Optical and Radio Polarimetry of the M87 Jet at 02 Resolution
Optical and Radio Polarimetry of the M87 Jet at 02 Resolution
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DOI：
10.1086/300844
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发表时间：
1999-01
期刊：
影响因子：
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通讯作者：
E. Perlman;J. Biretta;F. Zhou;William B. Sparks;F. Macchetto
中科院分区：
文献类型：
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作者：
E. Perlman;J. Biretta;F. Zhou;William B. Sparks;F. Macchetto
我们讨论了1994-1995年间M87喷射的光学（HST/WFPC2 F555W）和无线电（15 GHz VLA）偏振观测。两个观测的角分辨率都是~ 0。″2，在M87的距离相当于15pc。许多结区高度极化（~ 40%-50%，接近光学薄同步辐射的理论最大值），表明磁场高度有序。在结间区域也观察到高度极化。光学偏振图和射电偏振图有许多相似之处，在两者中，磁场基本上与喷流平行，除了在“激波样”结区（HST-1、A和C的一部分），磁场与喷流垂直。我们确实观察到无线电和光学偏振结构之间的显著差异，特别是在内部喷流中的明亮结，这使我们对喷流的径向结构有了重要的了解。与射电不同的是，在HST-1、D、E和f节的上游端，光磁场位置角垂直于喷流，并且在这些节中通量最大的位置，光偏振明显减小。相比之下，在这些区域中观测到的磁场位置角在大多数区域保持与喷流平行，并且无线电极化的减少较小。其他喷流区域的差异更小。光学和射电偏振测量结果之间的许多差异可以用一种模型来解释，即冲击发生在射流内部，高能量电子集中在那里，并主导着光学中的极化和非极化发射，而射电图显示，在靠近射流表面的B平行区域，低能电子的贡献很大。
We discuss optical (HST/WFPC2 F555W) and radio (15 GHz VLA) polarimetry observations of the M87 jet taken during 1994–1995. The angular resolution of both observations is ∼0.″2, which at the distance of M87 corresponds to 15 pc. Many knot regions are very highly polarized (∼40%–50%, approaching the theoretical maximum for optically thin synchrotron radiation), suggesting highly ordered magnetic fields. High degrees of polarization are also observed in interknot regions. The optical and radio polarization maps share many similarities, and in both, the magnetic field is largely parallel to the jet, except in the "shocklike" knot regions (parts of HST-1, A, and C), where it becomes perpendicular to the jet. We do observe significant differences between the radio and optical polarized structures, particularly for bright knots in the inner jet, giving us important insight into the radial structure of the jet. Unlike in the radio, the optical magnetic field position angle becomes perpendicular to the jet at the upstream ends of knots HST-1, D, E, and F. Moreover, the optical polarization appears to decrease markedly at the position of the flux maxima in these knots. In contrast, the magnetic field position angle observed in the radio remains parallel to the jet in most of these regions, and the decreases in radio polarization are smaller. More minor differences are seen in other jet regions. Many of the differences between optical and radio polarimetry results can be explained in terms of a model whereby shocks occur in the jet interior, where higher energy electrons are concentrated and dominate both polarized and unpolarized emissions in the optical, while the radio maps show strong contributions from lower energy electrons in regions with B parallel, near the jet surface.