My research focuses on energy transport processes in active galactic nuclei (AGN). I am particularly interested in accretion onto supermassive black holes, the formation and propagation of relativistic jets, and how these jets inject energy into and interact with their ambient environments. I place a particular emphasis on combining multiwavelength observations in my research: in the X-ray with the Chandra, XMM-Newton, and Suzaku satellites; in the optical and infrared with the Hubble Space Telescope, Spitzer Space Telescope, and Multiple Mirror Telescope (MMT); and in the radio with the VLA and MERLIN ground-based radio observatories. Between 2002 and 2005 I worked at the University of Bristol, UK, and the Harvard-Smithsonian Center for Astrophysics for my PhD. I am currently a Chandra/HETG Postdoctoral Associate at MIT's Kavli Institute for Astrophysics and Space Research. I also hold a research affiliation with Harvard University, at the Harvard-Smithsonian Center for Astrophysics. Please also find a copy of my CV.
Accretion Flows and Jets
Accretion is a fundamental process associated with the generation and transportation of energy in the immediate vicinity of black holes. I am interested in the formation and structure of accretion flows, especially the interplay and evolution of both standard, geometrically thin, optically thick disks, and radiatively inefficient (possibly advection-dominated) optically thin flows. In turn, the dynamics of the accretion flow have a strong influence on material being ejected nearby black holes, and I am particularly interested in the observational properties of jets. I use the Chandra HETGS instrument to perform detailed Fe K&alpha line-spectroscopy, and combine this with CCD spectroscopic observations with Chandra ACIS, XMM-Newton, and Suzaku to infer the structure of the accretion flow and surrounding circumnuclear torus.
Energy Transport in Radio-Loud AGN
Radio-loud AGN (radio galaxies and radio quasars) are the 10% of the AGN population that eject powerful relativistic twin jets of particles. Jets act as energy-carrying channels, and transport vast quantities of energy from the Schwarzschild radius scale on which they are created, out to cosmological distances. Understanding how jets are formed and dissipate their energy is therefore crucial for our understanding of the Universe. I use radio and multiwavelength observations to (1) study the particle-acceleration process in jets, (2) understand how the most powerful jet terminate in strong shocks, called hotspots, and (3) study the influence of jets on their gaseous environments, and determine how this affects black-hole accretion through feedback mechanisms.
Outflows and Circumnuclear Emission in Seyfert Galaxies
Seyfert galaxies are radio-quiet sources, but they are not always radio-silent. In particular, several Seyfert galaxies eject relatively weak jets, which mean that they may represent an important link between truly radio-quiet AGN and radio galaxies and quasars. I have ongoing projects to search for, and constrain the X-ray and [OIII] properties of these "radio-loud Seyferts". With these data, I aim to study the competing processes of AGN photoionization and radio-jet shock heating, which in turn gives insights into the connection between accretion and jet formation in AGN. The image below shows a radio, [OIII], and X-ray image of a jet in the Seyfert galaxy NGC 2110, together with the `disturbed' circumnuclear environment through which it propagates.
![Radio (green), [OIII] (red), and Chandra (blue) multiwavelength composite image of the nucleus, jet, and circumnuclear environment in NGC 2110](images/ngc2110.jpg)