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Дата индексирования: Sun Apr 10 04:20:27 2016
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A new sample of faint Gigahertz Peaked Spectrum radio sources
Snellen, I. A. G. Schilizzi, R. T. de Bruyn, A. G. Miley, G. K.
Rengelink, R. B. Roettgering, H. J. Bremer, M. N.
Astronomy and Astrophysics Supplement, v.131, p.435-449
The Westerbork Northern Sky Survey (WENSS) has been used to select a
sample of Gigahertz Peaked Spectrum (GPS) radio sources at flux
densities one to two orders of magnitude lower than bright GPS sources
investigated in earlier studies. Sources with inverted spectra at
frequencies above 325 MHz have been observed with the
WSRT\footnotetext{The Westerbork Synthesis Radio telescope (WSRT) is
operated by the Netherlands Foundation for Research in Astronomy with
financial support from the Netherlands Organisation for Scientific
Research (NWO).} at 1.4 and 5 GHz and with the VLA\footnotetext{The Very
Large Array (VLA) is operated by the U.S. National Radio Astronomy
Observatory which is operated by the Associated Universities, Inc. under
cooperative agreement with the National Science Foundation.} at 8.6 and
15 GHz to select genuine GPS sources. This has resulted in a sample of
47 GPS sources with peak frequencies ranging from ~ 500 MHz to >15 GHz,
and peak flux densities ranging from ~ 40 to ~ 900 mJy. Counts of GPS
sources in our sample as a function of flux density have been compared
with counts of large scale sources from WENSS scaled to 2 GHz, the
typical peak frequency of our GPS sources. The counts can be made
similar if the number of large scale sources at 2 GHz is divided by 250,
and their flux densities increase by a factor of 10. On the scenario
that all GPS sources evolve into large scale radio sources, these
results show that the lifetime of a typical GPS source is ~ 250 times
shorter than a typical large scale radio source, and that the source
luminosity must decrease by a factor of ~ 10 in evolving from GPS to
large scale radio source. However, we note that the redshift
distributions of GPS and large scale radio sources are different and
that this hampers a direct and straightforward interpretation of the
source counts. Further modeling of radio source evolution combined with
cosmological evolution of the radio luminosity function for large
sources is required.