Polarization Shadows of Extragalactic Sources by the Local Magneto-ionic Ism

We report depolarization of extragalactic sources in the NRAO VLA Sky Survey (NVSS) by local structures in the interstellar medium. The sky density of polarized sources drops by a factor 2 – 4 in regions with angular scales ∼ 10 • , implying up to 40% depolarization on average per source. Some of these polarization shadows are associated with H ii regions… CONTINUE READING