Minghao Guo

From the calendar

Accurately modeling supermassive black hole (SMBH) feeding and feedback from galactic to event horizon scales is a formidable task, since it spans nine orders of magnitude in spatial scale and must be followed over an extended timescale. I will present a series of ``zoom-in'' simulations that follow gas inflow from galactic scales down to the event horizon of black holes. The simulations revealed how turbulent, magnetized gas with radiative cooling naturally organizes into various flow structures: cold filaments that feed the galaxy center, thick magnetized disks that form on intermediate scales, and hot, turbulent flows near the black hole. Furthermore, I will 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 ~ 10^5 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 ~(10r_g/r_B)^{1/2} with a feedback efficiency of ~1% for vanishing spin, and ~ 10% for spin a ~ 0.9. Our new method likewise holds significant promise for applications to many other problems that need to cover vast spatial and temporal scales, from stellar evolution to collapsars, to fallback accretion, to long term transients of TDE, to modeling of ``little red dots''.