Mass and gas profiles in A1689: joint X-ray and lensing analysis

We carry out a comprehensive joint analysis of high-quality HST/ACS and Chandra measurements of A1689, from which we derive mass, temperature, X-ray emission and abundance profiles. The X-ray emission is smooth and symmetric, and the lensing mass is centrally concentrated indicating a relaxed cluster. Assuming hydrostatic equilibrium we deduce a 3D mass profile that agrees simultaneously with both the lensing and X-ray measurements. However, the projected temperature profile predicted with this 3D mass profile exceeds the observed temperature by ~30 per cent at all radii, a level of discrepancy comparable to the level found for other relaxed clusters. This result may support recent suggestions from hydrodynamical simulations that denser, more X-ray luminous small-scale structure can bias observed temperature measurements downward at about the same (~30 per cent) level. We determine the gas entropy at 0.1r_vir (where r_vir is the virial radius) to be ~800 keV cm², as expected for a high-temperature cluster, but its profile at >0.1r_vir has a power-law form with index ~0.8, considerably shallower than the ~1.1 index advocated by theoretical studies and simulations. Moreover, if a constant entropy `floor' exists at all, then it is within a small region in the inner core, r < 0.02r_vir, in accord with previous theoretical studies of massive clusters.