Gravitational fluctuations of the galaxy distribution

Aims. We study the statistical properties of the gravitational field generated by galaxy distributionobserved by the Sloan Digital Sky Survey (DR7).We characterize the probability density functionof gravitational force fluctuations and relate its limiting behaviors to the correlation properties ofthe underlying density field. In addition, we study whether the PDF converges to an asymptoticshape within sample volumes.Methods. We consider several volume-limited samples of the Sloan Digital Sky Survey and wecompute the gravitational force probability density function (PDF). The gravitational force iscomputed in spheres of varying radius as is its PDF.Results. We find that (i) the PDF of the force displays features that can be understood in termsof 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.Conclusions. Our main conclusion is that fluctuations in the gravitational force field generated bygalaxy structures are also relevant on scales 100Mpc/h. By assuming that the gravitational fluctuations in the galaxy distribution reflect those in the whole matter distribution, and that peculiarvelocities and accelerations are simply correlated, we may conclude that large-scale fluctuationsin the galaxy density field may be the source of the large-scale flows recently observed.