Mass, shape and thermal properties of Abell 1689 using a multiwavelength X-ray, lensing and Sunyaev-Zel'dovich analysis

Knowledge of the mass and concentration of galaxy clusters is crucial for an understanding of their formation and evolution. Unbiased estimates require an understanding of the shape and orientation of the halo as well as its equilibrium status. We propose a novel method to determine the intrinsic properties of galaxy clusters from a multiwavelength data set, spanning from X-ray spectroscopic and photometric data to gravitational lensing to the Sunyaev-Zel'dovich effect. The method relies on two non-informative geometrical assumptions: the distributions of total matter or gas are approximately ellipsoidal and co-aligned; they have different, constant axial ratios but share the same degree of triaxiality. Weak and strong lensing probe the features of the total mass distribution in the plane of the sky. X-ray data measure the size and orientation of the gas in the plane of the sky. Comparison with the Sunyaev-Zel'dovich amplitude fixes the elongation of the gas along the line of sight. These constraints are deprojected as a result of Bayesian inference. The mass distribution is described as a Navarro-Frenk-White halo with arbitrary orientation, and the gas density and temperature are modelled with parametric profiles. We have applied the method to Abell 1689. Independently of the priors, the cluster is massive, M₂₀₀ = (1.3 ± 0.2) × 10¹⁵ M_⊙, and overconcentrated, c₂₀₀ = 8 ± 1, but it is still consistent with theoretical predictions. The total matter is triaxial (minor to major axial ratio ∼0.5 ± 0.1, exploiting priors from N-body simulations) with the major axis nearly orientated along the line of sight. The gas is rounder (minor to major axial ratio ∼0.6 ± 0.1) and deviates from hydrostatic equilibrium. The contribution of non-thermal pressure is ∼20-50 per cent in the inner regions, ≲ 300 kpc, and ∼25 ± 5 per cent at ∼1.5 Mpc. This picture of A1689 was obtained with a small number of assumptions and in a single framework, suitable for application to a large variety of clusters.