The IRAS view of the local universe

We summarise results for the predicted density and peculiar velocity fields from the PSCz survey, consisting of redshifts for 15,000 IRAS galaxies covering 84% of the sky to a depth of 25,000 kms(-1). We have used a generalisation of the "Path Interchange Zeldovich Approximation" (PIZA) technique to determine the velocity field; the most remarkable feature is a coherent large-scale flow along the baseline connecting the Local Supercluster, Centaurus and the Shapley Concentration. By comparison of the predicted and observed bulk flows we find an implied value of the combined density and biassing parameter beta = 0.50 +/- 0.1. We re-examine the PSCz dipole, with improved redshift completeness at low-latitudes and using PIZA to estimate real-space distances. We find the dipole to be stable between 80 and 180h(-1)Mpc (where h = H-0/100 kms(-1) Mpc(-1)), although there appears to be a significant contribution to the dipole around 200 h(-1)Mpc. The overall misalignment with the CMB dipole remains at 20 degrees. The implied value of P depends on the exact treatment; we derive values in the range beta = 0.40 - 0.55 with a statistical error of +/-0.1. We also present the density field and a preliminary dipole analysis from the almost completed "Behind The Plane" (BTP) survey, which extends the PSCz to cover 93% of the sky including the proposed core of the Great Attractor. We find a density peak at (325 degrees,-5 degrees ,3500 km s(-1)), about half as massive as Centaurus or Pavo-Indus, and forming part of a continuous filament linking them across the Galactic Plane. We also find evidence for a much larger "Greater Attractor" directly behind the GA, at a distance of 125 h(-1)Mpc, and more massive than the Shapley concentration. At large distances the dipole direction is in much improved agreement with the CMB: at 250 - 300 h(-1)Mpc, the misalignment is only 5-10 degrees, and this is consistent with the shot noise errors. The J(3)-weighted dipole, which in principal is expected to agree better with the CMB, gives a misalignment of 13 degrees. The dipole direction is somewhat dependent on the corrections made for the redshift incompleteness, and may also be affected by unquantified incompleteness in the BTP survey close to the Galactic Centre. The dipole amplitude implies a value for the parameter beta of 0.44 +/- 0.1. Values much larger than beta = 0.5, while not formally ruled out, give cumulative dipoles with monotonic growth and without convergence, as expected from the rocket effect for an overestimated beta.