On the redshift cut-off for steep-spectrum radio sources |
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| Authors: | Matt J. Jarvis Steve Rawlings Chris J. Willott Katherine M. Blundell Steve Eales Mark Lacy |
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| Affiliation: | 1Astrophysics, Department of Physics, Keble Road, Oxford OX1 3RH;2Sterrewacht Leiden, Postbus 9513, 2300 RA Leiden, the Netherlands;3Department of Physics and Astronomy, University of Wales College of Cardiff, PO Box 913, Cardiff CF2 3YB;4Institute of Geophysics and Planetary Physics, L-413 Lawrence Livermore National Laboratory, Livermore, CA 94550, USA;5Department of Physics, University of California, 1 Shields Avenue, Davis, CA 95616, USA |
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| 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. Though 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, incorporating 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 and . We find that 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 probability ratios of and for spatially flat cosmologies with and 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 and Jarvis & Rawlings, in line with the expectations of unified schemes. |
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| Keywords: | galaxies: active galaxies: luminosity function, mass function radio continuum: galaxies |
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