Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: On the Nature of the NGC 1275 System   Sub-arcsecond images, taken in B, R, and H-Alpha filters, and area
spectroscopy obtained with the WIYN 3.5-m telescope provide the basis for an
investigation of the unusual structures in the stellar body and ionized gas in
and around the Perseus cluster central galaxy, NGC 1275. Our H-Alpha filter is
tuned to gas at the velocity of NGC 1275, revealing complex, probably
unresolved, small-scale features in the extended ionized gas, located up to
50/h kpc from NGC 1275. The mean H-Alpha surface brightness varies little along
the outer filaments; this, together with the complex excitation state
demonstrated by spectra, imply that the filaments are likely to be tubes, or
ribbons, of gas. The morphology, location and inferred physical parameters of
the gas in the filaments are consistent with a model whereby the filaments form
through compression of the intracluster gas by relativistic plasma emitted from
the active nucleus of NGC 1275. Imaging spectroscopy with the Densepak fiber
array on WIYN suggests partial rotational support of the inner component of low
velocity ionized gas. We confirm and extend evidence for features in the
stellar body of NGC 1275, and identify outer stellar regions containing very
blue, probably very young, star clusters. We interpret these as evidence for
recent accretion of a gas-rich system, with subsequent star formation. We
suggest that two main processes, which may be causally connected, are
responsible for the rich phenomenology of the NGC 1275 system -- NGC 1275
experienced a recent merger/interaction with a group of gas-rich galaxies, and
recent outflows from its AGN have compressed the intracluster gas, and perhaps
the gas in the infalling galaxies, to produce a complex web of filaments.
(Abridged)

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The categories of this paper are: eess
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The categories of this paper are: bayes-an
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The categories of this paper are: nucl-th
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The categories of this paper are: cmp-lg
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The categories of this paper are: q-fin
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The categories of this paper are: hep-ph
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The categories of this paper are: plasm-ph
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The categories of this paper are: comp-gas
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The categories of this paper are: nucl-ex
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The categories of this paper are: patt-sol
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The categories of this paper are: alg-geom
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The categories of this paper are: cond-mat
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The categories of this paper are: mtrl-th
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The categories of this paper are: solv-int
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The categories of this paper are: math-ph
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The categories of this paper are: chao-dyn