Accuracy of the thin-lens approximation in strong lensing by smoothly truncated dark matter haloes

TL;DR

This study evaluates the accuracy of the thin-lens approximation in strong gravitational lensing by truncated dark matter haloes, finding errors below 0.5% and identifying the optimal truncation radius.

Contribution

It provides a quantitative assessment of the thin-lens approximation's accuracy for NFW halo models with soft truncation in strong lensing scenarios.

Findings

Mass error from thin-lens approximation is below 0.5%.

Optimal tidal radius is at most 10 times the virial radius.

Supports use of thin-lens approximation in strong lensing mass estimates.

Abstract

The accuracy of mass estimates by gravitational lensing using the thin-lens approximation applied to Navarro-Frenk-White mass models with a soft truncation mechanism recently proposed by Baltz, Marshall and Oguri is studied. The gravitational lens scenario considered is the case of the inference of lens mass from the observation of Einstein rings (strong lensing). It is found that the mass error incurred by the simplifying assumption of thin lenses is below 0.5%. As a byproduct, the optimal tidal radius of the soft truncation mechanism is found to be at most 10 times the virial radius of the mass model.