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The outflowing momentum flux of the jet cocoon at the Bondi radius regulates the intermediate-mass black hole accretion

Presentation #112.07 in the session AGN and Quasars I.

Published onJun 29, 2022
The outflowing momentum flux of the jet cocoon at the Bondi radius regulates the intermediate-mass black hole accretion

We utilize high-resolution hydrodynamic simulations of 0.4-1.6 pc boxes to study the jet propagation and its effect on black hole accretion of ~100 solar mass black holes in primordial gas. We systematically vary the background gas density and temperature, black hole feedback efficiency, and the jet models. As the jet propagates, it shocks heat the surrounding gas and forms a jet cocoon. The cocoon consists of a rapid-cooling cold phase at the edge in pressure equilibrium with the background gas and an over-pressured sub or trans-sonic phase of reverse shock gas filling the cocoon interior. We found that the width of the jet cocoon roughly follows a scaling from the momentum conservation in the jet direction and the energy conservation in the vertical direction. Depending on the gas properties and the jet model, the cocoon can either remain an elongated shape to a large radius or isotropize before reaching the Bondi radius forming a bubble. Heavier jets with lower velocity result in a cocoon resembling the former scenario. Higher background gas also leads to an elongated cocoon as the resulting mass fluxes scale superlinear to the gas density. In all cases, the momentum flux of the isotropic component of the cocoon matches the inflow momentum flux at the Bondi radius, which ultimately regulates the black hole accretion.

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