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C. T. Liu (American Museum of Natural History), D. J. Pisano (CSIRO/Australia Telescope National Facility), E. M. Wilcots (University of Wisconsin)
We have conducted an H I and optical survey of the environments around 41 isolated field galaxies, to search for nearby gaseous remnants predicted to exist by galaxy formation models. These galaxies were selected to be isolated, quiescent, and morphologically unpeculiar, to limit H I detections to primordially infalling gas rather than tidally disrupted material. The optical photometric data allow us to search for stars associated with the gas, and to measure the properties of those stellar populations. We detected 13 gaseous companions around 10 of the 41 galaxies, down to a detection limit of ~107 solar masses of H I. The optical data show that all of these companions appear to contain stars. This result suggests that H I clouds without stars discovered around galaxies are not primordial, but most likely have either a tidal or ejecta origin.