The IRAS PSCz dipole

We use the PSCz IRAS galaxy redshift survey to analyse the cosmological gal axy 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 sp herical 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 a n 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 t he voids found from the PSCz data base. The dipole for the whole PSCz sample appears to have converged within a dis tance of 200 h(-1) Mpc and yields a value for beta = Omega(0.6)/beta - 0.75 (-0.08)(+0.11), consistent with earlier determinations from IRAS samples by a variety of methods. For b=1, the 2 sigma range for Omega(0) is 0.43-1.02 . The direction of the dipole is within 13 degrees of the cosmic microwave ba ckground (CMB) dipole, the main uncertainty in direction being associated w ith the masked area behind the Galactic plane. The improbability of further major contributions to the dipole amplitude coming from volumes larger tha n those surveyed here means that the question of the origin of the CMB dipo le is essentially resolved.