Antisymmetry in the Faraday Rotation Sky Caused by a Nearby Magnetized Bubble

Abstract

Rotation measures of pulsars and extragalactic point sources have been known to reveal large-scale antisymmetries in the Faraday rotation sky with respect to the Galactic plane and halo that have been interpreted as signatures of the mean magnetic field in the Galactic halo. We describe Faraday rotation measurements of the diffuse Galactic polarized radio emission over a large region in the northern Galactic hemisphere. Through application of Rotation Measure Synthesis we achieve sensitive Faraday rotation maps with high angular resolution, capable of revealing fine-scale structures of about 1 deg in the Faraday rotation sky. Our analysis suggests that the observed antisymmetry in the Faraday rotation sky at b > 0 deg is dominated by the magnetic field around a local HI bubble at a distance of approx. 100 pc, and not by the magnetic field of the Galactic halo. We derive physical properties of the magnetic field of this shell, which we find to be 20 - 34 uG strong. It is clear that the diffuse polarized radio emission contains important information about the local magneto-ionic medium, which cannot yet be derived from Faraday rotation measures of extragalactic sources or pulsars alone.

Published in Astrophysical Journal Letters 724 (2010) L48-L52

References in corpus (2)

• Radio observational constraints on Galactic 3D-emission models
• The Vertical Structure of Warm Ionised Gas in the Milky Way

Cited by in corpus (20)

• Planck intermediate results. XIX. An overview of the polarized thermal emission from Galactic dust
• Magnetic Fields in the Milky Way
• Faraday tomography of the local interstellar medium with LOFAR: Galactic foregrounds towards IC342
• Comparison of algorithms for determination of rotation measure and Faraday structure I. 1100 - 1400 MHz
• Constraints from Faraday rotation on the magnetic field structure in the Galactic halo
• The Galactic Magneto-Ionic Medium Survey: Moments of the Faraday Spectra
• Practical Modeling of Large-Scale Galactic Magnetic Fields: Status and Prospects
• The Galactic Magnetic Field and Ultrahigh-Energy Cosmic Ray Deflections
• Properties of the Magneto-ionic Medium in the Halo of M51 revealed by Wide-band Polarimetry
• The Global Magneto-Ionic Medium Survey: Polarimetry of the Southern Sky from 300 to 480 MHz
• The POlarised GLEAM Survey (POGS) II: Results from an All-Sky Rotation Measure Synthesis Survey at Long Wavelengths
• Through thick or thin: Multiple components of the magneto-ionic medium towards the nearby $\mathrm{H}\mathrm{II}$ region Sharpless 2-27 revealed by Faraday tomography
• The Global Magneto-Ionic Medium Survey: A Faraday Depth Survey of the Northern Sky Covering 1280-1750 MHz
• The Fan Region at 1.5 GHz. I: Polarized synchrotron emission extending beyond the Perseus Arm
• The Complex Large-scale Magnetic Fields in the First Galactic Quadrant as Revealed by the Faraday Depth Profile Disparity
• The coherent magnetic field of the Milky Way halo, Local Bubble and Fan Region
• Polarized Synchrotron Foreground Assessment for CMB Experiments
• The Huge Magnetic Toroids in the Milky Way Halo
• A three-dimensional model for the reversal in the local large-scale interstellar magnetic field
• TRIShUL: Technique for Reconstructing magnetic Interstellar Structure Using starLight polarization