GAMA/WiggleZ: The 1.4GHz radio luminosity functions of high- and
  low-excitation radio galaxies and their redshift evolution to z=0.75
  We present radio Active Galactic Nuclei (AGN) luminosity functions over the
redshift range 0.005 < z < 0.75. The sample from which the luminosity functions
are constructed is an optical spectroscopic survey of radio galaxies,
identified from matched Faint Images of the Radio Sky at Twenty-cm survey
(FIRST) sources and Sloan Digital Sky Survey (SDSS) images.The radio AGN are
separated into Low Excitation Radio Galaxies (LERGs) and High Excitation Radio
Galaxies (HERGs) using the optical spectra. We derive radio luminosity
functions for LERGs and HERGs separately in the three redshift bins (0.005 < z
< 0.3, 0.3 < z < 0.5 and 0.5 < z <0.75). The radio luminosity functions can be
well described by a double power-law. Assuming this double power-law shape the
LERG population displays little or no evolution over this redshift range
evolving as ~$(1+z)^{0.06}$ assuming pure density evolution or ~ $(1+z)^{0.46}$
assuming pure luminosity evolution. In contrast, the HERG population evolves
more rapidly, best fitted by ~$(1+z)^{2.93}$ assuming a double power-law shape
and pure density evolution. If a pure luminosity model is assumed the best
fitting HERG evolution is parameterised by ~$(1+z)^{7.41}$. The characteristic
break in the radio luminosity function occurs at a significantly higher power
(~1 dex) for the HERG population in comparison to the LERGs. This is consistent
with the two populations representing fundamentally different accretion modes.
