Real-world CMB lensing quadratic estimator power spectrum response

I describe a method to estimate response matrices of Cosmic Microwave Back-ground (CMB) lensing power spectra estimators to the true sky power under realistic conditions. Applicable to all lensing reconstruction pipelines based on quadratic estimators (QE), it uses a small number of Gaussian CMB Monte-Carlos and specially designed QE's in order to obtain sufficiently accurate matrices with little computational effort. This method may be used to improve the modelling of CMB lensing band-powers by incorporating at least some of the non-idealities encountered in CMB lensing reconstruction. These non-idealities always include masking, and often inhomogeneous filtering, either in the harmonic domain or pixel space. I obtain these matrices for Planck latest lensing reconstructions, and then show that the residual couplings induced by masking explain very well the residual multiplicative bias seen on the Planck simulations, removing the need for an empirical correction.

Automated summary

This method proposes a way to estimate the response matrices of CMB lensing power spectra estimators to the true sky power in realistic conditions. By using a small number of Gaussian CMB Monte-Carlos and specially designed quadratic estimators (QE), accurate matrices can be obtained with minimal computational effort. It can be used to improve the modeling of CMB lensing band-powers by incorporating some of the non-idealities encountered in CMB lensing reconstruction. The method shows that the residual couplings induced by masking can explain the observed residual multiplicative bias on Planck simulations, eliminating the need for an empirical correction.