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Dark Matter Structure in Galaxies

星系中的暗物质结构

基本信息

批准号：
17540210
负责人：
CHIBA Masashi
金额：
$ 1.09万
依托单位：
Tohoku University
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
2005
资助国家：
日本
起止时间：
2005 至 2006
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/en/grant/KAKENHI-PROJECT-17540210/
关键词：
Astrophysics Dark Matter

项目摘要

We investigate the extended source size effects on gravitational lensing in which a lens consists of a smooth potential and small mass clumps ("substructure lensing"). We first consider a lens model that consists of a clump modeled as a singular isothermal sphere (SIS) and a primary lens modeled as an external background shear and convergence. For this simple model, we derive analytic formulae for (de)magnification of circularly symmetric top-hat sources with three types of parity for their lensed images, namely, positive, negative and doubly negative parities. Provided that the source size is sufficiently larger than the Einstein radius of an SIS, we find that in the positive (doubly-negative) parity case, an extended source is always magnified (demagnified) in comparison with an unperturbed macrolens system, whereas in the negative parity case, (de)magnification effect which depends on a sign of convergence minus unity is weaker than those in other parities. It is shown that a measurement of distortion pattern in a multiply lensed image enables us to break the degeneracy between the lensing effects of a clump mass and those of a clump distance if lensing parameters of the relevant macrolens model are determined from the position and flux of multiple images. We also show that an actual density profile of a clump can be directly measured by analyzing a "fine structure" in a multiply lensed image within the Einstein radius of a clump.

我们研究了扩展源尺寸对引力透镜效应的影响，其中透镜由平滑势和小质量团块（“子结构透镜”）组成。我们首先考虑一个透镜模型，该模型由建模为奇异等温球 (SIS) 的团块和建模为外部背景剪切和会聚的主透镜组成。对于这个简单的模型，我们推导了圆形对称平顶光源的放大（缩小）解析公式，其透镜图像具有三种类型的奇偶校验，即正奇偶校验、负奇偶校验和双负奇偶校验。假设光源尺寸足够大于SIS的爱因斯坦半径，我们发现在正（双负）宇称情况下，与未受扰动的微透镜系统相比，扩展光源总是被放大（缩小），而在负宇称情况下，取决于收敛符号减去统一的放大（缩小）效应比其他宇称弱。结果表明，如果相关微距透镜模型的透镜参数是根据多个图像的位置和通量确定的，那么对多透镜图像中的畸变模式的测量使我们能够打破团块质量的透镜效应与团块距离的透镜效应之间的简并性。我们还表明，通过分析团块爱因斯坦半径内的多透镜图像中的“精细结构”，可以直接测量团块的实际密度分布。