The Weak Lensing Bispectrum Induced By Gravity

TL;DR

This paper extends the analysis of the weak lensing bispectrum by estimating its amplitude in various configurations and redshifts using simulations, highlighting the need for improved theoretical models for future surveys.

Contribution

It provides a comprehensive estimation of the weak lensing bispectrum in multiple configurations and redshifts, comparing results with theoretical predictions and identifying modeling limitations.

Findings

Theoretical models predict general trends but lack accuracy in the squeezed limit.

Simulations reveal discrepancies between theory and measurements, especially at certain configurations.

More precise theoretical modeling is necessary for upcoming all-sky weak lensing surveys.

Abstract

Recent studies have demonstrated that {\em secondary} non-Gaussianity induced by gravity will be detected with a high signal-to-noise (S/N) by future and even by on-going weak lensing surveys. One way to characterise such non-Gaussianity is through the detection of a non-zero three-point correlation function of the lensing convergence field, or of its harmonic transform, the bispectrum. A recent study analysed the properties of the squeezed configuration of the bispectrum, when two wavenumbers are much larger than the third one. We extend this work by estimating the amplitude of the (reduced) bispectrum in four generic configurations, i.e., {\em squeezed, equilateral, isosceles} and {\em folded}, and for four different source redshifts $z_s=0.5,1.0,1.5,2.0$, by using an ensemble of all-sky high-resolution simulations. We compare these results against theoretical predictions. We find that, while the theoretical expectations based on widely used fitting functions can predict the general trends of the reduced bispectra, a more accurate theoretical modelling will be required to analyse the next generation of all-sky weak lensing surveys. The disagreement is particularly pronounced in the squeezed limit.