case western reserve university



The HI Environments of Galaxies: Clues to Galaxy Formation

Eric Wilcots (Wisconsin)

The combination of wide-field HI imaging and sensitive single-pointing observations with the Very Large Array and and the Australia Telescope Compact Array over the past few years has uncovered a wealth of neutral gas lurking in the immediate environments of a number of galaxies. Sorting through the various detections of gas around galaxies, one finds that it tends to come in three flavors: very extended and smooth; very extended, but either morphologically or kinematically (or both!) chaotic; and discrete clumps of gas, some of which seem to be devoid of stars.

The role of this far-flung HI in the evolution of the host galaxy remains uncertain, but studies of HI around galaxies are excellent probes of the processes by which galaxies formed in the first place and provide critical tests of popular galaxy formation models. I will present a review of what we know about HI around galaxies in a number of different environments and what those studies are telling us about how galaxies form.