The study of the intensity fluctuation power spectrum of individual supernova remnants (SNRs) can reveal the structures present at sub-pc scales, and also constrain the physical process that generates those structures. There are various effects, such as the remnant shell thickness, projection of a three-dimensional structure onto a two-dimensional observational plane, and the presence of diffuse "foreground" emission, which causes the observed power spectrum to deviate from the intrinsic power spectrum of the fluctuations. Here, we report results from a systematic study of these effects, using direct numerical simulations, in the measured power spectrum. For an input power-law power spectrum, independent of the power-law index, we see a break in the observed power law at a scale which depends on the shell thickness of a shell-type SNR, and the three-dimensional turbulence changes to two-dimensional turbulence beyond that scale. We also report how the estimated power spectrum is expected to deviate from the intrinsic SNR power spectrum in the presence of additional diffuse Galactic synchrotron emission (DGSE) around the remnant shell. For a reasonable choice of the parameters, if the intrinsic SNR power spectrum is shallower than the DGSE power spectrum, the SNR contribution dominates at small angular scales of the estimated power spectra. On the other hand, if the SNR power spectrum is relatively steeper, the original power spectra is recovered only over a small window of angular scales. This study shows how detailed modeling may be used to infer the true power spectrum from the observed SNR intensity fluctuations power spectrum, which in turn can be used to constrain the nature of the turbulence that gives rise to these small scale structures.

中文翻译：

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超新星遗迹的角功率谱：结构、几何形状和漫反射前景的影响

对单个超新星遗迹 (SNR) 的强度波动功率谱的研究可以揭示亚 pc 尺度上存在的结构，并限制产生这些结构的物理过程。有多种影响，例如残余壳厚度、三维结构在二维观测平面上的投影以及存在漫射“前景”发射，导致观测功率谱偏离固有功率谱的波动。在这里，我们报告了在测量的功率谱中使用直接数值模拟对这些影响进行系统研究的结果。对于独立于幂律指数的输入幂律功率谱，我们看到观察到的幂律在取决于壳型 SNR 的壳厚度的尺度上出现中断，并且超出该尺度的三维湍流变为二维湍流。我们还报告了在残余壳周围存在额外的漫反射银河同步加速器发射 (DGSE) 的情况下，估计的功率谱预计如何偏离固有 SNR 功率谱。对于参数的合理选择，如果固有 SNR 功率谱比 DGSE 功率谱浅，则 SNR 贡献在估计功率谱的小角尺度上占主导地位。另一方面，如果 SNR 功率谱相对更陡峭，则原始功率谱只能在角标度的小窗口上恢复。这项研究显示了如何使用详细的建模从观察到的 SNR 强度波动功率谱推断真实功率谱，