Active Galactic Nuclei (AGN) - An active galaxy contains a compact core, or nucleus, of emission that is embedded in an otherwise typical-looking galaxy. This galaxy nucleus shines at all wavelengths of the electromagnetic spectrum and is seen to be bright compared to the rest of the galaxy. Its light may also be highly variable and some AGN even change their major visual characteristics with time. In galaxies with very dense cores, the X-rays from the center can penetrate material outward from the nucleus and this provide scientists with unique insights into the physical processes occurring there. Our science team performs X-ray observations and modeling of processes in these AGN systems. At the very center of an AGN lies a supermassive black hole. Dense material from the surrounding regions can accrete onto the black hole releasing large amounts of gravitational energy. X-rays from these accreting black-hole systems can tell us about the extreme conditions in the vicinity of the black hole as well as out to the parsec-scale circumnuclear environment. X-rays coming from very close to the black hole are also gravitationally redshifted, introducing a characteristic distortion in spectral features, such as the iron K fluorescence line that is broadened by relativistic effects. Some objects are also opaque to most light, including soft X-rays, but these can be explored with multi-wavelength observations that pair the hard X-rays with the infrared.
An HST image of an active galaxy.
An HST image of an active galaxy. Galaxies also produce outflows. We are interested in how AGN interact with the gas in the galaxy around them. We are also interested in how AGN winds contribute to galactic outflows. These hot winds create extended X-ray sources that can be observed with missions like XMM-Newton and Chandra. Using hydro simulations on the 1-2 kpc scale, we model these outflows and generate synthetic emission maps and X-ray emission lines. These models allow us to study a broad range of parameters such as AGN power, wind orientation, ISM density, and galactic mass. Models and observations can put constraints on the total mass of the outflow, and allow studies of the multi-phase nature of the galactic outflow.
simulated AGN wind carves a cavity inside the gaseous disk of a galaxy
A simulated AGN wind carves a cavity inside the gaseous disk of a galaxy. The pressure inside the cavity has begun to push streams of gas up off the disk of the galaxy

Current Group Members

Selected Research and Presented Papers

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