Magnetic Field Structure of the Large Magellanic Cloud from Faraday Rotation Measures of Diffuse Polarized Emission

TL;DR

This study maps the magnetic field of the Large Magellanic Cloud using polarization data, revealing a large-scale quadrupolar structure and smaller filaments influenced by tidal interactions with the Small Magellanic Cloud.

Contribution

First detailed polarization-based magnetic field mapping of the LMC, demonstrating a quadrupolar large-scale field and identifying smaller filaments linked to galactic interactions.

Findings

Large-scale magnetic field is quadrupolar, consistent with dynamo theory.

Diffuse polarized emission indicates a coherent magnetic field in the LMC's halo.

Filaments are associated with H I arms and may be shaped by tidal interactions.

Abstract

We present a study of the magnetic field of the Large Magellanic Cloud (LMC), carried out using diffuse polarized synchrotron emission data at 1.4 GHz acquired at the Parkes Radio Telescope and the Australia Telescope Compact Array. The observed diffuse polarized emission is likely to originate above the LMC disk on the near side of the galaxy. Consistent negative rotation measures (RMs) derived from the diffuse emission indicate that the line-of-sight magnetic field in the LMC's near-side halo is directed coherently away from us. In combination with RMs of extragalactic sources that lie behind the galaxy, we show that the LMC's large scale magnetic field is likely to be of quadrupolar geometry, consistent with the prediction of dynamo theory. On smaller scales, we identify two brightly polarized filaments southeast of the LMC, associated with neutral hydrogen arms. The filaments' magnetic field potentially aligns with the direction towards the Small Magellanic Cloud. We suggest that tidal interactions between the Small and the Large Magellanic Clouds in the past 10^9 years is likely to have shaped the magnetic field in these filaments.