Dark Matter Subhalo Evaporation by Coulomb-like Interaction with Galactic Gas

TL;DR

This paper investigates how Coulomb-like interactions between dark matter and galactic gas cause subhalo evaporation, providing new constraints on dark matter properties that surpass existing cosmological and direct detection limits.

Contribution

It introduces a novel method to constrain Coulomb-like dark matter interactions using subhalo evaporation near the Milky Way, improving upon previous bounds from cosmology and direct detection.

Findings

Subhalo survival constrains Coulomb-like scattering strength.

Evaporation limits are stronger than CMB and BAO bounds for sub-GeV dark matter.

Bounds translate into improved direct detection constraints for sub-MeV dark matter.

Abstract

Coulomb-like interactions typically has a cross section scales with velocity dependence as $\sigma=\sigma_0 v^{-4}$. The momentum transfer rate between a slightly charged dark matter and ionized particles increases significantly at low velocity, and it produces prominent evaporation effects on small-sized dark matter overdensities. We show that when subhalos encounter the hot gases near the Milky Way's disc, their survival can place stringent limits on Coulomb-like scattering strength. For $M<10^5 M_\odot$ subhalos to survive a kilo-parsec distance from the galactic center, with a dark matter mass in the sub-GeV range, the evaporation limit becomes one order of magnitude stronger than the limits from current cosmic microwave background and baryon acoustic oscillation data. We also interpret our bounds into the electron-recoil direct detection cross section, and show that the evaporation effect can lead to a stronger constraint on Coulomb-like interaction for sub-MeV dark matter in comparison with direct detection experiments.