PIRSA:24040112

Video URL

https://pirsa.org/24040112

Bridging Scales in Black Hole Accretion and Feedback: Magnetized Bondi Accretion in 3D GRMHD

Cho, H. (2024). Bridging Scales in Black Hole Accretion and Feedback: Magnetized Bondi Accretion in 3D GRMHD. Perimeter Institute for Theoretical Physics. https://pirsa.org/24040112

Cho, Hyerin. Bridging Scales in Black Hole Accretion and Feedback: Magnetized Bondi Accretion in 3D GRMHD. Perimeter Institute for Theoretical Physics, Apr. 25, 2024, https://pirsa.org/24040112 

          @misc{ scivideos_PIRSA:24040112,
            doi = {10.48660/24040112},
            url = {https://pirsa.org/24040112},
            author = {Cho, Hyerin},
            keywords = {Strong Gravity},
            language = {en},
            title = {Bridging Scales in Black Hole Accretion and Feedback: Magnetized Bondi Accretion in 3D GRMHD},
            publisher = {Perimeter Institute for Theoretical Physics},
            year = {2024},
            month = {apr},
            note = {PIRSA:24040112 see, \url{https://scivideos.org/index.php/pirsa/24040112}}
          }

Hyerin Cho Harvard University

Talk numberPIRSA:24040112
DOI10.48660/24040112
Source RepositoryPIRSA
Collection
Talk Type Scientific Series
Subject

Abstract

Fueling and feedback couple supermassive black holes (SMBHs) to their host galaxies across many orders of magnitude in spatial and temporal scales, making this problem notoriously challenging to simulate. We use a multi-zone computational method based on the general relativistic magneto-hydrodynamic (GRMHD) code KHARMA that allows us to span 7 orders of magnitude in spatial scale, to simulate accretion onto a non-spinning SMBH from an external medium with Bondi radius ~ 2e5 G*M/c^2, where M is the SMBH mass. For the classic idealized Bondi problem, spherical gas accretion without magnetic fields, our simulation results agree very well with the general relativistic analytic solution. Meanwhile, when the accreting gas is magnetized, the SMBH magnetosphere becomes saturated with a strong magnetic field. The density profile varies as ~ r^(-1) rather than r^(-3/2) and the accretion rate is consequently suppressed by over 2 orders of magnitude below the Bondi rate. We find continuous energy feedback from the accretion flow to the external medium at a level of 1% of the accreted rest mass energy (~ 0.01 Mdot * c^2). Energy transport across these widely disparate scales occurs via turbulent convection triggered by magnetic field reconnection near the SMBH. Thus, strong magnetic fields that accumulate on horizon scales transform the flow dynamics far from the SMBH and naturally explain observed extremely low accretion rates compared to the Bondi rate, as well as at least part of the energy feedback.

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