The mass distribution of RX J1347–1145 from strong lensing

Aims:We determine the central mass distribution of galaxy cluster RX J1347-1145 using strong gravitational lensing. Methods: High-resolution HST/ACS images of the galaxy cluster RX J1347-1145 have enabled us to identify several new multiple-image candidates in the cluster, including a 5-image system with a central image. The multiple-images allow us to construct an accurate 2-dimensional mass map of the central part of the cluster. The modelling of the cluster mass includes the most prominent cluster galaxies modelled as truncated isothermal spheres and a smooth halo component that is described with 2 parametric profiles. The mass reconstruction is done using a Markov chain Monte Carlo method that provides us with a total projected mass density, as well as with estimates for the parameters of interest and their respective errors. Results: Inside the Einstein radius of the cluster (~35'', or ~200 kpc, for a source at redshift 1.8), we obtain a total mass of (2.6 ± 0.1) × 1014~Msun. The mass profile of the cluster is well-fitted by both a Navarro, Frenk, and White profile with a moderate concentration of c = 5.3+0.4-0.6 and r200 = 3.3+0.2-0.1 Mpc, and a non-singular isothermal sphere with velocity dispersion σ = 1949 ± 40 km s-1 and a core radius of rc = 20 ± 2''. The mass profile agrees with previous mass estimates based on the X-ray emission from the hot intra-cluster gas, although the X-ray mass estimates are systematically lower than what we obtain with gravitational lensing.