Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: The Brightness of the Galactic Radio Loops at 1420 MHz: Some Indications
  for the Existence of Loops V and VI   In this article we use 1420 MHz data to demonstrate the likely reality of
Galactic radio Loops V and VI. We further estimate distances and spectral
indices for both these and the four main radio loops. In the cases of Loops I -
IV, radio spectral indices are calculated from the mean brightnesses at 1420
and 820/404 MHz. The spectral indices of Loops V and VI are obtained from $T -
T$ plots between 1420 and 408 MHz. Using the supernova remnant (SNR) hypothesis
for the origin of radio loops, distances are calculated from the surface
brightnesses and the angular diameters at 1420 MHz. We also study how results
for brightnesses and distances of radio loops agree with current theories of
SNR evolution. For this purpose, the ambient density and initial explosion
energy of the loops are discussed. We also discuss applications of different
$\Sigma - D$ relations. The results obtained confirm a non-thermal origin and
nearby locations for the Galactic radio loops. Therefore, we have indications
that they are very old SNRs that evolve in low ambient densities, with high
initial explosion energies.

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The categories of this paper are: comp-gas
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The categories of this paper are: quant-ph
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The categories of this paper are: nucl-th
4
The categories of this paper are: cond-mat
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The categories of this paper are: adap-org
5
The categories of this paper are: gr-qc
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The categories of this paper are: q-fin
31
The categories of this paper are: ao-sci
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The categories of this paper are: alg-geom
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The categories of this paper are: chem-ph
2
The categories of this paper are: math
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The categories of this paper are: chao-dyn
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The categories of this paper are: math-ph
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The categories of this paper are: econ
1
The categories of this paper are: cs
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The categories of this paper are: nlin