Astronomy and Astrophysics – Astrophysics
Scientific paper
2000-06-06
Mon.Not.Roy.Astron.Soc. 319 (2000) 121
Astronomy and Astrophysics
Astrophysics
19 pages, including 8 figures, accepted for publication in MNRAS
Scientific paper
10.1046/j.1365-8711.2000.03801.x
We use data from the Parkes Half-Jansky Flat-Spectrum (PHJFS) sample (Drinkwater et al. 1997) to constrain the cosmic evolution in the co-moving space density of radio sources in the top decade of the flat-spectrum radio luminosity function (RLF). A consistent picture for the high-redshift evolution is achieved using both simple parametric models, which are the first to allow for distributions in both radio luminosity and spectral index, and variants of the V / V_max test, some of which incorporate the effects of radio spectral curvature. For the most luminous flat-spectrum objects, the PHJFS sample is extremely similar to that used by Shaver et al. (1996, 1998) to argue for an abrupt `redshift cut-off': a decrease by a factor ~30 in space density between a peak redshift z~2.5 and z~5. Our analysis finds that the observable co-moving volume is too small to make definitive statements about any redshift cut-off for the most luminous flat-spectrum sources, although both constant-space density (no cut-off) models and models with cut-offs as abrupt as those envisaged by Shaver et al. are outside the 90% confidence region. The inference that the decline in space density is most likely to be gradual, by a factor ~4 between z~2.5 and z~5, is in accordance with previous work on the RLF by Dunlop & Peacock (1990), but different to the abrupt decline favoured by studies of optically-selected quasars. Dust obscuration provides one explanation for this difference. We show that a significant fraction of the most radio-luminous flat-spectrum objects are Giga-Hertz Peaked Spectrum (GPS) rather than Doppler-Boosted (DB) sources, complicating any interpretation of the redshift cut-off.
Jarvis Matt J.
Rawlings Steve
No associations
LandOfFree
On the redshift cut-off for flat-spectrum radio 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 On the redshift cut-off for flat-spectrum radio sources, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and On the redshift cut-off for flat-spectrum radio sources will most certainly appreciate the feedback.
Profile ID: LFWR-SCP-O-482256