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Low mass galaxies in the Local Group are dominated by dark matter andcomprise the well studied ``dwarf Spheroidal" (dSph) class, with typical massesof $10^{9-10}M_\odot$ and also the equally numerous ``ultra faint dwarfs"(UFD), discovered recently, that are distinctly smaller and denser with massesof only $10^{7-8}M_\odot$. This bimodality amongst low mass galaxies contrastswith the scale free continuity expected for galaxies formed under gravity, asin the standard Cold Dark Matter (CDM) model for heavy particles. Within eachdwarf class we find the core radius $R_c$ is inversely related to velocitydispersion $\sigma$, quite the opposite of standard expectations, butindicative of dark matter in a Bose-Einstein state, where the UncertaintyPrinciple requires $R_c \times \sigma$ is fixed by Planks constant, $h$. Thecorresponding boson mass, $m_b=h/R_c \sigma$, differs by one order of magnitudebetween the UDF and dSph classes, with $10^{-21.4}$eV and $10^{-20.3}$eVrespectively. Two boson species is reinforced by parallel relations seenbetween the central density and radius of UDF and dSph dwarfs respectively,each matching the steep prediction, $\rho_c \propto R_c^{-4}$, for solitoncores in the ground state. Furthermore, soliton cores accurately fit thestellar profiles of UDF and dSph dwarfs where prominent, dense cores appearsurrounded by low density halos, as predicted by our simulations. Multiplebosons may point to a String Theory interpretation for dark matter, where adiscrete mass spectrum of axions is generically predicted to span many decadesin mass, offering a unifying "Axiverse" interpretation for the observed"diversity" of dark matter dominated dwarf galaxies.

Dwarf Galaxies United by Dark Bosons