Repeated Imaging of Massive Black Hole Binary Orbits with Millimeter Interferometry: measuring black hole masses and the Hubble constant

Very long baseline interferometry (VLBI) at millimeter (mm) wavelengths is being employed to resolve event-horizon scale structure of the environment surrounding the Milky-Way black hole, at an angular resolution of a few tens of micro-arcseconds. The same approach could also resolve the orbital separation of a population of massive black hole binaries (MBHBs). Modeling the inspiral of binaries due to gravitational wave emission and gas and requiring binary orbital periods of less than 10 years, we estimate that there may exist ~100 resolvable MBHBs that are bright enough to be observed by mm-wavelength VLBI instruments over the entire sky, at redshifts z
Published in The Astrophysical Journal