A search for distant radio galaxies from SUMSS and NVSS: II. Optical Spectroscopy?.

This is the second in a series of papers presenting observations and results for a sample of 76 ultra-steep-spectrum (USS) radio sources in the southern hemisphere designed to nd galaxies at high redshift. Here we focus on the optical spectroscopy program for 53 galaxies in the sample. We report 35 spectroscopic redshifts, based on observations with the Very Large Telescope (VLT), the New Technology Tele-scope (NTT) and the Australian National University's 2.3m telescope; they include ve radio galaxies with z> 3. Spectroscopic redshifts for the remaining 18 galaxies could not be conrmed: three are occulted by Galactic stars, eight show continuum emission but no discernible spectral lines, whilst the remaining seven galaxies are un-detected in medium-deep VLT integrations. The latter are either at very high redshift (z> 7) or heavily obscured by dust. A discussion of the eciency of the USS tech-nique is presented. Based on the similar space density of z> 3 radio galaxies in our sample compared with other USS-selected samples, we argue that USS selection at 843{1400MHz is an ecient and reliable technique for nding distant radio galaxies. Key words: surveys { radio continuum: general { radio continuum: galaxies { galaxies: active { galaxies: high-redshift