On the origin of the neutral hydrogen supershells: the ionized progenitors and the limitations of the multiple supernovae hypothesis
arXiv:0803.3952 · doi:10.1086/588210
Abstract
Here we address the question whether the ionized shells associated with giant HII regions can be progenitors of the larger HI shell-like objects found in the Milky Way and other spiral and dwarf irregular galaxies. We use for our analysis a sample of 12 HII shells presented recently by Relaño et al. (2005, 2007). We calculate the evolutionary tracks that these shells would have if their expansion is driven by multiple supernovae explosions from the parental stellar clusters. We find, contrary to Relaño et al. (2007), that the evolutionary tracks of their sample HII shells are inconsistent with the observed parameters of the largest and most massive neutral hydrogen supershells. We conclude that HII shells found inside giant HII regions may represent the progenitors of small or intermediate HI shells, however they cannot evolve into the largest HI objects unless, aside from the multiple supernovae explosions, an additional energy source contributes to their expansion.
arXiv commentAccepted for publication in ApJ, tentatively scheduled for the ApJ July 1, 2008, v681n1 issue. 19 pages, 4 figures
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