Program: GS-2009B-Q-95

The recently-completed Australia Telescope 20 GHz (AT20G) survey provides by far the largest and most complete sample of high-frequency radio sources yet obtained, and offers new insights into the nature of the high-frequency active galaxy population. It is already clear that the high-frequency radio population (which is dominated by blazars and radio-loud QSOs) is very different from that seen at lower frequencies. We propose to obtain redshifts and optical spectra for a subset of optically bright AT20G sources so that we can map out their redshift and luminosity distribution and investigate the effects of relativistic beaming. We expect a large overlap between our AT20G sample and the gamma-ray blazars detected by Fermi. Our results will also be of great value for future CMB missions like Planck, for which the AT20G sources can be used to characterise the foreground point-source population.