Local supercluster dynamics: external tidal impact of the PSCz sample traced by optimized numerical least action method

Description

We assess the extent to which the flux-limited IRAS PSCz redshift survey encapsulates the complete or major share of matter inhomogeneities responsible for the external tidal forces affecting the peculiar velocity flow within the Local Supercluster and its immediate surroundings. We here investigate this issue on the basis of artificially constructed galaxy catalogs. Two large unconstrained N-body simulations of cosmic structure formation in two different cosmological scenarios form the basis of this study. From these N-body simulations a set of galaxy mock catalogs is selected. From these a variety of datasets is selected imitating the observational conditions of either the local volume-limited Local Supercluster mimicking NBG catalog or the deeper magnitude-limited PSCz catalog. The mildly nonlinear dynamics in the "mock" Local Supercluster and PSCz velocities are analyzed by means of the Least Action Principle technique in its highly optimized implementation of the Fast Action Method. By comparing the velocities in these reconstructions with the "true" velocities of the corresponding galaxy mock catalogs we assess the extent and nature of the external tidal influence on the Local Supercluster volume. We find that the dynamics in the inner 30 h-1 Mpc volume is strongly affected by the external forces. Most of the external forces can be traced back to a depth of no more than 100 h-1 Mpc. This is concluded from the fact that the FAM reconstructions of the 100 h-1 Mpc PSCz volume appear to have included most gravitational influences. In addition, we demonstrate that for all considered cosmological models the bulk flow and shear components of the tidal velocity field generated by the external distribution of PSCz galaxies provides sufficient information for representing the full external tidal force field.

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