Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: The detection of non-thermal radio continuum spokes and the study of
  star formation in the Cartwheel   New sensitive Very Large Array 20 cm continuum observations of the Cartwheel,
the prototypical collisional ring galaxy, were carried out with the principal
aim of tracing supernova remnants that are expected to lie in the wake of the
expanding ring and in the ring itself. We detect predominantly non-thermal
radio continuum emission from regions associated with 13 ring HII complexes.
The emission interior to the ring is confined to structures that resemble
spokes of the wheel. The spokes start near bright HII complexes, and extend to
around 6 arcsec (4 kpc) inward in the direction of the geometrical center of
the ring. There is no apparent positional coincidence between the radio
continuum and optical spokes. Radial distribution of intensity along the spokes
suggests that the past star formation rate (SFR) in the Cartwheel was much
lower than the current SFR. New Halpha observations were used to revise the
current SFR in the Cartwheel. The revised value is 18 Msun/yr, which is a
factor of 4 lower than the value reported previously, but is in good agreement
with the SFR estimated from far infrared luminosity. About 30% of the observed
20 cm continuum non-thermal emission seems to originate in processes that are
not related to star formation. Revised SFR in the Cartwheel is comparable to
that in the rest of the ring galaxies.

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The categories of this paper are: funct-an
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The categories of this paper are: supr-con
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The categories of this paper are: comp-gas
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The categories of this paper are: dg-ga
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The categories of this paper are: chao-dyn
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The categories of this paper are: patt-sol
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The categories of this paper are: chem-ph
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The categories of this paper are: math
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The categories of this paper are: cond-mat
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The categories of this paper are: stat
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The categories of this paper are: hep-ph
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The categories of this paper are: econ
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The categories of this paper are: nlin
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The categories of this paper are: adap-org
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The categories of this paper are: mtrl-th
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The categories of this paper are: plasm-ph