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Published October 1, 1981 | Published
Journal Article Open

Models of radio source evolution - II. The 2700-MHz source count


Our technique for deriving cosmological evolution from source counts and identifications is applied to data at 2700 MHz. The analysis is carried out on the assumption that two populations with different evolutionary behaviours appear in surveys at this frequency: 'steep-spectrum' sources with extended radio structures, and 'non-steep-spectrum' sources with compact structures, the majority of which are identified with QSOs. The 2700-MHz data add constraints to the evolution deduced for the 'steep-spectrum' sources from low-frequency data; in particular, of the two types of model obtained in our analysis of the 408-MHz data, only one now appears tenable. The present results for 'non-steep-spectrum' sources agree with the results from luminosity – volume tests on samples of 'flat-spectrum' QSOs – the change in space density with epoch appears less dramatic than for the powerful radio sources with steep spectra and extended radio structures.

Additional Information

© 1981 Royal Astronomical Society. Provided by the NASA Astrophysics Data System. Received 1981 January 9; in original form 1980 July 28. Published: 01 October 1981. JVW thanks the Royal Society for support via a Jaffe Donation Research Fellowship. TJP thanks the SRC for a Research Studentship held during early stages of the investigation, and the US NSF for partial support during the later stages. We are very grateful to the referee for a number of helpful comments.

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