A High-Resolution Study of the HiContent of Local Group Dwarf Irregular Galaxy WLM

Dwarf irregular galaxies are unique laboratories for studying the interactionbetween stars and the interstellar medium in low mass environments. We presentthe highest spatial resolution observations to date of the neutral hydrogencontent of the Local Group dwarf irregular galaxy WLM. We find that WLM'sneutral hydrogen distribution is typical for a galaxy of its type and size andderive an HI mass of 6.3e7 Msun for WLM. In addition, we derive an HI extentfor WLM of 30 arcmin, which is much less than the 45 arcmin extent found byHuchtmeier, Seiradakis, and Materne (1981). We show that the broken ring ofhigh column density neutral hydrogen surrounding the center of WLM is likelythe result of star formation propagating out from the center of the galaxy. Theyoung stars and Ha emission in this galaxy are mostly correlated with the highcolumn density neutral hydrogen. The gap in the central ring is the result ofstar formation in that region using up, blowing out, or ionizing all of theneutral hydrogen. Like many late-type galaxies, WLM's velocity field isasymmetric with the approaching (northern) side appearing to be warped and asteeper velocity gradient for the approaching side than for the receding sidein the inner region of the galaxy. We derive a dynamical mass for WLM of 2.16e9Msun.