http://arxiv.org/abs/2108.01916
Baryonic gas falling onto a primordial black hole (PBH) emits photons via the free-free process. These photons can contribute the diffuse free-free background radiation in the frequency range of the cosmic microwave background radiation (CMB). We show that the intensity of the free-free background radiation from PBHs depends on the mass and abundance of PBHs. In particular, considering the growth of a dark matter (DM) halo around a PBH by non-PBH DM particles strongly enhances the free-free background radiation. This enhancement allows us to obtain the tight constraint on the PBH abundance with mass $M_{\rm PBH} > 10 M_\odot$. Comparison with the CMB free-free foreground component in high galactic latitude measured by Planck, our constraint on the PBH abundance fraction to the total DM, $f_{\rm{PBH}}$, is $f_{\rm{PBH}}<1.2\times10^{-5}(M_{\rm{PBH}}/100M_{\odot})^{-2.3}$. We also discuss the impact of the free-free radiation from PBHs on the measurement of 21-cm background radiation from high redshifts, including the EDGES anomaly.
H. Tashiro, K. Abe and T. Minoda
Thu, 5 Aug 21
27/57
Comments: 6 pages, 3 figures
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