Astronomy and Astrophysics – Astrophysics
Scientific paper
1999-03-15
Astronomy and Astrophysics
Astrophysics
LaTeX, 13 pages. Accepted by MNRAS. For related papers see http://www.ast.cam.ac.uk/~snellen
Scientific paper
10.1046/j.1365-8711.1999.02636.x
We present spectroscopic observations of a sample of faint Gigahertz Peaked Spectrum (GPS) radio sources drawn from the Westerbork Northern Sky Survey (WENSS). Redshifts have been determined for 19 (40%) of the objects. The optical spectra of the GPS sources identified with low redshift galaxies show deep stellar absorption features. This confirms previous suggestions that their optical light is not significantly contaminated by AGN-related emission, but is dominated by a population of old (>9 Gyr) and metal-rich (>0.2 [Fe/H]) stars, justifying the use of these (probably) young radio sources as probes of galaxy evolution. The optical spectra of GPS sources identified with quasars are indistinguishable from those of flat spectrum quasars, and clearly different from the spectra of Compact Steep Spectrum (CSS) quasars. The redshift distribution of the GPS quasars in our radio-faint sample is comparable to that of the bright samples presented in the literature, peaking at z ~ 2-3. It is unlikely that a significant population of low redshift GPS quasars is missed due to selection effects in our sample. We therefore claim that there is a genuine difference between the redshift distributions of GPS galaxies and quasars, which, because it is present in both the radio-faint and bright samples, can not be due to a redshift-luminosity degeneracy. It is therefore unlikely that the GPS quasars and galaxies are unified by orientation, unless the quasar opening angle is a strong function of redshift. We suggest that the GPS quasars and galaxies are unrelated populations and just happen to have identical observed radio-spectral properties, and hypothesise that GPS quasars are a sub-class of flat spectrum quasars.
Bremer Malcolm N.
de Bruyn Ger A.
Miley George K.
R"ottgering Huub J. A.
Schilizzi Richard T.
No associations
LandOfFree
Optical spectroscopy of faint gigahertz peaked spectrum sources does not yet have a rating. At this time, there are no reviews or comments for this scientific paper.
If you have personal experience with Optical spectroscopy of faint gigahertz peaked spectrum sources, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Optical spectroscopy of faint gigahertz peaked spectrum sources will most certainly appreciate the feedback.
Profile ID: LFWR-SCP-O-164593