A study of cool core resiliency and entropy mixing in simulations of
  galaxy cluster mergers
  We present results from a suite of binary merging cluster simulations. The
hydrodynamical cluster simulations are performed employing a smoothed particle
hydrodynamics (SPH) formulation in which gradient errors are strongly reduced
by means of an integral approach. We consider adiabatic as well as radiative
simulations, in which we include gas cooling, star formation and energy
feedback from supernovae. We explore the effects of merging on the
thermodynamic structure of the intracluster gas of the final merger remnant. In
particular, we study how core entropy is generated during the merging and the
stability properties of the initial cool-core profile against disruption. To
this end, we consider a range of initial mass ratio and impact parameters.
Final entropy profiles of our adiabatic merging simulations are in good accord
with previous findings (ZuHone 2011), with cool-cores being disrupted for all
of the initial merging setups. For equal-mass off-axis mergers, we find that a
significant contribution to the final primary core entropy is due to
hydrodynamic instabilities generated by rotational motions, which are induced
by tidal torques during the first pericenter passage. In radiative simulations,
cool-cores are more resilient against heating processes; nonetheless, they are
able to maintain their integrity only in the case of off-axis mergers with very
unequal masses. We suggest that these results are robust against changes in the
gas physical modeling, in particular to the inclusion of AGN thermal feedback.
  Our findings support the view that the observed core cluster morphology
emerges naturally in a merging cluster context, and conclude that the merging
angular momentum is a key parameter in shaping the thermodynamical properties
of the final merger remnant.
