Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: On the origin of the neutral hydrogen supershells: the ionized
  progenitors and the limitations of the multiple supernovae hypothesis   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 Rela\~no 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 Rela\~no 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.

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The categories of this paper are: patt-sol
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The categories of this paper are: mtrl-th
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The categories of this paper are: eess
9
The categories of this paper are: nlin
2
The categories of this paper are: math
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The categories of this paper are: solv-int
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The categories of this paper are: acc-phys
1
The categories of this paper are: cs
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The categories of this paper are: nucl-ex
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The categories of this paper are: hep-ex
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The categories of this paper are: nucl-th
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The categories of this paper are: math-ph
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The categories of this paper are: chao-dyn
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The categories of this paper are: stat
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The categories of this paper are: econ
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The categories of this paper are: dg-ga