The magnetic environment of the Orion-Eridanus superbubble as revealed by Planck

Abstract

Using the 353-GHz polarization observations by the Planck satellite we characterize the magnetic field in the Orion-Eridanus superbubble, a nearby expanding structure that spans more than 1600 square degrees in the sky. We identify a region of both low dispersion of polarization orientations and high polarization fraction associated with the outer wall of the superbubble identified in the most recent models of the large-scale shape of the region. We use the Davis-Chandrasekhar-Fermi method to derive plane-of-the-sky magnetic field strengths of tens of μG toward the southern edge of the bubble. The comparison of these values with existing Zeeman splitting observations of HI in emission suggests that the large-scale magnetic field in the region was primarily shaped by the expanding superbubble.