Environment matters: stronger magnetic fields in satellite galaxies

TL;DR

This study reveals that satellite galaxies exhibit significantly stronger magnetic fields than isolated dwarfs of similar mass, emphasizing the environment's role in magnetic field amplification and its implications for astronomical observations.

Contribution

It provides the first high-resolution cosmological simulation analysis showing environment-driven magnetic field amplification in satellite galaxies.

Findings

Satellite galaxies have 2-8 times stronger magnetic fields than isolated dwarfs.

Magnetic field amplification occurs mainly after the first close encounter with the host galaxy.

The amplification factors can reach up to approximately 15, with diverse mechanisms involved.

Abstract

Magnetic fields are ubiquitous in the universe and an important component of the interstellar medium. It is crucial to accurately model and understand their properties in different environments and across all mass ranges of galaxies to interpret observables related to magnetic fields correctly. However, the assessment of the role of magnetic fields in galaxy evolution is often hampered by limited numerical resolution in cosmological simulations, in particular for satellite galaxies. To this end, we study the magnetic fields in high-resolution cosmological zoom simulations of disk galaxies (with $M_{200}\approx10^{10}$ to $10^{13}\,\mathrm{M}_\odot$) and their satellites within the Auriga galaxy formation model including cosmic rays. We find significantly higher magnetic field strengths in satellite galaxies compared to isolated dwarfs with a similar mass or star-formation rate, in particular after they had their first close encounter with their host galaxy. These are stronger on average by factors of 2-8 when compared at the same total mass, with a large scatter, ranging up to factors of $\sim$15. While this result is ubiquitous and independent of resolution in the satellites that are past their first infall, there seems to be a wide range of amplification mechanisms acting together. Our result highlights the importance of considering the environment of dwarf galaxies when interpreting their magnetic field properties as well as related observables such as their gamma-ray and radio emission, the latter being particularly relevant for future observations such as with the SKA observatory.