Gravitational Lensing with Three-Dimensional Ray Tracing

TL;DR

This paper introduces a new three-dimensional ray-tracing code for gravitational lensing that avoids the common thin-lens approximation, aiming to improve accuracy in predicting lensing effects on high-redshift sources.

Contribution

The paper develops and analyzes an innovative 3D ray-tracing method that enhances the precision of gravitational lensing simulations compared to traditional thin-lens approaches.

Findings

The new code accurately models lensing near Schwarzschild and NFW profiles.

Preliminary comparisons show differences from standard multiple lens-plane methods.

Numerical parameter choices significantly affect the code's efficiency and accuracy.

Abstract

High redshift sources suffer from magnification or demagnification due to weak gravitational lensing by large scale structure. One consequence of this is that the distance-redshift relation, in wide use for cosmological tests, suffers lensing-induced scatter which can be quantified by the magnification probability distribution. Predicting this distribution generally requires a method for ray-tracing through cosmological N-body simulations. However, standard methods tend to apply the multiple thin-lens approximation. In an effort to quantify the accuracy of these methods, we develop an innovative code that performs ray-tracing without the use of this approximation. The efficiency and accuracy of this computationally challenging approach can be improved by careful choices of numerical parameters; therefore, the results are analysed for the behaviour of the ray-tracing code in the vicinity of Schwarzschild and Navarro-Frenk-White lenses. Preliminary comparisons are drawn with the multiple lens-plane ray-bundle method in the context of cosmological mass distributions for a source redshift of $z_{s}=0.5$.