s repository of research publications and other research outputs Radio galaxies in the 2 SLAQ Luminous Red Galaxy Survey I The evolution of low power radio galaxies to z 0
We have combined optical data from the 2dF SDSS (Sloan Digital Sky Survey) LRG (Luminous Red Galaxy) and QSO (quasi stellar object) (2SLAQ) redshift survey with radio measurements from the 1.4 GHz VLA (Very Large Array) FIRST (Faint Images of the Radio Sky at Twentycm) and NVSS (NRAO VLA Sky Survey) surveys to identify a volume limited sample of 391 radio galaxies at redshift 0.4 z 0.7. By determining an accurate radio luminosity function for luminous early type galaxies in this redshift range, we can investigate the cosmic evolution of the radio galaxy population over a wide range in radio luminosity. The low power radio galaxies in our LRG sample (those with 1.4 GHz radio luminosities in the range 1024 to 1025 W Hz 1, corresponding to Fanaroff Riley I (FR I) radio galaxies in the local Universe) undergo significant cosmic evolution over the redshift range 0 z 0.7, consistent with pure luminosity evolution of the form (1 z)k where k 2.0 0.3. Our results appear to rule out (at the 6 7s level) models in which low power radio galaxies undergo no cosmic evolution. The most powerful radio galaxies in our sample (with radio luminosities above 1026 W Hz 1) may undergo more rapid evolution over the same redshift range. The evolution seen in the low power radio galaxy population implies that the total energy input into massive early type galaxies from active galactic nucleus (AGN) heating increases with redshift, and was at least 50 per cent higher at z 0.55 (the median redshift of the 2SLAQ LRG sample) than in the local universe.