The evolution of void-filled cosmological structures

We simulate the growth and evolution of voids in the large-scale distribution of galaxies. For arbitrary value of the cosmological density parameter OMEGA, we examine one-, two-, and three-dimensional models. In these models void-filled cosmological structures evolve from a high number density of shallow initial voids with unspecified origin. The growth rate of a void decreases significantly at the cosmic time corresponding to OMEGA = 0. 5. In models constructed in two and three dimensions, suitable initial conditions lead to cellular structure with faceted voids similar to those observed in redshift surveys. These structures form for OMEGA OMEGA⁰. 6^. If OMEGA is large, the appearance of voids and walls in redshift space can be very different from their appearance in real space when the adjacent voids differ significantly in size; voids and walls can masquerade for each other. The maximum size of a three-dimensional void that can be misidentified in redshift space is 1/5 OMEGA⁰. 6^ relative to its neighbors. The three-dimensional models indicate that the redshift maps are a rather good guide to the structure in real space. For the 5000 km s^-1^ maximum void size in the CfA survey, structures in redshift space on scales less than 1000 km s^-1^ are uncertain if OMEGA = 1. For smaller OMEGA, the scale for such severe distortion is smaller. A first approximation to the differential outflow velocity of an undisturbed wall (between identified voids) in three dimensions is Vₒut_ ~ H₀_ (d₁_- d₂_) 1/10OMEGA⁰. 6^, where d₁_ and d₂_ are the diameters of the adjacent voids along the direction perpendicular to the wall. It should be possible, in future three-dimensional simulations, to test or improve this estimate. Then measurement of the outflow velocities of walls could limit the value of OMEGA₀_.