Simulating magnetic fields in the Antennae galaxies

TL;DR

This paper presents high-resolution simulations of the Antennae galaxies that include magnetic fields, star formation, and feedback, demonstrating how galaxy mergers amplify magnetic fields to observed levels and reproduce observed radio features.

Contribution

It introduces a self-consistent simulation approach that models magnetic field amplification during galaxy mergers, matching observed magnetic and radio properties.

Findings

Magnetic fields are amplified to ~10 μG regardless of initial seed strength.

Simulated radio and polarization maps match observed structures.

Galaxy mergers efficiently drive cosmic magnetic field evolution.

Abstract

We present self-consistent high-resolution simulations of NGC4038/4039 (the "Antennae galaxies") including star formation, supernova feedback and magnetic fields performed with the N-body/SPH code Gadget, in which magnetohydrodynamics are followed with the SPH method. We vary the initial magnetic field in the progenitor disks from 1 nG to 100 muG. At the time of the best match with the central region of the Antennae system the magnetic field has been amplified by compression and shear flows to an equilibrium field of approximately 10 muG, independent of the initial seed field. These simulations are a proof of the principle that galaxy mergers are efficient drivers for the cosmic evolution of magnetic fields. We present a detailed analysis of the magnetic field structure in the central overlap region. Simulated radio and polarization maps are in good morphological and quantitative agreement with the observations. In particular, the two cores with the highest synchrotron intensity and ridges of regular magnetic fields between the cores and at the root of the southern tidal arm develop naturally in our simulations. This indicates that the simulations are capable of realistically following the evolution of the magnetic fields in a highly non-linear environment. We also discuss the relevance of the amplification effect for present day magnetic fields in the context of hierarchical structure formation.