散射增宽分辨像中折射子结构的理论与模拟
Theory and Simulations of Refractive Substructure in Resolved Scatter-Broadened Images
摘要：
在无线电波段，星际介质的散射会扭曲天文源的外观。在散射系综上求平均，结果是源的模糊图像。然而，Narayan & Goodman（1989）和Goodman & Narayan（1989）表明，对于不完全平均，散射在点源的图像中引入了折射子结构，该点源既是持久的又是宽带的。我们表明，这个子结构淬火，但不平滑的扩展源。因此，当散射加宽与未散射的源尺寸相当或超过未散射的源尺寸时，散射可以将虚假的紧凑特征引入到图像中。此外，我们推导出有效的策略来数值计算现实的散射图像，我们提出的模拟特征的例子。我们的研究结果表明，折射子结构是一个重要的考虑正在进行的任务在最高的角分辨率，我们讨论了具体的影响射电天文和事件视界望远镜。
英文摘要：
At radio wavelengths, scattering in the interstellar medium distorts the appearance of astronomical sources. Averaged over a scattering ensemble, the result is a blurred image of the source. However, Narayan & Goodman (1989) and Goodman & Narayan (1989) showed that for an incomplete average, scattering introduces refractive substructure in the image of a point source that is both persistent and wideband. We show that this substructure is quenched but not smoothed by an extended source. As a result, when the scatter-broadening is comparable to or exceeds the unscattered source size, the scattering can introduce spurious compact features into images. In addition, we derive efficient strategies to numerically compute realistic scattered images, and we present characteristic examples from simulations. Our results show that refractive substructure is an important consideration for ongoing missions at the highest angular resolutions, and we discuss specific implications for RadioAstron and the Event Horizon Telescope.
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