Sub-keV dark matter can strongly ionize molecular clouds

TL;DR

This paper demonstrates that ionization measurements of dense molecular clouds can impose strong constraints on sub-keV dark matter models, offering a novel astrophysical approach to dark matter detection.

Contribution

It introduces a new method using molecular cloud ionization to constrain sub-keV dark matter models, improving existing limits and outlining future enhancements.

Findings

Established robust constraints on dark matter models between 30 eV and 10 keV.

Showed molecular cloud ionization as a powerful probe for sub-keV dark matter.

Projected improved constraints with refined astrophysical modeling.

Abstract

We show that the ionization of dense molecular clouds can be used to set strong constraints on dark matter models producing UV/X-ray photons in their annihilation or decay. We place robust and competitive constraints on various dark matter models, such as axion-like particles, scalars and sterile neutrinos, for masses between $\sim30$~eV and $10$~keV, and project forecasts to illustrate the potential of this target. We discuss how these constraints can be significantly improved by considering a more refined sample of molecular clouds near the Galactic Center and above the Galactic plane, a detailed modeling of the cosmic-ray ionization contribution and, potentially, a more refined analysis of the gas density in clouds through dust extinction maps. Thus, ionization of molecular clouds emerges as one of the most powerful tools for probing sub-keV dark matter.