Subhaloes in Self-Interacting Galactic Dark Matter Haloes

TL;DR

This paper uses N-body simulations to explore a new self-interacting dark matter model with velocity-dependent interactions, showing it can produce galaxy-like structures with cores consistent with observations, unlike standard cold dark matter.

Contribution

It introduces a novel velocity-dependent self-interacting dark matter model and demonstrates its compatibility with observed galaxy satellite properties through detailed simulations.

Findings

Main halo develops a small core (~1 kpc) with standard density profile outside

Subhaloes form large density cores, altering inner velocity profiles

Model aligns with observed properties of Milky Way dwarf spheroidals

Abstract

We present N-body simulations of a new class of self-interacting dark matter models, which do not violate any astrophysical constraints due to a non-power-law velocity dependence of the transfer cross section which is motivated by a Yukawa-like new gauge boson interaction. Specifically, we focus on the formation of a Milky Way-like dark matter halo taken from the Aquarius project and re-simulate it for a couple of representative cases in the allowed parameter space of this new model. We find that for these cases, the main halo only develops a small core (~1 kpc) followed by a density profile identical to that of the standard cold dark matter scenario outside of that radius. Neither the subhalo mass function nor the radial number density of subhaloes are altered in these models but there is a significant change in the inner density structure of subhaloes resulting in the formation of a large density core. As a consequence, the inner circular velocity profiles of the most massive subhaloes differ significantly from the cold dark matter predictions and we demonstrate that they are compatible with the observational data of the brightest Milky Way dSphs in such a velocity-dependent self-interacting dark matter scenario. Specifically, and contrary to the cold dark matter case, there are no subhaloes that are more concentrated than what is inferred from the kinematics of the Milky Way dSphs. We conclude that these models offer an interesting alternative to the cold dark matter model that can reduce the recently reported tension between the brightest Milky Way satellites and the dense subhaloes found in cold dark matter simulations.