Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Deep low-frequency observations with the Giant Metrewave Radio
  Telescope: a search for relic radio emission   We present deep multifrequency observations using the Giant Metrewave Radio
Telescope at 153, 244, 610 and 1260 MHz of a field centered on J0916+6348, to
search for evidence of fossil radio lobes which could be due to an earlier
cycle of episodic activity of the parent galaxy, as well as halos and relics in
clusters of galaxies. We do not find any unambiguous evidence of episodic
activity in a list of 374 sources, suggesting that such activity is rare even
in relatively deep low-frequency observations. We examine the spectra of all
the sources by combining our observations with those from the Westerbork
Northern Sky Survey, NRAO VLA Sky Survey and the Faint Images of the Radio Sky
at Twenty-centimeters survey. Considering only those which have measurements at
a minimum of three different frequencies, we find that almost all sources are
consistent with a straight spectrum with a median spectral index,
$\alpha\sim$0.8 (S$(\nu)\propto\nu^{-\alpha}$), which appears steeper than
theoretical expectations of the injection spectral index. We identify 14 very
steep-spectrum sources with $\alpha\geq$1.3. We examine their optical fields
and discuss the nature of some of these sources.

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The categories of this paper are: hep-ph
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The categories of this paper are: hep-ex
29
The categories of this paper are: funct-an
14
The categories of this paper are: math-ph
10
The categories of this paper are: q-bio
25
The categories of this paper are: patt-sol
35
The categories of this paper are: mtrl-th
30
The categories of this paper are: q-alg
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The categories of this paper are: hep-th
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The categories of this paper are: hep-lat
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The categories of this paper are: nucl-ex
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The categories of this paper are: atom-ph
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The categories of this paper are: gr-qc
33
The categories of this paper are: plasm-ph
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The categories of this paper are: acc-phys
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The categories of this paper are: adap-org