Boosting small-scale structure via primordial black holes and implications for sub-GeV dark matter annihilation

TL;DR

This paper investigates how primordial black holes can enhance dark matter annihilation signals by promoting early structure formation, especially impacting sub-GeV dark matter models.

Contribution

It introduces a novel scenario where PBHs induce early minihalo formation, boosting dark matter annihilation signals for light DM below 1 GeV.

Findings

Primordial black holes lead to early small-scale structure formation.

Enhanced substructure increases dark matter annihilation signals.

Scenario is particularly relevant for sub-GeV dark matter.

Abstract

We explore the possibility that the annihilation of dark matter (DM) is boosted due to enhanced substructure in the presence of primordial black holes (PBHs) which constitute a sub-component of DM. The PBHs can generate entropy fluctuations at the small scales which trigger early structure formation, and a large fraction of the whole DM can reside in these collapsed objects that formed at high redshift ($z\gtrsim 100$). Such early forming minihalos consequently possess higher densities than those in the conventional scenarios (without PBHs) and would be more resilient to tidal disruptions. Our scenarios of the annihilation boost due to DM substructures are of particular interest for light ($< 1$ GeV) DM which has been less explored compared to heavier DM in the presence of the PBHs.