Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: FIRST-based survey of Compact Steep Spectrum sources, III. MERLIN and
  VLBI observations of subarcsecond-scale objects   According to a generally accepted paradigm, small intrinsic sizes of Compact
Steep Spectrum (CSS) radio sources are a direct consequence of their youth, but
in later stages of their evolution they are believed to become large-scale
sources. However, this notion was established mainly for strong CSS sources. In
this series of papers we test this paradigm on 60 weaker objects selected from
the VLA FIRST survey. They have 5-GHz flux densities in the range 150 <
S_{5GHz} < 550 mJy and steep spectra in the range 0.365 \le \nu \le 5 GHz. The
present paper is focused on sources that fulfill the above criteria and have
angular sizes in the range 0.2\arcsec - 1\arcsec. Observations of 19 such
sources were obtained using MERLIN in "snapshot" mode at 5 GHz. They are
presented along with 1.7-GHz VLBA and 5-GHz EVN follow-up snapshot observations
made for the majority of them. For one of the sources in this subsample,
1123+340, a full-track 5-GHz EVN observation was also carried out. This study
provides an important element to the standard theory of CSS sources, namely
that in a number of them the activity of their host galaxies probably switched
off quite recently and their further growth has been stopped because of that.
In the case of 1123+340, the relic of a compact "dead source" is particularly
well preserved by the presence of intracluster medium of the putative cluster
of galaxies surrounding it. The observed overabundance of compact sources can
readily be explained in the framework of the scenario of "premature" cessation
of the activity of the host galaxy nucleus. It could also explain the
relatively low radio flux densities of many such sources and, in a few cases,
their peculiar, asymmetric morphologies. We propose a new interpretation of
such asymmetries based on the light-travel time argument.

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The categories of this paper are: q-alg
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The categories of this paper are: quant-ph
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The categories of this paper are: bayes-an
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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: cs
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The categories of this paper are: hep-th
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The categories of this paper are: physics
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The categories of this paper are: gr-qc
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The categories of this paper are: mtrl-th
12
The categories of this paper are: nucl-th
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The categories of this paper are: supr-con
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The categories of this paper are: dg-ga
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The categories of this paper are: patt-sol
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The categories of this paper are: chem-ph
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The categories of this paper are: acc-phys