An adapted filter function for density split statistics in weak lensing

TL;DR

This paper introduces a new angular filter function for density split statistics in weak lensing that improves correlation with matter distribution and enhances the signal-to-noise ratio, aiding cosmological analysis.

Contribution

The paper develops an adapted filter function matched to shear and galaxy density signals, outperforming the traditional top-hat filter in weak lensing analyses.

Findings

Better correlation between matter and galaxy distribution with the adapted filter.

Increased signal-to-noise ratio for bias constraints.

Enhanced sensitivity to different cosmologies, except very high σ8.

Abstract

Context. The density split statistics in weak gravitational lensing analyses probes the correlation between regions of different (foreground) galaxy number densities and their weak lensing signal, measured by the shape distortion of background galaxies. Aims. In this paper, we reconsider density split statistics, by constructing a new angular filter function that is adapted to the expected relation between galaxy number density and shear pattern, in a way that the filter weighting the galaxy number density is matched to the filter that is used to quantify the shear signal. Methods. We use the results of numerical ray-tracing simulations, specifically through Millennium Simulation supplemented by a galaxy distribution based on a semi-analytic model, to construct a matched pair of adapted filter functions for the galaxy density and the tangential shear signal. We compare the performance of our new filter to the previously used top-hat filter, applying both to a different and independent set of numerical simulations (SLICS, cosmo-SLICS). Results. We show that the adapted filter yields a better correlation between the total matter and the galaxy distribution. Furthermore, the adapted filter provides a larger signal-to-noise ratio to constrain the bias between the total matter and the galaxy distribution, and we show that it is, in general, a more sensitive discriminator between different cosmologies, with the exception of cosmologies with very large $\sigma_8$ values. All analyses lead to the conclusion that our adapted filter should be favored in future density split statistic works.