Weak Lensing Skew-Spectrum

TL;DR

This paper introduces the skew-spectrum statistic for weak lensing convergence maps, tests it against simulations, and explores its applications across different redshifts, scales, and CMB data, including effects of noise and masking.

Contribution

It presents a new skew-spectrum statistic for weak lensing, derives a closed-form expression for gravity-induced non-Gaussianity, and extends analysis to CMB lensing with post-Born corrections.

Findings

Skew-spectrum effectively characterizes non-Gaussianity in weak lensing maps.

Post-Born corrections are significant for CMB lensing skew-spectrum.

Method incorporates mask and noise effects in skew-spectrum estimation.

Abstract

We introduce the skew-spectrum statistic for weak lensing convergence $\kappa$ maps and test it against state-of-the-art high-resolution all-sky numerical simulations. We perform the analysis as a function of source redshift and smoothing angular scale for individual tomographic bins. We also analyse the cross-correlation between different tomographic bins. We compare the numerical results to fitting-functions used to model the bispectrum of the underlying density field as a function of redshift and scale. We derive a closed form expression for the skew-spectrum for gravity-induced secondary non-Gaussianity. We also compute the skew-spectrum for the projected $\kappa$ inferred from Cosmic Microwave Background (CMB) studies. As opposed to the low redshift case we find the post-Born corrections to be important in the modelling of the skew-spectrum for such studies. We show how the presence of a mask and noise can be incorporated in the estimation of a skew-spectrum.