The IRAS PSCz dipole

We use the PSCzIRAS galaxy redshift survey to analyse the cosmological galaxy dipole out to a distance of 300 h−1 Mpc. The masked area is filled in three different ways, first by sampling the whole sky at random, secondly by using neighbouring areas to fill a masked region, and thirdly using a spherical harmonic analysis. The method of treatment of the mask is found to have a significant effect on the final calculated dipole. The conversion from redshift space to real space is accomplished by using an analytical model of the cluster and void distribution, based on 88 nearby groups, 854 clusters and 163 voids, with some of the clusters and all of the voids found from the PSCz data base. The dipole for the whole PSCz sample appears to have converged within a distance of 200 h−1 Mpc and yields a value for , consistent with earlier determinations from IRAS samples by a variety of methods. For b=1, the 2σ range for Ω0 is 0.43–1.02. The direction of the dipole is within 13° of the cosmic microwave background (CMB) dipole, the main uncertainty in direction being associated with the masked area behind the Galactic plane. The improbability of further major contributions to the dipole amplitude coming from volumes larger than those surveyed here means that the question of the origin of the CMB dipole is essentially resolved.