The Atacama Cosmology Telescope: measuring radio galaxy bias through cross-correlation with lensing

Understand

We correlate the positions of radio galaxies in the FIRST survey with the CMB lensing convergence estimated from the Atacama Cosmology Telescope over 470 square degrees to determine the bias of these galaxies.

• We remove optically cross-matched sources below redshift $z=0.2$ to preferentially select Active Galactic Nuclei (AGN).
• We measure the angular cross-power spectrum $C_l^{\kappa g}$ at $4.4\sigma$ significance in the multipole range $100<l<3000$, corresponding to physical scales between $\approx$ 2--60 Mpc at an effective redshift $z_{\rm eff}= 1.5$.
• Modelling the AGN population with a redshift-dependent bias, the cross-spectrum is well fit by the Planck best-fit $\Lambda$CDM cosmological model.