Wind from the Hot Accretion Flow and Super-Eddington Accretion Flow

TL;DR

This paper reviews the theoretical and observational progress on winds from hot and super-Eddington accretion flows around black holes, emphasizing their properties, origins, and significance in galactic feedback.

Contribution

It synthesizes recent theoretical and observational findings, highlighting the role of magnetic fields and black hole spin in shaping accretion flow winds, and compares their impact with jets.

Findings

Wind from hot accretion flows is confirmed by recent observations.

Magnetic fields and black hole spin significantly influence wind properties.

Winds are more crucial than jets in active galactic nuclei feedback.

Abstract

Wind is believed to be widespread in various black hole accretion flows. However, unlike the wind from thin disks, which have substantial observational evidence, the wind from hot accretion flows is difficult to observe due to the extremely high temperatures causing the gas to be almost fully ionized. Its existence was controversial until recent theoretical work demonstrated its presence and strength, which was subsequently confirmed by observations. Although there have been some new observations recently, the main progress still comes from theoretical studies. These studies investigate the effects of different magnetic fields and black hole spins on the wind, providing insights into properties such as mass flux and wind velocity. Wind is typically produced locally within the Bondi radius, and even wind generated on a small scale can propagate far beyond this radius. The situation with super-Eddington wind is similar, despite some recent observations, the main advances rely on theoretical studies. Recent research comparing the momentum and energy of wind and jets suggests that wind plays a more crucial role in active galactic nuclei feedback than jets, whether the wind originates from hot accretion flows or super-Eddington accretion flows.