Advancing weak lensing and intrinsic galaxy alignment studies into the era of precision cosmology

将弱透镜和内在星系排列研究推进到精密宇宙学时代

• 批准号: ST/J004421/1
• 负责人: Benjamin Joachimi
• 金额: $ 55.16万
• 依托单位: University of Edinburgh
• 依托单位国家: 英国
• 项目类别: Fellowship
• 财政年份: 2012
• 资助国家: 英国
• 起止时间: 2012 至 无数据
• 项目状态: 已结题
• 来源: https://gtr.ukri.org/projects?ref=ST%2FJ004421%2F1
• 关键词: Advancing; weak; lensing; intrinsic; galaxy

Cosmologists can nowadays successfully explain the key features of the Universe in a consistent framework. However it is puzzling that 95% of the cosmic ingredients appear to be in exotic forms of matter whose nature is still obscure. One finds that all astronomical objects, ranging from galaxies up to the largest structures, weigh more than the amount of light which they emit suggests. Hence, the majority of matter must be of a yet unknown, non-luminous type, termed dark matter. Furthermore, the geometry of the Universe and its accelerating expansion hint at the existence of dark energy, an even more exotic component that supposedly makes up three quarters of the total cosmic energy budget.Gravitational lensing is one of the most powerful ways of revealing the nature of dark matter and dark energy. Einstein's theory of relativity tells us that massive bodies deflect light such that a galaxy can focus the light from a background source like a magnifying glass - it acts as a gravitational lens. Similar to the effects close to the rim of a magnifying glass, the images of distant galaxies are distorted by the deflections of light by the matter along the line of sight. Measuring these tiny distortions on billions of galaxies, we can probe the distribution of matter between those galaxies and Earth, which in turn is determined by the properties of dark matter and dark energy. This method of analysing large numbers of distorted galaxy images with statistical tools is called cosmic shear.My work aims at determining the properties of the dark building blocks of the Universe with high precision, using cosmic shear measured on large fractions of the sky. I am going to combine measurements of galaxy image distortions with those of galaxy positions, velocities, and distances to go even further and test whether our theory of gravity is still correct on cosmological scales. To make the most of upcoming cosmological data sets, as e.g. produced by the European Euclid satellite whose design I have contributed to, I am going to develop and apply new measurement methods and analysis tools which allow us to access information that has remained unused hitherto.Obtaining highly accurate measurements is crucial, but it is equally important that they do not suffer from so-called "systematic errors": undetected deviations from the true result which would produce wrong answers and lead us to incorrect conclusions, much like measuring masses with a balance that has a faulty scale. A serious systematic error is caused by galaxies which are deformed and aligned by the gravitational pull exerted by matter in their neighbourhood. This effect, called intrinsic alignment, mimics the distortions that we want to measure in cosmic shear and thus causes strong systematic errors if ignored. However, intrinsic galaxy alignment is not only a nuisance to cosmic shear measurements, but can provide us with valuable insight into processes of galaxy formation and evolution which are still largely unknown at present. To improve both our understanding of galaxies and the control of cosmic shear systematic errors, I will undertake the hitherto biggest effort of measuring and analysing intrinsic alignments, combining large data sets taken with telescopes at the world's best observational sites on Hawaii and the Canary Islands, in the Atacama desert and Australia.By studying cosmic shear and intrinsic galaxy alignments jointly, I will be able to extract a maximum of information from each of these cosmological probes, yielding unique insights into both the dark and bright Universe.

如今，宇宙学家可以在一致的框架中成功解释宇宙的关键特征。然而，令人费解的是，95% 的宇宙成分似乎都是奇异的物质形式，其性质仍然模糊。人们发现，所有天体，从星系到最大的结构，其重量都超过它们发出的光量。因此，大多数物质必定是一种未知的、不发光的类型，称为暗物质。此外，宇宙的几何形状及其加速膨胀暗示着暗能量的存在，暗能量是一种更奇特的成分，据说占宇宙总能量预算的四分之三。引力透镜是揭示本质的最有力方法之一暗物质和暗能量。爱因斯坦的相对论告诉我们，大质量的物体会偏转光线，这样星系就可以像放大镜一样聚焦来自背景源的光线——它充当引力透镜。与放大镜边缘附近的效果类似，遥远星系的图像会因视线上的物质对光的偏转而扭曲。通过测量数十亿个星系上的这些微小扭曲，我们可以探测这些星系和地球之间的物质分布，而这又是由暗物质和暗能量的特性决定的。这种用统计工具分析大量扭曲星系图像的方法称为宇宙剪切。我的工作旨在利用在大部分天空上测量的宇宙剪切，高精度地确定宇宙黑暗构件的特性。我将把星系图像扭曲的测量与星系位置、速度和距离的测量结合起来，进一步测试我们的引力理论在宇宙尺度上是否仍然正确。为了充分利用即将到来的宇宙学数据集，例如由我参与设计的欧洲欧几里得卫星产生的，我将开发和应用新的测量方法和分析工具，使我们能够访问迄今为止尚未使用的信息。获得高精度的测量至关重要，但同样重要他们不会遭受所谓的“系统误差”：与真实结果存在未被发现的偏差，这会产生错误的答案并导致我们得出错误的结论，就像用天平测量质量时天平有缺陷一样。严重的系统误差是由邻近物质施加的引力而变形和排列的星系引起的。这种效应称为内在对准，它模仿了我们想要在宇宙剪切力中测量的扭曲，因此如果忽略的话会导致严重的系统误差。然而，星系的内在排列不仅对宇宙剪切测量造成干扰，而且可以为我们提供对目前仍知之甚少的星系形成和演化过程的宝贵见解。为了提高我们对星系的理解和对宇宙剪切系统误差的控制，我将采取迄今为止最大的努力来测量和分析内在排列，结合在夏威夷和加那利群岛世界上最好的观测地点用望远镜拍摄的大型数据集，在阿塔卡马沙漠和澳大利亚。通过共同研究宇宙剪切和内在星系排列，我将能够从每个宇宙学探测器中提取最大的信息，从而对黑暗和明亮产生独特的见解宇宙。

项目成果

Flat-Sky Pseudo-Cls Analysis for Weak Gravitational Lensing

弱引力透镜的平空伪 Cls 分析

• DOI: http://dx.10.48550/arxiv.1612.04664
• 发表时间: 2016
• 作者: Asgari M

KiDS-i-800: comparing weak gravitational lensing measurements from same-sky surveys

KiDS-i-800：比较同一天空观测的弱引力透镜测量

• DOI: http://dx.10.1093/mnras/sty859
• 发表时间: 2018
• 期刊: Monthly Notices of the Royal Astronomical Society
• 影响因子: 4.8
• 作者: Amon A

On the complementarity of galaxy clustering with cosmic shear and flux magnification

论星系团与宇宙剪切和通量放大的互补性

• DOI: http://dx.10.1093/mnras/stt2060
• 发表时间: 2014
• 期刊: Monthly Notices of the Royal Astronomical Society
• 影响因子: 4.8
• 作者: Duncan C

Testing the lognormality of the galaxy and weak lensing convergence distributions from Dark Energy Survey maps

从暗能量勘测图中测试星系的对数正态性和弱透镜会聚分布

• DOI: 10.1093/mnras/stw2106
• 发表时间: 2016-05-06
• 期刊: Monthly Notices of the Royal Astronomical Society
• 影响因子: 4.8
• 作者: L. Clerkin;D. Kirk;M. Manera;O. Lahav;F. Abdalla;A. Amara;D. Bacon;C. Chang;E. Gaztañaga
• 通讯作者: E. Gaztañaga

KiDS+2dFLenS+GAMA: testing the cosmological model with the EG statistic

KiDS 2dFLenS GAMA：用 EG 统计量测试宇宙模型

• DOI: 10.1093/mnras/sty1624
• 发表时间: 2017-11-29
• 期刊: Monthly Notices of the Royal Astronomical Society
• 影响因子: 4.8
• 作者: A. Amon;C. Blake;C. Heymans;C. D. Leonard;M. Asgari;Maciej Bilicki;A. Choi;T. Erben;K. Glazebrook;J. Harnois;H. Hildebr;t;t;H. Hoekstra;B. Joachimi;S. Joudaki;K. Kuijken;C. Lidman;J. Loveday;D. Parkinson;E. Valentijn;C. Wolf
• 通讯作者: C. Wolf