Galactic halos of self-interacting dark matter

TL;DR

This paper investigates how dark matter self-interactions influence galaxy formation, showing that such interactions can reduce halo concentration but may also cause halo instability and particle ejection.

Contribution

It provides a simple yet effective numerical analysis demonstrating the impact of dark matter self-interactions on galactic halo structure and stability.

Findings

Self-interacting dark matter reduces halo central concentration.

Strong interactions can cause halo instability and particle ejection.

Halo instability occurs on a timescale comparable to the Hubble time.

Abstract

Recent, very accurate simulations of galaxy formation have revealed that the standard cold dark matter model has great difficulty in explaining the detailed structure of galaxies. One of the major problems is that galactic halos are too centrally concentrated. Dark matter self-interactions have been proposed as a possible means of resolving this inconsistency. Here, we investigate quantitatively the effect of dark matter self interactions on formation of galactic halos. Our numerical framework is extremely simple, while still keeping the essential physics. We confirm that strongly self-interacting dark matter leads to less centrally concentrated structures. Interestingly, we find that for a range of different interaction strengths, the dark matter halos are unstable to particle ejection on a timescale comparable to the Hubble time.