Oral Presentation

Merger Shocks in Simulated Galaxy Clusters

Author(s): Ji-Hoon Ha (UNIST), Dongsu Ryu (UNIST) and Hyesung Kang (Pusan National University)

Presenter: Ji-Hoon Ha (Ulsan National Institute of Science and Technology (UNIST))

Shock waves have been observed in the cluster outskirts. They are commonly interpreted as being induced by mergers of sub-clumps, so are called “merger shocks”. We here report a study of the properties of merger shocks in merging galaxy clusters with a set of cosmological simulations for the large-scale structure formation of the universe. As a representative case, we focus on the case where sub-clumps with mass ratio ~ 2 go through an almost head-on merger. Because of the turbulent nature of hierarchical clustering, the surfaces of merger shocks are not uniform, but composed of parts with different Mach numbers. As merger shocks propagate out from the cores to the cluster outskirts, the average Mach number increases in time. The shocks propagating along the merger axis could be observed as X-ray shocks and/or radio relics. The kinetic energy through the shocks peaks at ~ 1 Gyr after shock launching, or at ~ 1 - 2 Mpc from the core. The most energetic shocks are found to have the kinetic-energy weighted Mach number ~ 2 - 3 and the CR-energy weighted Mach number~ 3 - 4. We then discuss the observational implications of our results.