Prof. Xun Shi (Yunnan U.)

The Intracluster ‘Stratosphere’: Dynamics and Thermodynamics

Turbulent motions in the intracluster medium (ICM) area key piece of puzzle in the astrophysics and cosmology of galaxy clusters. A series of recent studies have demonstrated the importance of density stratification in the evolution of ICM turbulent motions. The buoyancy effect induced by ICM density stratification introduces qualitative changes to the turbulence morphology, and opens up a new channel of energy flow between the kinetic and the potential energy which likely explains the radial dependence of ICM non-thermal pressure as found in cosmological simulations. On the other hand, turbulence dissipation is found to be the major heating mechanism of the ICM especially at inner radii r < r500c from a novel analysis of cosmological hydro-simulations. Major merger events can excite runaway merger shocks that propagate to very large radii, some even reach and join with the accretion shock and becoming the outer boundary of the ICM. Turbulence is driven behind the shock fronts, and dissipates on a radial-dependent time scale. These suggest that the ICM is heated more in an ‘inside–out’ fashion rather than ‘outside–in’ as depicted in the classical smooth accretion picture. [link]

Place: KIAA-auditorium

Time: Thursday, April 8, 2021 - 4:00PM to Thursday, April 8, 2021 - 5:00PM