Determining Omega from Peculiar Velocities

The large-scale dynamics of matter is inferred from the observed peculiar velocities of galaxies via the POTENT procedure. The smoothed fields of velocity and mass-density fluctuations are recovered from the current data of about 3000 galaxies. The cosmological density parameter Omega can then be constrained in three ways: (a) by comparing the density fields of mass and galaxies, (b) by using the velocity field in voids, and (c) by investigating quasilinear deviations from Gaussian fluctuations. The results indicate a high value of Omega near unity; values in the range 0.1-0.3 are rejected with high confidence.