Intrinsic alignments in the cross-correlation of cosmic shear and cosmic microwave background weak lensing

Abstract

Abstract We demonstrate that the intrinsic alignment of galaxies with large-scale tidal fields sources an extra contribution to the recently detected cross-correlation of galaxy shear and weak lensing of the microwave background. The extra term is the analogy of the ‘GI’ term in standard cosmic shear studies, and results in a reduction in the amplitude of the cross-correlation. We compute the intrinsic alignment contribution in linear and non-linear theory, and show that it can be at roughly the 15 per cent level for the Canada–France–Hawaii Telescope Stripe 82 redshift distribution, if the canonical amplitude of intrinsic alignments is assumed. The new term can therefore potentially reconcile the apparently low value of the measured cross-correlation with standard Λ cold dark matter. We discuss various small-scale effects in the signal and the dependence on the source redshift distribution. We discuss the exciting possibility of self-calibrating intrinsic alignments with a joint analysis of cosmic shear and weak lensing of the microwave background.