Ultra Fast Outflows: Galaxy-Scale Active Galactic Nucleus Feedback

TL;DR

This study uses 3D hydrodynamical simulations to demonstrate that Ultra Fast Outflows from AGN significantly influence galaxy evolution by dispersing interstellar medium and regulating black hole growth.

Contribution

It provides the first detailed simulation-based analysis of UFO feedback effects on the multi-phase ISM in galaxies.

Findings

UFOs effectively transfer momentum to dense clouds via ram pressure.

Feedback operates similarly to relativistic jets on kiloparsec scales.

Cloud distribution affects the strength of negative feedback.

Abstract

We show, using global 3D grid-based hydrodynamical simulations, that Ultra Fast Outflows (UFOs) from Active Galactic Nuclei (AGN) result in considerable feedback of energy and momentum into the interstellar medium (ISM) of the host galaxy. The AGN wind interacts strongly with the inhomogeneous, two-phase ISM consisting of dense clouds embedded in a tenuous hot hydrostatic medium. The outflow floods through the inter-cloud channels, sweeps up the hot ISM, and ablates and disperses the dense clouds. The momentum of the UFO is primarily transferred to the dense clouds via the ram pressure in the channel flow, and the wind-blown bubble evolves in the energy-driven regime. Any dependence on UFO opening angle disappears after the first interaction with obstructing clouds. On kpc scales, therefore, feedback by UFOs operates similarly to feedback by relativistic AGN jets. Negative feedback is significantly stronger if clouds are distributed spherically, rather than in a disc. In the latter case the turbulent backflow of the wind drives mass inflow toward the central black hole. Considering the common occurrence of UFOs in AGN, they are likely to be important in the cosmological feedback cycles of galaxy formation.