The halo density profiles with non-standard N-body simulations

Abstract

We propose a new numerical procedure to simulate a single dark halo of any size and mass in a hierarchical framework coupling the extended Press‐Schechter formalism (EPSF) to N-body simulations. The procedure consists of assigning cosmological initial conditions to the particles of a single halo with the EPSF technique and following only the dynamical evolution using a serial N-body code. The computational box is fixed with a side of 0.5 h −1 Mpc. This allows us to simulate galaxy cluster haloes using appropriate scaling relations, to ensure savings in computing time and code speed. The code can describe the properties of haloes composed of collisionless or collisional dark matter. For collisionless cold dark matter particles, the Navarro‐ Frenk‐White profile is reproduced for galactic haloes as well as galaxy cluster haloes. Using this numerical technique, we study some characteristics of haloes assumed to be isolated or placed in a cosmological context in the presence of weak self-interacting dark matter: the soft core formation and the core collapse. The self-interacting dark matter cross-section per unit mass is assumed to be inversely proportional to the particle collision velocity:σ/mx ∝ 1/v.