We simulate a particle moving in “quantum matter” – that is, material which is described by a wave function that responds to its own gravitational field. This captures “dynamical friction” experienced by a black hole moving within ultralight dark matter. We recover known analytic results but also simulate a black hole moving in a ULDM soluton and show that the black hole orbit can be “reheated” by the perturbed soliton.
Abstract
We simulate the gravitational dynamics of a massive object interacting with ultralight/fuzzy dark matter (ULDM/FDM), nonrelativistic quantum matter described by the Schrödinger-Poisson equation. We first consider a point mass moving in a uniform background, and then a supermassive black hole (SMBH) moving within a ULDM soliton. After replicating simple dynamical friction scenarios to verify our numerical strategies, we demonstrate that the wake induced by a moving mass in a uniform medium may undergo gravitational collapse that dramatically increases the drag force, albeit in a scenario unlikely to be encountered astrophysically. We broadly confirm simple estimates of dynamical friction timescales for a black hole at the center of a halo but see that a large moving point mass excites coherent “breathing modes” in a ULDM soliton. These can lead to “stone skipping” trajectories for point masses which do not sink uniformly toward the center of the soliton, as well as stochastic motion near the center itself. These effects will add complexity to SMBH-ULDM interactions and to SMBH mergers in a ULDM universe.
- Wang and Easther
- Dynamical friction from ultralight dark matter
- Phys. Rev. D 105, 063523 or ArXiV:2110.03428
“Stone skipping” trajectories — over multiple orbits a black hole sinks into an ultralight dark matter soliton. For some starting radii it “pumps” the soliton which can then “reheat” the black hole back into a larger orbit. This “stone-skipping” can repeat over several cycles.