LOCAL GRAVITY AND PECULIAR VELOCITY - PROBES OF COSMOLOGICAL MODELS

We study the convergence of the peculiar gravitational acceleration of the Local Group deduced from galaxy distribution and its alignment with the microwave background dipole in the framework of linear theory and conditional probability. Using the observed velocity of 600 km s-1 as a constraint we predict the acceleration generated within a volume of finite depth for general density fluctuations power spectrum. We apply this formalism to the cold-dark-matter (CDM) and isocurvature baryon (PIB) family of models and compare it with IRAS and optical flux and redshift dipoles. A biased (σρ = 0.6) CDM model is consistent with the observed small misalignment and the convergence of the IRAS redshift dipole (at 85% and 32% confidence level, respectively). The PIB models exhibit a wide range of behavior depending on the free parameters. The PIB model which fits best the bulk flows (Ψ0 = 0.4 and a spectral index of -1), is consistent only at the level of 8% and 3%, respectively. Consequently, the estimated Ψ0 in the CDM case is reasonably good, but the above PIB model has a large scatter in Ψ0. We find these observational tests to be useful probes of cosmological models.