A Semi-analytic Ray-tracing Algorithm for Weak Lensing

TL;DR

This paper introduces a semi-analytic ray-tracing algorithm for weak lensing that directly computes shear and convergence from N-body simulations, offering improved efficiency and accuracy for large-scale sky surveys.

Contribution

The authors develop a novel line-of-sight ray-tracing method using analytic formulae, bypassing the need for numerical integrations and projected 2D lens planes.

Findings

Efficient computation of weak lensing fields from 3D mass distributions.

Accurate shear and convergence measurements suitable for large surveys.

Simplified implementation compared to traditional methods.

Abstract

We propose a new ray-tracing algorithm to measure the weak lensing shear and convergence fields directly from N-body simulations. We calculate the deflection of the light rays lensed by the 3-D mass density field or gravitational potential along the line of sight on a grid-by-grid basis, rather than using the projected 2-D lens planes. Our algorithm uses simple analytic formulae instead of numerical integrations in the computation of the projected density field along the line of sight, and so is computationally efficient, accurate and straightforward to implement. This will prove valuable in the interpretation of data from the next generation of surveys that will image many thousands of square degrees of sky.