FR I射电星系3C 31和Hydra A周围磁离子介质的结构
Structures of the magnetoionic media around the FR I radio galaxies 3C 31 and Hydra A
摘要：
我们使用高品质的VLA图像的Fanaroff和莱利I类射电星系3C 31在六个频率范围内1365至8440 MHz的探索的空间尺度和起源的旋转措施（RM）波动的视线上的射电源。我们分析的偏振度的分布表明，在早期的工作中所看到的源的南北两侧之间的大的去偏振不对称性在很大程度上消失的分辨率增加。我们发现，在低分辨率下看到的去极化的结果主要是从未解决的梯度在法拉第屏幕前面的同步辐射等离子体。我们建立了在短波长极限的剩余偏振度应遵循烧伤法律，我们适合这样的法律，我们的数据来估计在高分辨率的剩余去偏振。我们发现，所观察到的RM变化在选定的地区的3C 31是一致的磁波动的功率谱在前面的3C 31的幂律斜率变化显着的尺度上采样我们的数据。在小于5 kpc的尺度上，功率谱只能具有Kolmogorov湍流所期望的形式。在更大的尺度上，我们发现一个更平坦的斜坡。我们还比较了全球变化的RM在3C 31与周围磁离子介质中的磁场波动的三维模拟的结果。我们表明，我们的数据是一致的场分布，有利于垂直于射流轴的平面-可能是因为无线电源已经疏散了周围介质中的一个大的空腔。我们还将我们的分析技术的情况下，水螅A，在周围介质中的源所产生的腔的形状和大小是已知的X射线数据。（节录）
英文摘要：
We use high-quality VLA images of the Fanaroff & Riley Class I radio galaxy 3C 31 at six frequencies in the range 1365 to 8440MHz to explore the spatial scale and origin of the rotation measure (RM) fluctuations on the line of sight to the radio source. We analyse the distribution of the degree of polarization to show that the large depolarization asymmetry between the North and South sides of the source seen in earlier work largely disappears as the resolution is increased. We show that the depolarization seen at low resolution results primarily from unresolved gradients in a Faraday screen in front of the synchrotron-emitting plasma. We establish that the residual degree of polarization in the short-wavelength limit should follow a Burn law and we fit such a law to our data to estimate the residual depolarization at high resolution. We show that the observed RM variations over selected areas of 3C 31 are consistent with a power spectrum of magnetic fluctuations in front of 3C 31 whose power-law slope changes significantly on the scales sampled by our data. The power spectrum can only have the form expected for Kolmogorov turbulence on scales <5 kpc. On larger scales we find a flatter slope. We also compare the global variations of RM across 3C 31 with the results of three-dimensional simulations of the magnetic-field fluctuations in the surrounding magnetoionic medium. We show that our data are consistent with a field distribution that favours the plane perpendicular to the jet axis - probably because the radio source has evacuated a large cavity in the surrounding medium. We also apply our analysis techniques to the case of Hydra A, where the shape and the size of the cavities produced by the source in the surrounding medium are known from X-ray data. (Abridged)
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