Dark matter density profiles: a comparison of nonextensive theory with N-body simulations

¹ Institut für Astro- und Teilchenphysik, Leopold-Franzens-Universität Innsbruck, Technikerstr. 25, 6020 Innsbruck, Austria e-mail: Thomas.Kronberger@uibk.ac.at
² Institut für Astrophysik, Universität Göttingen, Friedrich-Hund-Platz 1, 37077 Göttingen, Germany

Received: 30 November 2005
Accepted: 11 March 2006

Abstract

Density profiles of simulated galaxy cluster-sized dark matter haloes are analysed in the context of a recently introduced nonextensive theory of dark matter and gas density distributions. Nonextensive statistics accounts for long-range interactions in gravitationally coupled systems and is derived from the fundamental concept of entropy generalization. The simulated profiles are determined down to radii of ≈1% of R₂₀₀. The general trend of the relaxed, spherically averaged profiles is accurately reproduced by the theory. For the main free parameter κ, measuring the degree of coupling within the system, and linked to physical quantities as the heat capacity and the polytropic index of the self-gravitating ensembles, we find a value of -15. The significant advantage over empirical fitting functions is provided by the physical content of the nonextensive approach.