Magnetic fields in nearby galaxies: Low-frequency radio observations

星系尺度上组织良好的磁场的起源是星系外天体物理学中的一个基本问题。对于理论模型，需要在大多数相关尺度上对磁场强度和方向进行约束，从与湍流有关的最小尺度到与向星系间环境流出有关的最大尺度。LOFAR提供的低频射电连续体观测将使我们能够特别解决后一个问题。该项目重点研究正常螺旋星系和大质量不规则星系内部和周围的磁场，使用低频射电连续体观测，具有前所未有的角分辨率和灵敏度。在低频率下，低能量宇宙射线电子追踪磁场到更大的星系半径，法拉第旋转的分析比以前的方法对更小的磁场强度敏感。特别是，我们将通过无线电频谱指数图分析相对论性电子的能量增益和损失过程，星系盘和晕中磁场的强度和结构，相对论性电子的体积速度及其与热气体流动模式和星系发电机产生的磁场的关系。

The origin of the well organised magnetic fields on galactic scales is a fundamental problem in extragalactic astrophysics. For theoretical models, constraints with regard to the magnetic field strength and orientation on most relevant scales are required, from the smallest scales related to turbulence, to the largest scales related to outflows into the intergalactic environment. Radio continuum observations at low frequencies as provided by LOFAR will allow us to address in particular the latter problem. This Project focuses on investigations of magnetic fields in and around normal spiral galaxies and massive irregular galaxies using low-frequency radio continuum observations with unprecedented angular resolution and sensitivity. At low frequencies the low-energy cosmic-ray electrons trace the magnetic fields to much larger galactic radii, and the analysis of the Faraday rotation is sensitive to much smaller magnetic field strengths than previous methods. Especially, we will analyse the energy gain and loss processes of the relativistic electrons via radio spectral index maps, the strength and structure of magnetic fields in galaxy disks and halos, the bulk speed of the relativistic electrons and their relation to the flow patterns of thermal gas and to the magnetic fields generated by galactic dynamos.