Self-Interacting Superfluid Dark Matter Droplets
  We assume dark matter (DM) to be a Bose--Einstein condensate (BEC) of
nonrelativistic ultralight scalar particles with repulsive contact
interactions. Such model predicts cored halos with rotation curves that obey a
universal equation in the inner region. A simultaneous fit to a selection of
galaxies from the SPARC database chosen with the sole criterion of being
strongly DM dominated even within $r \lesssim 1$ kpc, shows that the data are
consistent with the presence of a BEC of particles of mass $m \simeq 2.2 \times
10^{-22}$ eV/c$^2$ and repulsive interactions characterized by a scattering
length $a_s \simeq 7.8 \times 10^{-77}$ m. Such small interactions induce a
natural minimum scale length for the size of DM structures that makes all cores
similar in length ($\sim 1$ kpc) and contributes to lower their central
densities.
