SN1993J的射电遗迹：演化复杂结构的仪器解释
The radio remnant of SN1993J: an instrumental explanation for the evolving complex structure
摘要：
利用甚长基线干涉测量（VLBI）技术模拟了超新星1993J在8.4GHz的图像。一个球对称源模型卷积与现实的紫外平面分布，连同标准的成像程序，以评估仪器的影响程度上恢复的亮度分布。为了便于直接比较SN 1993 J的模拟和已发表的VLBI图像，观测到的紫外覆盖率是根据发现后几年的实际VLBI观测确定的。基础源模型只表现出径向变化的密度分布，没有方位角的依赖性，即使这个模型是形态简单，模拟的VLBI观测定性地再现了许多报告的VLBI观测的方位角的功能，如外观和复杂的方位角结构和视旋转壳的演变。我们证明，这样的功能是无情地耦合到UV平面采样。峰值和周围壳材料之间的亮度对比在模拟中并不突出（当然，这假设没有基于天线或基线的幅度或相位误差，这意味着没有自校准程序将在模型中包含任何此类特征）。结论是，不完整的UV平面采样对这种性质的观测的最终图像有巨大的影响。差分成像揭示了高达8 σ水平的残留发射。在使用干涉观测直接推断超新星等天体的结构时，应特别小心。
英文摘要：
We present simulated images of Supernova 1993J at 8.4 GHz using Very Long Baseline Interferometry (VLBI) techniques. A spherically symmetric source model is convolved with realistic uv-plane distributions, together with standard imaging procedures, to assess the extent of instrumental effects on the recovered brightness distribution. In order to facilitate direct comparisons between the simulations and published VLBI images of SN1993J, the observed uv-coverage is determined from actual VLBI observations made in the years following its discovery. The underlying source model only exhibits radial variation in its density profile, with no azimuthal dependence and, even though this model is morphologically simple, the simulated VLBI observations qualitatively reproduce many of the azimuthal features of the reported VLBI observations, such as appearance and evolution of complex azimuthal structure and apparent rotation of the shell. We demonstrate that such features are inexorably coupled to the uv-plane sampling. The brightness contrast between the peaks and the surrounding shell material are not as prominent in the simulations (which of course assume no antenna- or baseline-based amplitude or phase errors, meaning no self-calibration procedures will have incorporated any such features in models). It is conclusive that incomplete uv-plane sampling has a drastic effect on the final images for observations of this nature. Difference imaging reveals residual emission up to the 8 sigma level. Extreme care should be taken when using interferometric observations to directly infer the structure of objects such as supernovae.
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