Mitchell Revalski, 5th year
NSF Graduate Research Fellow
PhD Subject: Quantifying Feedback from Narrow Line Region Outflows in Nearby Active Galaxies
Research: Observations with telescopes on the ground and in space suggest that nearly all massive galaxies have a supermassive black hole lurking in their centers. These black holes are millions or even billions of times more massive than our Sun, but are extremely dense and compact, emitting no light of their own. To learn about their growth and evolution, we study “active galaxies” where the black hole is actively consuming gas, dust, and stars from the surrounding galaxy. This process compresses and heats up the gas, causing it to emit light and glow like a neon sign. We can study this light with telescopes through spectroscopy, which reveals that the light is so intense that it prevents some material from falling into the black hole by driving it away in a “galactic wind”, also called “mass outflows”. Understanding these outflows is important, as they may control how the black hole grows and strongly affect the surrounding galaxy.
The goal of my research is to precisely measure how much material is contained in these mass outflows as well as how fast it is moving. We can then compare the energy in these outflows to theoretical predictions and determine if they will significantly impact the evolution of the galaxy over time. This process may have been particularly important in the early universe where active galaxies could drive very powerful winds as they formed, but these galaxies are very far away and difficult to observe with telescopes. I focus on nearby active galaxies that are less powerful, but we can study their outflows in great detail and map how they change as they flow away from the black hole.
To accomplish this, I use spectroscopy and imaging from the Hubble Space Telescope to measure the amount of light coming from different elements in these hot, glowing mass outflows. These data allow us to determine the speed at which the gas is moving, and then I create computer models to match the observations and determine the amount of gas present. I truly enjoy my research as it allows me to explore the full range of techniques in astronomy, from taking the observations with telescopes, processing and measuring it, and then modeling it to try and understand the physical implications of our results. I am able to tackle this project thanks to the resources and guidance available in the Department of Physics and Astronomy at Georgia State University. We have access to telescopes around the world to obtain new data on the galaxies we are studying, while the faculty serve as expert mentors to guide us through our research and train us as next generation researchers.