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

Abstract

We investigate the impact of radiation from primordial black holes (PBHs), in the mass range of ${10}^{15}\ensuremath{\lesssim}{M}_{\mathrm{PBH}}\ensuremath{\lesssim}{10}^{17}\text{ }\text{ }\mathrm{g}$ and ${10}^{2}\ensuremath{\lesssim}{M}_{\mathrm{PBH}}\ensuremath{\lesssim}{10}^{4}{M}_{\ensuremath{\bigodot}}$, on the 21-cm angular-power spectrum in the dark ages. PBHs in the former mass range affect 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 affect the 21-cm angular-power spectrum. Taking into account the effects of PBHs, we find that in the dark ages, $30\ensuremath{\lesssim}z\ensuremath{\lesssim}100$, 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 orbit or on the far side surface of the Moon.