Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: The Cuspy LINER Nucleus of the S0/a Galaxy NGC 2681   The nucleus of the bulge-dominated, multiply-barred S0/a galaxy NGC 2681 is
studied in detail, using high resolution Hubble Space Telescope FOC and NICMOS
imaging and FOS spectroscopy. The ionised gas central velocity dispersion is
found to increase by a factor ~2 when narrowing the aperture from R~1.5"
(ground) to R~0.1" (FOS). Dynamical modeling of these velocity dispersions
suggests that NGC 2681 does host a supermassive black hole (BH) for which one
can estimate a firm mass upper limit M_BH < 6*10^7 Solar Masses. This upper
limit is consistent with the relation between the central BH mass and velocity
dispersion M_BH - sigma known for other galaxies. The emission line ratios
place the nucleus of NGC 2681 among LINERs. It is likely that the emission line
region comes from a rather mild, but steady, feeding of gas to the central BH
in this galaxy. The inner stellar population lacks any measurable color
gradient (to a radius of 0.6 kpc) from the infrared to the ultraviolet,
consistently with FOC, FOS and IUE data, all indicating that this system
underwent a starburst ~1 Gyr ago that encompassed its whole interior, down to
its very center. The most likely source of such a widely-distributed starburst
is the dumping of tidally-extruded gas from a galaxy neighbor. If so, then NGC
2681 can be considered as the older brother of M82, seen face-on as opposed to
the edge-on view we have for M82.

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The categories of this paper are: stat
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The categories of this paper are: ao-sci
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The categories of this paper are: atom-ph
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The categories of this paper are: quant-ph
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The categories of this paper are: gr-qc
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The categories of this paper are: dg-ga
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The categories of this paper are: adap-org
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The categories of this paper are: nucl-ex
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The categories of this paper are: math-ph
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The categories of this paper are: q-alg
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The categories of this paper are: mtrl-th
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The categories of this paper are: cs
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The categories of this paper are: cmp-lg
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The categories of this paper are: plasm-ph
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The categories of this paper are: econ
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The categories of this paper are: q-bio