Event Details

Obscured and reddened quasars at the peak of galaxy formation: searching for multi-scale quasar winds

Rachael Alexandroff

Feb 13, 2018

Astrophysics Seminar

Bell Room

Black holes of masses one million to one billion times that of the sun are now believed to reside at the centers of almost all massive galaxies in the universe including our own Milky Way. Though small on the scale of a galaxy and negligible for the overall galaxy dynamics, these supermassive black holes are now thought to play a crucial role in the evolution of their host galaxy. Feedback from the actively accreting supermassive black hole or ‘quasar’, in the form of galaxy-scale winds, is necessary to shut-off star formation and thus inhibit the growth of very massive galaxies and to drive correlations between black hole and galaxy properties. Nevertheless, such a mechanism is not yet well supported by observational evidence, especially at the peak of galaxy formation (z~2.5). I will present new multi-wavelength results from a sample of quasars at the peak of galaxy formation and black hole growth that may represent the “blowout phase” of AGN evolution where we see quasar feedback in action. The combination of various observational techniques allows us to probe, if indirectly, scales from the broad-line region all the way to the entire host galaxy and to understand the nature of the multi-component outflow (both ionized and molecular components). In particular, Keck spectropolarimetry results argue for the presence of dusty outflows on scales of the emission line region while near-infrared spectroscopy reveals some of the most extreme ionized gas velocities observed (> 5000 km/s), indicating wind speeds too large to be contained by the galaxy potential. Finally, a dearth of CO (1-0) emission as traced by the Very Large Array indicates the molecular gas necessary for star formation may have been removed from the host galaxy. Taken together, these results provide a robust observational window into important mechanisms of galaxy growth and quenching via quasar feedback.

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