The local radio-galaxy population at 20 GHz
  We have made the first detailed study of the high-frequency radio-source
population in the local universe, using a sample of 202 radio sources from the
Australia Telescope 20 GHz (AT20G) survey identified with galaxies from the 6dF
Galaxy Survey (6dFGS). The AT20G-6dFGS galaxies have a median redshift of
z=0.058 and span a wide range in radio luminosity, allowing us to make the
first measurement of the local radio luminosity function at 20 GHz.
  Our sample includes some classical FR-1 and FR-2 radio galaxies, but most of
the AT20G-6dFGS galaxies host compact (FR-0) radio AGN which appear lack
extended radio emission even at lower frequencies. Most of these FR-0 sources
show no evidence for relativistic beaming, and the FR-0 class appears to be a
mixed population which includes young Compact Steep-Spectrum (CSS) and
Gigahertz-Peaked Spectrum (GPS) radio galaxies.
  We see a strong dichotomy in the Wide-field Infrared Survey Explorer (WISE)
mid-infrared colours of the host galaxies of FR-1 and FR-2 radio sources, with
the FR-1 systems found almost exclusively in WISE `early-type' galaxies and the
FR-2 radio sources in WISE `late-type' galaxies.
  The host galaxies of the flat- and steep-spectrum radio sources have a
similar distribution in both K--band luminosity and WISE colours, though
galaxies with flat-spectrum sources are more likely to show weak emission lines
in their optical spectra. We conclude that these flat-spectrum and
steep-spectrum radio sources mainly represent different stages in radio-galaxy
evolution, rather than beamed and unbeamed radio-source populations.
