  We investigate the viability of a simple dark matter (DM) model consisting of
a single fermion in the context of galactic dynamics. We use a consistent
approach that does not presume a particular DM density profile but instead
requires that the DM+baryon system is in hydrostatic equilibrium. Using a
phenomenological baryon density profile, the model then predicts the DM
distribution with a core like behavior close to the galactic center. The
presence of supermassive black holes (SMBHs) in the center of large galaxies
arises naturally in this framework. Using data from a set of large elliptical
and spiral galaxies, and from a small set of dwarf galaxies, we find that the
model can explain most of the bulk galactic properties, as well as some of the
features observed in the rotation curves, provided the DM mass is in the
$\mathcal{O}$(50 eV) range. More precise tests of the model require better
modeling of the baryon profile and better control on the uncertainties in the
data.
