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

## TL;DR

This study measures the linear bias of radio-loud active galactic nuclei at redshift 0.3 using CMB lensing cross-correlation, revealing their typical environment as rich groups or clusters.

## Contribution

First measurement of RLAGN bias at z~0.3 via CMB lensing cross-correlation, providing insights into their typical dark matter halo masses and environments.

## Key findings

- Detected cross-power signal at 3σ significance.
- Estimated RLAGN bias as 2.5 ± 0.8, corresponding to halo mass ~10^14 M_sun.
- Removing cluster-associated RLAGN lowers the bias estimate.

## Abstract

We present a new measurement of the linear bias of radio loud active galactic nuclei (RLAGN) at $z\approx0.3$ and $L_{\rm 1.4GHz}>10^{23}\,{\rm W\,Hz^{-1}}$ 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 $3\sigma$ 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 $\log_{10}(M_{\rm h} /h^{-1} M_\odot)=14.0^{+0.3}_{-0.5}$. When RLAGN associated with optically-selected clusters are removed we measure a lower bias corresponding to $\log_{10}(M_{\rm h} /h^{-1} M_\odot)=13.7^{+0.4}_{-1.0}$. These observations support the view that powerful RLAGN typically inhabit rich group and cluster environments.