Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Threshold Star Formation Effects in the Peculiar Galaxy Arp~10 (=~VV
  362)   We present images of the peculiar galaxy Arp~10 which reveal two rings of
concurrent star formation. Apart from a bright ring visible on early
photographs of the system, an even brighter inner ring of \ion{H}{2} regions is
found within the nuclear bulge of the galaxy. A very faint ring-arc of
\ion{H}{2} regions is also seen associated with a third outer ring or shell. An
investigation of the H$\alpha$ fluxes in the rings reveals an increase in the
emission where the ring surface density in the R-band light exceeds
21.3$\pm$0.2 mag arcsec$^{-2}$. If the R-band light is dominated by old stars
in the underlying density wave, then the results suggest evidence for a Star
Formation law which exhibits a threshold dependence on the strength of the
density wave in the rings. Even if the R-band continuum in the ring is heavily
contaminated with red light from the underlying young stars then a smaller, but
still significant non-linear enhancement in the star formation rates (SFR) in
one segment of the second ring is required to explain the results. In either
case, strong trends in the SFR with azimuth around Ring~2 are in good agreement
with off-center collisional ring galaxy models.

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The categories of this paper are: mtrl-th
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The categories of this paper are: q-bio
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The categories of this paper are: comp-gas
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The categories of this paper are: hep-ph
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The categories of this paper are: acc-phys
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The categories of this paper are: ao-sci
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The categories of this paper are: bayes-an
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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: cmp-lg
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The categories of this paper are: adap-org
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The categories of this paper are: q-fin
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The categories of this paper are: supr-con
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The categories of this paper are: econ
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The categories of this paper are: hep-th