Speaker
Description
The origin of turbulent motion of the intracluster medium (ICM) has been a longstanding open question, and X-ray observations of the new generation, such as XRISM and eROSITA, shed further light on it. Stirring by substructures (member galaxies and dark matter subhaloes) orbiting within a galaxy cluster is a possible mechanism to generate and maintain the ICM turbulence. We develop a semi-analytic model considering three processes of energy transfer from substructures to the ICM (dynamical friction, ram pressure and sloshing), and propagation and dissipation of the deposited energy. The model reproduces the gas velocity structure derived from hydrodynamical simulations. We find that dynamical friction and ram pressure are responsible to explain the significant turbulence (> 1000 km/s) in the cluster outskirts (> 1 Mpc), while sloshing explains the mild turbulence (~100 km/s) in the cluster centre. In the talk, we will also argue the role of substructures infalling toward the cluster for the first time from outside the virial radius of the dark matter halo of the cluster.
