Primordial magnetic field constraints from the end of reionization

• Published in: Monthly notices of the Royal Astronomical Society. Letters Vol. 418; no. 1; pp. L143 - L147
• Main Authors: Schleicher, Dominik R. G., Miniati, Francesco
• Format: Journal Article
• Language: English
• Published: Oxford, UK Blackwell Publishing Ltd 21.11.2011
• Subjects: cosmology: theory; Cut-off; dark ages; dark ages, reionization, first stars; first stars; Galaxies; galaxies: high-redshift; galaxies: magnetic fields; intergalactic medium; Ionization; Luminosity; Magnetic fields; Mathematical models; reionization; Strength
• ISSN: 1745-3925; 1745-3933
• DOI: 10.1111/j.1745-3933.2011.01162.x

ABSTRACT Primordial magnetic fields generated in the early Universe are subject of considerable investigation, and observational limits on their strength are required to constrain the theory. Due to their impact on the reionization process, the strength of primordial fields can be limited using the latest data on reionization and the observed UV luminosity function of high‐redshift galaxies. Given the steep faint‐end slope of the luminosity function, faint galaxies contribute substantial ionizing photons, and the low‐luminosity cut‐off has an impact on the total budget thereof. Magnetic pressure from primordial fields affects such cut‐off by preventing collapse in haloes with mass below 1010 M, with B0 the comoving field strength. In this Letter, the implications of these effects are consistently incorporated in a simplified model for reionization, and the uncertainties due to the cosmological parameters, the reionization parameters and the observed UV luminosity function are addressed. We show that the observed ionization degree at z∼ 7 leads to the strongest upper limit of B0≲ 2–3 nG. Stronger limits could follow from measurements of high ionization degree at z > 7.