由局部磁离子ISM引起的河外源的极化阴影
Polarization shadows of extragalactic sources by the local magneto-ionic ISM
摘要：
本文报道了NRAO VLA巡天（NVSS）中河外源在星际介质局部结构下的去极化现象。天空中偏振源的密度下降了2 - 4倍，在区域的角度尺度约。10度，意味着每个源平均去极化高达40%。其中一些偏振阴影与HII区域有关，但有三个与去偏振弥漫的银河系辐射区域有关。极化阴影的深度和H-α强度之间不存在相关性，这表明某些阴影与磁场中的结构有关。至少一些偏振阴影是由NVSS中的部分带宽去偏振引起的。或者，一些可能是由旋转测量中具有小尺度（< 1 arcsec）变化的区域引起的。
英文摘要：
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 approx. 10 degrees, implying up to 40% depolarization on average per source. Some of these polarization shadows are associated with HII regions, but three are associated with regions of depolarized diffuse Galactic emission. The absence of a correlation between the depth of polarization shadows and H-alpha intensity suggests that some shadows are related to structure in the magnetic field. At least some polarization shadows are caused by partial bandwidth depolarization in the NVSS. Alternatively, some may be caused by regions with small scale (< 1 arcsec) variations in rotation measure.
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