A new case of gravitational lensing
A new case of gravitational lensing
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引力透镜的新案例
作者：
J. Surdej;P. Magain;J. Swings;U. Borgeest;T. Courvoisier;R. Kayser;K. Kellermann;H. Kühr;S. Refsdal
甚至在1979年发现第一个引力透镜系统1之前（参见参考文献2，最近对其他已发表的候选者的评论），人们认识到，在一个定义明确的类星体样本中对引力透镜发生的统计评估对于更好地理解类星体光度函数和可能的类星体现象本身3，测试宇宙学模型4，5和探测宇宙中不同尺度的亮物质和暗物质分布4 -6。一年前，我们开始在智利拉西拉的欧洲南方天文台（ESO）进行系统搜索，在选定的高亮度类星体样本中寻找引力透镜系统; Mv<-29.0。这些物体是引力透镜类星体图像的有希望的候选者，具有角秒和亚角秒的分离（J.S.例如，手稿的准备和参考文献7和8）。自一九八六年十二月以来，我们已发现四宗可能的个案。本文简要介绍了我们首次发现的引力透镜系统UM 673 = Q 0142 -100 = PHL 37039 -11。它由两个图像组成，A（mR = 16.9）和B（mR = 19.1），在红移zq = 2.719处由2.2弧分开。透镜星系（mR <$19，ZL <$0.49）也被发现，它位于两个类星体图像连线的附近，距离较暗的一个图像约0.8弧。对这个系统应用引力验光法，得出透镜星系的质量为M0 = 2.4× 1011 M，到达类星体的两条光路之间最可能的旅行时间差为δt = 7周（假设H 0 = 75 km s-1 Mpc-1，q 0 = 0）。
Even before the discovery of the first gravitational lens system1 in 1979 (see ref. 2 for a recent review of the other published candidates), it was recognized that a statistical evaluation of the occurrence of gravitational lensing within a well-defined sample of quasars is important to understand better the quasar luminosity function and possibly the QSO phenomenon itself3, to test cosmological models4,5 and to probe the luminous and dark matter distribution on various scales in the Universe4–6. A year ago, we began a systematic search from the European Southern Observatory (ESO) at La Silla, Chile, for gravitational lens systems in a selected sample of highly luminous quasars; Mv<–29.0. These objects are promising candidates for gravitationally lensed QSO images with arc-second and sub-arc-second separations (J.S. et al., manuscript in preparation and refs 7 and 8). Since December 1986, we have identified four possible cases. Here we give a brief description of our first identified gravitational lens system UM673 = Q0142–100 =PHL37039–11. It consists of two images, A (mR = 16.9) and B (mR = 19.1), separated by 2.2arcs at a redshift zq = 2.719. The lensing galaxy (mR≈ 19, ZL≈0.49) has also been found. It lies very near the line connecting the two QSO images, ˜0.8 arc s from the fainter one. Application of gravitational optometry to this system leads to a value M0≈2.4×1011M⊙ for the mass of the lensing galaxy and to δt≈7 weeks for the most likely travel-time difference between the two light paths to the QSO (assuming H0= 75 km s–1 Mpc–1,q0 = 0).