Source-lens clustering and intrinsic-alignment bias of weak-lensing estimators^⋆

Institut de Physique Théorique, CEA Saclay, CNRS, URA 2306, 91191 Gif-sur-Yvette Cedex, France
e-mail: patrick.valageas@cea.fr

Received: 26 June 2013
Accepted: 11 October 2013

Abstract

Aims. We estimate the amplitude of the source-lens clustering bias and of the intrinsic-alignment bias of weak-lensing estimators of the two-point and three-point convergence and cosmic-shear correlation functions.

Methods. We use a linear galaxy bias model for the galaxy-density correlations, as well as a linear intrinsic-alignment model. For the three-point and four-point density correlations, we use analytical or semi-analytical models, based on a hierarchical ansatz or a combination of one-loop perturbation theory with a halo model.

Results. For two-point statistics, we find that the source-lens clustering bias is typically several orders of magnitude below the weak-lensing signal, except when we correlate a very low-redshift galaxy (z₂ ≲ 0.05) with a higher redshift galaxy (z₁ ≳ 0.5), where it can reach 10% of the signal for the shear. For three-point statistics, the source-lens clustering bias is typically on the order of 10% of the signal, as soon as the three galaxy source redshifts are not identical. The intrinsic-alignment bias is typically about 10% of the signal for both two-point and three-point statistics. Thus, both source-lens clustering bias and intrinsic-alignment bias must be taken into account for three-point estimators aiming at a better than 10% accuracy.