Gravitational fluctuations of the galaxy distribution
  We study the statistical properties of the gravitational field generated by
galaxy distribution observed bythe Sloan Digital Sky Survey (DR7). We
characterize the probability density function of gravitational force
fluctuations and relate its limiting behaviors to the correlation properties of
the underlying density field. In addition, we study whether the PDF converges
to an asymptotic shape within sample volumes. We consider several
volume-limited samples of the Sloan Digital Sky Survey and we compute the
gravitational force probability density function (PDF). The gravitational force
is computed in spheres of varying radius as is its PDF. We find that (i) the
PDF of the force displays features that can be understood in terms of galaxy
two-point correlations and (ii) density fluctuations on the largest scales
probed, i.e. r~100 Mpc/h, still contribute significantly to the amplitude of
the gravitational force. Our main conclusion is that fluctuations in the
gravitational force field generated by galaxy structures are also relevant on
scales ~ 100 Mpc/h. By assuming that the gravitational fluctuations in the
galaxy distribution reflect those in the whole matter distribution, and that
peculiar velocities and accelerations are simply correlated, we may conclude
that large-scale fluctuations in the galaxy density field may be the source of
the large-scale flows recently observed.
