3D model of magnetic fields evolution in dwarf irregular galaxies

TL;DR

This study models magnetic field evolution in dwarf irregular galaxies, demonstrating that even slow rotation can amplify magnetic fields and that these galaxies can significantly contribute to intergalactic magnetism.

Contribution

It provides a 3D dynamo model tailored to dwarf irregular galaxies, accounting for their unique slow rotation, weak shear, and star formation variability.

Findings

Slow rotation still amplifies magnetic fields in dIrr galaxies.

Rapid rotation with low shear enhances dynamo efficiency.

Galaxies can eject magnetic energy into intergalactic space.

Abstract

Radio observations show that magnetic fields are present in dwarf irregular galaxies (dIrr) and its strength is comparable to that found in spiral galaxies. Slow rotation, weak shear and shallow gravitational potential are the main features of a typical dIrr galaxy. These conditions of the interstellar medium in a dIrr galaxy seem to unfavourable for amplification of the magnetic field through the dynamo process. Cosmic-ray driven dynamo is one of the galactic dynamo model, which has been successfully tested in case of the spiral galaxies. We investigate this dynamo model in the ISM of a dIrr galaxy. We study its efficiency under the influence of slow rotation, weak shear and shallow gravitational potential. Additionally, the exploding supernovae are parametrised by the frequency of star formation and its modulation, to reproduce bursts and quiescent phases. We found that even slow galactic rotation with a low shearing rate amplifies the magnetic field, and that rapid rotation with a low value of the shear enhances the efficiency of the dynamo. Our simulations have shown that a high amount of magnetic energy leaves the simulation box becoming an efficient source of intergalactic magnetic fields.