Gravothermal collapse of self-interacting dark-matter halos with anisotropic velocity distributions

TL;DR

This paper investigates how different velocity anisotropies in self-interacting dark matter halos affect the timescale of gravothermal collapse, revealing that anisotropy can significantly alter collapse timing.

Contribution

It introduces self-consistent initial conditions with anisotropic velocity distributions to study their impact on gravothermal collapse timescales.

Findings

Collapse times vary by more than a factor of two with different anisotropies.

Velocity distribution anisotropy influences the evolution of dark matter halos.

Variations in collapse times may depend on changes in velocity-dispersion profiles.

Abstract

Self-gravitating galactic halos composed of self-interacting dark matter exhibit the formation of a highly dense core at the galactic center--a gravothermal collapse. Analytic models to describe this evolution have been developed and calibrated to numerical simulations initialized with isotropic particle velocity distributions, an assumption not necessarily warranted by the theory of halo formation. Here we study the dependence of the timescale for gravothermal collapse on the velocity distribution. To do so, we consider self-consistent initial conditions for halos with the same density distribution but with different velocity distributions. We consider models with constant anisotropy and with an anisotropy that increases with radius. The velocity distributions that we explore have collapse times that differ from that assuming isotropic distributions by more than a factor of two. We argue that these variations may depend on the global changes in velocity-dispersion profiles in these anisotropic models and not just on the degree of anisotropy.