The role of soft photon injection and heating in 21 cm cosmology

Abstract

The ARCADE radio excess and EDGES measurement remain puzzling. A link between the two has been previously considered, however, in this work we highlight an important related effect that was not analyzed in detail before. By performing cosmological thermalization calculations with soft photon injection using {\tt CosmoTherm}, we show that for the 21 cm signal generation the interplay between enhanced radio spectral distortions and the associated heating can hide a significant radio excess before the reionzation era. We illustrate this effect for a simple power-law soft photon source in decaying particle scenarios. Even if simplistic, the uncovered link between CMB spectral distortions and 21 cm cosmology should apply to a much broader range of scenarios. This could significantly affect the constraints derived from existing and future 21 cm observations on the evolution of the ambient radio background. In particular, scenarios that would be ruled out by existing data without heating could become viable solutions once the heating is accounted for in the modelling. Our calculations furthermore highlight the importance of global 21 cm observations reaching into the dark ages, where various scenarios can potentially be distinguished.

Comments welcome

References in corpus (15)

• CMB Constraints on WIMP Annihilation: Energy Absorption During the Recombination Epoch
• The Global 21 Centimeter Background from High Redshifts
• Signature of Excess Radio Background in the 21-cm Global Signal and Power Spectrum
• Beyond y and μ: the shape of the CMB spectral distortions in the intermediate epoch, 1.5x10^4 < z < 2x10^5
• The contribution of the Unresolved Extragalactic Radio Sources to the Brightness Temperature of the sky
• Creation of the CMB spectrum: precise analytic solutions for the blackbody photosphere
• Thermalization of large energy release in the early Universe
• Radio background and IGM heating due to Pop III supernovae explosions
• TRIS II: search for CMB spectral distortions at 0.60, 0.82 and 2.5 GHz
• CMB anisotropy and BBN constraints on pre-recombination decay of dark matter to visible particles
• Improved calculations of electron-ion Bremsstrahlung Gaunt factors for astrophysical applications
• Can accreting primordial black holes explain the excess radio background?
• Cosmic Radio Background from Primordial Black Holes at Cosmic Dawn
• The COSmic Monopole Observer (COSMO)
• BISOU: a balloon project to measure the CMB spectral distortions

Cited by in corpus (3)

• Constraints on the state of the IGM at $z\sim 8-10$ using redshifted 21-cm observations with LOFAR
• Predictions of the 21cm global signal in the JWST and ALMA era
• L-BASS: a project to produce an absolutely calibrated 1.4 GHz sky map, I -- Scientific rationale and system overview