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

We present a new measurement of the linear bias of radio-loud active galactic nuclei (RLAGNs) at z ≈ 0.3 and L_1.4GHz>10^{23} {W Hz^{-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 3σ and use the amplitude of the cross-power spectrum to estimate the linear bias of RLAGNs, b = 2.5 ± 0.8, corresponding to a typical dark matter halo mass of log _{10}(M_h /h^{-1} M_⊙)=14.0^{+0.3}_{-0.5}. When RLAGNs associated with optically selected clusters are removed we measure a lower bias corresponding to log _{10}(M_h /h^{-1} M_⊙)=13.7^{+0.4}_{-1.0}. These observations support the view that powerful RLAGNs typically inhabit rich group and cluster environments.