Saturday, December 1, 2012

Ultra Fast Outflows: Galaxy-Scale Active Galactic Nucleus Feedback. (arXiv:1211.5851v1 [astro-ph.CO])

Ultra Fast Outflows: Galaxy-Scale Active Galactic Nucleus Feedback. (arXiv:1211.5851v1 [astro-ph.CO]):
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.

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