引力透镜的微扰
Perturbation of Gravitational Lensing
摘要：
引力透镜系统可以被角度接近但距离不同的“流氓系统”扰动。一个质点受到另一个质点的扰动，可以看作是双散射二质点（DSTP）透镜的大分离近似。所得到的有效透镜取决于扰动器是否比主透镜系统更接近或更远离观察者。当扰动体是第一个散射体时，焦散面小于大间距二元透镜的焦散面;当扰动体是最后一个散射体时，焦散面与大间距二元透镜的焦散面相似。模拟星系的引力透镜，除了在不同红移的扰动的常切变外，还需要额外的项。研究了双散射双分布质量透镜。受扰星系的行为就像一个椭圆--或一个质点--因为椭圆质量分布的偶极矩为零。
英文摘要：
A gravitational lens system can be perturbed by "rogue systems" in angular proximities but at different distances. A point mass perturbed by another point mass can be considered as a large separation approximation of the double scattering two point mass (DSTP) lens. The resulting effective lens depends on whether the perturber is closer to or farther from the observer than the main lens system. The caustic is smaller than that of the large separation binary lens when the perturber is the first scatterer; the caustic is similar in size with the large separation binary lens when the perturber is the last scatterer. Modelling of a gravitational lensing by a galaxy requires extra terms other than constant shear for the perturbers at different redshifts. Double scattering two distributed mass (DSTD) lens is considered. The perturbing galaxy behaves as a monopole -- or a point mass -- because the dipole moment of the elliptic mass distribution is zero.
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