On the origin of cosmological magnetic fields.
The origin of cosmological magnetic fields is a major open question in cosmology. Recent high energy gamma ray observations suggest that a substantial fraction of the intergalactic space may be magnetized. Numerous mechanisms for generating magnetic fields at cosmological scales have been proposed, operating mainly in the primordial Universe. However post-recombination mechanisms based on well established physics exist too. After a brief review of cosmological magnetogenesis scenarios, I will focus on a particular model of astrophysical nature: During the so-called 'Cosmic Dawn', the first luminous sources formed in the Universe, and photoionized the neutral intergalactic medium surrounding them. I will show where, under which conditions and up to which strengths, this process has generated magnetic fields on intergalactic scales, thus contributing to the magnetization of the Universe before, and alongside the first stages of cosmological structure formation.