Star Formation Triggering Mechanisms in Dwarf Galaxies: The Far‐Ultraviolet, Hα, and H<scp>i</scp>Morphology of Holmberg II

Abstract

Far-ultraviolet (FUV), Hα, and HI observations of dwarf galaxy Holmberg II are used to investigate the means by which star formation propagates in galaxies lacking 1 NASA Space Grant Fellow, University of Alabama 1995-1997 1 global internal triggering mechanisms such as spiral density waves. The observations trace the interaction between sites of massive star formation and the neutral and ionized components of the surrounding ISM in this intrinsically simple system. Both local and large-scale triggering mechanisms related to massive star formation are seen, suggesting that feedback from massive stars is a microscopic process operating in all galaxies to a certain degree. The data emphasize the importance of local conditions in regulating star formation from evidence such as massive stars inside ionized shells, compact HII regions surrounding aging clusters, and stars formed in chains of progressing age. Surface brightness profiles show current activity correlates with the time averaged level of past star formation at a given radius demonstrating a reliance on local conditions. Large-scale triggering