Mach number distributions of simulated merger shocks

Abstract

According to the hierarchical structure formation of the large-scale structure of the universe, small clumps continuously merge to form galaxy clusters. Such mergers between clusters cause energetic shock waves in the intracluster medium (ICM), which are called merger shocks. Merger shocks play an important role, such as the acceleration of cosmic ray electrons in the ICM. Th is phenomenon has been observed as radio sources, radio relics. To investigate the properties of merger shocks, we performed a set of cosmological hydrodynamic simulations, and generated merging galaxy cluster samples. Since each merger shock consists of not a single Mach number (Ms) but a range of multiple Mach numbers, we first investigate the probability distribution function (PDF) of Mach numbers. PDFs of our simulated merger shocks show a similar trend; it has a right-skewed distribution with a peak at Ms ~ 2-4. Also, most merger shocks have Ms in the range of Ms ~ 2-5, but include a tail of high Mach numbers, Ms ~ 5-8. We examine how the Mach number distribution of merger shocks depends on the merger parameters, such as mass ratio and impact parameter. We here present the Mach number distributions of simulated merger shocksand their dependence on merger arameters.