Large Scale Peculiar Velocities: Effects from Superclusters

Abstract

We study the gravitational influence of very large scale structures, as traced by clusters of galaxies, on the Local Group [LG] motion and the large scale flows. We derive from the distribution of Abell clusters within $300~$Mpc/h the overdensity field on a 3--D grid of spacing $5~$Mpc/h, then we solve the Poisson equation for the peculiar potential and finally obtain the peculiar velocity field. Quite interestingly, from this global solution we: i) recover within $\sim 10^o$ the direction of the LG motion in the Cosmic Microwave Background [CMB] frame, ii find that the Great Attractor itself moves wrt to the CMB frame, iii) derive $β_c^{-1} \equiv b_c Ω_0^{-0.6} = 5.3 \pm 0.20$ from a preliminary comparison with the Mark~II catalog of peculiar velocities, iv) derive estimates for the bulk flow in spheres which fairly agree with the level derived from POTENT and the Spiral samples, v) find that the Lauer \& Postman [L\&P] bulk flow has too a large amplitude to be in agreement with our results.