Sarah Gallagher Talk – University of Copenhagen

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Dark Cosmology Centre > Calendar DARK > DARK Calendar 2014 > Sarah Gallagher Talk

Sarah Gallagher Talk

Dr. Sarah Gallagher, Department of Physics and Astronomy, University of Western Ontario

Title: Winds, Winds Every Where: Radiatively Driven Outflows from Supermassive Black Holes

Abstract:

Supermassive black holes reside in the centers of every massive galaxy. In relatively brief spurts, black holes grow as luminous quasars through the infall of material through an accretion disk.

Remarkably, the light from the accretion disk can outshine all of the stars in the host galaxy by a factor of a thousand, and this radiation can also drive energetic mass outflows. Mass ejection in the form of winds or jets appears to be as fundamental to quasar activity as accretion, and can be directly observed in many objects with broadened
and blue-shifted UV emission and absorption features.  A convincing argument for radiation pressure driving this ionized outflow -- and thus the importance of the shape of the spectral energy distribution in shaping it -- can be made within the dust sublimation radius. Beyond, radiation pressure is still important, but high energy photons
from the central engine can now push on dust grains.  This physics underlies the dusty wind picture for the putative obscuring torus.

I will describe our model of the dusty wind and evaluate its success in accounting for observed properties of quasars such their mid-infrared spectral energy distributions, ratios of naked-to-hidden objects, and the column densities of important ions.