Dark Matter tested with satellites
  Recently, the distribution of velocity dispersion as far as 400kpc around red
isolated galaxies was derived from statistical studies of satellites in the
SDSS (Klypin & Prada 2009). This could help to constrain dark matter models at
intermediate scales. We compare the predictions of different DM distributions,
LCDM with NFW or cored profiles, and also modified gravity models, with
observations. It is shown how the freedom in the various parameters (radial
distribution of satellites, velocity anisotropy, external field effect),
prevents to disentangle the models, which all can give pretty good fits to the
data. In all cases, realistic radial variations of velocity anisotropy are used
for the satellites, and a constant stellar-mass to light ratio for the host
galaxies.
