Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Radio spectral characteristics of the supernova remnant Puppis A and
  nearby sources   This paper presents a new study of the spectral index distribution of the
supernova remnant (SNR) Puppis A. The nature of field compact sources is also
investigated according to the measured spectral indices. This work is based on
new observations of Puppis A and its surroundings performed with the Australia
Telescope Compact Array in two configurations using the Compact Array
Broad-band Backend centered at 1.75 GHz. We find that the global spectral index
of Puppis A is -0.563 +/- 0.013. Local variations have been detected, however
this global index represents well the bulk of the SNR. At the SE, we found a
pattern of parallel strips with a flat spectrum compatible with small-scale
filaments, although not correlated in detail. The easternmost filament agrees
with the idea that the SN shock front is interacting with an external cloud.
There is no evidence of the previously suggested correlation between emissivity
and spectral index. A number of compact features are proposed to be evolved
clumps of ejecta based on their spectral indices, although dynamic measurements
are needed to confirm this hypothesis. We estimate precise spectral indices for
the five previously known field sources, two of which are found to be double
(one of them, probably triple), and catalogue 40 new sources. In the light of
these new determinations, the extragalactic nature previously accepted for some
compact sources is now in doubt.

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The categories of this paper are: econ
5
The categories of this paper are: gr-qc
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The categories of this paper are: quant-ph
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The categories of this paper are: solv-int
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The categories of this paper are: hep-lat
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The categories of this paper are: acc-phys
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The categories of this paper are: alg-geom
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The categories of this paper are: patt-sol
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The categories of this paper are: cs
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The categories of this paper are: nlin
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The categories of this paper are: nucl-ex
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The categories of this paper are: funct-an
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The categories of this paper are: chem-ph
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The categories of this paper are: comp-gas
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The categories of this paper are: nucl-th
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The categories of this paper are: q-alg