Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: The Radio Emission from the Ultra-Luminous Far-Infrared Galaxy NGC 6240   We present new radio observations of the ``prototypical'' ultra-luminous far-
infrared galaxy NGC~6240, obtained using the VLA at 20~cm in `B' configuration
and at 3.6~cm in `A' configuration. These data, along with those from four
previous VLA observations, are used to perform a comprehensive study of the
radio emission from NGC~6240. Approximately 70\% (~3 x 10$^{23}$ W~Hz$^{-1}$)
of the total radio power at 20 cm originates from the nuclear region ( <~ 1.5
kpc), of which half is emitted by two unresolved ($R <~ 36 pc) cores and half
by a diffuse component. The radio spectrum of the nuclear emission is
relatively flat ($\alpha$ =~ 0.6; $S_{\nu} \propto \nu^{-\alpha}$). The
supernova rate required to power the diffuse component is consistent with that
predicted by the stellar evolution models of Rieke \etal (1985). If the radio
emission from the two compact cores is powered by supernova remnants, then
either the remnants overlap and form hot bubbles in the cores, or they are very
young ( <~ 100 yr). Nearly all of the other 30\% of the total radio power comes
from an ``arm-like'' region extending westward from the nuclear region. The
western arm emission has a steep spectrum ($\alpha$ =~ 1.0), suggestive of
aging effects from synchrotron or inverse-Compton losses, and is not correlated
with starlight; we suggest that it is synchrotron emission from a shell of
material driven by a galactic superwind. Inverse-Compton scattering of
far-infrared photons in the radio sources is expected to produce an X-ray flux
of ~2-6 x 10$^{-14}$ erg/s/cm2 in the 2-10 keV band. No significant radio
emission is detected from or near the possible ultra-massive ``dark core''
hypothesized by Bland-Hawthorn, Wilson \& Tully (1991).

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The categories of this paper are: math
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The categories of this paper are: eess
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The categories of this paper are: atom-ph
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The categories of this paper are: mtrl-th
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The categories of this paper are: comp-gas
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The categories of this paper are: q-bio
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The categories of this paper are: nucl-ex
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The categories of this paper are: bayes-an
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The categories of this paper are: stat
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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: cs
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The categories of this paper are: plasm-ph
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The categories of this paper are: adap-org
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The categories of this paper are: ao-sci
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The categories of this paper are: hep-lat