Winds from Black Hole Accretion Flows: Formation and Their Interaction with ISM

Abstract

Black hole hot accretion flows occur in the regime of relatively low accretion rates and are operating in the nuclei of most of the galaxies in the universe. In this chapter, I will review one of the most important progresses in recent years in this field, which is about the wind or outflow. This progress is mainly attributed to the rapid development of numerical simulations of accretion flows, combined with observations on, e.g., Sgr A*, the supermassive black hole in the Galactic center. The following topics will be covered: theoretically why do we believe strong winds exist; where and how are they produced and accelerated; what are their main properties such as mass flux and terminal velocity; the comparison of the properties between wind and “disk-jet”; the main observational evidences for wind in Sgr A*; and one observational manifestation of the interaction between wind and interstellar medium, namely the formation of the Fermi bubbles in the Galactic center.