2007ApJ...659..331Y

The Local Group galaxy Phoenix has the properties of a dwarf spheroidal galaxy, but an adjacent H I cloud has been recently found to be at the same radial velocity as the stars. The proximity suggests that this cloud is associated with the most recent (≤100 Myr) star formation in Phoenix. We have obtained relatively high sensitivity and high resolution H I imaging with the VLA with the goal of distinguishing between different processes for displacing the gas from the galaxy. Due to the outer curvature of the H I cloud, it appears that expulsion from the galaxy by winds from supernovae is more likely than ram pressure stripping. The isolation of the galaxy makes tidal stripping highly unlikely. Using a star formation history constructed from HST imaging, we construct a simple kinematic model that implies that the H I cloud is still gravitationally bound to the galaxy. Gas that is expelled from the centers of dwarf galaxies but remains gravitationally bound may explain the episodic star formation observed in several dwarfs. In the specific case of Phoenix, there may be future star formation in this currently dSph-like galaxy.