Molecular Ionization Rates and Ultracompact Dark Matter Minihalos

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 γ-ray excess.

Ultracompact minihalos associated with stellar-mass primordial black holes

“…In addition to gravitational or dynamical signals associated with UCMHs, there could be further signals from these UCMHs, if the dark matter annihilation is sufficiently efficient. For instance, they can give local ionization hot spots that could be an ionization source in molecular clouds [57].…”