Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Ionized and neutral gas in the peculiar star/cluster complex in NGC 6946   The characteristics of ionized and HI gas in the peculiar star/cluster
complex in NGC 6946, obtained with the 6-m telescope (BTA) SAO RAS, the Gemini
North telescope, and the Westerbork Synthesis Radio Telescope (WSRT), are
presented. The complex is unusual as hosting a super star cluster, the most
massive known in an apparently non-interacting giant galaxy. It contains a
number of smaller clusters and is bordered by a sharp C-shaped rim. We found
that the complex is additionally unusual in having peculiar gas kinematics. The
velocity field of the ionized gas reveals a deep oval minimum, ~300 pc in size,
centered 7" east of the supercluster. The Vr of the ionized gas in the dip
center is 100 km/s lower than in its surroundings, and emission lines within
the dip appear to be shock excited. This dip is near the center of an HI hole
and a semi-ring of HII regions. The HI (and less certainly, HII) velocity
fields reveal expansion, with the velocity reaching ~30 km/s at a distance
about 300 pc from the center of expansion, which is near the deep minimum
position. The super star cluster is at the western rim of the minimum. The
sharp western rim of the whole complex is plausibly a manifestation of a
regular dust arc along the complex edge. Different hypotheses about the complex
and the Vr depression origins are discussed, including a HVC/dark mini-halo
impact, a BCD galaxy merging, and a gas outflow due to release of energy from
the supercluster stars.

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The categories of this paper are: nlin
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The categories of this paper are: cs
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The categories of this paper are: acc-phys
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The categories of this paper are: math
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The categories of this paper are: nucl-th
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The categories of this paper are: q-fin
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The categories of this paper are: nucl-ex
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The categories of this paper are: plasm-ph
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The categories of this paper are: q-bio
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The categories of this paper are: math-ph
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The categories of this paper are: chem-ph
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The categories of this paper are: quant-ph
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The categories of this paper are: atom-ph
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The categories of this paper are: hep-th
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The categories of this paper are: funct-an
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The categories of this paper are: eess