Comparison of algorithms for determination of rotation measure and Faraday structure I. 1100 - 1400 MHz
X. H. Sun, L. Rudnick, Takuya Akahori, C. S. Anderson, M. R. Bell, J. D. Bray, J. S. Farnes, S. Ideguchi, K. Kumazaki, T. O'Brien, S. P. O'Sullivan, A. M. M. Sc… 展开作者
X. H. Sun, L. Rudnick, Takuya Akahori, C. S. Anderson, M. R. Bell, J. D. Bray, J. S. Farnes, S. Ideguchi, K. Kumazaki, T. O'Brien, S. P. O'Sullivan, A. M. M. Scaife, R. Stepanov, J. Stil, K. Takahashi, R. J. van Weeren, M. Wolleben
(abridged) We run a Faraday structure determination data challenge to benchmark the currently available algorithms including Faraday synthesis (previously called RM synthesis in the literature), wavelet, compressive sampling and $QU$-fitting. The frequency set is similar to POSSUM/GALFACTS with a 300 MHz bandwidth from 1.1 to 1.4 GHz. We define three figures of merit motivated by the underlying science: a) an average RM weighted by polarized intensity, RMwtd, b) the separation $Δϕ$ of two Faraday components and c) the reduced chi-squared. Based on the current test data of signal to noise ratio of about 32, we find that: (1) When only one Faraday thin component is present, most methods perform as expected, with occasional failures where two components are incorrectly found; (2) For two Faraday thin components, QU-fitting routines perform the best, with errors close to the theoretical ones for RMwtd, but with significantly higher errors for $Δϕ$. All other methods including standard Faraday synthesis frequently identify only one component when $Δϕ$ is below or near the width of the Faraday point spread function; (3) No methods, as currently implemented, work well for Faraday thick components due to the narrow bandwidth; (4) There exist combinations of two Faraday components which produce a large range of acceptable fits and hence large uncertainties in the derived single RMs; in these cases, different RMs lead to the same Q, U behavior, so no method can recover a unique input model.
GMIMS-DRAGONS: A Faraday Depth Survey of the Northern Sky Covering 350-1030 MHz
University of British Columbia, Okanagan Campus（不列颠哥伦比亚大学奥卡纳根校区）；Dominion Radio Astrophysical Observatory, Herzberg Research Centre for Astronomy and Astrophysics, National Research Council Canada（加拿大国家研究理事会赫茨伯格天文学与天体物理学研究中心 Dominion 射电天文台）；University of Western Ontario（韦仕敦大学（原西安大略大学））；University of Calgary（卡尔加里大学）；INAF-Istituto di Radioastronomia（意大利国家天体物理研究所射电天文研究所）；University of Waterloo（滑铁卢大学）；Caltech Owen’s Valley Radio Observatory（加州理工学院欧文谷射电天文台）；Chalmers University of Technology, Onsala Space Observatory（查尔姆斯理工大学翁萨拉空间天文台）；University of South Carolina（南卡罗来纳大学）；University of Tasmania（塔斯马尼亚大学）；Radboud University（拉德堡德大学）；INAF – Osservatorio Astrofisico di Arcetri（意大利国家天体物理研究所阿切尔蒂天文台）
Spectropolarimetry with the Giant Metrewave Radio Telescope at 610 MHz: a case study of two Southern Compact Group fields
我们目前610兆赫的光谱偏振图像从巨型米波射电望远镜（GMRT）。我们详细讨论了GMRT的全偏振模式的属性，并提供了仪器的偏振性能的技术表征。我们表明，该望远镜可用于宽视场分光偏振。旋转测量合成的应用导致在法拉第空间中的几十微焦的水平的灵敏度。作为该仪器的能力的演示，我们提出了两个南方契约组-鹤四重奏和USCG S 063的意见。观测结果与其他无线电和红外数据进行了比较，以限制组成员的光谱指数，偏振分数和法拉第深度。无线电连续辐射是从天鹤座四重奏中的所有四个星系和USCG S 063中的一个星系中检测到的。线性偏振是从NGC 7552的环核星暴环，NGC 7582的活动核和三个扩展的射电星系在天鹤座四重奏场的背景中检测到的。这些背景源允许分类FR-I和X形射电星系。没有证据表明，在任何星系群与群内介质的相互作用。
Faraday Tomography with the SKA: A New Era of Cosmic Magnetism Studies
Universidad de Santiago de Chile（圣地亚哥智利大学）；University of Manchester（曼彻斯特大学）；Alan Turing Institute（艾伦·图灵研究所）；The University of Calgary（卡尔加里大学）；University of Cape Town（开普敦大学）；National Research Council Canada（加拿大国家研究委员会）；University of Tasmania（塔斯马尼亚大学）
Low-frequency Faraday rotation measures towards pulsars using LOFAR: probing the 3-D Galactic halo magnetic field
我们确定了法拉第旋转措施（RM）对137个恒星在北方天空中，使用低频阵列（LOFAR）在110-190 MHz的观测。这是迄今为止最大的低频RM目录，由于数据的低频和宽带宽，在RM合成方法的帮助下，平均将现有RM测量的精度提高了20倍。我们首次报告了25个卫星的RM。对RM进行了电离层法拉第旋转校正，以将我们的星表精度提高到约0.1 rad m $^{\rm -2}$。电离层RM校正是目前测量不确定度的最大贡献者。此外，我们发现，法拉第色散函数对pixels是非常法拉第薄-大多数小于0.001 rad m $^{\rm -2}$。我们使用这些新的精确RM测量（结合现有的RM，分散措施和距离估计），以估计星系晕磁场的尺度高度：2.0 $\pm$ 0.3千秒差距的银河系象限I和II以上和以下的银河系平面（我们也评估这些地区的尺度高度分别）。总的来说，我们最初的低频目录提供了有关银河系磁场三维结构的有价值的信息。
Correcting Ionospheric Faraday Rotation for the VLA and MeerKAT
National Radio Astronomy Observatory（国家射电天文台）；South African Radio Astronomy Observatory（南非射电天文台）；Rhodes University（罗德斯大学）；Dominion Radio Astrophysical Observatory（加拿大国家射电天文台）
