On density and velocity fields and beta from the IRAS PSCz survey

Abstract

We present a version of the Fourier Bessel method first introduced by Fisher et al (1994) and Zaroubi et al (1994) with two extensions: (a) we amend the formalism to allow a generic galaxy weight which can be constant rather than the more conventional overweighting of galaxies at high distances, and (b) we correct for the masked zones by extrapolation of Fourier Bessel modes rather than by cloning from the galaxy distribution in neighbouring regions. We test the procedure extensively on N-body simulations and find that it gives generally unbiased results but that the reconstructed velocities tend to be overpredicted in high-density regions. Applying the formalism to the PSZz redshift catalog, we find that beta = 0.7 +/- 0.5 from a comparison of the reconstructed Local Group velocity to the CMB dipole. From an anisotropy test of the velocity field, we find that beta = 1 CDM models models normalized to the current cluster abundance can be excluded with 90% confidence. The density and velocity fields reconstructed agree with the fields found by Branchini et al (1998) in most points. We find a back-infall into the Great Attractor region (Hydra-Centaurus region) but tests suggest that this may be an artifact. We identify all the major clusters in our density field and confirm the existence of some previously identified possible ones.