The role of magnetic fields in ram pressure stripping of satellite galaxies in the circumgalactic medium around massive galaxies

ABSTRACT The presence of magnetic fields in galaxies and their haloes could have important consequences for satellite galaxies moving through the magnetized circumgalactic medium (CGM) of their host. We therefore study the effect of magnetic fields on ram pressure stripping of satellites in the CGM of massive galaxies. We use cosmological ‘zoom-in’ simulations of three massive galaxy haloes ($M_{\rm {200c}} = 10^{12.5-13}$ M$_\odot$), each simulated with and without magnetic fields. Across our full sample of satellite galaxies (11 with magnetic fields and 10 without), we find that the fraction of gas retained after infall through the CGM shows no population-wide impact of magnetic fields. However, for the most massive satellites, we find that twice as much gas is stripped without magnetic fields. The evolution of a galaxy’s stripped tail is also strongly affected. Magnetic fields reduce turbulent mixing, inhibiting the dispersion of metals into the host CGM. This suppressed mixing greatly reduces condensation from the CGM onto the stripped tail. By studying the magnetic field structure, we find evidence of magnetic draping and attribute differences in the stripping rate to the draping layer. Differences in CGM condensation are attributed to magnetic field lines aligned with the tail suppressing turbulent mixing. We simulate one halo with enhanced resolution in the CGM and show these results are converged with resolution, though the structure of the cool gas in the tail is not. Our results show that magnetic fields can play an important role in ram pressure stripping in galaxy haloes and should be included in simulations of galaxy formation.