AI 中文总结
本研究结合宇宙射线与磁场的自洽模型，利用普朗克卫星数据，发现银晕有序环形磁场强度为3.2-4.3微高斯，且银晕尺度4千秒差距的模型更受青睐，证实银晕存在旋转量未探测到的有序随机磁场。
AI 中文摘要
全天同步辐射偏振观测是探测银河系大规模有序磁场的主要手段，该磁场包含相干分量和有序随机分量。然而，从同步辐射观测得到的磁场强度估算值依赖于所采用的宇宙射线电子模型，而该模型本身又取决于整个银河系的磁场结构与强度。本研究旨在通过自洽处理宇宙射线电子，结合Xu & Han经本地污染校正的旋转量测得的最新相干磁场结构，来限制银晕大规模有序磁场的强度。我们将普朗克卫星30 GHz同步辐射偏振图与联合处理宇宙射线和磁场、并受直接宇宙射线测量及多频数据约束的大规模同步辐射模型进行对比。由于推导的磁场强度取决于银晕尺度，我们对不同的宇宙射线传播银晕尺度进行了探究。我们观测到与模型预测相比存在显著的大规模同步辐射过量，这要求银晕中存在有序环形磁场分量，其峰值强度为3.2-4.3微高斯，具体数值取决于所假设的银晕尺度。我们还发现，银晕尺度为4千秒差距的宇宙射线传播模型更受普朗克同步辐射偏振图的青睐。该结果表明，有序磁场比Xu & Han从旋转量测得的相干磁场强4-6倍，证实了银晕中存在旋转量无法探测到的有序随机磁场。若将同步辐射过量完全归因于本地泡，则需要本地泡具有非标准性质，这一解释不受支持。
英文摘要
All-sky synchrotron polarization observations are the primary probe of the Galactic large-scale ordered magnetic field, which includes both coherent and ordered random components. However, magnetic-field strength estimates from synchrotron observations depend on the assumed cosmic-ray electron model, which itself depends on the magnetic-field configuration and strength throughout the Galaxy. We aim to constrain the strength of the large-scale ordered magnetic field in the Galactic halo through a self-consistent treatment of cosmic-ray electrons with the latest coherent magnetic-field configuration inferred by Xu & Han from rotation measures corrected for local contamination. We compare the Planck 30 GHz synchrotron polarization maps with our large-scale synchrotron models that jointly treat cosmic rays and magnetic fields and are constrained by direct cosmic-ray measurements and multifrequency data. Since the inferred field strength depends on the halo size, we explore different cosmic-ray propagation halo sizes. We observe a significant large-scale synchrotron excess relative to model predictions, which requires an ordered toroidal magnetic-field component in the halo with a peak strength of 3.2-4.3 microG, depending on the assumed halo size. We also find that the cosmic-ray propagation model with a 4 kpc halo size is preferred by the Planck synchrotron polarization maps. This result shows that the ordered magnetic field is 4-6 times stronger than the coherent field inferred from rotation measures by Xu & Han, establishing the presence of an ordered random field in the Galactic halo that is not traced by rotation measures. Attributing the synchrotron excess entirely to the Local Bubble would require non-standard Local Bubble properties, disfavoring this interpretation.
CommentsAccepted for publication in A&A
