The third-order correlation functions of galaxy-galaxy lensing

三阶星系-星系透镜（G3L）有望成为研究暗物质/星系联系的引力透镜的下一代工具。正如提议者和他们的合作者所证明的那样，G3L很容易从现有的和即将到来的数据（如CFHTLS）中测量出来，具有很高的意义。然而，对于G3L新的相关功能究竟反映了什么，我们仍然缺乏更深入的了解。对G3L相关函数之一G的初步研究——涉及到透镜对的叠加剪切信号——意味着它为探测星系对的共同（暗）物质环境提供了一种工具。这里提出的项目旨在提高我们对G3L，特别是G的理论认识，此外，根据现有和即将到来的观测数据，在暗物质密度场中测试现有的星系形成和演化模型。为了加深对G3L的理论理解，我提出了两个关于G3L的博士论文项目。首先，提出了G3L在两种不同复杂性水平（简化晕模型和复杂晕模型）下的理论建模方案。这些模型最终将用于解释观测数据。第二个项目将暗物质和星系模型的预测与观测数据进行对比。这一步的目标是为现有星系模型的改进提供输入。此外，该项目通过包含相关星系的径向距离信息，提高了从G中提取的统计信息的数量。最后，两位学生将考虑迄今为止未被探索的G的变体，将其呈现为不同星系类型之间的相互关联函数。

Third-order galaxy-galaxy lensing (G3L) promises to be the next generation tool in gravitational lensing for investigating the dark matter/galaxy connection. As the proposers demonstrated with their collaborators, G3L is readily measured with high significance from existing and upcoming data such as the CFHTLS. We still lack, however, a deeper understanding of what exactly is reflected in the new correlation functions of G3L. Preliminary work on one of the G3L correlation functions G – involving the stacked shear signal about pairs of lenses – implies that it provides a tool for probing the common (dark) matter environment of galaxy pairs. The project proposed here aims at advancing our theoretical understanding about G3L, in particular G, and, moreover, at testing existing models for galaxy formation and evolution within the dark matter density field against the available and upcoming observational data. To achieve better theoretical understanding, two doctoral thesis projects on G3L are proposed. First, a project on the theoretical modelling of G3L on two different complexity levels (a simplified and a sophisticated halo model) is proposed. The models will eventually be used to interpret observational data. A second project confronts forecasts from dark matter and galaxy models with the observational data. It is the goal of this step to provide input for improvements of existing galaxy models. Moreover, this project improves the amount of statistical information extracted from G by including radial distance information of the galaxies involved. Finally, both students will consider a hitherto unexplored variant of G, rendering it a cross-correlation function between different galaxy types.