Weak Lensing Mass Reconstruction: Flexion vs Shear

TL;DR

This paper compares the effectiveness of gravitational shear and flexion in reconstructing dark matter distribution, finding shear more reliable for convergence maps on feasible scales.

Contribution

It provides a direct comparison of shear and flexion techniques, highlighting the limitations of flexion in dark matter mapping.

Findings

Flexion is less sensitive than shear for convergence map reconstruction.

Flexion alone is insufficient for mapping dark matter on small scales.

Shear remains the more effective method for dark matter distribution mapping.

Abstract

Weak gravitational lensing has proven to be a powerful tool to map directly the distribution of dark matter in the Universe. The technique, currently used, relies on the accurate measurement of the gravitational shear that corresponds to the first-order distortion of the background galaxy images. More recently, a new technique has been introduced that relies on the accurate measurement of the gravitational flexion that corresponds to the second-order distortion of the background galaxy images. This technique should probe structures on smaller scales than that of a shear analysis. The goal of this paper is to compare the ability of shear and flexion to reconstruct the dark matter distribution by taking into account the dispersion in shear and flexion measurements. Our results show that the flexion is less sensitive than shear for constructing the convergence maps on scales that are physically feasible for mapping, meaning that flexion alone not be used to do convergence map reconstruction, even on small scales.