Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: A 15-Kiloparsec X-Ray Disk in the Elliptical Galaxy NGC 1700   We present Chandra observations of the young elliptical galaxy NGC 1700. The
X-ray isophotes are highly flattened between semimajor axes of 30 and 80
arcseconds, reaching a maximum ellipticity of approximately 0.65 at 60 arcsec
(15 kpc). The surface brightness profile in the spectrally soft, flattened
region is shallower than that of the starlight, indicating that the emission
comes from hot gas rather than stellar sources. The flattening is so extreme
that the gas cannot be in hydrostatic equilibrium in any plausible potential. A
likely alternative is that the gas has significant rotational support. A simple
model, representing isothermal gas distributed about a particular angular
momentum, can reproduce the X-ray morphology while staying consistent with
stellar kinematics. The specific angular momentum of the gas matches that of
the stars in the most isophotally distorted outer part of the galaxy, and its
cooling time matches the time since the last major merger. We infer that the
gas was acquired in that merger, which involved a pre-existing elliptical
galaxy with a hot ISM. The hot gas carried the angular momentum of the
encounter, and has since gradually settled into a rotationally flattened,
cooling disk.

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The categories of this paper are: comp-gas
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The categories of this paper are: gr-qc
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The categories of this paper are: econ
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The categories of this paper are: nlin
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The categories of this paper are: patt-sol
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The categories of this paper are: hep-lat
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The categories of this paper are: math-ph
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The categories of this paper are: funct-an
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The categories of this paper are: q-alg
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The categories of this paper are: ao-sci
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The categories of this paper are: math
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The categories of this paper are: chem-ph
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The categories of this paper are: cmp-lg
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The categories of this paper are: q-bio
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The categories of this paper are: quant-ph
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The categories of this paper are: hep-ex