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arXiv 1604.06552astro-ph.GAastro-ph.HE
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W50/SS433系统中大尺度磁场与电离气体的相互作用

Interacting Large-Scale Magnetic Fields and Ionised Gas in the W50/SS433 System

J. S. Farnes, B. M. Gaensler, C. Purcell, X. H. Sun, M. Haverkorn, E. Lenc, S. P. O'Sullivan, T. Akahori

摘要:

W50/SS 433系统是一个不寻常的银河系外流驱动的物体,其起源存在争议。我们已经使用了澳大利亚望远镜紧凑阵列(ATCA),观察一个新的198指向马赛克,覆盖$3^\circ \times 2^\circ$,并提出了最高灵敏度的全斯托克斯数据的W50到目前为止,使用宽场,宽带成像超过2 GHz的带宽为中心,在2.1 GHz。我们还提出了一个互补的H $α$马赛克创建使用艾萨克牛顿望远镜光度H $α$调查北银河平面(IPHAS)。W50的磁性结构与当时流行的假设一致,即该星云是一个复活的壳状超新星遗迹(SNR),已被SS 433的喷流重新激活。我们观察到强烈的去极化效应,与扩散H $α$发射,可能是由于空间变化的法拉第旋转测量(RM)的波动$\ge48$ 61拉德米$^{-2}$规模$\le4.5$ 6 pc。我们还报告发现了许多微弱的H $α$丝,这些丝与W50的中心区域明确相关。这些细丝暗示着SNR的冲击辐射,几乎所有的都有无线电对应物。此外,RM-梯度被检测到整个中心区域的W50,我们解释为一个环磁场的对称轴偏移$\approx90^{\circ}$的东西射流对齐轴,并意味着进化过程的射流和SNR必须耦合。一个单独的RM-梯度与终止冲击在东部耳朵,我们解释为一个环状场位于那里的冲击射流与星周介质相互作用。未来的光学观测将能够使用新的H $α$细丝来探测W50外壳的运动学,这可能会对W50的形成历史进行明确的实验。

英文摘要:

The W50/SS433 system is an unusual Galactic outflow-driven object of debatable origin. We have used the Australia Telescope Compact Array (ATCA) to observe a new 198 pointing mosaic, covering $3^\circ \times 2^\circ$, and present the highest-sensitivity full-Stokes data of W50 to date using wide-field, wide-band imaging over a 2 GHz bandwidth centred at 2.1 GHz. We also present a complementary H$α$ mosaic created using the Isaac Newton Telescope Photometric H$α$ Survey of the Northern Galactic Plane (IPHAS). The magnetic structure of W50 is found to be consistent with the prevailing hypothesis that the nebula is a reanimated shell-like supernova remnant (SNR), that has been re-energised by the jets from SS433. We observe strong depolarization effects that correlate with diffuse H$α$ emission, likely due to spatially-varying Faraday rotation measure (RM) fluctuations of $\ge48$ to 61 rad m$^{-2}$ on scales $\le4.5$ to 6 pc. We also report the discovery of numerous, faint, H$α$ filaments that are unambiguously associated with the central region of W50. These thin filaments are suggestive of a SNR's shock emission, and almost all have a radio counterpart. Furthermore, an RM-gradient is detected across the central region of W50, which we interpret as a loop magnetic field with a symmetry axis offset by $\approx90^{\circ}$ to the east-west jet-alignment axis, and implying that the evolutionary processes of both the jets and the SNR must be coupled. A separate RM-gradient is associated with the termination shock in the Eastern ear, which we interpret as a ring-like field located where the shock of the jet interacts with the circumstellar medium. Future optical observations will be able to use the new H$α$ filaments to probe the kinematics of the shell of W50, potentially allowing for a definitive experiment on W50's formation history.

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