The impact of Lyman-α emission line heating and cooling on the cosmic dawn 21-cm signal
Abstract
Allowing for enhanced Lyα photon line emission from Population III dominated stellar systems in the first forming galaxies, we show the 21-cm cosmic dawn signal at 10<z<30 may substantially differ from standard scenarios. Energy transfer by Lyα photons emerging from galaxies may heat intergalactic gas if HII regions within galaxies are recombination bound, or cool the gas faster than by adiabatic expansion if reddened by winds internal to the haloes. In some cases, differential 21-cm antenna temperatures near -500 mK may be achieved at 15<z<25, similar to the signature detected by the EDGES 21-cm cosmic dawn experiment.
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