On the origin of the voids in the galaxy distribution

Abstract

The distribution of galaxies on scales larger than approximately 10 Mpc/h seems to be characterized by large voids, (20-40) Mpc/h in diameter and of amplitude delta approximately -(0.7-0.8). It was previously argued that the mere existence of such voids poses a severe problem to all dissipationless clustering theories. Here it is shown that the voids may, in fact, be a natural outcome of a dissipationless clustering scenario if both adiabatic and isothermal density perturbations exist primordially. When the nonlinear evolution of spherical voids of this type is followed for adiabatic perturbations with an index n greater than -1, it is seen that they become surrounded by a shell of positive density contrast. Their structure is insensitive to Omega 0 while their dynamics is quite sensitive to it. The maximum peculiar velocity (relative to Hubble flow) within the void is found to be: v(p)/v(H) approximately (0.4-0.5) for Omega 0 = 1.0, approximately (0.2-0.25) for Omega 0 = 0.45, and approximately equal to or less than 0.09 for Omega 0 = 0.1.