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 (similar to 35 '', or similar to 200 kpc, for a source at redshift 1.8), we obtain a total mass of (2.6 +/- 0.1) x 10(14) M(circle dot). 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(-0.6)(+0.4) and r(200) = 3.3(-0.1)(+0.2) Mpc, and a non-singular isothermal sphere with velocity dispersion s = 1949 +/- 40 km s(-1) and a core radius of r(c) = 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.