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We performed a set of cosmological simulations of major mergers in galaxyclusters to study the evolution of merger shocks and the subsequent injectionof turbulence in the post-shock region and in the intra-cluster medium (ICM).The computations were done with the grid-based, adaptive mesh refinement hydrocode Enzo, using an especially designed refinement criteria for refiningturbulent flows in the vicinity of shocks. A substantial amount of turbulenceenergy is injected in the ICM due to major merger. Our simulations show thatthe shock launched after a major merger develops an ellipsoidal shape and getsbroken by the interaction with the filamentary cosmic web around the mergingcluster. The size of the post-shock region along the direction of shockpropagation is about 300 kpc h^-1, and the turbulent velocity dispersion inthis region is larger than 100 km s^-1. Scaling analysis of the turbulenceenergy with the cluster mass within our cluster sample is consistent withM^(5/3), i.e. the scaling law for the thermal energy in the self-similarcluster model. This clearly indicates the close relation between virializationand injection of turbulence in the cluster evolution. We found that the ratioof the turbulent to total pressure in the cluster core within 2 Gyr after themajor merger is larger than 10%, and it takes about 4 Gyr to get relaxed, whichis substantially longer than typically assumed in the turbulent re-accelerationmodels, invoked to explain the statistics of observed radio halos. Strikingsimilarities in the morphology and other physical parameters between oursimulations and the "symmetrical radio relics" found at the periphery of themerging cluster A3376 are finally discussed. In particular, the interactionbetween the merger shock and the filaments surrounding the cluster couldexplain the presence of "notch-like" features at the edges of the doublerelics.

Evolution of shocks and turbulence in major cluster mergers