Can accreting primordial black holes explain the excess radio background?

Abstract

The excess radio background seen at $\simeq 0.1-10\mathrm{GHz}$ has stimulated much scientific debate in the past years. Recently, it was pointed out that the soft photon emission from accreting primordial black holes may be able to explain this signal. We show that the expected ultraviolet photon emission from these accreting black holes would ionize the universe completely at $z>6$ and thus wash out the 21 cm absorption signature at $z\simeq$ 20 as well as be in tension with existing cosmic microwave background anisotropy and average spectral distortion limits. We discuss possible augmentations of the model; however, it seems that an explanation of radio excess by accreting primordial black holes is not well-justified.

Accepted version

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Cited by in corpus (10)

• The CosmoVerse White Paper: Addressing observational tensions in cosmology with systematics and fundamental physics
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• The role of soft photon injection and heating in 21 cm cosmology
• Exploiting synergies between JWST and cosmic 21-cm observations to uncover star formation in the early Universe
• Cosmic Radio Background from Primordial Black Holes at Cosmic Dawn
• A closer look at dark photon explanations of the excess radio background
• Cosmic mysteries and the hydrogen 21-cm line: bridging the gap with lunar observations
• Relic neutrino decay solution to the excess radio background
• Impact of primordial black holes on the formation of the first stars and galaxies
• Constraining broad photon spectrum injections from exotic and astrophysical sources