The Event Horizon Telescope will generate horizon scale images of the black hole in the center of the Milky Way, Sgr A*. Image reconstruction using interferometric visibilities rests on the assumption of a stationary image. We explore the limitations of this assumption using high-cadence disk- and jet-dominated GRMHD simulations of Sgr A*. We also employ analytic models that capture the basic characteristics of the images to understand the origin of the variability in the simulated visibility amplitudes. We find that, in all simulations, the visibility amplitudes for baselines oriented parallel and perpendicular to the spin axis of the black hole follow general trends that do not depend strongly on accretion-flow properties. This suggests that fitting Event Horizon Telescope observations with simple geometric models may lead to a reasonably accurate determination of the orientation of the black hole on the plane of the sky. However, in the disk-dominated models, the locations and depths of the minima in the visibility amplitudes are highly variable and are not related simply to the size of the black hole shadow. This suggests that using time-independent models to infer additional black hole parameters, such as the shadow size or the spin magnitude, will be severely affected by the variability of the accretion flow.
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机译：事件地平线望远镜将生成银河系中心Sgr A *上黑洞的地平线标度图像。使用干涉可见性的图像重建基于静止图像的假设。我们使用Sgr A *的高节奏磁盘和喷气控制GRMHD模拟来探索此假设的局限性。我们还采用了捕获图像基本特征的解析模型，以了解模拟可见性幅度中的可变性起因。我们发现，在所有模拟中，平行于和垂直于黑洞自旋轴的基线的可见性幅度遵循总体趋势，而这些趋势并不强烈依赖于吸积流特性。这表明将事件地平线望远镜的观测值与简单的几何模型进行拟合可能会导致合理准确地确定黑洞在天空平面上的方向。但是，在以圆盘为主导的模型中，可见度振幅中最小值的位置和深度高度可变，并且与黑洞阴影的大小并不简单相关。这表明使用与时间无关的模型来推断其他黑洞参数，例如阴影大小或自旋幅度，将受到吸积流变化的严重影响。
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