Radio bounds on the mixed dark matter scenarios of primordial black holes and WIMPs

TL;DR

This paper investigates radio emissions from mixed dark matter models involving primordial black holes and WIMPs, setting upper bounds on PBH abundance based on synchrotron radiation observations, and finds PBHs are negligible compared to WIMPs.

Contribution

It provides new constraints on primordial black hole abundance in mixed dark matter scenarios using radio emission data, considering WIMP annihilation effects around PBHs.

Findings

Upper bounds on PBH fraction are between 10^{-8} and 10^{-5}.

PBH contribution to dark matter is negligible compared to WIMPs.

Synchrotron radio emission constrains mixed dark matter models.

Abstract

We study the synchrotron radio emission in the mixed dark matter scenarios consisting of the primordial black holes (PBHs) and the self-annihilating WIMPs (weakly interacting massive particles). The WIMPs can form the ultracompact minihalos around PBHs and the annihilation enhancement from these dense halos can lead to the efficient synchrotron radiation at the radio frequency in the presence of galactic magnetic fields. The upper bound of PBH fraction with respect to the total dark matter abundance is of order $10^{-8}\sim 10^{-5}$ depending on the electroweak scale WIMP mass ($m_{\chi}=10\sim 1000$ GeV) and the WIMP annihilation channel (e.g. a hadronic $\chi \chi \rightarrow b \bar{b}$ or a leptonic $\chi \chi \rightarrow e^+ e^-$ channel). The PBH contribution to the total dark matter abundance is hence negligible when the other component of dark matter is composed of the conventional electroweak scale WIMPs.