用地面和空间合成甚长基线干涉测量数据估算黑洞参数
Black hole parameter estimation with synthetic Very Long Baseline Interferometry data from the ground and from space
摘要：
事件视界望远镜（EHT）拍摄了M87中超大质量黑洞的阴影。一个广义相对论磁流体力学（GMRHD）模型库适合观测数据，提供黑洞参数的约束。我们研究了未来的实验可以更好地现实地约束这些参数并测试引力理论。我们使用2017年，2021年和扩展的EHT阵列，从M87的GRMHD图像库中获取的代表性输入模型生成逼真的合成230 GHz数据。合成数据通过EHT使用的数据简化管道运行。此外，我们模拟观测在230，557和690 GHz的事件视界成像仪（EHI）空间VLBI的概念。使用EHT参数估计管道之一，我们适合GRMHD库图像的合成数据和调查如何黑洞参数估计的影响，不同的阵列和重复的观测。重复观测在限制黑洞和吸积参数中起着重要的作用，因为变化的源结构被平均掉了。EHT的适度扩展已经导致更强的参数约束。来自太空的高频观测排除了我们库中大约15%的GRMHD模型，强烈约束了磁通量和黑洞自旋。1 $σ$约束的黑洞质量提高了5倍，重复的高频空间阵列的观测相比，目前的地面阵列的观测。如果黑洞的自旋、磁化和电子温度分布可以独立地受到约束，那么对于给定的黑洞质量，用EHI可以测试出阴影的大小约为0.5%，这就允许测试与广义相对论的偏差。通过对银河系中心人马座黑洞A* 的观测，克尔度规的高精度测试变得触手可及。
英文摘要：
The Event Horizon Telescope (EHT) has imaged the shadow of the supermassive black hole in M87. A library of general relativistic magnetohydrodynamics (GMRHD) models was fit to the observational data, providing constraints on black hole parameters. We investigate how much better future experiments can realistically constrain these parameters and test theories of gravity. We generate realistic synthetic 230 GHz data from representative input models taken from a GRMHD image library for M87, using the 2017, 2021, and an expanded EHT array. The synthetic data are run through a data reduction pipeline used by the EHT. Additionally, we simulate observations at 230, 557, and 690 GHz with the Event Horizon Imager (EHI) Space VLBI concept. Using one of the EHT parameter estimation pipelines, we fit the GRMHD library images to the synthetic data and investigate how the black hole parameter estimations are affected by different arrays and repeated observations. Repeated observations play an important role in constraining black hole and accretion parameters as the varying source structure is averaged out. A modest expansion of the EHT already leads to stronger parameter constraints. High-frequency observations from space rule out all but ~15% of the GRMHD models in our library, strongly constraining the magnetic flux and black hole spin. The 1$σ$ constraints on the black hole mass improve by a factor of five with repeated high-frequency space array observations as compared to observations with the current ground array. If the black hole spin, magnetization, and electron temperature distribution can be independently constrained, the shadow size for a given black hole mass can be tested to ~0.5% with the EHI, which allows tests of deviations from general relativity. High-precision tests of the Kerr metric become within reach from observations of the Galactic Center black hole Sagittarius A*.
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