The Ties that Bind? Galactic Magnetic Fields and Ram Pressure Stripping

TL;DR

This study uses magnetohydrodynamic simulations to explore how galactic magnetic fields influence ram pressure stripping in cluster galaxies, revealing effects on gas dynamics, tail structure, and potential ICM magnetization.

Contribution

First MHD simulations of ram pressure stripping including galactic magnetic fields, showing their impact on gas velocities, tail morphology, and magnetic energy growth.

Findings

Magnetic fields cause larger, more unmixed tails.

Magnetic fields in the disk slow near-disk gas velocities.

Magnetic energy in tails grows with length, surviving over 100 kpc.

Abstract

One process affecting gas-rich cluster galaxies is ram pressure stripping, i.e. the removal of galactic gas through direct interaction with the intracluster medium. Galactic magnetic fields may have an important impact on the stripping rate and tail structure. We run the first magnetohydrodynamic simulations of ram pressure stripping that include a galactic magnetic field, using 159 pc resolution throughout our entire domain in order to resolve mixing throughout the tail. We find very little difference in the total amount of gas removed from the unmagnetized and magnetized galaxies, although a magnetic field with a radial component will initially accelerate stripped gas more quickly. In general, we find that magnetic fields in the disk lead to slower velocities in the stripped gas near the disk and faster velocities farther from the disk. We also find that magnetic fields in the galactic gas lead to larger unmixed structures in the tail. Finally, we discuss whether ram pressure stripped tails can magnetize the ICM. We find that the total magnetic energy density grows as the tail lengthens, likely through turbulence. There are microGauss-strength fields in the tail in all of our MHD runs, which survive to at least 100 kpc from the disk (the edge of our simulated region), indicating that the area-filling factor of magnetized tails in a cluster could be large.