The clustering of radio galaxies: biasing and evolution versus stellar mass

TL;DR

This study analyzes the large-scale clustering of radio galaxies within the b5CDM model, revealing how radio activity depends on stellar mass and redshift, and providing models for bias and luminosity functions.

Contribution

It introduces a new constraint on the evolution of radio activity with stellar mass and redshift, and models the biasing factor and luminosity function of radio galaxies.

Findings

Biasing factor at z=0.5 is approximately 2.09.

Radio activity fraction evolves as M_*^{b1_0+b1_1 z} with new constraints on b1_1.

Redshift-dependent biasing function fits well with data.

Abstract

We study the angular clustering of $\sim 6\times 10^5$ NVSS sources on scales $\gtrsim 50 h^{-1}$ 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 (SHM) relation. For redshifts $z\lesssim 0.7$, the fraction of radio activity versus stellar mass evolves as $f_{_{\rm RL}}\sim M_*^{\alpha_0+\alpha_1 z}$ where $\alpha_0=2.529{\pm0.184}$ and $\alpha_1=1.854^{+0.708}_{-0.761}$. The estimate on $\alpha_0$ is largely driven by the results of Best et al. (2005), while the constraint on $\alpha_1$ is new. We derive a biasing factor $b(z=0.5)=2.093^{+0.164}_{-0.109}$ between radio galaxies and the underlying mass.The function $b(z)=0.33z^2+0.85 z +1.6$ 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.