Ying-He Celeste Lü

 Ying-He Lü

Contact Information

111 Astronomy Building
1002 W. Green St.
Urbana, IL
MC 221
Graduate Student
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Research Interests

  • Computational Astrophysics
  • Galaxy Clusters
  • Active Galactic Nuclei
  • Structure Formation
  • Black Hole Accretion & Jets

Research Description

We study feedback from active galactic nuclei (AGN) using adaptive mesh refinement (AMR) hydrodynamics simulations of galaxy cluster cores. AGN feedback modeling in simulations usually involves a subgrid model and considerable simplification of the complex physics involved in the region surrounding the AGN's central super-massive black hole (SMBH). We have developed a new sink particle method that incorporates black hole accretion and jet launching in a more physically realistic manner. We measure the accretion rate through an artificial control surface with an inner boundary condition that allows us to consider accretion of cold gas blobs. Our jet model includes the effect of precession to deposit feedback energy in a more distributed manner. With the model embedded in the AMR hydrodynamics code FLASH, we have conducted simulations of the central few kiloparsecs of the intracluster medium (ICM) in cluster cores. We address how jet precession interacts with turbulent motions in the ICM and determine whether it can help regulate accretion and feedback. We find that, while turbulent driving itself enhances the kinetic energy of the ICM and triggers accretion, with precessing jets and weaker turbulent driving, the gas primarily passes through strong shocks produced by the jet, and cavity-like structures are formed. However, the situation changes with stronger turbulence: the jet material gets blown away, and the accretion process is enhanced by inflow of hot gas, allowing more energy to be deposited in the ICM. This coupling between jet precession and turbulent driving thus helps to regulate AGN feedback. We compare our method and results with magnetohydrodynamic (MHD) simulations of jet production and propagation on smaller scales and discuss convergence with resolution and jet size. The results can help us better understand from a theoretical perspective why most galaxy clusters with cool cores lack evidence of recent star formation.

Education

  • BS Physics, Peking University, 2013