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From Inside Out: Bridging the Bondi and Event Horizon Scales using 3D GRMHD Simulations

Presentation #100.84 in the session AGN.

Published onJul 01, 2023
From Inside Out: Bridging the Bondi and Event Horizon Scales using 3D GRMHD Simulations

When a supermassive black hole (SMBH) feeds on its host galaxy, it launches energetic mechanical outflows and emits radiation. Such active galactic nuclei (AGN) can launch relativistic jets that blow away and heat up the ambient gas via a process known as AGN feedback. This feedback is key to understanding galaxy evolution and star formation. However, following the complex dynamics of gas accretion is currently computationally prohibitive, due to the disparate length and time scales between the SMBH and its galaxy. Attempting to bridge this gap, we have performed state-of-the-art long-duration general relativistic magnetohydrodynamic (GRMHD) simulations that follow the accretion of magnetized gas from the SMBH’s sphere of influence (Bondi radius RB) down to the event horizon (Rg). We vary the ambient gas degree of rotation, the SMBH spin, and the Bondi radius, with the latter reaching the largest scale separation to date RB/Rg = 1000, in a single GRMHD simulation. The infall of rotating gas self-consistently forms an accretion disk, and the SMBH launches magnetized relativistic jets. Under the pressure of the infalling gas, the jets intermittently turn on and off, erratically wobble, and inflate pairs of cavities in different directions. This morphology resembles the rare X-shaped radio galaxies (XRGs), first time created in a GRMHD simulation, without any special initial conditions. Stable jets are produced when the SMBH accretes enough magnetic flux that it transitions to a magnetically arrested disk (MAD) state, characterized by particularly strong jets that drill through the ambient gas and propagate well outside the Bondi sphere. We reliably measured the fraction of the Bondi sphere gas that reaches the central SMBH, which agrees with the observationally inferred value. For a given Bondi radius, the maximum accretion rate suppression is weakly affected by the size of the accretion disk. Surprisingly, at very late times, the sense of disk rotation and magnetic fields continuously flip, quenching the jets. Thereafter, the system exits the MAD state and the newly formed jets become erratic again, which has not been seen before in the presence of unlimited large-scale magnetic flux.

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