Radio galaxies in the 2SLAQ Luminous Red Galaxy Survey: I. The evolution of low-power radio galaxies to z~0.7

• Main Authors: Sadler, Elaine M, Cannon, Russell D, Mauch, Tom, Hancock, Paul J, Wake, David A, Ross, Nic, Croom, Scott M, Drinkwater, Michael J, Edge, Alastair C, Eisenstein, Daniel, Hopkins, Andrew M, Johnston, Helen, Nichol, Robert, Pimbblet, Kevin A, De Propris, Roberto, Roseboom, Isaac G, Schneider, Donald P, Shanks, Tom
• Format: Journal Article
• Language: English
• Published: 01-12-2006
• Subjects: Physics - Astrophysics of Galaxies; Physics - Cosmology and Nongalactic Astrophysics; Physics - Earth and Planetary Astrophysics; Physics - High Energy Astrophysical Phenomena; Physics - Instrumentation and Methods for Astrophysics; Physics - Solar and Stellar Astrophysics
• DOI: 10.48550/arxiv.astro-ph/0612019

We have combined optical data from the 2dF-SDSS Luminous Red Galaxy and QSO
(2SLAQ) redshift survey with radio measurements from the 1.4 GHz VLA FIRST and
NVSS 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
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 10^{24} to 10^{25} W/Hz, corresponding to 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 6-7 sigma
level) models in which low-power radio galaxies undergo no cosmic evolution.
The most powerful radio galaxies in our sample (with radio luminosities above
10^{26} W/Hz) 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 AGN heating increases
with redshift, and was roughly 50% higher at z~0.55 (the median redshift of the
2SLAQ LRG sample) than in the local universe.