Faint 1.4-GHz radio sources in the 2dF Galaxy Redshift Survey

Abstract We have used the Australia Telescope Compact Array (ATCA) to search for faint radio sources in a ∼3 deg2 region of sky covered by the 2dF Galaxy Redshift Survey (2dFGRS). Over the region surveyed, the 1σ noise level at 1.4 GHz ranges from 20 μJy to 1 mJy. The survey region includes 365 2dFGRS galaxies, of which 316 have good-quality spectra (176 early-type galaxies or active galactic nuclei, and 140 star-forming galaxies). The fraction of 2dFGRS galaxies detected as radio sources in our survey rises from ∼4 per cent at a 3σ detection limit of 0.3 mJy to 12 per cent at 75 μJy, with roughly equal numbers of star-forming galaxies and active galactic nuclei (AGNs) being detected. The radio luminosity function derived from this sample agrees with earlier determinations, and we find that while the mean redshift of the radio-detected galaxies increases toward lower flux densities for star-forming galaxies, it remains roughly constant for the AGN/early-type radio detections. We discuss possible observing strategies for a submJy radio survey of a larger 2dFGRS region, and show that a survey covering 100 deg2 could measure the global evolution of the star formation density to z∼ 0.1 in a way which is less affected by reddening than traditional measurements using optical emission lines and ultraviolet photometry.