Reionization during the dark ages from a cosmic axion background
- Gran Sasso Science Institute, Viale Francesco Crispi 7, 67100 L'Aquila (Italy)
- Institute for Particle Physics Phenomenology, Department of Physics, Durham University, South Road, Durham DH1 3LE (United Kingdom)
- Dipartimento Interateneo di Fisica ''Michelangelo Merlin'', Via Amendola 173, 70126 Bari (Italy)
- Dipartimento di Matematica e Fisica ''Ennio De Giorgi'', Via Arnesano, 73100 Lecce (Italy)
Recently it has been pointed out that a cosmic background of relativistic axion-like particles (ALPs) would be produced by the primordial decays of heavy fields in the post-inflation epoch, contributing to the extra-radiation content in the Universe today. Primordial magnetic fields would trigger conversions of these ALPs into sub-MeV photons during the dark ages. This photon flux would produce an early reionization of the Universe, leaving a significant imprint on the total optical depth to recombination τ. Using the current measurement of τ and the limit on the extra-radiation content Δ N {sub eff} by the Planck experiment we put a strong bound on the ALP-photon conversions. Namely we obtain upper limits on the product of the photon-ALP coupling constant g {sub a} {sub γ} times the magnetic field strength B down to g {sub a} {sub γ} B ∼> 6 × 10{sup −18} GeV{sup −1} nG for ultralight ALPs.
- OSTI ID:
- 22667582
- Journal Information:
- Journal of Cosmology and Astroparticle Physics, Vol. 2016, Issue 05; Other Information: Country of input: International Atomic Energy Agency (IAEA); ISSN 1475-7516
- Country of Publication:
- United States
- Language:
- English
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