Constraints on Primordial Magnetic Fields from the Lyman-{\alpha} forest

TL;DR

This study uses cosmological hydrodynamic simulations of the Lyman-alpha forest to place new constraints on primordial magnetic fields, finding upper limits around 0.3 nG and suggesting a possible hint of magnetic field effects.

Contribution

First to utilize full hydrodynamic simulations of the Lyman-alpha forest to constrain primordial magnetic fields, providing the tightest bounds to date.

Findings

Hint of extra power consistent with B~0.2 nG

Conservative analysis yields B < 0.30 nG

Sets new lower limit on k_peak > 30 Mpc^{-1}

Abstract

We present the first constraints on primordial magnetic fields from the Lyman-$\alpha$ forest using full cosmological hydrodynamic simulations. At the scales and redshifts probed by the data, the flux power spectrum is extremely sensitive to the extra power induced by primordial magnetic fields in the linear matter power spectrum, at a scale that we parametrize with $k_{\rm peak}$. We rely on a set of more than a quarter million flux models obtained by varying thermal, reionization histories and cosmological parameters. We find a hint of extra power that is well fitted by the PMF model with $B\sim 0.2$ nG, corresponding to $k_{\rm peak}\sim 20$ Mpc$^{-1}$. However, when applying very conservative assumptions on the modelling of the noise, we obtain a 3$\sigma$ C.L. lower limit $k_{\rm peak}> 30$ Mpc$^{-1}$ which translates into the tightest bounds on the strength of primordial intergalactic magnetic fields: $B < 0.30$ nG (for fixed, nearly scale-invariant $n_{\rm B}=-2.9$).