THE ORIGIN OF NEUTRAL HYDROGEN CLOUDS IN NEARBY GALAXY GROUPS: EXPLORING THE RANGE OF GALAXY INTERACTIONS

We combine high-resolution N-body simulations with deep observations of neutral hydrogen (H I) in nearby galaxy groups in order to explore two well-known theories of H I cloud formation: H I stripping by galaxy interactions and dark-matter minihalos with embedded H I gas. This paper presents new data from three galaxy groups-Canes Venatici I, NGC 672, and NGC 45-and assembles data from our previous galaxy group campaign to generate a rich H I cloud archive to compare to our simulated data. We find no H I clouds in the Canes Venatici I, NGC 672, or NGC 45 galaxy groups. We conclude that H Iclouds in our detection space are most likely to be generated through recent, strong galaxy interactions. We find no evidence of H I clouds associated with dark-matter halos above M-H (I) similar to 10(6) M-circle dot, within +/- 700 km s(-1) of galaxies, and within 50 kpc projected distance of galaxies.