  The rotation curves of spiral galaxies obey strong scaling relations. These
include the Tully-Fisher and baryonic Tully-Fisher relations, and the mass
discrepancy--acceleration relation. These relations can be used to place
constraints on the mass-to-light ratios of stars. Once the stellar mass is
constrained, the distribution of dark matter follows. The shape of the dark
matter distribution is consistent with the expectations of NFW halos exterior
to 1 kpc, but the amplitude is wrong. This is presumably related to the
long-standing problem of the normalization of the Tully-Fisher relation and may
imply a downturn in the amplitude of the power spectrum at small scales. More
fundamentally, the persistent success of MOND remains a troubling fact.

Astrophysics