星际散射对银心（人马座A*）辐射偏振性质影响的研究

This project is aimed to study the interstellar scattering effects on the polarization properties of Sagittarius A* (Sgr A*), the compact radio source in Galactic Center. The polarizations in centimeter to sub-millimeter band are mainly considered. The advanced algorithm for calculation of Faraday coefficients developed by the applicant is going to be adopted to simulate the intrinsic polarization properties of emission in the vicinity of central super-massive black hole in Sgr A*. A new code based on Monte Carlo algorithm is going to be developed to simulate the external effects caused by interstellar scattering, and to predict the spectra of both circular and linear polarization which can be detected in real observations. By the comparison between the intrinsic spectra and the external one of polarizations, the origin of polarization in Sgr A* is going to be investigated, and the relationship between observational data of polarizations and the viewing angle of the central black hole will be established. In addition, the parameters of current radio telescopes which work in millimeter and sub-millimeter band will be considered, to study the feasibility of testing the theoretical polarization properties in practice. This project provides functional support from theoretical view on future observational designs.

本项目将研究星际散射对银河系中心射电源人马座A*辐射的偏振性质的影响。该研究集中在厘米至亚毫米波段，将利用申请人研究所得的在国际上具有优势的法拉第系数计算方法模拟人马座A*中央黑洞附近辐射物质的内禀偏振性质，同时通过Monte Carlo算法模拟外部星际散射效应，得到可被实际观测的圆偏振与线偏振光谱。通过对内禀光谱和散射后光谱的比较，来探究人马座A*偏振辐射的起源，并重新确立偏振观测数据与中央黑洞视向角之间的关系。该项目将进一步结合现有的毫米及亚毫米波段工作台站的实际参数，讨论实际观测检验理论偏振性质的可行性，为将来的观测设计提供非常实用的理论支持。

本课题期间主要搭建了二维无力场数值模拟原创平台、以及相配套的半解析数值计算程序。其中数值模拟程序得到了基本调试，可以进入试用阶段。而半解析数值计算程序得已经得到应用、并获得成果。我们对银心中央黑洞的观测现象做了后续研究。在此基础上，针对银河系中心区域磁星的发现，我们利用原创程序做了大量与磁星相关的理论工作，以在新的国际研究热点中占先。我们为磁星巨型闪耀这一罕见而特殊的现象提出了一个灾变爆发模型。对于以往理论工作中粗略描述的“通量绳加电流片”的磁层磁场位型，我们率先给出了精确的数学表达，并且并且做了详细的定量计算。该模型不但能够解释巨型闪耀，还足以解释巨型闪耀之后在射电波段观测到的“余辉”现象。我们在磁星磁场位型构造上所取得的成果将进一步应用到银心磁星上。此外，我们对M87黑洞及喷流也做了初步研究。我们认为M87喷流的驱动者有可能是中央黑洞的时空拖曳。本课题资助期间共发表SCI文章4篇。