Gravothermal evolution of dark matter halos with differential elastic scattering. Issue 9 (1st September 2022)

• Record Type: Journal Article
• Authors: Yang, Daneng; Yu, Hai-Bo
• Is Part Of: Journal of cosmology and astroparticle physics. Volume 2022:Issue 9(2022)
• Publication Date: 2022-09-01
• Subjects: dark matter simulations -- astrophysical fluid dynamics -- dark matter theory; Cosmology -- Periodicals; Astrophysics -- Periodicals; 523.0105
• DOI: 10.1088/1475-7516/2022/09/077
• Languages: English
• ISSNs: 1475-7516

Abstract

Abstract: We study gravothermal evolution of dark matter halos in the presence of differential self-scattering that has strong velocity and angular dependencies. We design controlled N-body simulations to model Rutherford and Møller scatterings in the halo, and follow its evolution in both core-expansion and -collapse phases. The simulations show the commonly-used transfer cross section underestimates the effects of dark matter self-interactions, but the viscosity cross section provides an accurate approximation for modeling angular-dependent dark matter scattering. We investigate thermodynamic properties of the halo, and find that the three moments of the Boltzmann equation under the fluid approximation are satisfied. We further propose a constant effective cross section, which integrates over the halo's characteristic velocity dispersion with weighting kernels motivated by kinetic theory of heat conduction. The effective cross section provides a good approximation to differential self-scattering for most of the halo evolution. It indicates that we can map astrophysical constraints on a constant self-interacting cross section to an SIDM model with velocity- and angular-dependent scatterings.