DISCOVERY OF SUBSTRUCTURE IN THE SCATTER-BROADENED IMAGE OF SGR A*
DISCOVERY OF SUBSTRUCTURE IN THE SCATTER-BROADENED IMAGE OF SGR A*
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在 SGR A* 的散射加宽图像中发现基底结构
DOI：
10.1088/2041-8205/794/1/l14
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发表时间：
2014
期刊：
影响因子：
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通讯作者：
V. Soglasnov
中科院分区：
文献类型：
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作者：
C. Gwinn;Y. Kovalev;Y. Kovalev;Michael D. Johnson;V. Soglasnov
我们在著名的银河中心射电源人马座 A* (Sgr A*) 的光滑散射盘内检测到了子结构。我们使用甚长基线阵列和格林班克望远镜在 1.3 厘米波长下观察到了这种结构，基线长达 3000 公里，足以完全解析平均散射盘。理论上预测这种结构是星际介质中大规模等离子体波动折射的结果。加上广泛研究的角展宽 θd 与观测波长 λ 的 θd∝λ2 缩放比例，我们的观测表明星际湍流的光谱很浅，内部尺度大于 300 km。从平均散射的反卷积推断，子结构与 1.3 cm 波长下约 1 mas 的固有尺寸一致。对子结构的进一步观察可以对散射材料的特性和 Sgr A* 的固有尺寸设置更强的限制。这些限制将指导我们理解事件视界望远镜在毫米波长图像中的散射展宽效应和黑洞附近的发射物理现象。
We have detected substructure within the smooth scattering disk of the celebrated Galactic center radio source Sagittarius A* (Sgr A*). We observed this structure at 1.3 cm wavelength with the Very Long Baseline Array together with the Green Bank Telescope, on baselines of up to 3000 km, long enough to completely resolve the average scattering disk. Such structure is predicted theoretically as a consequence of refraction by large-scale plasma fluctuations in the interstellar medium. Along with the much-studied θd∝λ2 scaling of angular broadening θd with observing wavelength λ, our observations indicate that the spectrum of interstellar turbulence is shallow with an inner scale larger than 300 km. The substructure is consistent with an intrinsic size of about 1 mas at 1.3 cm wavelength, as inferred from deconvolution of the average scattering. Further observations of the substructure can set stronger constraints on the properties of scattering material and on the intrinsic size of Sgr A*. These constraints will guide our understanding of the effects of scatter broadening and the emission physics near the black hole in images with the Event Horizon Telescope at millimeter wavelengths.