Local gaseous filaments

Cosmological simulations indicate there is a web of low density gas strung between galaxies and galaxy clusters. This material is responsible for the formation of galaxies and galaxy clusters at high redshift and remains as a reservoir of material for the continuing evolution of galaxies in the local universe. In addition, the processes of star formation and merging may enrich and replenish some of this intergalactic material. To understand the evolution of galaxies and their connection with large-scale structure, we must understand how the galaxies and the lower density intergalactic gas detected in absorption are related. In the past, the relationship between intergalactic gas and galaxies has primarily been investigated by optically surveying regions surrounding Ly-alpha absorption systems. To address the connection between gaseous intergalactic filaments and the gaseous component of galaxies we have completed a large survey of the HI environment surrounding low redshift Ly-alpha absorbers (cz < 5000 km s^-1). The survey used the Parkes and Arecibo Radio Telescopes, and the Australia Telescope Compact Array to probe the HI environment of > 25 low redshift absorbers. This wealth of data on the gaseous environment of Ly-alpha absorbers allows us to search for previously undetected gas-rich galaxies near the lines of sight, and investigate the correlation between absorbers and gaseous large scale structure. The first results from the survey indicate that while most absorbers do not seem to arise in the halos of gas-rich galaxies, there is a correlation between the presence of intergalactic gas, galaxies, and large scale structure