Patrick B. Hall
Associate Professor of Astronomy
Astrophysics and Astronomy
Active galactic nuclei (quasars); distant galaxies and clusters of galaxies.
When matter spirals into a supermassive black hole at the center of a galaxy, a kind of friction can heat the matter up until it shines brightly enough to be seen all the way across the universe: we call such objects quasars. My fascination with quasars makes them my main research interest. I do most of my research using online databases from large astronomical surveys, supplemented by the occasional proposal for telescope time.
I am interested in understanding more clearly the dynamics of gas spiralling around black holes in quasars. That knowledge will improve our ability to infer the physical properties of quasars and their black holes (such as mass and spin) from the details of the light they produce. I am particularly interested in outflows of gas from quasars. Much of the mass spiralling around in a quasar ends up in the black hole, but some of it is flung outwards and is sometimes visible in the spectrum of the quasar. Establishing the connections between those absorption lines and the emission lines seen in most quasars will help us understand how quasars work and how galaxies form.
I am also interested in gravitational lensing, which can take a small, faint galaxy and stretch it out into a long, luminous arc. With one of my students I am investigating how well the gas surrounding random galaxies can be characterized when it is seen silhouetted against the light of a luminous arc. This may be a project for the next generation of ground-based telescopes, which will be 30 meters in diameter.