Detection of a universal core-halo transition in dwarf galaxies as predicted by Bose-Einstein dark matter

Most nearby classical dwarf galaxies are now known to be surrounded by large halos of stars extending to over $2~{\rm kpc}$, adding to the puzzling properties of these dark matter dominated galaxies. Simulations of dark matter as a Bose Einstein condensate, $\psi$DM, predict large halos surrounding a soliton core with a marked density transition at the core radius, set by the de Broglie wavelength. This transition is a prominent hallmark of $\psi$DM because the ground state forms a standing wave soliton that is much denser than the halo of excited states. Here we identify this predicted transition at a radius of $\simeq 1.0~{\rm kpc}$ in the stellar profiles of dwarfs lying beyond the Milky Way, corresponding to a boson mass of $m_\psi \simeq 1.1^{+0.2}_{-0.1}\times 10^{-22}{\rm eV}$, assuming stars trace the mass. Clear transitions are also evident for most classical dwarfs that orbit the Milky Way, with pronounced amplitudes indicating significant tidal stripping as anticipated in $\psi$DM simulations of orbiting dwarfs (Schive, Chieuh \& Broadhurst 2020), where the halo is more easily stripped than the stable soliton core. Furthermore, the shallow slope of the observed halos accurately matches the tidal stripping simulation. We conclude that $\psi$DM accounts well for the observed family of classical dwarf profiles with tidal stripping included, in contrast to heavy particle, cold dark matter, CDM, where low mass galaxies should be concentrated and core-less, quite unlike the extensive core-halo structure observed.