Influences of accreting primordial black holes on the global 21 cm signal in the dark ages

Understand

Baryonic matter can be accreted on to primordial back holes (PBHs) formed in the early Universe.

• The radiation from accreting PBHs is capable of altering the evolution of the intergalactic medium (IGM), leaving marks on the global 21 cm signal in the dark ages.
• For accreting PBHs with mass $M_{\rm PBH}=10^{3}(10^{4})~M_{\odot}$ and mass fraction $f_{\rm PBH}=10^{-1}(10^{-3})$, the brightness temperature deviation $\Delta \delta T_{b}$ reaches $\sim 18~(26)~\rm mK$ at redshift $z\sim 90$ ($\nu \sim 16~\rm MHz$), and the gradient of the brightness temperature $d\delta T_{b}/d\nu$ reaches $ \sim 0.8~(0.5)~\rm mK~MHz^{-1}$ at frequency $\nu\sim 28~\rm MHz$ ($z\sim 50$).
• For larger PBHs with higher mass fraction, the brightness temperature deviation is larger in the redshift range $z\sim 30-300$ ($\nu\sim 5-46~\rm MHz$), and the gradient is lower at the frequency range $\nu \sim 20-60~\rm MHz$ ($z\sim 23-70$).