CONSTRAINTS ON THE RADIAL MASS DISTRIBUTION OF DARK MATTER HALOS FROM ROTATION CURVES

Rotation curves place important constraints on the radial mass distribution of dark matter halos, ρ(r). At large radii, rotation curves tend to become asymptotically flat. For ρ(r) ∝ r^α, this implies α ≈ -2, which persists as far out as can be measured. At small radii, the data strongly prefer dark matter halos with constant density cores (α ≈ 0) over the cuspy halos (α ≤ -1) predicted by cosmological simulations. As better data have been obtained, this cusp-core problem has become more severe.