Star formation thresholds in low surface brightness dwarf galaxies

The results of a comparative study of star formation thresholds in gas-rich, low surface brightness, dwarf galaxies are presented. Approximately half the galaxies in the study were "high M-H/L-B" galaxies. which appear to have inefficient star formation properties. The comparison sample comprised of otherwise "normal" dwarf galaxies, with moderate current star formation rates. In all systems, sites of active star formation were associated with local peaks in the HI column density. For both types of galaxies, the azimuthally averaged gas column density is low. Similar to other LSB systems, the global gas densities are well below the critical threshold for star formation throughout the system. Thus, star formation is inhibited globally but occurs locally in these gas-rich dwarf galaxies.