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arXiv 1502.03741astro-ph.HEastro-ph.CO
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根据高分辨率射电干涉观测的河外射电喷流的性质

The nature of extragalactic radio-jets from high-resolution radio-interferometric observations

Manel Perucho

摘要:

河外喷流是射电噪声活跃星系的一个共同特征。所观察到的射流与整体气流的关系的性质尚不清楚。特别是,目前尚不清楚使用甚长基线干涉测量技术(VLBI)观测秒差距尺度喷流是否揭示了沿喷流发展和传播的波浪状结构,或追踪喷流本身。在这篇文章中,我回顾了在过去几年中收集的证据,表明螺旋射电喷流的脊线不对应于观测文物。这一结论是通过对类星体S5~0836+710射电喷流在不同频率和历元的VLBI观测研究得出的。在误差范围内,喷流中发射的脊线在所有频率上都是一致的。此外,在不同时期观察到的脊线之间的微小差异揭示了横向于射流传播轴的波浪状运动。我也讨论了类似的结果,虽然有不同的解释,由其他作者获得。目前的挑战是测量这些波的传播速度,并试图用简单的扰动或开尔文-亥姆霍兹不稳定性来描述它们,这将有助于理解波发展的物理条件。这一问题只能通过高分辨率观测来解决,例如通过空间无线电天线Radioastron可以实现的观测。

英文摘要:

Extragalactic jets are a common feature of radio-loud active galaxies. The nature of the observed jets in relation to the bulk flow is still unclear. In particular it is not clear whether the observations of parsec-scale jets using the very long baseline interferometric technique (VLBI) reveal wave-like structures that develop and propagate along the jet, or trace the jet flow itself. In this contribution I review the evidence collected during the last years showing that the ridge-lines of helical radio-jets do not correspond to observational artifacts. This conclusion was reached by studying a number of VLBI observations of the radio jet in the quasar S5~0836+710 at different frequencies and epochs. The ridge-line of the emission in the jet coincides at all frequencies within the errors. Moreover, small differences between the ridge-lines as observed at different epochs reveal wave-like motion transversal to the jet propagation axis. I also discuss similar results, albeit with different interpretations, obtained by other authors. The current challenge is to measure the propagation velocities of these waves and to try to characterise them in terms of simple perturbations or Kelvin-Helmholtz instability, which would help understanding the physical conditions of the flow where the waves develop. This problem can only be tackled by high-resolution observations such as those that can be achieved by the space radio-antenna Radioastron.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

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