Collaborative international efforts under the name of the Event HorizonTelescope project, using sub- mm very long baseline interferometry, are soonexpected to provide the first images of the shadow cast by the candidatesupermassive black hole in our Galactic center, Sagittarius A*. Observations ofthis shadow would provide direct evidence of the existence of astrophysicalblack holes. Although it is expected that astrophysical black holes aredescribed by the axisymmetric Kerr solution, there also exist many other blackhole solutions, both in general relativity and in other theories of gravity,which cannot presently be ruled out. To this end, we present calculations ofblack hole shadow images from various metric theories of gravity as describedby our recent work on a general parameterisation of axisymmetric black holes[R. Konoplya, L. Rezzolla and A. Zhidenko, Phys. Rev. D 93, 064015 (2016)]. Analgorithm to perform general ray-tracing calculations for any metric theory ofgravity is first outlined and then employed to demonstrate that even forextremal metric deformation parameters of various black hole spacetimes, thisparameterisation is both robust and rapidly convergent to the correct solution.
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机译：不久，国际上以Event HorizonTelescope项目名义开展的国际合作，预计将使用亚毫米甚长的基线干涉测量技术，以提供由我们银河中心射手座A *候选超大质量黑洞投射的阴影的第一张图像。对这一阴影的观察将提供天体物理黑洞存在的直接证据。尽管可以通过轴对称Kerr解描述天体黑洞，但从广义相对论和其他引力理论来看，还存在许多其他黑洞解决方案，目前尚不能排除。为此，我们提出了根据各种重力度量理论对黑洞阴影图像的计算，正如我们最近对轴对称黑洞的一般参数化所描述的那样。 Konoplya，L。Rezzolla和A. Zhidenko，物理学。 D 93，064015（2016）。首先概述了对重力的任何度量理论进行通用射线追踪计算的算法，然后证明了该算法，即使对于各种黑洞时空的极度度量变形参数，该参数也具有鲁棒性并且可以迅速收敛到正确的解。
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