Measuring dark matter ellipticity of Abell 901/902 using Particle Based Lensing

TL;DR

This paper introduces a non-parametric method to measure the ellipticity and alignment of dark matter halos in the Abell 901/902 supercluster using Particle Based Lensing, providing insights into their shapes and orientations.

Contribution

It presents an improved Particle Based Lensing technique for non-parametric mass mapping and compares parametric and non-parametric ellipticity measurements in a supercluster.

Findings

Measured axis ratio of 0.37±0.1 for A901b

Measured axis ratio of 0.54+0.08−0.09 for the Southwest Group

Found consistency between methods for A901b but discrepancies for the Southwest Group

Abstract

We present a non-parametric measure of the ellipticity and the alignment of the dark matter halos in Abell 901/902 supercluster. This super-cluster is a system of four separate peaks in a $0.5^{\circ}\times0.5^{\circ}$ field of view. We map the mass distribution of each individual peak using an improved version of Particle Based Lensing (PBL) and measure the ellipticity of the dark matter halos associated with two of the peaks directly from the mass map and by fitting them to a singular isothermal ellipse. The parametric and non-parametric measurements are consistent for A901b while the position angle for the Southwest Group is different for the two techniques. We account for this discrepancy to substructure present in the Southwest Peak. We estimate an axis ratio of $0.37\pm 0.1$ for A901b and $0.54^{+0.08}_{-0.09}$ for the Southwest Group.