Modeling Dark-Matter Halos. Verification of the Entropy Approach to the Cusp Problem

Abstract

The entropy approach to the problem of the formation of a dark-matter halo is analyzed and verified. The model described predicts that the density profile of the halo is determined by the sum of the initial entropy associated with fluctuations of the matter density in the early Universe and the entropy generated in the course of the formation of the halo. The model also predicts the formation of halos without cusps in most galaxies with high initial entropy. Special numerical models are used to measure the initial entropy of the halo, which proves to be an order of magnitude lower than the values calculated using the linear theory, suggesting that most galactic-mass halos should possess cusps.