Dwarf spheroidal galaxy kinematics and spiral galaxy scaling laws
  Kinematic surveys of the dwarf spheroidal (dSph) satellites of the Milky Way
are revealing tantalising hints about the structure of dark matter (DM) haloes
at the low-mass end of the galaxy luminosity function. At the bright end,
modelling of spiral galaxies has shown that their rotation curves are
consistent with the hypothesis of a Universal Rotation Curve whose shape is
supported by a cored dark matter halo. In this paper, we investigate whether
the internal kinematics of the Milky Way dSphs are consistent with the
particular cored DM distributions which reproduce the properties of spiral
galaxies. Although the DM densities in dSphs are typically almost two orders of
magnitude higher than those found in (larger) disk systems, we find consistency
between dSph kinematics and Burkert DM haloes whose core radii r0 and central
densities {\rho}0 lie on the extrapolation of the scaling law seen in spiral
galaxies: log {\rho}0 \simeq {\alpha} log r0 + const with 0.9 < {\alpha} < 1.1.
We similarly find that the dSph data are consistent with the relation between
{\rho}0 and baryon scale length seen in spiral galaxies. While the origin of
these scaling relations is unclear, the finding that a single DM halo profile
is consistent with kinematic data in galaxies of widely varying size,
luminosity and Hubble Type is important for our understanding of observed
galaxies and must be accounted for in models of galaxy formation.
