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Session 66 - Galaxies.
Display session, Thursday, June 11
Atlas Ballroom,
Analysis of expanding HI supershells in a large sample of galaxies has benefited greatly from a recently developed automated method for finding and accurately characterizing bubble-like structures. Thilker, Braun, and Walterbos (1998) described a 3D pattern recognition method for use with spectral-line datacubes. Mashchenko, Thilker, and Braun (1998) refined the procedure, incorporating realistic projected supershell models as template patterns. We have applied the automated method to a sample of 11 nearby spiral galaxies. Here we present characteristics of all HI supershells observed in these systems. Our analysis suggests a possible correlation between the global rate of star formation (SFR) and the total kinetic energy of supershells in a galaxy. We also discuss the observed supershell size distribution, making comparison with the theoretical predictions of Oey amp; Clarke (1997). Finally, in selected regions, we examine properties of the 21-cm line profile attributable to shell expansion. It appears that superbubble structures may be largely responsible for the presence of low-level, high velocity wings in the CNM, as traced by the high-brightness network (HBN) of Braun (1997).
