arXivDaily arXiv每日学术速递 周一至周五更新
arXiv 2004.13435astro-ph.GA
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强透镜II的星系质量分布:椭圆幂律模型

Galaxy mass profiles from strong lensing II: The elliptical power-law model

Conor M. O'Riordan, Stephen J. Warren, Daniel J. Mortlock

摘要:

我们给出了一个系统的分析约束$σ_γ$对质量剖面斜率$γ$可获得时,拟合一个奇异的幂律椭球模型,以典型的强透镜观测的扩展源。这些结果扩展了我们以前对循环系统的分析。我们从676个模拟观察中得出我们的结果,这些模拟观察覆盖了一系列图像配置,每个图像都是用图像中的固定信噪比$S=100$创建的。我们使用理论和简化模型的组合来分析结果,该模型识别对每个透镜化图像中的各个通量和位置的约束的贡献。有以下主要結果: 1.对于任意的透镜椭圆率,两个像系的约束条件$σ_γ$可以用文献1的结果很好地描述,并转换到椭圆坐标系;我们推导了源与透镜轴对准的系统的$σ_γ$的解析表达式;对于两像系统和对准系统,$σ_γ$都受到通量不确定性的限制;根据光源尺寸,离轴四像系统的约束条件比双像系统的约束条件好2到8倍,并且随着透镜椭圆率的增加而改善。我们证明,在这些系统中,$γ$的约束仅来自图像的互补位置信息,而不使用通量。互补性随着源与轴的偏移的增加而改善,使得对于$S=100$,当源接近焦散时出现最佳约束$σ_γ<0.01$。

英文摘要:

We present a systematic analysis of the constraints $σ_γ$ on the mass profile slope $γ$ obtainable when fitting a singular power-law ellipsoid model to a typical strong lensing observation of an extended source. These results extend our previous analysis of circular systems, Paper I. We draw our results from 676 mock observations covering a range of image configurations, each created with a fixed signal to noise ratio $S=100$ in the images. We analyse the results using a combination of theory and a simplified model which identifies the contribution to the constraints of the individual fluxes and positions in each of the lensed images. The main results are: 1. For any lens ellipticity, the constraints $σ_γ$ for two image systems are well described by the results of Paper I, transformed to elliptical coordinates; 2. We derive an analytical expression for $σ_γ$ for systems with the source aligned with the axis of the lens; 3. For both two-image systems and aligned systems, $σ_γ$ is limited by the flux uncertainties; 4. The constraints for off-axis four-image systems are a factor of two to eight better, depending on source size, than for two-image systems, and improve with increasing lens ellipticity. We show that the constraints on $γ$ in these systems derive from the complementary positional information of the images alone, without using flux. The complementarity improves as the offset of the source from the axis increases, such that the best constraints $σ_γ<0.01$, for $S=100$, occur when the source approaches the caustic.

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