Enhancing the Cosmic Shear Power Spectrum

TL;DR

This paper explores a transformation technique called clipping on weak lensing convergence fields to improve cosmological parameter constraints, showing significant gains even with realistic shape noise levels.

Contribution

It demonstrates that combining original and clipped convergence power spectra enhances information content and tightens cosmological constraints despite shape noise.

Findings

Clipping improves the information content of convergence power spectra.

Combined analysis reduces likelihood contour area by over a factor of three.

The method is robust against realistic shape noise levels.

Abstract

Applying a transformation to a non-Gaussian field can enhance the information content of the resulting power spectrum, by reducing the correlations between Fourier modes. In the context of weak gravitational lensing, it has been shown that this gain in information content is significantly compromised by the presence of shape noise. We apply clipping to mock convergence fields, a technique which is known to be robust in the presence of noise and has been successfully applied to galaxy number density fields. When analysed in isolation the resulting convergence power spectrum returns degraded constraints on cosmological parameters. However substantial gains can be achieved by performing a combined analysis of the power spectra derived from both the original and transformed fields. Even in the presence of realistic levels of shape noise, we demonstrate that this approach is capable of reducing the area of likelihood contours within the $\Omega_m - \sigma_8$ plane by more than a factor of three.