Hierarchical Clustering: Angular Momentum Density Anti-Correlation

Extract

The growth of angular momentum in a general clustering scenario is analyzed and its dependence on the primordial density perturbation, δ_o, is calculated. High density peaks are found to evolve into low angular momentum and low spin parameter (η = J E^½ G⁻¹ M^−5/2) systems. The basic mechanism behind this anti-correlation is that anisotropic structure, which leads to the growth of angular momentum, is statistically uncorrelated with δ_o. The collapse time, on the other hand, depends on δ_o and it is this time scale which determines the angular momentum of bound objects. Three cases are studied: (1) Lagrangian sphere (quasi-linear evolution): J (1σ)/J(3σ) = 3.3 and η (1σ)/η (3σ) = 1.9 where δ is given in σ(= <δ²>^1/2)units.