Observations of dark and luminous matter: the radial distribution of
  satellite galaxies around massive red galaxies
  We study the projected radial distribution of satellite galaxies around more
than 28,000 Luminous Red Galaxies (LRGs) at 0.28<z<0.40 and trace the
gravitational potential of LRG groups in the range 15<r/kpc<700. We show that
at large radii the satellite number density profile is well fitted by a
projected NFW profile with r_s~270 kpc and that at small radii this model
underestimates the number of satellite galaxies. Utilizing the previously
measured stellar light distribution of LRGs from deep imaging stacks we
demonstrate that this small scale excess is consistent with a non-negligible
baryonic mass contribution to the gravitational potential of massive groups and
clusters. The combined NFW+scaled stellar profile provides an excellent fit to
the satellite number density profile all the way from 15 kpc to 700 kpc. Dark
matter dominates the total mass profile of LRG halos at r>25 kpc whereas
baryons account for more than 50% of the mass at smaller radii. We calculate
the total dark-to-baryonic mass ratio and show that it is consistent with
measurements from weak lensing for environments dominated by massive early type
galaxies. Finally, we divide the satellite galaxies in our sample into three
luminosity bins and show that the satellite light profiles of all brightness
levels are consistent with each other outside of roughly 25 kpc. At smaller
radii we find evidence for a mild mass segregation with an increasing fraction
of bright satellites close to the central LRG.
