Towards an understanding of third-order galaxy-galaxy lensing
Towards an understanding of third-order galaxy-galaxy lensing
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DOI：
10.1051/0004-6361/201218993
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发表时间：
2012-02
影响因子：
6.5
通讯作者：
P. Simon;P. Schneider;D. Kubler
中科院分区：
文献类型：
--
作者：
P. Simon;P. Schneider;D. Kubler
上下文。三阶星系-星系透镜(G3L)是下一代星系-星系透镜(GGL)技术，它测量透镜对的过剩剪切或透镜的过剩剪切-剪切关联。从它们的定义来看，很明显，这些统计数据评估了星系位置和投射物质密度之间的三点相关性。目标。对于这些新的统计数据的未来应用，我们的目标是对G3L有一个更直观的理解，以分离出可能可以测量的主要特征。方法：研究方法。我们构造了一个用于星系和伴生物质分布的玩具模型(“孤立透镜模型”；ILM)，以确定两个G3L关联函数和传统GGL在简化背景下的测量量。ILM假设单透镜星系嵌入在任意物质晕中，然而，这些物质晕在统计上与任何其他晕或透镜位置是独立的(“孤立的”)。星系团及其常见的星系团物质光晕是聚集较小光晕的结果。特别是，在ILM中，任何大小星系团的平均质量与星系数之比都不会改变。结果。仅靠GGL和星系团不能将ILM与任何更复杂的场景区分开来。然而，透镜-透镜-剪切相关器与二阶统计量相结合，使我们能够检测与ILM的偏差。这可以用文中定义的差值信号来量化。我们用ILM证明了这个相关器拾取了星系团内星系对的过剩物质分布，而红移很好的透镜对只抑制了相关器的总振幅。幅度抑制可以归一化。透镜-透镜-剪切相关器对物质晕之间的变化很敏感。原则上，它可以被设计成限制光晕的椭圆度，而不需要发光示踪剂，甚至不需要随机的光晕子结构。
Context. Third-order galaxy-galaxy lensing (G3L) is a next generation galaxy-galaxy lensing (GGL) technique that either measures the excess shear about lens pairs or the excess shear-shear correlations about lenses. From their definition it is clear that these statistics assess the three-point correlations between galaxy positions and projected matter density. Aims. For future applications of these novel statistics, we aim at a more intuitive understanding of G3L to isolate the main features that possibly can be measured. Methods. We construct a toy model (“isolated lens model”; ILM) for the distribution of galaxies and associated matter to determine the measured quantities of the two G3L correlation functions and traditional GGL in a simplified context. The ILM presumes single lens galaxies to be embedded inside arbitrary matter haloes that, however, are statistically independent (“isolated”) from any other halo or lens position. Clusters of galaxies and their common cluster matter haloes are a consequence of clustering smaller haloes. In particular, the average mass-to-galaxy number ratio of clusters of any size cannot change in the ILM. Results. GGL and galaxy clustering alone cannot distinguish an ILM from any more complex scenario. The lens-lens-shear correlator in combination with second-order statistics enables us to detect deviations from a ILM, though. This can be quantified by a difference signal defined in the paper. We demonstrate with the ILM that this correlator picks up the excess matter distribution about galaxy pairs inside clusters, whereas pairs with lenses well separated in redshift only suppress the overall amplitude of the correlator. The amplitude suppression can be normalised. The lens-lens-shear correlator is sensitive to variations among matter haloes. In principle, it could be devised to constrain the ellipticities of haloes, without the need for luminous tracers, or maybe even random halo substructure.