KiDS-450: Enhancing cosmic shear with clipping transformations

TL;DR

This paper introduces a novel 'clipping' transformation technique for cosmic shear measurements that suppresses non-linear high-density regions, leading to improved constraints on cosmological parameters from KiDS-450 data.

Contribution

The paper presents the first application of clipping transformations in cosmic shear analysis, demonstrating enhanced parameter constraints and developing methods to mitigate observational effects.

Findings

Clipping improves $S_8$ constraints by 17% with KiDS-450 data.

Developed methodology to account for masking and shot noise effects.

Validated the approach using numerical simulations.

Abstract

We present the first "clipped" cosmic shear measurement using data from the Kilo-Degree Survey (KiDS-450). "Clipping" transformations suppress the signal from the highest density, non-linear regions of cosmological fields. We demonstrate that these transformations improve constraints on $S_8=\sigma_8(\Omega_{\rm{m}}/0.3)^{0.5}$ when used in combination with conventional two-point statistics. For the KiDS-450 data, we find that the combined measurements improve the constraints on $S_8$ by 17%, compared to shear correlation functions alone. We determine the expectation value of the clipped shear correlation function using a suite of numerical simulations, and develop methodology to mitigate the impact of masking and shot noise. Future improvements in numerical simulations and mass reconstruction methodology will permit the precise calibration of clipped cosmic shear statistics such that clipping can become a standard tool in weak lensing analyses.