天文学进展2011，Vol.29Issue(4)：422-440,19.
引力透镜和弱引力透镜的新方法
Gravitational Lensing and the New Method in Weak Gravitational Lensing
摘要
Abstract
Gravitational lensing is one of the most powerful tools in astrophysics. In particular it is significant in the explorations of extra-solar planets, in the investigations of the dark universe (dark matter and dark energy), and in testing gravity at cosmological scales. The great advantage of gravitational lensing is that it is directly dependent on gravity only, and does not depend on the nature of dark matter or complicated baryonic physics.First, we review the fundamental theory and approximations of gravitational lensing in which matter distribution (such as a stars, galaxies, galaxy clusters or large scale structure (LSS)) bends light propagating between a distant source and the observer. We discuss three types of gravitational lensing based on the scale of the lensing system: micro, weak, and strong lensing and their applications in extra-solar planet searches (micro lensing) and constraining density profile of dark matter halos (strong lensing). Then we report and review new progresses in gravitational lensing and introduce a new interpretation of gravitational lensing by employing the split of wavefront.Second, we discuss the use of weak lensing in cosmology. Gravitational lensing can be split into convergence and shear terms. The convergence magnifies the fluxes of background galaxies by increasing their sizes, while the shear stretches them tangentially around the foreground mass. Since the distortion of the shape and size of the galaxies is weak and tiny, significant shear effects can only be detected statistically using large number of background galaxies. This effect is known as cosmic shear. In the past decade, there are a number of works focusing on using cosmic shear effect to study the LSS and to constrain cosmological parameters. However, weak lensing measurements through cosmic shear still suffers from observational uncertainties and systematics such as the intrinsic alignment and the shapeerror of galaxies.Finally, we introduce a new method to reconstruct weak lensing through cosmic magnification. The cosmic magnification changes the galaxy number density with respect to the distortion of images by cosmic shear. The magnification effect of increasing flux and solid angle either enhances or suppresses galaxy number density, depending on the logarithmic slope (a) of the galaxy luminosity function at the observational flux limit. Cosmic magnification effect introduces extra correlations in galaxy clustering and correlates galaxies at widely separated redshifts. It has been shown that weighting each background object by it's a-1 can significantly improve the cosmic magnification measurement. However, we find that this weighting function is optimal only for sparse background populations in which intrinsic clustering is negligible with respect to shot noise. We derive the optimal weighting function for the general case including scale dependent and scale independent weights. Our weighting function outperforms the commonly used weighting function a - 1 by larger factors for surveys with denser background populations. We believe our optimal weighting function for cosmic magnification measurement will be useful in BigBOSS, CFHTLS, COSMOS, DES, Euclid, LSST, SKA, WFIRST, etc.关键词
引力透镜/波阵面/宇宙放大/宇宙学/暗物质/暗能量Key words
Gravitational lensing/ wave front/ cosmic magnification/ cosmology/ dark matter/ dark energy分类
天文与地球科学引用本文复制引用
杨晓峰..引力透镜和弱引力透镜的新方法[J].天文学进展,2011,29(4):422-440,19.基金项目
国家自然科学基金(Y045081001,0942234001) （Y045081001,0942234001）
