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Session 43 - The Diffuse ISM: Milky Way and Beyond.
Display session, Tuesday, June 11
Great Hall,
We present a comparative analysis of the distribution and kinematics of H I gas in several nearby irregular galaxies at various levels of star formation activity. NGC 1569 is distinguishable for containing two recently formed ``super star clusters'', yet its HI distribution lacks the supershells and filaments that normally characterize starburst galaxies. In contrast, IC 10 is actively forming stars and its ISM has been punctured and blown apart by the cumulative effects of the underlying massive stellar population. We compare these two actively star-forming galaxies with the more quiescent IC 1613 and Sextans A. While the HI gas coincident with the modest HII regions in IC 1613 is filamentary, the inner part of the galaxy appears to have been swept clean of neutral gas by the latest round of star formation. The HI in the center of Sextans A is more complex, containing 3 distinct velocity structures. In comparing the distribution of HI in these galaxies we postulate that we are seeing how the evolution of the structure of the ISM in irregular galaxies reflects the evolution of the underlying star formation activity.
