Accretion in active galactic nuclei and disk-jet coupling

TL;DR

This paper reviews the current understanding of accretion processes in active galactic nuclei and the formation of relativistic jets, emphasizing the importance of observational constraints due to limited microphysical understanding.

Contribution

It synthesizes existing models of accretion and jet formation in AGN, highlighting the challenges posed by unknown microphysics and magnetic fields.

Findings

Models are constrained by observations due to limited microphysical knowledge.

Magnetic fields play a crucial role but are not fully understood.

Progress is hindered by the lack of detailed microphysical understanding.

Abstract

We review the current state of understanding how accretion onto a black hole proceeds and what are they key elements needed to form relativistic jets. Since the theoretical progress is severely halted by the lack of deep understanding of the microphysics involved, particularly in the presence of strong magnetic fields, all proposed solutions have a status of models, and their selection has to be based directly on observational constraints.