Speaker
Description
Feedback processes by active galactic nuclei in the centres of galaxy clusters appear to prevent large-scale cooling flows and impede star formation. However, the detailed heating mechanisms remain uncertain. Promising heating scenarios invoke the dissipation of Alfvén waves that are generated by streaming cosmic rays (CRs) or the dissipation of cluster turbulence. In order to study the idea of CR heating, we use three-dimensional magneto-hydrodynamical simulations with the Arepo code that follow the evolution of jet-inflated bubbles filled with CRs in a turbulent, magnetized cluster atmosphere. We find that a single injection event recovers the correct CR distribution and heating rate for a successful heating model in Perseus over a duty cycle of 30 Myrs. In order to study the idea of turbulent heating, we analyzed the impact of active galactic nuclei (AGN)-induced turbulence on X-ray line broadening and compared our results to recent Hitomi data. We find that AGN jets drive turbulence, which however remains localized in the wake of the buoyantly rising bubbles after the jets have terminated. Cluster turbulence as inferred from broadened X-ray lines and Faraday rotation measures must hence be driven by other processes such as precipitation due to thermal instability or cosmological infall. In the final part, we present new simulations that study the interplay of radiative cooling and heating induced by AGN jets that self-regulate the cooling cluster cores and may provide the long-thought solution to the cooling flow problem in galaxy clusters.
Keywords
AGN; CR feedback; MHD simulations; galaxy clusters;
| Subcategory | Theoretical Results |
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