Self calibration of gravitational shear-galaxy intrinsic ellipticity correlation in weak lensing surveys

TL;DR

This paper introduces a self-calibration method for mitigating the gravitational shear-intrinsic ellipticity correlation in weak lensing surveys, improving the accuracy of cosmic shear measurements.

Contribution

It proposes a novel approach to extract and convert the intrinsic alignment correlation using photometric redshifts, enhancing weak lensing analysis.

Findings

Method can significantly reduce GI contamination in simplified models

Scaling relation effectively converts I-g to GI correlation

Approach robust against various complexities

Abstract

The galaxy intrinsic alignment is a severe challenge to precision cosmic shear measurement. We propose to self-calibrate the induced gravitational shear-galaxy intrinsic ellipticity correlation (the GI correlation, \citealt{Hirata04b}) in weak lensing surveys with photometric redshift measurement. (1) We propose a method to extract the intrinsic ellipticity-galaxy density cross correlation (I-g) from the galaxy ellipticity-density measurement in the same redshift bin. (2) We also find a generic scaling relation to convert the extracted I-g correlation to the demanded GI correlation. We perform concept study under simplified conditions and demonstrate its capability to significantly reduce the GI contamination. We discuss the impact of various complexities on the two key ingredients of the self-calibration technique, namely the method to extract the I-g correlation and the scaling relation between the I-g and the GI correlation. We expect none of them is likely able to completely invalidate the proposed self-calibration technique.