Cosmology with the shear-peak statistics

TL;DR

This paper introduces a peak function based on weak-lensing shear peaks, demonstrating its potential to constrain cosmological parameters and improve upon traditional cosmic-shear methods when combined.

Contribution

It presents a novel peak function approach for cosmology, leveraging large-scale structure projections to enhance parameter constraints.

Findings

Peak statistics provide competitive constraints with cosmic-shear tomography.

Combining peak statistics with cosmic shear yields tighter cosmological constraints.

The method effectively utilizes false positives from structure projection for cosmological insights.

Abstract

Weak-lensing searches for galaxy clusters are plagued by low completeness and purity, severely limiting their usefulness for constraining cosmological parameters with the cluster mass function. A significant fraction of `false positives' are due to projection of large-scale structure and as such carry information about the matter distribution. We demonstrate that by constructing a "peak function", in analogy to the cluster mass function, cosmological parameters can be constrained. To this end we carried out a large number of cosmological N-body simulations in the \Omega_m-\sigma_8 plane to study the variation of this peak function. We demonstrate that the peak statistics is able to provide constraints competitive with those obtained from cosmic-shear tomography from the same data set. By taking the full cross-covariance between the peak statistics and cosmic shear into account, we show that the combination of both methods leads to tighter constraints than either method alone can provide.