High-redshift radio galaxies from the Molonglo Catalogue

Abstract

We report the results of radio and optical observations of a sample of southern hemisphere radio galaxies selected from the Molonglo Reference Catalogue. The sources were selected to have 408 MHz flux densities greater than 0.9 Jy and low-frequency spectral indices steeper than -0.9. VLA 6 cm maps and optical identifications of 13 sources are presented. All of these sources are identified with faint galaxies, many of which have extended optical structures with morphologies characteristic of high-redshift (z > 0.8) radio galaxies. Long-slit spectroscopic observations have yielded redshifts for 11 of the galaxies, 5 of which are at z > 2. The most distant source in the present sample, 0316 - 257, has a redshift of 3.13, while the median redshift for the sample is 1.6. Our results for this subsample suggest that our total sample of 150 sources may contain ~40 galaxies with z > 2. We have imaged four of our galaxies having z > 2 in the light of Ly α. Three of these have highly extended Ly α emission distributed along their radio axes.