Black Hole Accretion and Feedback: From the Event Horizon to Galactic Scales

Abstract

Astrophysical black holes (BHs) shape galaxy evolution by interacting with their surroundings via accretion and feedback, yet these processes remain poorly understood across a wide range of scales and accretion regimes. In this thesis, we address two fundamental questions in BH accretion and feedback. First, how do supermassive BHs and galaxies co-evolve over their lifetimes? The bidirectional interaction between galaxies and their central supermassive BHs spans many orders of magnitude in both space and time. This vast dynamic range has made conventional simulations prohibitively expensive, limiting them to either small (BH) or large (galactic) scales. We present a novel ``multizone'' simulation method that, for the first time, captures the coupling between the BH event horizon and galactic scales. Leveraging this unprecedented dynamic range, we derive from first principles a prescription for BH accretion and feedback in the hot accretion mode, that can be adopted in large-scale simulations where BHs are unresolved. Additionally, using this approach, together with independent small-scale studies, we provide evidence that many BH-scale simulations likely probe short-lived accretion states, rather than the state reached over long-term evolution. Second, we investigate the physical mechanisms that determine BH accretion states. In regimes where both the standard cold thin disk and hot accretion solutions are available, observations indicate a preference for the hot mode, though the physical origin of this preference remains unclear. Building on the evaporation model in the literature, we present an analytical framework that provides an intuitive explanation for this behavior and extend it to incorporate additional physical processes, such as heating via magnetic fields.