A black hole is an object which possesses such a strong gravitational pull that it creates a region of space around itself from which nothing can escape. A supermassive black hole (SMBH) is a black hole with a mass ranging from hundreds of thousands to billions of solar masses. These enormous objects are found in the hearts of most massive galaxies, including our own Milky Way. While no light can escape the black hole itself, we can still study these objects in detail from their effects on gas and stars close to them.

Supermassive black holes are important in a variety of astrophysical contexts and on a wide range of physical scales. On large scales, feedback effects from actively-feeding SMBHs, including relativistic jets and powerful winds, are in part responsible for the quenching of star formation in galaxies. This feedback can also heat up gas in clusters of galaxies, which can proceed to strip star-forming gas from other nearby galaxies.

On the small-scale end, mergers of SMBHs are an important source of low-frequency gravitational wave emission, and are a potentially significant path for SMBH mass and spin evolution. The galaxy merger to SMBH merger process has also been suggested as being the principal mechanism behind the observed scaling relationships between large-scale galactic properties and central SMBH mass.

It is known that most large galaxies contain central SMBHs and that galaxy mergers are a regular occurrence in our universe. We therefore expect that some of these mergers should result in a galaxy containing two SMBHs. Over time and through a variety of physical processes, these SMBHs will sink toward the center of the galaxy and become gravitationally bound to one another, forming a SMBH binary. These binaries should themselves result in eventual SMBH mergers, which are potentially important as a channel for SMBH mass and spin evolution, co-evolution between SMBHs and their host galaxy, and as a source of low-frequency gravitational waves detectable by LISA and pulsar timing array (PTA) collaborations. To confirm that these mergers do occur and set upper limits on the rates of their occurrence, we would like to be able to identify their precursors, close-separation SMBH binaries, using electromagnetic observations.

Unfortunately, direct detection of close-separation (i.e., sub-parsec) SMBH binaries is impossible with current instruments due to the tiny angular separations involved. To circumvent these limitations, I am currently working on using simulations of close-separation SMBH binaries to discern time-varying signals that can be used to identify binaries using time-domain monitoring with existing instruments. These simulations will be run for a wide range of SMBH masses and separations to determine the periods of variability in Optical, UV, and X-ray wavelengths characteristic to given values of the binary parameters. In this way, we can develop a new technique for identifying SMBH binaries which transcends the resolving limitations of modern observational instruments.

It has long been known that a sizable fraction of active galactic nuclei (AGN) produce relativistic jets of plasma which emit strongly in the radio. However, when the Chandra X-ray telescope launched, it discovered that these radio jets were anomalously bright in the X-ray band. The mechanism behind this X-ray emission is still uncertain, but is generally believed to be inverse-Compton scattering of Cosmic Microwave Background (IC-CMB) photons up to X-ray energies by relativistic electrons in the jet. However, IC-CMB has been ruled out for several sources, casting further uncertainty on the source of this emission.

An alternative explanation is that the jet X-rays are produced by synchrotron emission from a second, higher-energy population of electrons. These higher-energy electrons would then, in turn, produce IC-CMB emission in the TeV energy range. I used multi-wavelength data of over 40 jets to predict the expected TeV emissions for these sources under this double-synchrotron model. These predictions were then compared to detection limits on upcoming TeV telescopes like the Cherenkov Telescope Array to develop a catalog of sources which could be used to test the predictions of this jet x-ray emission model.