Magnetic fields during high redshift structure formation

TL;DR

This study uses high-resolution cosmological simulations to investigate how turbulence in primordial halos amplifies magnetic fields during high-redshift structure formation, revealing significant magnetic field strengths relevant for early star formation.

Contribution

The paper introduces a turbulence subgrid-scale model in cosmological simulations to quantify unresolved turbulence and its role in magnetic field amplification during primordial halo formation.

Findings

Turbulence suppresses low-mass clump formation.

Magnetic fields can be amplified to ~10^{-5} G.

Efficient small-scale dynamo operation during early star formation.

Abstract

We explore the amplification of magnetic fields in the high-redshift Universe. For this purpose, we perform high-resolution cosmological simulations following the formation of primordial halos with \sim10^7 M_solar, revealing the presence of turbulent structures and complex morphologies at resolutions of at least 32 cells per Jeans length. Employing a turbulence subgrid-scale model, we quantify the amount of unresolved turbulence and show that the resulting turbulent viscosity has a significant impact on the gas morphology, suppressing the formation of low-mass clumps. We further demonstrate that such turbulence implies the efficient amplification of magnetic fields via the small-scale dynamo. We discuss the properties of the dynamo in the kinematic and non-linear regime, and explore the resulting magnetic field amplification during primordial star formation. We show that field strengths of \sim10^{-5} G can be expected at number densities of \sim5 cm^{-3}.