Molecular ionization rates and ultracompact dark matter minihalos

TL;DR

This paper proposes ultracompact dark matter minihalos as embedded sources of low-energy cosmic rays, explaining enhanced molecular ionization in the Galactic Center and potentially accounting for the Fermi gamma-ray excess.

Contribution

It introduces ultracompact minihalos of self-annihilating dark matter as a novel source of cosmic rays influencing molecular ionization in the Galactic Center.

Findings

Ultracompact minihalos can produce enough cosmic rays to explain enhanced ionization.

Dark matter annihilation channels depend on particle mass and model.

Minihalos may also explain the Fermi Galactic Centre gamma-ray excess.

Abstract

Molecular ionization in the Central Molecular Zone of our galaxy is enhanced over the typical galactic value by an order of magnitude or more. This cannot be easily explained for dense Galactic Center molecular complexes in the absence of embedded sources of low energy cosmic rays. We provide such a source in the form of ultracompact minihalos of self-annihilating dark matter for a variety of annihilation channels that depend on the particle mass and model. Such sources are motivated for plausible inflationary power spectrum parameters, and while possibly subdominant in terms of the total dark matter mass within the Galactic bulge, might also account for, or at least not be in tension with, the Fermi Galactic Centre {\gamma}-ray excess.