Impact of Point Spread Function Higher Moments Error on Weak Gravitational Lensing

TL;DR

This paper investigates how errors in higher moments of the PSF model affect weak gravitational lensing measurements, finding that current data errors are negligible for ongoing surveys but significant for future high-precision surveys like LSST.

Contribution

The study extends analysis of PSF errors in weak lensing by quantifying the impact of higher moments, which were previously less understood, on shear bias.

Findings

Current PSF higher moment errors induce ~0.05% shear bias.

This bias is negligible for ongoing surveys like HSC.

The bias becomes relevant for future surveys such as LSST.

Abstract

Weak gravitational lensing is one of the most powerful tools for cosmology, while subject to challenges in quantifying subtle systematic biases. The Point Spread Function (PSF) can cause biases in weak lensing shear inference when the PSF model does not match the true PSF that is convolved with the galaxy light profile. Although the effect of PSF size and shape errors - i.e., errors in second moments - is well studied, weak lensing systematics associated with errors in higher moments of the PSF model require further investigation. The goal of our study is to estimate their potential impact for LSST weak lensing analysis. We go beyond second moments of the PSF by using image simulations to relate multiplicative bias in shear to errors in the higher moments of the PSF model. We find that the current level of errors in higher moments of the PSF model in data from the Hyper Suprime-Cam (HSC) survey can induce a $\sim 0.05 $ per cent shear bias, making this effect unimportant for ongoing surveys but relevant at the precision of upcoming surveys such as LSST.