The Biermann Battery in Cosmological MHD Simulations of Population III Star Formation

TL;DR

This study presents the first 3D adaptive mesh refinement MHD simulations of Population III star formation including the Biermann Battery effect, showing that magnetic fields are generated but remain too weak to influence star formation dynamics.

Contribution

It introduces the first self-consistent 3D MHD simulations of Population III star formation with Biermann Battery effect, revealing the magnetic field generation process and its limited dynamical impact.

Findings

Magnetic fields reach ~10^-9 G in primordial halos.

Fields are generated early and grow via compression and shear.

Magnetic fields are too weak to affect star formation dynamics.

Abstract

We report the results of the first self-consistent three-dimensional adaptive mesh refinement magnetohydrodynamical simulations of Population III star formation including the Biermann Battery effect. We find that the Population III stars formed including this effect are both qualitatively and quantitatively similar to those from hydrodynamics-only (non-MHD) cosmological simulations. We observe peak magnetic fields of ~10^-9 G in the center of our star-forming halo at z ~ 17.55. The magnetic fields created by the Biermann Battery effect are predominantly formed early in the evolution of the primordial halo at low density and large spatial scales, and then grow through compression and by shear flows. The fields seen in this calculation are never large enough to be dynamically important (with beta >= 10^{15} at all times), and should be considered the minimum possible fields in existence during Population III star formation, and may be seed fields for the stellar dynamo or the magnetorotational instability at higher densities and smaller spatial scales.