A blueprint for detecting supersymmetric dark matter in the Galactic halo

TL;DR

This paper argues that detecting supersymmetric dark matter in the Milky Way's halo is most promising through diffuse gamma-ray signals from the main halo, challenging previous focus on small clumps.

Contribution

It demonstrates via large simulations that small-scale dark matter clumps have negligible impact on detectability, emphasizing the main halo as the primary source.

Findings

Diffuse dark matter in the main halo is the dominant detectable signal.

Small dark matter clumps likely contain no stars, confirming CDM predictions.

Detection of the main halo implies potential visibility of dark matter clumps.

Abstract

Dark matter is the dominant form of matter in the universe, but its nature is unknown. It is plausibly an elementary particle, perhaps the lightest supersymmetric partner of known particle species. In this case, annihilation of dark matter in the halo of the Milky Way should produce gamma-rays at a level which may soon be observable. Previous work has argued that the annihilation signal will be dominated by emission from very small clumps (perhaps smaller even than the Earth) which would be most easily detected where they cluster together in the dark matter halos of dwarf satellite galaxies. Here we show, using the largest ever simulation of the formation of a galactic halo, that such small-scale structure will, in fact, have a negligible impact on dark matter detectability. Rather, the dominant and likely most easily detectable signal will be produced by diffuse dark matter in the main halo of the Milky Way. If the main halo is strongly detected, then small dark matter clumps should also be visible, but may well contain no stars, thereby confirming a key prediction of the Cold Dark Matter (CDM) model.