leads to the conclusion that the total H i mass of intragroup clouds must be less than 10 per cent of the total H i 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.