Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Discovery of ultra-compact nuclear rings in three spiral galaxies   Ring-shaped morphologies of nuclear star-forming regions within the central
40-200 pc of disk galaxies have been barely resolved so far in three composite
Sy2 nuclei, the Sy2 Circinus galaxy and in three non-AGN galaxies. Such
morphologies resemble those of the standard 1 kpc-size nuclear rings that lie
in the inner Lindblad resonance regions of disk galaxies and, if they have a
similar origin, represent recent radial gas inflows tantalisingly close to the
central supermassive black holes. We aim to identify the population of such
ultra-compact nuclear rings (UCNRs) and study their properties in relation to
those of the host galaxies. From archival Hubble Space Telescope UV and Halpha
images and from dust structure maps of the circumnuclear regions in nearby
galaxies, we analyse the morphology of the star formation and dust,
specifically searching for ring structures on the smallest observable scales.
In a sample of 38 galaxies studied, we have detected a total of four new UCNRs,
30-130 pc in radius, in three different galaxies. Including our confirmation of
a previous UCNR detection, this yields a UCNR fraction of roughly 10%, although
our sample is neither complete nor unbiased. For the first time we resolve
UCNRs in two LINERs. Overall the UCNR phenomenon appears widespread and limited
neither to late-type galaxies nor exclusively to AGN hosts.

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The categories of this paper are: bayes-an
7
The categories of this paper are: hep-th
9
The categories of this paper are: nlin
30
The categories of this paper are: q-alg
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The categories of this paper are: q-fin
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The categories of this paper are: acc-phys
8
The categories of this paper are: hep-ex
4
The categories of this paper are: cond-mat
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The categories of this paper are: alg-geom
0
The categories of this paper are: hep-ph
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The categories of this paper are: nucl-th
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The categories of this paper are: patt-sol
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The categories of this paper are: econ
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The categories of this paper are: comp-gas
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The categories of this paper are: atom-ph
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The categories of this paper are: solv-int