Effects of simulated cosmological magnetic fields on the galaxy population

TL;DR

This study uses cosmological simulations to show that primordial magnetic fields above a certain strength suppress galaxy formation and alter galaxy properties, providing a new way to constrain early-universe magnetic fields.

Contribution

It demonstrates how varying primordial magnetic seed fields influence galaxy evolution, offering novel constraints on their initial strength through simulation results.

Findings

Magnetic fields above ~10^{-9} G suppress star formation.

Stronger seed fields lead to fewer and less massive galaxies.

Magnetic effects are detectable across all redshifts.

Abstract

We investigate the effects of varying the intensity of the primordial magnetic seed field on the global properties of the galaxy population in ideal magnetohydrodynamic cosmological simulations performed with the moving-mesh code AREPO. We vary the seed field in our calculations in a range of values still compatible with the current cosmological upper limits. We show that above a critical intensity of $\simeq 10^{-9}\,{\rm G}$, the additional pressure arising from the field strongly affects the evolution of gaseous structures, leading to a suppression of the cosmic star formation history, \rev{which is stronger for larger seed fields. This directly reflects into a lower total galaxy count above a fixed stellar mass threshold at all redshifts, and} a lower galaxy number density at fixed stellar mass and a less massive stellar component at fixed virial mass at all mass scales. These signatures may be used, in addition to the existing methods, to derive tighter constraints on primordial magnetic seed field intensities.