The Global Magneto-Ionic Medium Survey (GMIMS): The brightest polarized region in the Southern sky at 75 cm and its implications for Radio Loop II

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 brightest region in Southern polarized these frequencies. The region, G150-50, covers nearly 20deg$^2$, near (l,b)~(150 deg,-50 deg). GMIMS-LBS and complementary data higher frequencies (~0.6--30 GHz), apply Faraday tomography Stokes QU-fitting techniques. We find that magnetic field associated with G150-50 is both coherent primarily plane of sky, indications Radio Loop II. depth spectra across are broad contain a large-scale spatial gradient. model as an expanding shell, can reproduce observed rotation synchrotron emission band. QU-fitting, produced by several dispersive sources along line-of-sight. Alternatively, horizon effects cannot adding complexity high-frequency spectra. structure II dominates large fraction studies will need account for this object. Studies high angular resolution could mitigate effects, clarify nature G150-50.