Ultra-light Dark Matter is Incompatible with the Milky Way's Dwarf
  Satellites
  The density profiles of dwarf galaxies are a highly varied set. If the dark
matter is an ultra-light particle such as axions, then simulations predict a
distinctive and unique profile. If the axion mass is large enough to fit the
ultra-faint dwarf (UFD) satellites($m\gtrapprox 10^{-21}$ eV), then the models
do not fit the density profile of Fornax and Sculptor and are ruled out by more
than $3-\sigma$ confidence. If the axion mass is in the mass range that can fit
mass profiles of Fornax and Sculptor dwarf spheroidals, then its extended
profile implies enormous masses ($\approx10^{11}-10^{12}M_{\odot}$) for the
UFDs. These large masses for the UFDS are ruled out by more than $3-\sigma$
confidence by dynamical friction arguments. The tension would increase further
considering star formation histories and stellar masses of the UFDs. Unless
future ultra-light dark matter (ULDM) simulations with baryonic feedback show a
significant change in the density structure of the halos, the current data is
incompatible with the ULDM scenario. Relaxing the slope constraint from
classical dwarf galaxies would lead to excluding ULDM with mass less than
$6\times10^{-22}$ eV.
