Satellite galaxy velocity dispersions in the SDSS and modified gravity
  models
  The Sloan Digital Sky Survey (SDSS) provides data on several hundred thousand
galaxies. Precise location of these galaxies in the sky, along with information
about their luminosities and line-of-sight (Doppler) velocities allows one to
construct a three-dimensional map of their location and estimate their
line-of-sight velocity dispersion. This information, in principle, allows one
to test dynamical gravity models, specifically models of satellite galaxy
velocity dispersions near massive hosts. A key difficulty is the separation of
true satellites from interlopers. We sidestep this problem by not attempting to
derive satellite galaxy velocity dispersions from the data, but instead
incorporate an interloper background into the mathematical models and compare
the result to the actual data. We find that due to the presence of interlopers,
it is not possible to exclude several gravitational theories on the basis of
the SDSS data.
