Reconstructing the triaxiality of the galaxy cluster Abell 1689: solving the X-ray and strong lensing mass discrepancy

TL;DR

This study reconstructs the three-dimensional shape and physical parameters of galaxy cluster Abell 1689 using combined X-ray and lensing data, resolving previous mass discrepancies and supporting cold dark matter predictions.

Contribution

It introduces a novel method to determine the intrinsic triaxial shapes and parameters of galaxy clusters by combining X-ray and strong lensing data, addressing mass discrepancy issues.

Findings

Abell 1689 is modeled as a triaxial cluster with specific axial ratios.

Accounting for 3D geometry resolves X-ray and lensing mass discrepancies.

Inner DM density slope measured close to CDM predictions.

Abstract

We present the first determination of the intrinsic triaxial shapes and tree-dimensional physical parameters of both dark matter (DM) and intra-cluster medium (ICM) for the galaxy cluster Abell 1689. We exploit the novel method we recently introduced (Morandi et al. 2010) in order to infer the tree-dimensional physical properties in triaxial galaxy clusters by combining jointly X-ray and strong lensing data. We find that Abell 1689 can be modeled as a triaxial galaxy cluster with DM halo axial ratios 1.24 +/- 0.13 and 2.37 +/- 0.11 on the plane of the sky and along the line of sight, respectively. We show that accounting for the three-dimensional geometry allows to solve the discrepancy between the mass determined from X-ray and strong gravitational lensing observations. We also determined the inner slope of the DM density profile alpha: we measure alpha = 0.90 +/- 0.05 by accounting explicitly for the 3D structure for this cluster, a value which is close to the cold dark matter (CDM) predictions, while the standard spherical modeling leads to the biased value alpha = 1.16 +/- 0.04. Our findings dispel the potential inconsistencies arisen in the literature between the predictions of the CDM scenario and the observations, providing further evidences that support the CDM scenario.