On the redshift cut-off for steep-spectrum radio sources
ArXiv astro-ph/0106473 (2001)
Authors:
Matt J Jarvis, Steve Rawlings, Chris J Willott, Katherine M Blundell, Steve Eales, Mark Lacy
Abstract:
We use three samples (3CRR, 6CE and 6C*) selected at low radio frequency to
constrain the cosmic evolution in the radio luminosity function (RLF) for the
`most luminous' steep-spectrum radio sources. Although intrinsically rare, such
sources give the largest possible baseline in redshift for the complete
flux-density-limited samples currently available. Using parametric models to
describe the RLF which incorporate distributions in radio spectral shape and
linear size as well as the usual luminosity and redshift, we find that the data
are consistent with a constant comoving space density between z~2.5 and z~4.5.
We find this model is favoured over a model with similar evolutionary behaviour
to that of optically-selected quasars (i.e. a roughly Gaussian distribution in
redshift) with a probability ratio of ~25:1 and ~100:1 for spatially-flat
cosmologies with Omega_Lambda = 0 and Omega_Lambda = 0.7 respectively. Within
the uncertainties, this evolutionary behaviour may be reconciled with the
shallow decline preferred for the comoving space density of flat-spectrum
sources by Dunlop & Peacock (1990) and Jarvis & Rawlings (2000), in line with
the expectations of Unified Schemes.
