| Abstract | We present an H I and optical survey of 41 extremely isolated galaxies in an attempt to search for the gaseous remnants of the galaxy formation process, predicted to exist by hierarchical models of galaxy formation. By observing extremely isolated, quiescent, nonpeculiar galaxies we minimize the chances that any extragalactic H I found will be another galaxy, tidal debris, or ejecta from a galactic fountain or superwind. We have obtained new and archival data from the VLA and ATCA in a search for H I clouds down to MHI~107 Msolar around these galaxies. We found 13 H I-rich companions around 10 of the 41 galaxies surveyed. Optical imaging finds spatially coincident stars associated with all 13 companions. We find that the isolated galaxies have properties fairly similar to those of field galaxies, while the companions are similar to dwarf irregular galaxies. The presence of stars in all 13 companions suggests that H I clouds without stars discovered by other authors around field galaxies are not primordial and most likely have either a tidal or ejecta origin. |
