AGN outflows and the cluster cooling flow conundrum

Abstract

Temperature distributions within cores of galaxy clusters indicate gas in the core should cool down rapidly and contract. The cooling flow problem involves the hypothesis that the rapidly cooling gas should eventually condensate into unobserved molecular clouds. Active galactic nuclei (AGNs) are thought to be able to counter catastrophic cooling. This thesis provides an overview of the theory and design philosophy of hydrodynamical simulations and a hydrodynamical code called FLASH, which was created by Fryxell et al. (2000). This code is expanded with gravity and AGN outflow units to support the simulation of a pair of outflows in the intracluster medium whilst using classical fluid dynamics. The three simulation chapters involve a single parameter being varied and its impact on jet morphology and the heating process studied. The jet opening angle was found not to impact the heating process, while a study on wave heating demonstrated the presence of sound waves. The third project involved varying the jet heating power as a trade-off of thrust, while keeping the energy output constant. That proved to greatly influence the morphology of the backflow and the bubble inflation process. The simulations show that despite the superficial simplicity of the model, the results provide valuable insight into the physics behind an AGN outflow and the available heating mechanisms. Future challenges include the extension of the model, which would require more reliable data and hypotheses on cluster cores.

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ORCID for Antony J. Bird: orcid.org/0000-0002-6888-8937

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