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.

Speaker:
Xun Shi (Yunnan University)
Place:
KIAA-auditorium
Host:
Jing Wang
Time:
Thursday, April 8, 2021 – 4:00PM to Thursday, April 8, 2021 – 5:00PM
Biography:
Xun Shi is currently an associate professor at South-Western Institute for Astronomy Research at Yunnan university. She received her Bachelor’s degree at Peking University, and her PhD degree at University of Bonn, Germany. She was then a MPA fellow at the Max-Planck Institute for Astrophysics for six years until she joined Yunnan University in 2018. Her recent research interest includes astrophysics of the intracluster medium, the interstellar medium, and plasma lensing.