Images and photon ring signatures of thick disks around black holes
Images and photon ring signatures of thick disks around black holes
复制标题
黑洞周围厚圆盘的图像和光子环特征
DOI：
10.1051/0004-6361/202244339
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发表时间：
2022
影响因子：
6.5
通讯作者：
Wielgus, M.
中科院分区：
文献类型：
--
作者：
Vincent, F. H.;Gralla, S. E.;Lupsasca, A.;Wielgus, M.
高频甚长基线干涉测量（VLBI）观测现在可以解决来自邻近超大质量黑洞附近的源的事件视界尺度发射。未来的空间VLBI观测将访问黑洞图像的高度透镜的功能-光子环-这将提供特别尖锐的探针强场gravity.AimsFocusing的超大质量黑洞M 87* 的特殊情况下，我们的目标是探索各种各样的吸积流到克尔黑洞，并了解其相应的图像和vibrations。我们特别感兴趣的是在基线上的可见度空间，它编码的光子环的形状和测量可以提供一个严格的测试的Kerr hypothesis.MethodsWe开发了一个完全解析模型的固定，轴对称吸积流与一个可变的磁盘厚度和一个物质四速度，可以顺利地插入之间的纯方位角旋转和纯径向infall。为了确定这种流动的观测外观，我们数值积分的广义相对论辐射传输方程的克尔时空，注意包括热同步辐射和吸收的影响。然后，我们傅立叶变换得到的图像和分析其可见度振幅沿沿着方向平行和正交的黑洞自旋投影在observersky.ResultsOur图像一般显示一个婚礼蛋糕结构组成的离散，窄光子环（n= 1，2，.）堆叠在上面的更广泛的主要发射，围绕中心亮度抑郁症的模型依赖的大小。 在230 GHz时，= 1环总是可见的，但由于吸收，= 2环有时会被抑制。 在345 GHz时，介质在光学上更薄，然后= 2环在图像和可见度域中都显示清晰的签名。 我们还研究了热同步辐射发射率在赤道平面，并表明，它表现出指数依赖于半径的首选M 87* parameters.ConclusionsThe黑洞的阴影是一个依赖于模型的现象-即使是扩散，光学薄源-不应该被视为广义相对论的一个通用的预测。在345 GHz的观测是有希望的未来空间VLBI测量的光子环的形状，因为在这个频率的信号，然后= 2环持续存在，尽管在我们的模型中的磁盘厚度和非零吸收功能。 未来的工作需要调查这一结论是否适用于更广泛的合理模型。
ContextHigh-frequency very-long-baseline interferometry (VLBI) observations can now resolve the event-horizon-scale emission from sources in the immediate vicinity of nearby supermassive black holes. Future space-VLBI observations will access highly lensed features of black hole images – photon rings – that will provide particularly sharp probes of strong-field gravity.AimsFocusing on the particular case of the supermassive black hole M 87*, our goal is to explore a wide variety of accretion flows onto a Kerr black hole and to understand their corresponding images and visibilities. We are particularly interested in the visibility on baselines to space, which encodes the photon ring shape and whose measurement could provide a stringent test of the Kerr hypothesis.MethodsWe developed a fully analytical model of stationary, axisymmetric accretion flows with a variable disk thickness and a matter four-velocity that can smoothly interpolate between purely azimuthal rotation and purely radial infall. To determine the observational appearance of such flows, we numerically integrated the general-relativistic radiative transfer equation in the Kerr spacetime, taking care to include the effects of thermal synchrotron emission and absorption. We then Fourier transformed the resulting images and analyzed their visibility amplitudes along the directions parallel and orthogonal to the black hole spin projected on the observer sky.ResultsOur images generically display a wedding cake structure composed of discrete, narrow photon rings (n= 1, 2, …) stacked on top of broader primary emission that surrounds a central brightness depression of model-dependent size. At 230 GHz, then= 1 ring is always visible, but then= 2 ring is sometimes suppressed due to absorption. At 345 GHz, the medium is optically thinner and then= 2 ring displays clear signatures in both the image and visibility domains. We also examine the thermal synchrotron emissivity in the equatorial plane and show that it exhibits an exponential dependence on the radius for the preferred M 87* parameters.ConclusionsThe black hole shadow is a model-dependent phenomenon – even for diffuse, optically thin sources – and should not be regarded as a generic prediction of general relativity. Observations at 345 GHz are promising for future space-VLBI measurements of the photon ring shape, since at this frequency the signal of then= 2 ring persists despite the disk thickness and nonzero absorption featured in our models. Future work is needed to investigate whether this conclusion holds in a larger variety of reasonable models.