Confrontation of the Lauer and Postman Cluster Velocity Field with Models

Abstract

The large-scale bulk flow implied by the measurements of distances to brightest cluster members within 15,000 km/s by Lauer and Postman has the potential to put strong constraints on, or to even rule out, various models of large-scale structure. Using PM simulations 400$h^{-1}$ Mpc on a side of five cosmological models (Standard CDM, Tilted CDM, HDM, $Ω= 0.3$ CDM, and PBI), we present detailed Monte-Carlo simulations of the peculiar velocity data, which we use to assess the probability that any given model can explain the data. These models are ruled out at confidence levels ranging from 94\% (HDM) to 97\% (PBI). However, these results may be affected by the finite size of the simulation volume. If the observed bulk flow remains unchanged when calculated using a refined distance indicator with smaller scatter, all these models will be ruled out at high confidence levels.