Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Radio continuum emission in the northern Galactic plane: Sources and
  spectral indices from the THOR survey   Radio continuum surveys of the Galactic plane can find and characterize HII
regions, supernova remnants (SNRs), planetary nebulae (PNe), and extragalactic
sources. A number of surveys at high angular resolution (<25") at different
wavelengths exist to study the interstellar medium (ISM), but no comparable
high-resolution and high-sensitivity survey exists at long radio wavelengths
around 21cm. We observed a large fraction of the Galactic plane in the first
quadrant of the Milky Way (l=14.0-67.4deg and |b| < 1.25deg) with the Karl G.
Jansky Very Large Array (VLA) in the C-configuration covering six continuum
spectral windows. These data provide a detailed view on the compact as well as
extended radio emission of our Galaxy and thousands of extragalactic background
sources. We used the BLOBCAT software and extracted 10916 sources. After
removing spurious source detections caused by the sidelobes of the synthesised
beam, we classified 10387 sources as reliable detections. We smoothed the
images to a common resolution of 25" and extracted the peak flux density of
each source in each spectral window (SPW) to determine the spectral indices
$\alpha$ (assuming $I(\nu)\propto\nu^\alpha$). By cross-matching with catalogs
of HII regions, SNRs, PNe, and pulsars, we found radio counterparts for 840 HII
regions, 52 SNRs, 164 PNe, and 38 pulsars. We found 79 continuum sources that
are associated with X-ray sources. We identified 699 ultra-steep spectral
sources ($\alpha < -1.3$) that could be high-redshift galaxies. Around 9000 of
the sources we extracted are not classified specifically, but based on their
spatial and spectral distribution, a large fraction of them is likely to be
extragalactic background sources. More than 7750 sources do not have
counterparts in the SIMBAD database, and more than 3760 sources do not have
counterparts in the NED database.

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The categories of this paper are: adap-org
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The categories of this paper are: acc-phys
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The categories of this paper are: funct-an
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The categories of this paper are: cs
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The categories of this paper are: bayes-an
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The categories of this paper are: econ
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The categories of this paper are: mtrl-th
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The categories of this paper are: ao-sci
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The categories of this paper are: nlin
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The categories of this paper are: atom-ph
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The categories of this paper are: solv-int
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The categories of this paper are: hep-th
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The categories of this paper are: quant-ph
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The categories of this paper are: nucl-ex
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The categories of this paper are: cond-mat
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The categories of this paper are: chao-dyn