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 (δ_c) and its virial overdensity (Δ_V), 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 Δ_V are modified with respect to the standard spherical collapse model.