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% 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%) level. We determine the gas entropy at 0.1rvir (where rvir is the virial radius) to be ∼ 800 keV cm , as expected for a high temperature cluster, but its profile at > 0.1rvir 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 < 0.02rvir, in accord with previous theoretical studies of massive clusters.