Institute for Advanced Study Astrophysics Seminar

Discs of stars around super-massive black holes, like the one at the Galactic centre, evolve primarily via resonant relaxation, which is the process governing the evolution of the angular-momentum vectors of stellar orbits about the super-massive black hole. In the presence of a perturber (for example an intermediate-mass black hole), the disc can either respond by torquing the perturber until it aligns with it, or, if certain conditions obtain, by breaking up. In this talk, I will describe the process of ‘resonant dynamical friction’, which is responsible for the first option; and then I will describe the conditions under which the disc would be disrupted, drawing an analogy with the Hill radius for tidal interactions. If time permits, as an example of the second, I will show how a dense solitonic core, expected to form from axion-like dark matter, could potentially break the Milky Way’s nuclear disc. Thus, by observing this disc, we could learn about its history and about the presence of perturbers in the vicinity of the black hole, and even probe dark matter models, in a mass range which is mostly unconstrained.