Some accretion disks surrounding supermassive black holes in active galactic nuclei (AGN) are observed to host powerful water vapor maser emission. These astrophysical masers -- dubbed "megamasers" because of their large luminosities relative to Galactic counterparts -- have proven to be unique tools for studying the geometry and dynamics of AGN accretion disks on sub-parsec scales, where the black hole dominates the gravitational potential. The masing gas parcels act as test particles in this potential, and very long baseline interferometric (VLBI) observations reveal that they exhibit the ordered, Keplerian motion expected for orbits about a point mass. By combining the exquisite angular resolution provided by VLBI with multi-year spectral monitoring observations, we can exploit the simple dynamics of these systems to break the mass-distance degeneracy and make precise measurements of both quantities. In this talk I'll cover some background on AGN disk masers before presenting recent developments in the world of maser disk modeling. I'll describe our application of these improved models to the maser systems in the galaxies NGC 4258 and CGCG 074-064, and I'll wrap up with a brief discussion of the resulting constraints on the Hubble constant.
Dom is a postdoctoral fellow for the Event Horizon Telescope collaboration, working primarily on modeling and feature extraction techniques. He graduated in 2018 with a PhD in Astronomy from the University of Virginia, where he worked with Jim Braatz as a Reber Fellow at NRAO. Dom is also a member of the Megamaser Cosmology Project, and his other research interests include masers, supermassive black holes, and parameter exploration algorithms.
