The linear bias of radio galaxies at z~0.3 via cosmic microwave background lensing

Abstract

We present a new measurement of the linear bias of radio loud active galactic nuclei (RLAGN) at $z\approx 0.3$ and $L_{1.4GHz}>10^{23}\mathrm{W}\mathrm{H}{\mathrm{z}}^{-1}$ selected from the Best & Heckman (2012) sample, made by cross-correlating the RLAGN surface density with a map of the convergence of the weak lensing field of the cosmic microwave background from Planck. We detect the cross-power signal at a significance of $3\ddot{I}ƒ$ and use the amplitude of the cross-power spectrum to estimate the linear bias of RLAGN, $b=2.5\pm 0.8$, corresponding to a typical dark matter halo mass of ${\log }_{10}(M_{\mathrm{h}}/h^{-1}{M}_{\odot })=14.0_{-0.5}^{+0.3}$. When RLAGN associated with optically-selected clusters are removed we measure a lower bias corresponding to ${\log }_{10}(M_{\mathrm{h}}/h^{-1}{M}_{\odot })=13.7_{-1.0}^{+0.4}$. These observations support the view that powerful RLAGN typically inhabit rich group and cluster environments.

Accepted for publication in MNRAS Letters