Radio sources in the 2dF Galaxy Redshift Survey - II. Local radio luminosity functions for AGN and star-forming galaxies at 1.4 GHz

Abstract

We have cross-matched the 1.4 GHz NRAO VLA Sky Survey (NVSS) with the first 210 fields observed in the 2dF Galaxy Redshift Survey (2dFGRS), covering an effective area of 325 deg² (about 20% of the final 2dFGRS area). This yields a set of optical spectra of 912 candidate NVSS counterparts, of which we identify 757 as genuine radio IDs - the largest and most homogeneous set of radio-source spectra ever obtained. The 2dFGRS radio sources span the redshift range z = 0.005 to 0.438, and are a mixture of active galaxies (60%) and star-forming galaxies (40%). About 25% of the 2dFGRS radio sources are spatially resolved by NVSS, and the sample includes three giant radio galaxies with projected linear size greater than 1 Mpc. The high quality of the 2dF spectra means we can usually distinguish unambiguously between AGN and star-forming galaxies. We have made a new determination of the local radio luminosity function at 1.4 GHz for both active and star-forming galaxies, and derive a local star-formation density of 0.022±0.004 M_⊙ year⁻¹ per cubic Mpc⁻¹ (H₀ = 50 km s⁻¹ Mpc⁻¹).

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