Universality of galactic surface densities within one dark halo
  scale-length
  It was recently discovered that the mean dark matter surface density within
one dark halo scale length - the radius within which the volume density profile
of dark matter remains approximately flat - is constant across a wide range of
galaxies. This scaling relation holds for galaxies spanning a luminosity range
of 14 magnitudes and the whole Hubble sequence. Here we report that the
luminous matter surface density is also constant within one scale length of the
dark halo. This means that the gravitational acceleration generated by the
luminous component in galaxies is always the same at this radius. Although the
total luminous-to-dark matter ratio is not constant, within one halo scale
length it is constant. Our finding can be interpreted as a close correlation
between the enclosed surface densities of luminous and dark matter in galaxies.
