Chandra measurements of the distribution of mass in the luminous lensing cluster Abell 2390

Abstract

We present spatially-resolved X-ray spectroscopy of the luminous lensing cluster Abell 2390, using observations made with the Chandra observatory. The temperature of the X-ray gas is shown to rise with increasing radius within the central ~200 kpc of the cluster, and then remain approximately isothermal, with kT =11.5^{+1.5}_{-1.6} keV, out to the limits of the observations at r~1.0 Mpc. The total mass profile determined from the Chandra data has a form in good agreement with the predictions from numerical simulations. Using the parameterization of Navarro, Frenk & White (1997), we measure a scale radius r_s~0.9 Mpc and a concentration parameter c~4. The best-fit X-ray mass model is in good agreement with independent gravitational lensing results and optical measurements of the galaxy velocity dispersion in the cluster. The X-ray gas-to-total-mass ratio rises with increasing radius with f_gas = 21 \pm 10 per cent at r=0.9 Mpc. The azimuthally-averaged 0.3-7.0 keV surface brightness profile exhibits a small core radius and a clear `break' at r~500 kpc, where the slope changes from S_X \approxpropto r^{-1.5} to S_X \approxpropto r^{-3.6}. The data for the central region of the cluster indicate the presence of a cooling flow with a mass deposition rate of 200-300 solar masses per year and an age of 2-3 Gyr.