On the Origin of Cool Core Galaxy Clusters: Comparing X-Ray Observations
  with Numerical Simulations
  To better constrain models of cool core galaxy cluster formation, we have
used X-ray observations taken from the Chandra and ROSAT archives to examine
the properties of cool core and non-cool core clusters, especially beyond the
cluster cores. We produced X-ray images, surface brightness profiles, and
hardness ratio maps of 30 nearby rich Abell clusters (17 cool cores and 13
non-cool cores). We show that the use of double beta-models with cool core
surface brightness profiles and single beta-models for non-cool core profiles
yield statistically significant differences in the slopes (i.e., beta values)
of the outer surface brightness profiles, but similar cluster core radii, for
the two types of clusters. Hardness ratio profiles as well as
spectroscopically-fit temperatures suggest that non-cool core clusters are
warmer than cool core clusters of comparable mass beyond the cluster cores. We
compared the properties of these clusters with the results from analogously
reduced simulations of 88 numerical clusters created by the AMR Enzo code. The
simulated surface brightness profiles have steeper beta-model fits in the outer
cluster regions for both cool cores and non-cool cores, suggesting additional
ICM heating is required compared to observed cluster ICMs. Temperature and
surface brightness profiles reveal that the simulated clusters are over-cooled
in their cores. As in the observations, however, simulated hardness ratio and
temperature profiles indicate that non-cool core clusters are warmer than cool
core clusters of comparable mass far beyond the cluster cores. The general
similarities between observations and simulations support a model described in
Burns et al. 2008 suggesting that non-cool core clusters suffered early major
mergers destroying nascent cool cores.
