The Bias to Cosmic Microwave Background Lensing Reconstruction from the Kinematic Sunyaev-Zel'dovich Effect at Reionization

TL;DR

This paper examines the bias introduced by the kinematic Sunyaev-Zel'dovich effect on CMB lensing reconstruction, finding reionization-induced bias negligible but late-time kSZ bias potentially significant for future experiments.

Contribution

First analysis of reionization kSZ bias on CMB lensing, showing it is negligible, and updated assessment of late-time kSZ bias indicating it may be larger than previously thought.

Findings

Reionization kSZ bias is negligible for current and upcoming experiments.

Late-time kSZ bias can reach several percent of the lensing signal.

Updated simulations suggest a larger bias than earlier estimates.

Abstract

The power spectrum of reconstructed cosmic microwave background (CMB) lensing maps is a powerful tool for constraints on cosmological parameters like the sum of the neutrino masses and the dark energy equation of state. One possible complication is the kinematic Sunyaev-Zel'dovich (kSZ) effect, due to the scattering of CMB photons by moving electrons, which can bias the reconstruction of the CMB lensing power spectrum through both kSZ-lensing correlations and the non-Gaussianity of the kSZ temperature anisotropies. We investigate for the first time the bias to CMB lensing reconstruction from temperature anisotropies due to the reionization-induced kSZ signal and show that it is negligible for both ongoing and upcoming experiments based on current numerical simulations of reionization. We also revisit the bias induced by the late-time kSZ field, using more recent kSZ simulations. We find that it is potentially twice as large as found in earlier studies, reaching values as large as several percent of the CMB lensing power spectrum signal, indicating that this bias will have to be mitigated in upcoming data analyses.