A Parametric Model for the Shapes of Black Hole Shadows in Non-Kerr Spacetimes
A Parametric Model for the Shapes of Black Hole Shadows in Non-Kerr Spacetimes
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DOI：
10.3847/1538-4357/ab8bd1
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发表时间：
2019-07
期刊：
影响因子：
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通讯作者：
L. Medeiros;D. Psaltis;F. Özel
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文献类型：
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作者：
L. Medeiros;D. Psaltis;F. Özel
事件视界望远镜(EHT)正在拍摄第一张在地平线尺度上分辨的黑洞图像，以测量它们的阴影并探测吸积物理。检验天体物理黑洞是由爱因斯坦方程的克尔解描述这一假设的一个有希望的方法是，将黑洞投射到周围辐射上的阴影的大小和形状与克尔度规的预测进行比较。我们在这里开发了一个有效的参数框架来执行这一测试。我们对几个参数化的非Kerr度量进行了光线跟踪模拟，以创建一个大型的非Kerr阴影数据集，这些数据集探测每个度量的自由参数的允许参数空间。然后，我们对这组阴影进行主成分分析(PCA)，结果表明，只需要少量的成分就可以准确地重建这组阴影中的所有阴影。我们进一步证明，PCA分量的幅度与度量中的自由参数是平滑相关的，因此，这些PCA分量可以与EHT观测结果相适应，以便对这些度量的自由参数施加约束，这将有助于量化任何与Kerr解的潜在偏差。
The Event Horizon Telescope (EHT) is taking the first images of black holes resolved at horizon scales to measure their shadows and probe accretion physics. A promising avenue for testing the hypothesis that astrophysical black holes are described by the Kerr solution to Einstein’s equations is to compare the size and shape of the shadow a black hole casts on the surrounding emission to the predictions of the Kerr metric. We develop here an efficient parametric framework to perform this test. We carry out ray-tracing simulations for several parameterized non-Kerr metrics to create a large data set of non-Kerr shadows that probe the allowed parameter space for the free parameters of each metric. We then perform principal components analysis (PCA) on this set of shadows and show that only a small number of components are needed to accurately reconstruct all shadows within the set. We further show that the amplitude of the PCA components are smoothly related to the free parameters in the metrics and, therefore, that these PCA components can be fit to EHT observations in order to place constraints on the free parameters of these metrics that will help quantify any potential deviations from the Kerr solution.