MAGNETIC FIELD STRUCTURE OF THE LARGE MAGELLANIC CLOUD FROM FARADAY ROTATION MEASURES OF DIFFUSE POLARIZED EMISSION

Abstract

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