论文标题
用EHT极化法探测银河系中心的积聚湍流
Probing Accretion Turbulence in the Galactic Center with EHT Polarimetry
论文作者
论文摘要
据信，由差分旋转驱动的不稳定性生长的磁场对于积聚在黑洞上是必不可少的。这些不稳定性以动荡状态饱和。因此，射手座A*（SGR A*）的地平线分辨图像中的空间和时间变异将能够从经验上评估增生理论的这一关键方面。然而，星际散射模糊了银河中心的高频无线电图像，并引入了虚假的小规模结构，使图像中空间波动的解释变得复杂。我们探讨了星际散射对SGR A*两极分化图像的影响，并证明对于可靠的物理参数，中间散射是非生物的。因此，我们构建了一种散射缓解方案，该方案利用地平线分辨的极化毫米/亚毫米级VLBI观测值，以生成内在空间波动的统计测量，从而产生了基础积聚流动湍流。确定了最佳极化基础，对应于三个维度在磁场方向中波动的测量。我们使用模拟数据集验证了缓解方案，发现当前和将来的基于地面的实验将很容易地能够准确测量图像 - 拆卸功率谱。
Magnetic fields grown by instabilities driven by differential rotation are believed to be essential to accretion onto black holes. These instabilities saturate in a turbulent state; therefore, the spatial and temporal variability in the horizon-resolving images of Sagittarius A* (Sgr A*) will be able to empirically assess this critical aspect of accretion theory. However, interstellar scattering blurs high-frequency radio images from the Galactic center and introduces spurious small-scale structures, complicating the interpretation of spatial fluctuations in the image. We explore the impact of interstellar scattering on the polarized images of Sgr A* and demonstrate that for credible physical parameters, the intervening scattering is non-birefringent. Therefore, we construct a scattering mitigation scheme that exploits horizon-resolving polarized millimeter/submillimeter VLBI observations to generate statistical measures of the intrinsic spatial fluctuations and therefore the underlying accretion flow turbulence. An optimal polarization basis is identified, corresponding to measurements of the fluctuations in magnetic field orientation in three dimensions. We validate our mitigation scheme using simulated data sets and find that current and future ground-based experiments will readily be able to accurately measure the image-fluctuation power spectrum.
