论文标题
FARADAY断层扫描的迭代重建算法
An Iterative Reconstruction Algorithm for Faraday Tomography
论文作者
论文摘要
Faraday层析成像通过观察其磁节介质,提供了有关磁化天文对象的重要信息,例如类星体,星系或星系簇。观察到的线性极化光谱是反傅立叶变换以获得法拉第分散函数(FDF)的,为我们提供了沿视线的磁离子介质的层析成分分布。但是,由于仪器的波长有限,这种转换会导致FDF的重建差。当前的Faraday层析成像技术无法可靠地解决上述反问题,这显着困扰着宇宙磁性研究。我们提出了一种受信号修复区域的启发的新算法,称为Faraday层析成像(CRAFT)的约束和恢复迭代算法。这种与模型无关的算法在计算上是便宜的,仅需要弱的物理动机假设才能产生高保真性FDF重建。我们展示了银河系的现实合成模型FDF的应用,在该模型中,工艺表现出比其他流行的独立于模型无关的技术更大的潜力。对于更简单的FDF,也证明了观察频率覆盖对各种技术重建性能的依赖性。通过捕获源中FDF振幅的复杂多尺度特征,即使超过模型依赖性技术(即QU拟合),Craft也会提高改进。所提出的方法对于未来的宇宙磁性研究至关重要,尤其是从平方公里阵列及其前体的宽带极化数据中。我们将工艺代码公开可用。
Faraday tomography offers crucial information on the magnetized astronomical objects, such as quasars, galaxies, or galaxy clusters, by observing its magnetoionic media. The observed linear polarization spectrum is inverse Fourier transformed to obtain the Faraday dispersion function (FDF), providing us a tomographic distribution of the magnetoionic media along the line of sight. However, this transform gives a poor reconstruction of the FDF because of the instrument's limited wavelength coverage. The current Faraday tomography techniques' inability to reliably solve the above inverse problem has noticeably plagued cosmic magnetism studies. We propose a new algorithm inspired by the well-studied area of signal restoration, called the Constraining and Restoring iterative Algorithm for Faraday Tomography (CRAFT). This iterative model-independent algorithm is computationally inexpensive and only requires weak physically-motivated assumptions to produce high fidelity FDF reconstructions. We demonstrate an application for a realistic synthetic model FDF of the Milky Way, where CRAFT shows greater potential over other popular model-independent techniques. The dependence of observational frequency coverage on the various techniques' reconstruction performance is also demonstrated for a simpler FDF. CRAFT exhibits improvements even over model-dependent techniques (i.e., QU-fitting) by capturing complex multi-scale features of the FDF amplitude and polarization angle variations within a source. The proposed approach will be of utmost importance for future cosmic magnetism studies, especially with broadband polarization data from the Square Kilometre Array and its precursors. We make the CRAFT code publicly available.