On Scale-Dependent Cosmic Shear Systematic Effects

TL;DR

This paper examines how scale-dependent systematic effects influence cosmic shear measurements and cosmological parameter estimation, emphasizing the importance of survey strategy and scale modeling for accurate results.

Contribution

It introduces a detailed modeling of spatially varying residual ellipticity and size effects, analyzing their impact on cosmological parameters and proposing improved mitigation strategies.

Findings

Randomized survey strategies minimize biases but increase uncertainties.

Regular survey strategies cause large biases unless scales are modeled or removed.

Modeling systematic effects in real space improves bias mitigation.

Abstract

In this paper we investigate the impact that realistic scale-dependence systematic effects may have on cosmic shear tomography. We model spatially varying residual ellipticity and size variations in weak lensing measurements and propagate these through to predicted changes in the uncertainty and bias of cosmological parameters. We show that the survey strategy - whether it is regular or randomised - is an important factor in determining the impact of a systematic effect: a purely randomised survey strategy produces the smallest biases, at the expense of larger parameter uncertainties, and a very regularised survey strategy produces large biases, but unaffected uncertainties. However, by removing, or modelling, the affected scales (l-modes) in the regular cases the biases are reduced to negligible levels. We find that the integral of the systematic power spectrum is not a good metric for dark energy performance, and we advocate that systematic effects should be modelled accurately in real space, where they enter the measurement process, and their effect subsequently propagated into power spectrum contributions.