May 04, 2017 4:00 pm - Nielsen Hall 170 - Colloquium
Sarah Gallagher - Western University
The Biggest Blowhards: Windy Supermassive Black Holes

Supermassive black holes reside in the centres of every massive galaxy including our own Milky Way. 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 outflows. Mass ejection in the form of winds 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. Applying unsupervised and hierarchical clustering algorithms to quasar spectra, we can match windy quasars with specific emission-line properties sensitive to the shape of the ionizing continuum. Beyond the dust sublimation radius, 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’ll describe our model of the dusty wind and evaluate its successes and shortcomings in accounting for observed properties of quasars such their mid-infrared power and the fraction of hidden objects.



Postcards from the Universe

Jul 19, 2018 7:00 pm

Sam Noble Museum of Natural History - Dr. Nate Kaib
The Solar System's Adolescent Years

Postcards from the Universe

Aug 16, 2018 7:00 pm

Sam Noble Museum of Natural History - Dr. John Wisniewski
The Search for Habitable Planets


Sep 06, 2018 4:00 pm

Nielsen Hall 170 - Aida Wofford