Strong Lensing in Abell 1703: Constraints on the Slope of the Inner Dark Matter Distribution

TL;DR

This study uses strong lensing data from Abell 1703 to measure the inner dark matter density slope, finding it close to the NFW profile prediction, and discusses implications for dark matter distribution in galaxy clusters.

Contribution

First detailed strong lensing analysis of Abell 1703 that constrains the inner dark matter slope using multi-band imaging and spectroscopic data.

Findings

Dark matter slope .09^{+0.05}_{-0.11} within 5-50"

Concentration parameter c_{200} .5

Mass within 50" is 2.4 imes 10^{14} M_{\u00a0sun}

Abstract

In this article, we apply strong lensing techniques in Abell 1703, a massive X-ray luminous galaxy cluster at z=0.28. Our analysis is based on imaging data both from space and ground in 8 bands, complemented with a spectroscopic survey. Abell 1703 looks rather circular from the general shape of its multiply imaged systems and present a dominant giant elliptical cD galaxy in its centre. This cluster exhibits a remarkable bright 'central ring' formed by 4 bright images at z_{spec}=0.888 located very close to the cD galaxy, providing observational constraints that are potentially very interesting to probe the central mass distribution. The stellar contribution from the cD galaxy (~1.25 10^{12} M_{sun} within 7") is accounted for in our parametric mass modelling, and the underlying smooth dark matter component distribution is described using a generalized NFW profile parametrized with a central logarithmic slope \alpha. We find that within the range where observational constraints are present (from ~5" to ~50"), the slope of the dark matter distribution in Abell1703 is equal to 1.09^{+0.05}_{-0.11} (3\sigma confidence level). The concentration parameter is equal to c_{200} ~ 3.5, and the scale radius is constrained to be larger than the region where observational constraints are available. Within this radius, the 2D mass is equal to M(50")=2.4 10^{14} M_{\sun}. We cannot draw any conclusions on cosmological models at this point since we lack results from realistic numerical simulations containing baryons to make a proper comparison. We advocate the need for a sample of observed and simulated unimodal relaxed galaxy clusters in order to make reliable comparisons, and potentially provide a test of cosmological models.