Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Deep 610-MHz Giant Metrewave Radio Telescope observations of the Spitzer
  extragalactic First Look Survey field - III. The radio properties of
  Infrared-Faint Radio Sources   Infrared-Faint Radio Sources (IFRSs) are a class of source which are bright
at radio frequencies, but do not appear in deep infrared images. We report the
detection of 14 IFRSs within the Spitzer extragalactic First Look Survey field,
eight of which are detected near to the limiting magnitude of a deep R-band
image of the region, at R ~ 24.5. Sensitive Spitzer Space Telescope images are
stacked in order to place upper limits on their mid-infrared flux densities,
and using recent 610-MHz and 1.4-GHz observations we find that they have
spectral indices which vary between alpha = 0.05 and 1.38, where we define
alpha such that S = S_0 nu^(- alpha), and should not be thought of as a single
source population. We place constraints on the luminosity and linear size of
these sources, and through comparison with well-studied local objects in the
3CRR catalogue demonstrate that they can be modelled as being compact (< 20
kpc) Fanaroff-Riley Class II (FRII) radio galaxies located at high redshift (z
> 4).

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The categories of this paper are: atom-ph
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The categories of this paper are: chao-dyn
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The categories of this paper are: quant-ph
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The categories of this paper are: q-bio
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The categories of this paper are: cond-mat
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The categories of this paper are: alg-geom
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The categories of this paper are: physics
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The categories of this paper are: bayes-an
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The categories of this paper are: hep-ex
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The categories of this paper are: q-alg
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The categories of this paper are: funct-an
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The categories of this paper are: mtrl-th
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The categories of this paper are: nucl-ex
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The categories of this paper are: eess
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The categories of this paper are: math-ph
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The categories of this paper are: q-fin