LARGE-SCALE MOTIONS IN THE UNIVERSE - USING CLUSTERS OF GALAXIES AS TRACERS

Can clusters of galaxies be used to trace the large-scale peculiar vel ocity field of the universe? We answer this question by using large-sc ale cosmological simulations to compare the motions of rich clusters o f galaxies with the motion of the underlying matter distribution. Thre e models are investigated: Omega = 1 and Omega = 0.3 CDM, and Omega = 0.3 PBI models, all normalized to the COBE background fluctuations. We compare the cluster and mass distribution of peculiar velocities, bul k motions, velocity dispersions, and Mach numbers as a function of sca le for R greater than or equal to 50 h(-1) Mpc. We also present the la rge-scale velocity and potential maps of clusters and of the matter. W e find that clusters of galaxies trace well the large-scale velocity f ield and can serve as an efficient tool to constrain cosmological mode ls. The recently reported bulk motion of clusters 689 +/- 178 km s(-1) on similar to 150 h(-1) Mpc scale (Lauer and Postman 1994) is larger than expected in any of the models studied (less than or equal to 190 +/- 78 km s(-1)).