Ultra-Light Dark Matter Simulations and Stellar Dynamics: Tension in Dwarf Galaxies for $m < 5\times10^{-21} $ eV

Abstract

We present numerical simulations of dark matter and stellar dynamics in ultra light dark matter halos tailored to mimic dwarf galaxies. An important effect we observe is the dynamical evolution of the stellar half-light radius and velocity dispersion, which makes previous equilibrium models significantly incomplete. Based on half-light radius dynamical evolution, as well as velocity peaks due to soliton core condensation, we show that data from the Fornax, Carina, and Leo II dwarf galaxies disfavores particle masses in the range $ 5\times 10^{-22} \text{ eV} \lesssim m \lesssim 5\times10^{-21}$ eV. Smaller boson masses, around $m\approx1\times10^{-22}$ eV, could cause strong dynamical heating, but we caution that tidal stripping by the Milky Way could moderate the effect. A caveat in our analysis is the omission of stellar self-gravity, which could affect extrapolation back in time if the stellar body was much more compact in the past.