Cosmology: from Galaxy Surveys to Dark Matter and Dark Energy

最近的宇宙学测量支持一个“和谐”模型，在这个模型中，宇宙是平的，只有4%的普通物质，21%的冷暗物质和75%的暗能量。在接下来的十年里，将加大力度限制暗能量和暗物质的性质。最有希望的宇宙学探测之一是使用星系红移和成像测量。伦敦大学学院天体物理学是致力于用这样的观测来测量暗能量的领先机构之一。我们在拟议的暗能量调查(DES)、暗宇宙探测器(DUNE)和广域多目标光谱仪(WFMOS)中发挥着主导作用，所有这些都旨在将暗能量模型与数据进行对比。提交的提案是围绕这些调查和三个探测器建立的，以限制暗能量模型，即：星系团计数、包括重子声学振荡的星系群和宇宙透镜。此外，伦敦大学学院天体物理学将可以使用高性能计算系统。为了获得对暗能量的精确约束，将观测数亿个星系并估计它们的距离。这需要基于星系颜色的快速方法(光度学红移)。我们建议雇用一名PDRA和一名博士生，他们将利用这些基于颜色的方法探索星系团测量的前景，以及它们的系统影响。第二个PDRA和一名博士生将专注于宇宙透镜和相关系统学的研究。第三个PDRA将研究如何用光学测量来校准星团(由Sunyaev-Zel‘dovich效应探测到)，以及如何利用它们进行宇宙学测量。最后，第四个PDRA和一名博士生将从事N体和流体模拟工作，研究暗能量的结构形成特性，模拟星系团，并制作真实的模拟星表，用于预测和利用弱透镜和星系团调查。伦敦大学学院的宇宙学团队在这个项目中处于有利地位。申请者在分析大型星系调查、为弱透镜观测设计调查和预测星系团调查方面经验丰富。伦敦大学学院的宇宙学团队目前由3名工作人员、5名PDRA和7名博士生组成。由于PDRA助学金很快就会结束，正如提案中概述的那样，目前有3名学生是由初创企业助学金资助的，拟议的计划将允许这些努力继续下去。这是至关重要的，这样我们才能履行我们对拟议调查的承诺，并保持我们在英国和国际合作中上述科学领域的领先地位。

The recent cosmological measurements support a `concordance' model in which the universe is flat and contains only 4 % ordinary matter, 21 % cold dark matter and 75 % dark energy. The next decade will see increased efforts to constrain the nature of dark energy and dark matter. One of the most promising cosmological probes is the use of galaxy redshift and imaging surveys. UCL Astrophysics is one of leading institutions in the effort to measure dark energy with such surveys. We have leading roles in the proposed Dark Energy Survey (DES), the Dark Universe Explorer (DUNE) and a Wide Field Multi-Object Spectrograph (WFMOS), all designed to contrast dark energy models with data. The proposal submitted is built around these surveys and three probes to constrain dark energy models, namely: cluster counts, galaxy clustering including baryon accoustic oscillations and cosmic lensing. In addition UCL Astrophysics will have access to a High Performance Computing system. In order to obtain precision constraints on dark energy, hundreds of millions of galaxies will be observed and their distance estimated. This requires fast methods based on galaxy colours ('photometric redshifts'). We propose to employ one PDRA and one PhD student who will explore the prospect of galaxy clustering measurements with these colour-based methods, and their systematic impacts. The second PDRA and a PhD student will concentrate on the study of cosmic lensing and involved systematics. The third PDRA will investigate how clusters (detected by the Sunyaev-Zel'dovich effect) can be calibrated with optical surveys and how to exploit them for cosmological measurements. Finally the fourth PDRA and a PhD student will work on N-body and hydro-simulations, studying the structure formation properties of dark energy, simulating clusters of galaxies and producing realistic mock catalogs for forecasting and exploiting weak lensing and galaxy clustering surveys. The Cosmology team at UCL is well placed for this project. The applicants are experienced in the fields of analysing large galaxy surveys, designing surveys for weak lensing observations and forecasting galaxy cluster surveys. The Cosmology team at UCL currently consists of 3 staff members, 5 PDRAs and 7 PhD students. Since the PDRA grants finish shortly, as outlined in the proposal, and 3 of the current students are funded by start-up grants, the proposed program would allow the continuation of these efforts. This is essential so that we can fulfill our commitments towards the proposed surveys and maintain our leadership in the science areas mentioned above within the UK and the international collaborations.