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STScI Webcast

2018 Fall Science Colloquia

Black Hole Masses in Active Galaxies

Presented by: Misty Bentz (Georgia State University)
Category: Science Colloquia   Duration: 1 hour   Broadcast date: September 12, 2018
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One of the unexpected results from 25 years of observations with the Hubble Space Telescope is the discovery that supermassive black holes inhabit the centers of all massive galaxies, and these black holes appear to have a symbiotic relationship with their host galaxies. In order to further our understanding of this unexpected relationship, the masses of the black holes must be determined. However, black hole mass measurements are difficult to achieve because they require direct observations of the black hole's gravitational influence on luminous tracers. A few different techniques have been developed over the last 25 years to meet this goal. One technique, known as reverberation mapping, is exclusively applicable to active black holes but may be used for even the most distant quasars in our universe, providing a way to study black holes across history. On the other hand, the most widely used technique in the local universe requires exquisite spatial resolution and is based on observations of the bulk motions of stars deep in the nucleus of a (usually inactive) galaxy. I will introduce these techniques and describe our ongoing program to identify a small sample of galaxies where multiple black hole mass techniques can be applied to each galaxy. This effort includes our recently-approved JWST ERS program, as well as programs carried out on multiple moderate- and large-aperture ground-based telescopes. The results of this work will allow us to directly test these independent mass measurement techniques against each other, investigating whether all black hole masses are on the same scale and thus having implications for our understanding of the evolution of galaxies across the ~13 billion year history of the universe.