Powerful Outflows and Feedback from Active Galactic Nuclei
  Active Galactic Nuclei (AGN) represent the growth phases of the supermassive
black holes in the center of almost every galaxy. Powerful, highly ionized
winds, with velocities $\sim 0.1- 0.2c$ are a common feature in X--ray spectra
of luminous AGN, offering a plausible physical origin for the well known
connections between the hole and properties of its host. Observability
constraints suggest that the winds must be episodic, and detectable only for a
few percent of their lifetimes. The most powerful wind feedback, establishing
the $M -\sigma$ relation, is probably not directly observable at all. The $M -
\sigma$ relation signals a global change in the nature of AGN feedback. At
black hole masses below $M-\sigma$ feedback is confined to the immediate
vicinity of the hole. At the $M-\sigma$ mass it becomes much more energetic and
widespread, and can drive away much of the bulge gas as a fast molecular
outflow.
