A Combined EIS-NVSS Survey Of Radio Sources (CENSORS) III: Spectroscopic observations

TL;DR

This paper reports spectroscopic observations of 143 radio sources from the CENSORS survey, providing redshifts to study the evolution of radio sources and comparing observed distributions with theoretical models.

Contribution

It presents new spectroscopic redshift data for a significant sample of radio sources, enabling improved analysis of radio source evolution beyond previous models.

Findings

Secure redshifts for 63% of sources

Estimated redshifts for additional 8%

Observed redshift distribution does not match existing models

Abstract

The Combined EIS-NVSS Survey Of Radio Sources (CENSORS) is a 1.4GHz radio survey selected from the NRAO VLA Sky Survey (NVSS) and complete to a flux-density of 7.2mJy. It targets the ESO Imaging Survey (EIS) Patch D, which is a 3 by 2 square degree field centred on 09 51 36.0, -21 00 00 (J2000). This paper presents the results of spectroscopic observations of 143 of the 150 CENSORS sources. The primary motivation for these observations is to achieve sufficient spectroscopic completeness so that the sample may be used to investigate the evolution of radio sources. The observations result in secure spectroscopic redshifts for 63% of the sample and likely redshifts (based on a single emission line, for example) for a further 8%. Following the identification of the quasars and star-forming galaxies in the CENSORS sample, estimated redshifts are calculated for the remainder of the sample via the K-z relation for radio galaxies. Comparison of the redshift distribution of the CENSORS radio sources to distributions predicted by the various radio luminosity function evolution models of Dunlop & Peacock 1990, results in no good match. This demonstrates that this sample can be used to expand upon previous work in that field.