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Using the Global Magneto-Ionic Medium Survey (GMIMS) Low-Band South (LBS) southern sky polarization survey, covering 300 to 480 MHz at 81 arcmin resolution, we reveal the brightest region in the Southern polarized sky at these frequencies. The region, G150-50, covers nearly 20deg$^2$, near (l,b)~(150 deg,-50 deg). Using GMIMS-LBS and complementary data at higher frequencies (~0.6--30 GHz), we apply Faraday tomography and Stokes QU-fitting techniques. We find that the magnetic field associated with G150-50 is both coherent and primarily in the plane of the sky, and indications that the region is associated with Radio Loop II. The Faraday depth spectra across G150-50 are broad and contain a large-scale spatial gradient. We model the magnetic field in the region as an expanding shell, and we can reproduce both the observed Faraday rotation and the synchrotron emission in the GMIMS-LBS band. Using QU-fitting, we find that the Faraday spectra are produced by several Faraday dispersive sources along the line-of-sight. Alternatively, polarization horizon effects that we cannot model are adding complexity to the high-frequency polarized spectra. The magnetic field structure of Loop II dominates a large fraction of the sky, and studies of the large-scale polarized sky will need to account for this object. Studies of G150-50 with high angular resolution could mitigate polarization horizon effects, and clarify the nature of G150-50.
The Global Magneto-Ionic Medium Survey (GMIMS) is a project to map the diffuse polarized emission over the entire sky, Northern and Southern hemispheres, from 300 MHz to 1.8 GHz. With an angular resolution of 30 - 60 arcmin and a frequency resolution
Much data on the Galactic polarized radio emission has been gathered in the last five decades. All-sky surveys have been made, but only in narrow, widely spaced frequency bands, and the data are inadequate for the characterization of Faraday rotation
The Galactic interstellar medium hosts a significant magnetic field, which can be probed through the synchrotron emission produced from its interaction with relativistic electrons. Linearly polarized synchrotron emission is generated throughout the G
Faraday rotation occurs along every line of sight in the Galaxy; Rotation Measure (RM) synthesis allows a three-dimensional representation of the interstellar magnetic field. This study uses data from the Global Magneto-Ionic Medium Survey, a combina
The Southern HII Region Discovery Survey (SHRDS) is a 900 hour Australia Telescope Compact Array 4-10 GHz radio continuum and radio recombination line (RRL) survey of Galactic HII regions and infrared-identified HII region candidates in the southern