A universal temperature profile for galaxy clusters

We investigate the predicted present-day temperature profiles of the hot, X-ray-emitting gas in galaxy clusters for two cosmological models a current best-guess LambdaCDM model and a standard cold dark matter (SCDM) model. Our numerically simulated catalogs of clusters are derived from high-resolution (15 h(-1) kpc) simulations which make use of a sophisticated, Eulerian-based, adaptive mesh-refinement code that faithfully captures the shocks that are essential for correctly modeling cluster temperatures. We show that the temperature structure on Mpc scales is highly complex and non-isothermal. However, the temperature profiles of the simulated LambdaCDM and SCDM clusters are remarkably similar and drop off as T proportional to (1+r/a(x))(-delta), where a(x)similar tor(vir)/1.5 and deltasimilar to1.6. This decrease is in good agreement with the observational results of Markevitch et al. but diverges, primarily in the innermost regions, from their fit which assumes a polytropic equation of state. Our result is also in good agreement with a recent sample of clusters observed by BeppoSAX, though there is some indication of missing physics at small radii (r<0.2 r(vir)). We discuss the interpretation of our results and make predictions for new X-ray observations that will extend to larger radii than previously possible. Finally, we show that for r>0.2 r(vir), our universal temperature pro le is consistent with our most recent simulations, which include both radiative cooling and supernovae feedback.