Complex Faraday depth structure of Active Galactic Nuclei as revealed by broadband radio polarimetry
S. P. O'Sullivan, S. Brown, T. Robishaw, D. H. F. M. Schnitzeler, N. M. McClure-Griffiths, I. J. Feain, A. R. Taylor, B. M. Gaensler, T. L. Landecker, L. Harvey-Smith, E. Carretti
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Accepted for publication in MNRAS. 19 pages, 15 figures, 4 tables
We present a detailed study of the Faraday depth structure of four bright (> 1 Jy), strongly polarized, unresolved, radio-loud quasars. The Australia Telescope Compact Array (ATCA) was used to observe these sources with 2 GHz of instantaneous bandwidth from 1.1 to 3.1 GHz. This allowed us to spectrally resolve the polarization structure of spatially unresolved radio sources, and by fitting various Faraday rotation models to the data, we conclusively demonstrate that two of the sources cannot be described by a simple rotation measure (RM) component modified by depolarization from a foreground Faraday screen. Our results have important implications for using background extragalactic radio sources as probes of the Galactic and intergalactic magneto-ionic media as we show how RM estimations from narrow-bandwidth observations can give erroneous results in the presence of multiple interfering Faraday components. We postulate that the additional RM components arise from polarized structure in the compact inner regions of the radio source itself and not from polarized emission from Galactic or intergalactic foreground regions. We further suggest that this may contribute significantly to any RM time-variability seen in RM studies on these angular scales. Follow-up, high-sensitivity VLBI observations of these sources will directly test our predictions.
Wide field polarimetry around the Perseus cluster at 350 MHz
本文研究了迷人的扩散偏振结构在350 MHz，以前曾暂时归因于英仙座集群，更具体地说，试图找出是否结构位于（或附近）的英仙座集群，或在银河系。在全偏振状态下观测到了一个宽视场的八点韦斯特博克综合射电望远镜对英仙座星系团周围区域的拼接。频率范围为324至378 MHz，极化图的分辨率为2“x3”。使用法拉第旋转测量合成来处理图以对抗带宽去极化。RM立方体以3 rad m^{-2}为步长覆盖了-384到+381 rad m^{-2}的法拉第深度。在法拉第深度为-50到+100 rad m^{-2}之间，整个磁场都有辐射。检测到所有先前观察到的结构。然而，没有发现令人信服的证据支持这些结构与英仙座星团或英仙座-双鱼座超级星团中的大尺度结构地层气流的关联。相反，其中一个结构显然与1.41 GHz的银河系去极化通道有关。另一个偏振强度的大结构，以及法拉第深度为+30 rad m^{-2}的法拉第深度，与WHAM H-α图中运动距离为0.5 \pm 0.5 kpc的暗天体相吻合。所有朝向英仙座星系团的350 MHz的扩散偏振辐射很可能位于距离太阳1 kpc的范围内。发射偏振辐射的层小于40 pc/B||厚
Magnetic properties of the Abell 3391-3395 system revealed using wide-field MeerKAT polarimetry
Hamburger Sternwarte, University of Hamburg（汉堡天文台，汉堡大学）；GEPI, Observatoire de Paris, Université PSL, CNRS（巴黎天文台GEPI，巴黎文理研究大学，法国国家科学研究中心）；Department of Physics & Electronics, Rhodes University（罗德斯大学物理与电子系）；Departamento de Física de la Tierra y Astrofísica & IPARCOS-UCM, Universidad Complutense de Madrid（马德里康普顿斯大学地球与天体物理学系及IPARCOS-UCM）
Faraday Complexity and Depolarisation in a High-Rotation-Measure Radio Galaxy from the Spectra and Polarisation In Cutouts of Extragalactic Sources (SPICE-RACS) DR2
Indian Institute of Engineering Science and Technology（印度工程科学与技术学院）；Banwarilal Bhalotia College（班瓦里拉尔·巴洛蒂亚学院）
