Low-frequency Faraday rotation measures towards pulsars using LOFAR: probing the 3D Galactic halo magnetic field
Low-frequency Faraday rotation measures towards pulsars using LOFAR: probing the 3D Galactic halo magnetic field
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DOI：
10.1093/mnras/stz214
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发表时间：
2019-01
影响因子：
4.8
通讯作者：
C. Sobey;A. Bilous;J. Grießmeier;J. Hessels;A. Karastergiou;E. Keane;V. Kondratiev;M. Kramer
中科院分区：
文献类型：
--
作者：
C. Sobey;A. Bilous;J. Grießmeier;J. Hessels;A. Karastergiou;E. Keane;V. Kondratiev;M. Kramer
我们确定了法拉第旋转措施（RM）对137个双星在北方的天空，使用低频阵列（LOFAR）的观测在110-190兆赫。这个低频RM目录是迄今为止最大的，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。为了将星表的精度提高到10.1 rad m−2，我们对RM进行了电离层法拉第旋转的校正。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，朝向双光子的法拉第色散函数非常法拉第薄--大部分小于0.001 rad m−2。我们使用这些新的精确RM测量（结合现有的RM，色散测量和距离估计）来估计银河系晕磁场的标度高度：银河系平面上方和下方的银河系象限I和II为2.0 ± 0.3 kpc（我们还单独评估了这些区域的标度高度）。总的来说，我们最初的低频目录提供了有关银河磁场三维结构的有价值的信息。
We determined Faraday rotation measures (RMs) towards 137 pulsars in the northern sky, using Low-Frequency Array (LOFAR) observations at 110–190 MHz. This low-frequency RM catalogue, the largest to date, improves the precision of existing RM measurements on average by a factor of 20 – due to the low frequency and wide bandwidth of the data, aided by the RM-synthesis method. We report RMs towards 25 pulsars for the first time. The RMs were corrected for ionospheric Faraday rotation to increase the accuracy of our catalogue to ≈0.1 rad m−2. The ionospheric RM correction is currently the largest contributor to the measurement uncertainty. In addition, we find that the Faraday dispersion functions towards pulsars are extremely Faraday thin – mostly less than 0.001 rad m−2. We use these new precise RM measurements (in combination with existing RMs, dispersion measures, and distance estimates) to estimate the scale height of the Galactic halo magnetic field: 2.0 ± 0.3 kpc for Galactic quadrants I and II above and below the Galactic plane (we also evaluate the scale height for these regions individually). Overall, our initial low-frequency catalogue provides valuable information about the 3D structure of the Galactic magnetic field.