A study of the sensitivity of shape measurements to the input parameters of weak lensing image simulations

TL;DR

This paper investigates how input parameters in weak lensing image simulations affect shape measurement biases, emphasizing the importance of realistic galaxy populations and local source density for accurate cosmological inferences.

Contribution

It analyzes the sensitivity of multiplicative bias to simulation parameters, highlighting the need to account for local source density and faint galaxies in weak lensing studies.

Findings

Bias depends on local galaxy density.

Magnification affects faint galaxy counts and bias.

Archival HST data can help create realistic simulations.

Abstract

Improvements in the accuracy of shape measurements are essential to exploit the statistical power of planned imaging surveys that aim to constrain cosmological parameters using weak lensing by large-scale structure. Although a range of tests can be performed using the measurements, the performance of the algorithm can only be quantified using simulated images. This yields, however, only meaningful results if the simulated images resemble the real observations sufficiently well. In this paper we explore the sensitivity of the multiplicative bias to the input parameters of Euclid-like image simulations.We find that algorithms will need to account for the local density of sources. In particular the impact of galaxies below the detection limit warrants further study, because magnification changes their number density, resulting in correlations between the lensing signal and multiplicative bias. Although achieving sub-percent accuracy will require further study, we estimate that sufficient archival Hubble Space Telescope data are available to create realistic populations of galaxies.