Issue |
Astron. Astrophys. Suppl. Ser.
Volume 131, Number 3, September 1998
|
|
---|---|---|
Page(s) | 435 - 449 | |
DOI | https://doi.org/10.1051/aas:1998281 | |
Published online | 15 September 1998 |
A new sample of faint Gigahertz Peaked Spectrum radio sources*,**
1
Leiden Observatory, P.O. Box 9513, 2300 RA, Leiden, The Netherlands
2
Institute of Astronomy, Madingley Road, Cambridge CB3 0HA, UK
3
Joint Institute for VLBI in Europe, Postbus 2, 7990 AA, Dwingeloo The Netherlands
4
Netherlands Foundation for Research in Astronomy, Postbus 2, 7990 AA, Dwingeloo, The Netherlands
5
Kapteyn Institute, Postbus 800, 9700 AV, Groningen, The Netherlands
6
Institut d'Astrophysique de Paris, 98bis Boulevard Arago, 75014 Paris, France
Received:
21
January
1998
Accepted:
18
March
1998
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
at 1.4 and 5 GHz and with
the VLA
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 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.
Key words: galaxies: active / quasars / radio continuum: galaxies
© European Southern Observatory (ESO), 1998