Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Numerical simulations of expanding supershells in dwarf irregular
  galaxies. II. Formation of giant HI rings   We perform numerical hydrodynamic modeling of various physical processes that
can form an HI ring as is observed in Holmberg I. Three energetic mechanisms
are considered: multiple supernova explosions (SNe), a hypernova explosion
associated with a gamma ray burst (GRB), and the vertical impact of a high
velocity cloud (HVC). The total released energy has an upper limit of 10^54
ergs. We find that multiple SNe are in general more effective in producing
shells that break out of the disk than a hypernova explosion of the same total
energy. As a consequence, multiple SNe form rings with a high ring-to-center
contrast K<100 in the HI column density, whereas single hypernova explosions
form rings with K<10. Only multiple SNe can reproduce both the size (diameter
\~1.7 kpc) and the ring-to-center contrast (K ~ 15-20) of the HI ring in
Hoolmberg I. High velocity clouds create HI rings that are much smaller in size
(< 0.8 kpc) and contrast (K < 4.5) than seen in Holmberg I. We construct model
position-velocity (pV) diagrams and find that they can be used to distinguish
among different HI ring formation mechanisms. The observed pV-diagrams of
Holmberg I are best reproduced by multiple SNe. We conclude that the giant HI
ring in Holmberg I is most probably formed by multiple SNe. We also find that
the appearance of the SNe-driven shell in the integrated HI image depends on
the inclination angle of the galaxy. In nearly face-on galaxies, the integrated
HI image shows a ring of roughly constant HI column density surrounding a deep
central depression, whereas in considerably inclined galaxies (i > 45 deg) the
HI image is characterized by two kidney-shaped density enhancements and a mild
central depression.

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The categories of this paper are: math
30
The categories of this paper are: q-alg
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The categories of this paper are: q-fin
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The categories of this paper are: chao-dyn
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The categories of this paper are: bayes-an
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The categories of this paper are: gr-qc
32
The categories of this paper are: atom-ph
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The categories of this paper are: alg-geom
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The categories of this paper are: cs
34
The categories of this paper are: chem-ph
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The categories of this paper are: hep-ex
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The categories of this paper are: stat
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The categories of this paper are: hep-ph
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The categories of this paper are: hep-lat
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The categories of this paper are: q-bio
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The categories of this paper are: math-ph