  We present a new model for the creation of cool cores in rich galaxy clusters
within a LambdaCDM cosmological framework using the results from high spatial
dynamic range, adaptive mesh hydro/N-body simulations. It is proposed that
cores of cool gas first form in subclusters and these subclusters merge to
create rich clusters with cool, central X-Ray excesses. The rich cool clusters
do not possess ``cooling flows'' due to the presence of bulk velocities in the
intracluster medium in excess of 1000 km/sec produced by on-going accretion of
gas from supercluster filaments. This new model has several attractive features
including the presence of substantial core substructure within the cool cores,
and it predicts the appearance of cool bullets, cool fronts, and cool filaments
all of which have been recently observed with X-Ray satellites. This
hierarchical formation model is also consistent with the observation that cool
cores in Abell clusters occur preferentially in dense supercluster
environments. On the other hand, our simulations overproduce cool cores in
virtually all of our numerical clusters, the central densities are high, and
physical core temperatures are often below 1 keV (in contrast to recent
observations). We will discuss additional preliminary simulations to ``soften''
the cool cores involving star formation and supernova feedback.

Astrophysics