Speaker
Description
Ultralight dark matter (ULDM) has attracted significant attention as a compelling alternative to cold dark matter, yet it faces increasingly stringent constraints from observations of compact stellar systems and satellite galaxies. In this talk, I present a series of numerical simulation studies from our group that systematically reexamine these constraints. We first show how the almost-dark galaxy Nube with extremely diffuse stellar distribution can be naturally explained by ULDM dynamical heating. I then show that incorporating the realistic tidal potential of the Milky Way can substantially suppresses ULDM heating in satellite galaxies, significantly relaxing the tension for $m_a \sim 10^{-22}$ eV. Then N-body simulations also reveal that internal two-body relaxation competes with ULDM heating, invalidating simple heating-only limits for very compact systems below the de Broglie wavelength. These results indicate that previous idealized bounds may have been overly restrictive, and that ultralight dark matter remains a viable and well-motivated candidate.