Deviations from Spherical Symmetry, Typical Parameters of the Spherical Collapse Model, and Dark Energy Cosmologies

Abstract

We study how deviations from spherical symmetry of a system, produced by angular momentum, and shear stress, modify the spherical collapse model parameters, as linear density threshold for collapse of the non-relativistic component (δc) and its virial overdensity (ΔV), in Einstein–de Sitter and ΛCDM models. We modify the spherical collapse model to take account of the shear term and angular momentum term. We find that the non-spherical terms change the non-linear evolution of the system and that the collapse stops “naturally” at the virial radius. Moreover, values of the linear overdensity parameter and of ΔV are modified with respect to the standard spherical collapse model.