  We present detailed comparisons of the intracluster medium (ICM) in
cosmological Eulerian cluster simulations with deep Chandra observations of
nearby relaxed clusters. To assess the impact of galaxy formation, we compare
two sets of simulations, one performed in the non-radiative regime and another
with radiative cooling and several physical processes critical to various
aspects of galaxy formation: star formation, metal enrichment and stellar
feedback. We show that the observed ICM properties outside cluster cores are
well-reproduced in the simulations that include cooling and star formation,
while the non-radiative simulations predict an overall shape of the ICM
profiles inconsistent with observations. In particular, we find that the ICM
entropy in our runs with cooling is enhanced to the observed levels at radii as
large as half of the virial radius. We also find that outside cluster cores
entropy scaling with the mean ICM temperature in both simulations and Chandra
observations is consistent with being self-similar within current error bars.
We find that the pressure profiles of simulated clusters are also close to
self-similar and exhibit little cluster-to-cluster scatter. The X-ray
observable-total mass relations for our simulated sample agree with the Chandra
measurements to \~10%-20% in normalization. We show that this systematic
difference could be caused by the subsonic gas motions, unaccounted for in
X-ray hydrostatic mass estimates. The much improved agreement of simulations
and observations in the ICM profiles and scaling relations is encouraging and
the existence of tight relations of X-ray observables, such as Yx, and total
cluster mass and the simple redshift evolution of these relations hold promise
for the use of clusters as cosmological probes.
