Environment matters: stronger magnetic fields in satellite galaxies

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 $M_{200}\approx 10^{10}$ 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.

Published in MNRAS, 2025, Vol. 540, Issue 4, pp. 3431-3440. Updated author manuscript with minor clarifications to the abstract, additional analysis in Section 3, and two new figures in new Appendices B and C (11 pages, 7 figures)