Impact of radiation from primordial black holes on the 21-cm angular-power spectrum in the dark ages

TL;DR

This paper examines how radiation from primordial black holes influences the 21-cm angular-power spectrum during the dark ages, revealing that PBHs can significantly alter the spectrum and offering prospects for future observational constraints.

Contribution

It introduces a detailed analysis of PBH radiation effects on the 21-cm spectrum across different mass ranges and explores potential observational constraints from lunar-based radio telescopes.

Findings

PBH radiation decreases the 21-cm angular-power spectrum amplitude during dark ages.

The impact varies with PBH mass and abundance, affecting ionization and temperature.

Future lunar radio telescopes could constrain PBH dark matter fraction.

Abstract

We investigate the impact of radiation from primordial black holes (PBHs), in the mass range of $10^{15} \lesssim M_{\rm PBH} \lesssim 10^{17}~\rm g$ and $10^{2} \lesssim M_{\rm PBH} \lesssim 10^{4}~M_{\odot}$, on the 21-cm angular-power spectrum in the dark ages. PBHs in the former mass range effect the 21-cm angular-power spectrum through the evaporation known as Hawking radiation, while the radiation from the accretion process in the latter mass range. In the dark ages, radiation from PBHs can increase the ionization fraction and temperature of the intergalactic medium, change the global 21-cm differential brightness temperature and then effect the 21-cm angular-power spectrum. Taking into account the effects of PBHs, we find that in the dark ages, $30 \lesssim z \lesssim 100$, the amplitude of the 21-cm angular-power spectrum is decreased depending on the mass and mass fraction of PBHs. We also investigate the potential constraints on the mass fraction of PBHs in the form of dark matter for the future radio telescope in lunar obit or on the farside surface of the Moon.