THE CLUSTERING OF RADIO GALAXIES: BIASING AND EVOLUTION VERSUS STELLAR MASS

We study the angular clustering of similar to 6 x 10(5) NVSS sources on scales greater than or similar to 50h(-1) Mpc in the context of the Lambda CDM scenario. The analysis partially relies on the redshift distribution of 131 radio galaxies, inferred from the Hercules and CENSORS survey, and an empirical fit to the stellar-to-halo mass relation. For redshifts z less than or similar to 0.7, the fraction of radio activity versus stellar mass evolves as f(RL) similar to M-* (alpha 0+alpha 1z), where alpha(0) = 2.529 +/- 0.184 and alpha(1) = 1.854(-0.761)(+0.708). The estimate on alpha(0) is largely driven by the results of Best et al., while the constraint on alpha(1) is new. We derive a biasing factor b(z = 0.5) = 2.093(-0.109)(+0.164) between radio galaxies and the underlying mass. The function b(z) = 0.33z(2) + 0.85z + 1.6 fits well the redshift dependence. We also provide convenient parametric forms for the redshift-dependent radio luminosity function, which are consistent with the redshift distribution and the NVSS source count versus flux.