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This paper presents a new sample of Compact Radio sources at Low Redshift (CORALZ), which is used to study the onset and evolution of young radio-loud active galactic nuclei (AGN) and their environments. The CORALZ sample consists of 28 sources, of which 17 form a ∼95 per cent statistically complete sample with and , over the redshift range . The sample is selected from the Very Large Array (VLA) FIRST 1.4-GHz radio survey over an area of sky of 2850 deg2, cross-correlated with the APM Palomar Sky Survey (APM/POSS-I) catalogue. In contrast to most previous studies of young radio-loud AGN, no selection has been made on radio spectral characteristics. This is to enable investigation of the relation between radio spectra and morphologies, orientation and Doppler boosting in young radio sources, in an unbiased way. Remarkably, more than 90 per cent of the sources in the complete CORALZ sample are classified as Gigahertz Peaked Spectrum (six) or Compact Steep Spectrum (10) sources, and only one object shows indication of strong flux density variability. Several projects are under way to study this unique sample in detail, including investigation of the optical host galaxies and their emission line characteristics, radio morphologies and dynamical evolution, and the neutral hydrogen distribution and kinematics in absorption towards these strong compact radio sources. [ABSTRACT FROM AUTHOR]

ABSTRACT We have determined the central velocity dispersions and surface brightness profiles for a sample of powerful radio galaxies in the redshift range 0.06 < z < 0.31 , which were selected on the basis of their young radio source. The optical hosts follow the fundamental plane of elliptical galaxies, showing that young radio sources reside in normal ellipticals, as do other types of radio galaxies into which these objects are believed to evolve. As young radio sources are relatively straightforward to select and the contributions of the active galactic nuclei (AGN) light to the optical spectra are minimal, these objects can readily be used to study the evolution of the fundamental plane of elliptical galaxies out to z= 1 , independent of optical selection effects. The black hole masses, M[sub bh] , of the objects in our sample have been determined using the tight empirical relation of M[sub bh] with central velocity dispersion, σ[sub e] , and for literature samples of classical radio galaxies and optically selected ellipticals. Only the optically selected inactive galaxies are found to exhibit a correlation between M[sub bh] and radio luminosity. In contrast, the radio powers of the AGN in the samples do not correlate with M[sub bh] at all, with objects at a given black hole mass ranging over seven orders of magnitude in radio power. It is unlikely that beaming of the radio emission is responsible for the range in radio powers. We have been able to tie in the local population of powerful radio sources with its parent population of inactive elliptical galaxies: the local black hole mass function has been determined using the elliptical galaxy luminosity function and the Faber–Jackson and M[sub bh]–σ relations. This was combined with the fraction of radio-loud black holes as a function of M[sub bh] , as determined from the optically selected galaxy sample, to derive the local volume-density of radio galaxies and the distribution of their black hole masses. These are shown to be consistent with the local radio luminosity function and the distribution of black hole masses as found in the radio-selected samples, and confirms that elliptical galaxies comprise the large majority of the radio-loud population of active galaxies. [ABSTRACT FROM AUTHOR]