Strong Lensing Analysis of the Cluster RCS0224-0002 at $z=0.77$

TL;DR

This paper presents a detailed strong lensing analysis of cluster RCS0224-0002 at z=0.77, reconstructing its mass profile using a novel method and comparing it with X-ray data, revealing dark matter substructure and light-mass alignment.

Contribution

It introduces a new approach to fit extended multiple images with the Modified Hausdorff Distance and performs comprehensive error analysis using MCMC.

Findings

Mass profile fits a non-singular isothermal sphere.

Dark matter substructure is essential for modeling complex lensing features.

Lensing-derived mass agrees with X-ray measurements.

Abstract

We present a detailed mass reconstruction of the cluster RCS0224-0002 at $z=0.773$ from the strong lensing features observed with HST/WFPC2. The mass profile is reconstructed using a parametric approach. We introduce a novel method to fit extended multiple images based on the Modified Hausdorff Distance between observed arcs and the arcs reproduced by the model. We perform the detailed error analysis of the model parameter using the MCMC method. Our model reproduces all the observed strong lensing features of the RCS0224-0002 and predicts the redshift of one of the arcs systems to be $z\approx 2.65$ (the other system has an spectroscopic redshift of $z=4.87$). The reconstructed inner mass profile is well fitted by a non-singular isothermal sphere, rather than with an NFW model. Dark matter substructure, derived from the light distribution of the most luminous cluster members, is crucial for reproducing the complexity of the quadrupole image system, which could not be achieved otherwise. The reconstructed mass distribution closely follows the light, however it is significantly shifted from the X-ray emission of the gas. The mass of RCS0224-0002 derived from the lensing model, $\approx 2\times10^{14} M_\odot$ is in a very good agreement with the one obtained from the X-ray temperature measured with deep Chandra observations.