Using CMB lensing to constrain the multiplicative bias of cosmic shear

TL;DR

This paper proposes a novel method using cross-correlation between galaxy weak lensing data and CMB lensing to accurately constrain multiplicative bias, a key systematic in cosmic shear surveys, thereby improving cosmological measurements.

Contribution

The paper introduces a new approach leveraging CMB and galaxy lensing cross-correlation to constrain multiplicative bias in cosmic shear surveys.

Findings

Can constrain multiplicative bias to a few percent

Breaks degeneracy between matter power spectrum normalization and bias

Applicable to current and upcoming lensing surveys

Abstract

Weak gravitational lensing is one of the key probes of cosmology. Cosmic shear surveys aimed at measuring the distribution of matter in the universe are currently being carried out (Pan-STARRS) or planned for the coming decade (DES, LSST, EUCLID, WFIRST). Crucial to the success of these surveys is the control of systematics. In this work a new method to constrain one such family of systematics, known as multiplicative bias, is proposed. This method exploits the cross-correlation between weak lensing measurements from galaxy surveys and the ones obtained from high resolution CMB experiments. This cross-correlation is shown to have the power to break the degeneracy between the normalization of the matter power spectrum and the multiplicative bias of cosmic shear and to be able to constrain the latter to a few percent.