GAMA/WiggleZ: The 1.4GHz radio luminosity functions of high- and low-excitation radio galaxies and their redshift evolution to z=0.75

Journal article

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 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+0.17−0.18 assuming pure density evolution or ∼(1+z)0.46+0.22−0.24 assuming pure luminosity evolution. In contrast, the HERG population evolves more rapidly, best fitted by ∼(1+z)2.93+0.46−0.47 assuming a double power-law shape and pure density evolution. If a pure luminosity model is assumed, the best-fitting HERG evolution is parametrized by ∼(1+z)7.41+0.79−1.33 . 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.

Authors: Pracy, M; Ching, J; Sadler, E; Croom, S; Baldry, I

• Publication status: Published
• Peer review status: Peer reviewed
• Publisher: Oxford University Press
• Journal: Monthly Notices of the Royal Astronomical Society
• Volume: 460
• Issue: 1
• Pages: 2-17
• Publication date: 2016-07-21
• Acceptance date: 2016-04-14
• DOI: 10.1093/mnras/stw910
• EISSN: 1365-2966
• ISSN: 0035-8711
• Keywords: galaxies: evolution, accretion; radio continuum: galaxies; galaxies: active