Improving parametric mass modelling of lensing clusters through a perturbative approach

TL;DR

This paper introduces a hybrid parametric and free-form method for galaxy cluster mass modeling that improves the accuracy of lensing predictions, demonstrated on simulated data with significant error reduction.

Contribution

A novel combined parametric and free-form approach for cluster mass modeling that enhances flexibility and accuracy over traditional methods.

Findings

Improved reproduction of lensing constraints by a factor of 3-4.

Better accuracy in convergence field reconstruction.

High fidelity in reproducing lensing observables.

Abstract

We present a new method to model the mass distribution of galaxy clusters that combines a parametric and a free-form approach to reconstruct cluster cores with strong lensing constraints. It aims at combining the advantages of both approaches, by keeping the robustness of the parametric component with an increased flexibility thanks to a free-form surface of B-spline functions. We demonstrate the capabilities of this new approach on the simulated cluster Hera, which has been used to evaluate lensing codes for the analysis of the Frontier Fields clusters. The method leads to better reproduction of the constraints, with an improvement by a factor $\sim3-4$ on the root-mean-square error on multiple-image positions, when compared to parametric-only approaches. The resulting models show a better accuracy in the reconstruction of the amplitude of the convergence field while conserving a high fidelity on other lensing observables already well reproduced. We make this method publicly available through its implementation in the Lenstool software.