Accretion and Feedback from Galaxy to Event Horizon
Invited talk, Flatiron CCA numerical series, NYC, NY, USA
Accurately modeling supermassive black hole (SMBH) feeding and feedback from galactic to event horizon scales is a formidable task; the involved spatial scales span nearly nine orders of magnitude (from mpc to Mpc) and need to be resolved over an extended time period. We present a series of 3D (general relativistic) magnetohydrodynamic (GRMHD) simulations of the fueling of SMBHs on galactic scales, taking M87* as a typical case. The simulations reveal various accretion modes on different scales: magnetized filaments on scales \(\sim0.03-3\) kpc, a highly magnetized \(\beta \sim 10^{-3}\) thick disk within \(\sim 30\) pc, and a turbulent hot accretion flow within \(\sim0.3\) pc (\(10^3 r_{\rm g}\)) with strong outflows enough to balance the total cooling of the M87/Virgo hot halo out to \(\sim 50\) kpc. Furthermore, we present a “cyclic zoom” method to capture the dynamics of accretion flows across a vast range of spatial and temporal scales. The method can accelerate GRMHD simulations by \(\sim10^5\) times for problems with large scale separation. As applications, we simulate Bondi and rotating torus accretion onto black holes from galactic scales, covering an extremely large dynamic range. In Bondi accretion, the accretion rate is suppressed relative to the Bondi rate by \(\sim (10r_{\rm g}/r_{\rm B})^{1/2}\) with a feedback efficiency of \(\sim1\)% for vanishing spin, and \(\sim10\)% for spin \(a\sim 0.9\). Our new method likewise holds significant promise for applications to many other problems that need to cover vast spatial and temporal scales.