The Case Against Warm or Self-Interacting Dark Matter as Explanations
  for Cores in Low Surface Brightness Galaxies
  Warm dark matter (WDM) and self-interacting dark matter (SIDM) are often
motivated by the inferred cores in the dark matter halos of low surface
brightness (LSB) galaxies. We test thermal WDM, non-thermal WDM, and SIDM using
high-resolution rotation curves of nine LSB galaxies. We fit these dark matter
models to the data and determine the halo core radii and central densities.
While the minimum core size in WDM models is predicted to decrease with halo
mass, we find that the inferred core radii increase with halo mass and also
cannot be explained with a single value of the primordial phase space density.
Moreover, if the core size is set by WDM particle properties, then even the
smallest cores we infer would require primordial phase space density values
that are orders of magnitude smaller than lower limits obtained from the Lyman
alpha forest power spectra. We also find that the dark matter halo core
densities vary by a factor of about 30 from system to system while showing no
systematic trend with the maximum rotation velocity of the galaxy. This
strongly argues against the core size being directly set by large
self-interactions (scattering or annihilation) of dark matter. We therefore
conclude that the inferred cores do not provide motivation to prefer WDM or
SIDM over other dark matter models.
