Effects of Galaxy Formation on Thermodynamics of the Intracluster Medium

We present detailed comparisons of the intracluster medium (ICM) incosmological Eulerian cluster simulations with deep Chandra observations ofnearby relaxed clusters. To assess the impact of galaxy formation, we comparetwo sets of simulations, one performed in the non-radiative regime and anotherwith radiative cooling and several physical processes critical to variousaspects of galaxy formation: star formation, metal enrichment and stellarfeedback. We show that the observed ICM properties outside cluster cores arewell-reproduced in the simulations that include cooling and star formation,while the non-radiative simulations predict an overall shape of the ICMprofiles inconsistent with observations. In particular, we find that the ICMentropy in our runs with cooling is enhanced to the observed levels at radii aslarge as half of the virial radius. We also find that outside cluster coresentropy scaling with the mean ICM temperature in both simulations and Chandraobservations is consistent with being self-similar within current error bars.We find that the pressure profiles of simulated clusters are also close toself-similar and exhibit little cluster-to-cluster scatter. The X-rayobservable-total mass relations for our simulated sample agree with the Chandrameasurements to \~10%-20% in normalization. We show that this systematicdifference could be caused by the subsonic gas motions, unaccounted for inX-ray hydrostatic mass estimates. The much improved agreement of simulationsand observations in the ICM profiles and scaling relations is encouraging andthe existence of tight relations of X-ray observables, such as Yx, and totalcluster mass and the simple redshift evolution of these relations hold promisefor the use of clusters as cosmological probes.Comment: 14 pages, 6 figures. Matches version accepted to Ap