螺旋星系的积分极化
The Integrated Polarization of Spiral Galaxy Disks
摘要：
我们提出了附近的螺旋星系在4.8 GHz的综合偏振特性，螺旋星系盘的综合偏振模型作为倾角的函数。我们样本中的螺旋星系已经观察到积分分数偏振在< 1%到17.6%之间。在倾角小于50度时，分数极化主要取决于随机与规则磁场强度的比率。在更高的倾角，法拉第去极化与规则的磁场变得更加重要。对于更明亮的星系，特别是那些L_{4.8} > 2 x 10^{21} W/Hz的星系，观测到的偏振度较低（<4%）。对于没有棒的星系，积分辐射的偏振角与盘的视短轴一致。在我们的轴对称模型中，积分辐射的偏振角与波长无关。给出了随机取向螺旋星系在4.8GHz和1.4GHz频率下的分数偏振分布的模拟结果。我们的结论是，偏振测量，例如与SKA，未解决的螺旋星系允许使用大样本在本地宇宙和高红移的盘星系的磁场的统计研究。由于这些星系表现为理想的背景源，没有内部法拉第旋转，它们可以用来探测星系际介质中的大尺度磁场。
英文摘要：
We present integrated polarization properties of nearby spiral galaxies at 4.8 GHz, and models for the integrated polarization of spiral galaxy disks as a function of inclination. Spiral galaxies in our sample have observed integrated fractional polarization in the range < 1% to 17.6%. At inclinations less than 50 degrees, the fractional polarization depends mostly on the ratio of random to regular magnetic field strength. At higher inclinations, Faraday depolarization associated with the regular magnetic field becomes more important. The observed degree of polarization is lower (<4%) for more luminous galaxies, in particular those with L_{4.8} > 2 x 10^{21} W/Hz. The polarization angle of the integrated emission is aligned with the apparent minor axis of the disk for galaxies without a bar. In our axially symmetric models, the polarization angle of the integrated emission is independent of wavelength. Simulated distributions of fractional polarization for randomly oriented spiral galaxies at 4.8 GHz and 1.4 GHz are presented. We conclude that polarization measurements, e.g. with the SKA, of unresolved spiral galaxies allow statistical studies of the magnetic field in disk galaxies using large samples in the local universe and at high redshift. As these galaxies behave as idealized background sources without internal Faraday rotation, they can be used to detect large-scale magnetic fields in the intergalactic medium.
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