Gravitational fluctuations of the galaxy distribution

TL;DR

This study analyzes the statistical properties of gravitational force fluctuations caused by galaxy distributions in SDSS data, revealing significant large-scale contributions that may influence cosmic flows.

Contribution

It provides the first detailed characterization of the gravitational force PDF from galaxy data and links its features to galaxy correlations and large-scale fluctuations.

Findings

PDF of gravitational force influenced by galaxy two-point correlations

Large-scale fluctuations (~100 Mpc/h) significantly affect gravitational force amplitude

Gravitational fluctuations may explain observed large-scale cosmic flows

Abstract

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.