Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: The Nature of Dark Matter in Elliptical Galaxies: Chandra X-ray
  Observatory Observations of NGC 4636   We determine the total enclosed mass profile from 0.7 to 35 kpc in the
elliptical galaxy NGC 4636 based on the hot interstellar medium temperature
profile measured using the Chandra X-ray Observatory, and other X-ray and
optical data. The total mass increases as radius to the power 1.2 to a good
approximation over this range in radii, attaining a total of 1.5 trillion solar
masses (corresponding to a mass-to-light ratio of 40 solar masses per solar
visual luminosity) at 35 kpc. We find that at least half, and as much as 80%,
of the mass within the optical half-light radius is non-luminous, implying that
NGC 4636 has an exceptionally low baryon fraction. The large inferred dark
matter concentration and central dark matter density, consistent with the upper
end of the range expected for standard cold dark matter halos, imply that
mechanisms proposed to explain low dark matter densities in less massive
galaxies (e.g., self-interacting dark matter, warm dark matter, explosive
feedback) are not effective in elliptical galaxies (and presumably, by
extension, in galaxy clusters). The composite (black hole, stars, and dark
matter) mass distribution has a generally steep slope with no core, consistent
with gravitational lensing studies.

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The categories of this paper are: hep-ex
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The categories of this paper are: alg-geom
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The categories of this paper are: cmp-lg
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The categories of this paper are: gr-qc
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The categories of this paper are: cs
37
The categories of this paper are: supr-con
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The categories of this paper are: solv-int
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The categories of this paper are: mtrl-th
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The categories of this paper are: hep-ph
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The categories of this paper are: atom-ph
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The categories of this paper are: math
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The categories of this paper are: q-fin
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The categories of this paper are: math-ph
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The categories of this paper are: eess
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The categories of this paper are: adap-org
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The categories of this paper are: chao-dyn