The Galactic Faraday depth sky revisited
The Galactic Faraday depth sky revisited
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DOI：
10.1051/0004-6361/201935479
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发表时间：
2020-01-24
影响因子：
6.5
通讯作者：
Ensslin, Torsten A.
中科院分区：
文献类型：
--
作者：
Hutschenreuter, Sebastian;Ensslin, Torsten A.
上下文。银河系法拉第深度天空是银河系磁场和热电子分布的追踪器。它之前是根据对银河系外点源的偏振测量重建的。目标。在这里，我们通过使用更新的推理算法并考虑到由普朗克调查测量的自由-自由发射所追踪的电子发射来改进这些工作。在未来，由于SKA及其探路者的下一代法拉第旋转测量，数据情况将大大改善。考虑到这一点，本文的另一个目的是利用贝叶斯成像的一些最新进展来更新地图重建方法。方法：研究方法。为此，我们利用了信息场理论，这是一种在有噪音和不完整数据的情况下特别强大的推理方案。结果。通过在已有数据汇编中的应用，验证了新算法的有效性。尽管我们使用了完全相同的数据集，但还是有了一些新的发现；例如，总振幅场的非参数重建类似于银河系的自由-自由发射测量图。将这张排放测量地图合并到分析中，可以提供更详细的预测。联合推断使我们能够识别出与排放测量和法拉第数据之间假设的相关性存在偏差的区域，从而为我们指出具有明显不同物理特征的银河系结构。我们找到了磁场沿猎户座臂两个方向在视线内对齐的证据。
Context. The Galactic Faraday depth sky is a tracer for both the Galactic magnetic field and the thermal electron distribution. It was previously reconstructed from polarimetric measurements of extra-Galactic point sources. Aims. Here we improve on these works by using an updated inference algorithm and by taking into account the electron emission measure as traced by free-free emission measured by the Planck survey. In the future the data situation will improve drastically thanks to the next generation Faraday rotation measurements from the SKA and its pathfinders. Anticipating this, a further aim of this paper is to update the map reconstruction method with some of the latest developments in Bayesian imaging. Methods. To this end we made use of information field theory, an inference scheme that is particularly powerful in cases of noisy and incomplete data. Results. We demonstrate the validity of the new algorithm by applying it to an existing data compilation. Even though we used exactly the same data set, a number of novel findings are made; for example, a non-parametric reconstruction of an overall amplitude field resembles the free-free emission measure map of the Galaxy. Folding this emission measure map into the analysis provides more detailed predictions. The joint inference enables us to identify regions with deviations from the assumed correlations between the emission measure and Faraday data, thereby pointing us to Galactic structures with distinguishably different physics. We find evidence for an alignment of the magnetic field within the lines of sight along both directions of the Orion arm.