The large-scale distribution of IRAS galaxies and the predicted peculiar velocity field

Using the QDOT IRAS galaxy redshift survey, we construct a smoothed density field, corrected for peculiar velocity distortion, of a region of the local universe out to about ∼ |150h⁻¹| Mpc. Predicted peculiar velocities are calculated from this density field, assuming gravitational instability theory, and compared to observed velocities derived from the Tully–Fisher and |Dₙ-σ| techniques. A good correlation is seen, from which we estimate that |bIRASΩ-0.6| ≃ 1.16 ± 0.21, in general agreement with earlier results from analysis of the Local Group motion. It IRAS galaxies trace the mass on large scales, the universe has a density very close to the critical value.