Bridging Scales in Black Hole Accretion and Feedback: Relativistic Jet linking the Horizon to the Host Galaxy

TL;DR

This paper advances multizone GRMHD simulations to study relativistic jets from spinning black holes, revealing how feedback efficiency depends mainly on black hole spin rather than galactic scale properties, and providing a new subgrid model for cosmological simulations.

Contribution

It introduces technical improvements to multizone GRMHD simulations for spinning black holes and derives a feedback prescription applicable to cosmological models.

Findings

Relativistic jets with ~30% feedback efficiency are launched from spinning BHs.

BH accretion rate decreases with larger Bondi radius as R_B^{-1/2}.

Feedback efficiency remains ~30% regardless of Bondi radius, mainly influenced by BH spin.

Abstract

Simulating black hole (BH) accretion and feedback from the horizon to galactic scales is extremely challenging, as it involves a vast range of scales. Recently, our multizone method has successfully achieved global dynamical steady-states of hot accretion flows in three-dimensional general relativistic magnetohydrodynamic (GRMHD) simulations by tracking the bidirectional interaction between a non-spinning BH and its host galaxy. In this paper, we present technical improvements to the method and apply it to spin $a_*=0.9$ BHs, which power relativistic jets. We first test the new multizone set-up with a smaller Bondi radius, $R_B\approx400\,r_g$, where $r_g$ is the gravitational radius. The strongly magnetized accretion launches a relativistic jet with an intermediate feedback efficiency $\eta\sim30\,\%$, in between that of a prograde ($\eta\sim100\,\%$) and retrograde ($\eta\sim 10\,\%$) torus. Interestingly, both prograde and retrograde simulations also eventually converge to the same intermediate efficiency when evolved long enough, as accumulated magnetic fields remove gas rotation. We then extend strongly magnetized simulations to larger Bondi radii, $R_B\approx 2\times10^3,~2\times 10^4,~2\times 10^5\,r_g$. We find that the BH accretion rate $\dot{M}$ is suppressed with respect to the Bondi rate $\dot{M}_B$ as $\dot{M}/\dot{M}_B\propto R_B^{-1/2}$. However, despite some variability, the time-averaged feedback efficiency is $\eta\sim30\,\%$, independent of $R_B$. This suggests that BH feedback efficiency in hot accretion flows is mainly governed by the BH spin ($a_*$) rather than by the galactic properties ($R_B$). From these first-principles simulations, we provide a feedback subgrid prescription for cosmological simulations: $\dot{E}_{\rm fb}=2\times10^{-3}[R_B/(2\times10^5\,r_g)]^{-1/2}\dot{M}_Bc^2$ for BH spin $a_*=0.9$.