On the Energy Coupling Efficiency of AGN Outbursts in Galaxy Clusters

Abstract

Active galactic nucleus (AGN) jets are believed to be important in solving the cooling flow problem in the intracluster medium (ICM), while the detailed mechanism is still in debate. Here we present a systematic study on the energy coupling efficiency ${\eta }_{\mathrm{cp}}$, the fraction of AGN jet energy transferred to the ICM. We first estimate the values of ${\eta }_{\mathrm{cp}}$ analytically in two extreme cases, which are further confirmed and extended with a parameter study of spherical outbursts in a uniform medium using hydrodynamic simulations. We find that ${\eta }_{\mathrm{cp}}$ increases from $\sim 0.4$ for a weak isobaric injection to $\gtrsim 0.8$ for a powerful point injection. For any given outburst energy, we find two characteristic outburst powers that separate these two extreme cases. We then investigate the energy coupling efficiency of AGN jet outbursts in a realistic ICM with hydrodynamic simulations, finding that jet outbursts are intrinsically different from spherical outbursts. For both powerful and weak jet outbursts, ${\eta }_{\mathrm{cp}}$ is typically around $0.7-0.9$, partly due to the non-spherical nature of jet outbursts, which produce backflows emanating from the hotspots, significantly enhancing the ejecta-ICM interaction. While for powerful outbursts a dominant fraction of the energy transferred from the jet to the ICM is dissipated by shocks, shock dissipation only accounts for $\lesssim 30\%$ of the injected jet energy for weak outbursts. While both powerful and weak outbursts could efficiently heat cooling flows, powerful thermal-energy-dominated jets are most effective in delaying the onset of the central cooling catastrophe.

20 pages, 12 figures, slightly revised version, Accepted for publication in ApJ

References in corpus (15)

• Heating Hot Atmospheres with Active Galactic Nuclei
• The Co-Evolution of Galaxies and Supermassive Black Holes: Insights from Surveys of the Contemporary Universe
• Turbulent Heating in Galaxy Clusters Brightest in X-rays
• Feedback Heating by Cosmic Rays in Clusters of Galaxies
• A Very Deep Chandra Observation of the Galaxy Group NGC 5813: AGN Shocks, Feedback, and Outburst History
• Hot Atmospheres, Cold Gas, AGN Feedback and the Evolution of Early Type Galaxies: a Topical Perspective
• Do sound waves transport the AGN energy in the Perseus Cluster?
• Supernova Blastwaves in Low-density Hot Media: a Mechanism for Spatially Distributed Heating
• A Global Stability Analysis of Clusters of Galaxies with Conduction and AGN Feedback Heating
• Shock heating by FR I radio sources in galaxy clusters
• Hitomi observations of Perseus support heating by mixing
• Bubbles as tracers of heat input to cooling flows
• The Shape of X-ray Cavities in Galaxy Clusters: Probing Jet Properties and Viscosity
• Numerical modelling of the lobes of radio galaxies in cluster environments -- IV. Remnant radio galaxies
• Cavities, shocks and a cold front around 3C 320

Cited by in corpus (1)

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