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/J004421/2
• 负责人: Benjamin Joachimi
• 金额: $ 44.81万
• 依托单位: University College London
• 依托单位国家: 英国
• 项目类别: Fellowship
• 财政年份: 2013
• 资助国家: 英国
• 起止时间: 2013 至 无数据
• 项目状态: 已结题
• 来源: https://gtr.ukri.org/projects?ref=ST%2FJ004421%2F2
• 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，令人困惑的是，95％的宇宙成分似乎是具有异国情调的物质形式，其性质仍然晦涩难懂。人们发现，从星系到最大结构的所有天文物体的重量都超过了它们发出的光量。因此，大多数物质必须是一种未知的，非露骨的类型，称为暗物质。此外，宇宙的几何形状及其加速膨胀暗示了存在的存在，这是一种更具异国情调的成分，据说占宇宙总能量预算的四分之三，这是深色的镜头，是揭示暗物质和暗能量的性质的最有力的方法之一。爱因斯坦的相对论告诉我们，巨大的身体会偏转光线，使银河系可以从放大镜等背景源中聚焦光线 - 它充当引力镜头。与接近放大镜的边缘的效果相似，远处星系的图像被视线沿线物质的光偏转而扭曲。在数十亿个星系上测量这些微小的扭曲，我们可以探测这些星系和地球之间物质的分布，这又取决于暗物质和暗能量的特性。这种用统计工具分析大量扭曲的星系图像的方法称为宇宙剪切。我的工作旨在使用在天空的大比例上测得的宇宙剪切力来确定宇宙黑暗构件的特性。我将将星系图像扭曲的测量结果与星系位置，速度和距离的测量结果相结合，以进一步发展，并测试我们的重力理论在宇宙学量表上是否仍然正确。充分利用即将到来的宇宙学数据集，例如由欧洲欧几里德卫星制作的我的设计为我的设计，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。高度准确的衡量值至关重要，但同样重要的是，他们同样重要的是，他们不会遭受所谓的“系统性错误”的范围，而不是遇到了不可能的态度，而这会导致不正确的态度，而这些范围的态度是不可能的，而这将使您能够遇到任何问题。测量质量的平衡，其量表有故障。严重的系统误差是由星系引起的，这些星系被物质在其附近施加的重力拉力所畸形和对齐。这种效果称为固有的对准，模仿了我们要在宇宙剪切中测量的扭曲，因此如果被忽略会导致强烈的系统误差。但是，内在的星系对准不仅是对宇宙剪切测量值的滋扰，而且可以为我们提供对星系形成和进化过程的宝贵见解，而这些过程目前仍未知。 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这些宇宙学探针中的最大信息最大，对黑暗和明亮的宇宙产生了独特的见解。

项目成果

KiDS-450: cosmological parameter constraints from tomographic weak gravitational lensing

• DOI: 10.1093/mnras/stw2805
• 发表时间: 2016-06
• 期刊: Monthly Notices of the Royal Astronomical Society
• 影响因子: 4.8
• 作者: H. Hildebrandt;M. Viola;C. Heymans;S. Joudaki;K. Kuijken;C. Blake;T. Erben;B. Joachimi;D. Klaes

Galaxy Alignments: An Overview

• DOI: 10.1007/s11214-015-0177-4
• 发表时间: 2015-07
• 期刊: Space Science Reviews
• 影响因子: 10.3
• 作者: B. Joachimi;M. Cacciato;T. Kitching;A. Leonard;R. Mandelbaum;B. Schäfer;C. Sifón;H. Hoekstra

Cluster mass profile reconstruction with size and flux magnification on the HST STAGES survey.

• DOI: 10.1093/mnras/stw027
• 发表时间: 2016-01
• 期刊: Monthly notices of the Royal Astronomical Society
• 影响因子: 4.8
• 作者: C. Duncan;C. Heymans;A. Heavens;B. Joachimi

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

• DOI: 10.1093/mnras/stw2106
• 发表时间: 2017-04-01
• 期刊: MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
• 影响因子: 4.8
• 作者: Clerkin, L.;Kirk, D.;Walker, A. R.
• 通讯作者: Walker, A. R.

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

• DOI: 10.1093/mnras/stt2060
• 发表时间: 2013-06
• 期刊: Monthly Notices of the Royal Astronomical Society
• 影响因子: 4.8
• 作者: C. Duncan;B. Joachimi;A. Heavens;C. Heymans;H. Hildebrandt