标题： ALMA望远镜阵列的光谱偏振测量：明亮偏振射电星系的法拉第旋转 显示英文标题

标题： Spectropolarimetry with the Allen Telescope Array: Faraday Rotation toward Bright Polarized Radio Galaxies

摘要： 我们使用阿伦射电望远镜阵列(ATA)对37个明亮的极化射电源进行了观测，以对其法拉第旋转特性进行新颖的分析。每个源在调试阶段进行了观测，使用的频段为2到4个100MHz带宽，频率范围从1到2GHz。这些观测结果展示了ATA对数周期接收器的连续频率覆盖如何应用于法拉第旋转测量(RMs)的研究。我们使用RM合成来表明宽带数据可以找到单个源的多个RM成分。当以大约100rad/m2的RM分辨率进行观测时，大约四分之一的研究源具有高置信度的额外RM成分（亮度高于~40mJy）。这些额外成分贡献了总极化通量的10%-70%。这是首次在一个大型点源样本中识别出多个RM成分。对于我们的观测配置，这些额外的RM成分会使峰值RM的测量值偏移10-15rad/m2；更一般地，峰值RM的确定精度不能超过RM束的大小。将我们的1-2GHz RM谱与VLBA偏振图进行比较显示，这两种技术都可以识别源中的复杂法拉第结构。然而，在较低频率下，RM值和分数极化通常比高频VLBA图中的要小。除了少数例外，本研究的RMs与早期窄带全天空调查的结果一致。本研究还描述了偏振校准程序，并指出轴向ATA观测的线性偏振可以校准到Stokes I的0.2%精度。未来的研究方向包括研究活动星系核(AGNs)中时间依赖的RM结构，并实现准确的广域RM调查，以测试银河系和河外磁场模型。 显示英文摘要

摘要： We have observed 37 bright, polarized radio sources with the Allen Telescope Array (ATA) to present a novel analysis of their Faraday rotation properties. Each source was observed during the commissioning phase with 2 to 4 100-MHz bands at frequencies ranging from 1 to 2 GHz. These observations demonstrate how the continuous frequency coverage of the ATA's log-periodic receiver can be applied to the study of Faraday rotation measures (RMs). We use RM synthesis to show that wide-bandwidth data can find multiple RM components toward a single source. Roughly a quarter of the sources studied have extra RM components with high confidence (brighter than ~40 mJy), when observing with a RM resolution of roughly 100 rad/m2. These extra components contribute 10%-70% of the total polarized flux. This is the first time multiple RM components have been identified in a large sample of point sources. For our observing configuration, these extra RM components bias the measurement of the peak RM by 10-15 rad/m2 ; more generally, the peak RM cannot be determined more precisely than the RM beam size. Comparing our 1-2 GHz RM spectra to VLBA polarimetric maps shows both techniques can identify complicated Faraday structures in the sources. However, the RM values and fractional polarization are generally smaller at lower frequencies than in the higher-frequency VLBA maps. With a few exceptions, the RMs from this work are consistent with that of earlier, narrow-bandwidth, all-sky surveys. This work also describes the polarimetry calibration procedure and that on-axis ATA observations of linear polarization can be calibrated to an accuracy of 0.2% of Stokes I. Future research directions include studying the time-dependent RM structure in Active Galactic Nuclei (AGNs) and enabling accurate, wide-area RM surveys to test models of Galactic and extragalactic magnetic fields.