Exploring the Universe with radio and optical galaxy surveys

在过去的二十年里，我们进入了宇宙学的“黄金时代”。利用卫星和地面望远镜，我们收集了早期宇宙的高质量数据，主要是大爆炸后发出的光，以及晚期宇宙通过恒星和星系发出的光。然而，我们宇宙的很大一部分历史和体积仍然没有被探索。应对这一挑战的一种方法是观察中性氢(HI)发出的光。在大爆炸之后和第一个星系形成之前，中性氢(HI)充斥了宇宙很长一段时间。在那之后，HI位于星系内，所以我们也可以用它作为研究晚宇宙的一种新方法。这是我的主要研究领域；它令人兴奋，因为它为宇宙打开了一个新的观测窗口，可以推动我们对天体物理学和宇宙学的理解。在接下来的几年里，将使用射电望远镜进行精致灵敏度的HI测量，部分拟议的研究正在研究新技术，以最大限度地提高科学产出。我开创了一种新的观测方法，这种方法不需要对单个星系进行困难和昂贵的探测，而是以大的3D像素(跨越天空和长时间)绘制来自多个星系的整个HI通量图。我的目标是使用来自Meerkat和SKA阵列的HI强度映射数据，使用这种技术来提供宇宙的3D地图。Meerkat是一台位于南非卡鲁的射电望远镜，它是平方公里阵列(SKA)的探路者，SKA将成为世界上最大的射电望远镜。我的主要目标是建立一条完整的管道，用于对来自Meerkat和SKA等仪器的HI强度映射信号进行宇宙学分析。这一渠道还将考虑到HI和传统光学星系调查之间强大协同作用的可能性，包括交叉关联数据分析工具。这对于获得没有系统污染的测量是有用的，因为系统污染经常困扰着个别调查(但在合并调查时会丢失)，因此更可靠。我的目标是使用强度映射技术首次测量射电波长中的HI和宇宙学参数，利用多波长协同效应，并彻底改变我们对星系演化和暗能量的理解。我还在从事未来十年中规模最大、也是最好的两项光学星系调查--欧几里德卫星任务和地面大型天气观测望远镜，该望远镜的主要目标是测量暗能量并了解宇宙的初始条件。在欧几里德，我正在从事各种项目，包括构建一旦数据可用就将用于分析的软件工具。我还在致力于一项非常具有挑战性的任务，即对星系在小范围内聚集的方式进行建模，以便为宇宙学提取有用的信息。我还在使用量身定制的模拟来评估欧几里得将如何准确地测量最大的宇宙尺度，以便描述宇宙的初始条件。在欧几里德和LSST，我都在研究与无线电实验的协同效应。我的目标是找到创新的方法，以最佳方式将光学和无线电调查结合起来，以最大限度地提高它们的联合科学产出。使用这些调查的另一个令人兴奋的部分是将会有大量的数据可用。例如，SKA的第一阶段预计每年产生300 PB的数据产品。我的研究包括开发现代化和创新性的数据处理和分析管道，这是这些令人惊叹的调查成功所必需的。

During the last two decades we have entered a "golden era" of cosmology. Using satellites and ground based telescopes we have gathered high quality data from the very early Universe, essentially from light emitted right after the Big Bang explosion, as well as from the late Universe, through the light emitted from stars and galaxies.However, a big part of our Universe's history and volume remains unexplored. A way to attack this challenge is by observing the light emitted from the neutral hydrogen (HI) that filled the Universe for a long time after the Big Bang and before the first galaxies were formed. After that time HI resides within galaxies, so we can also use it as a novel way to study the late Universe. This is my main area of research; it is exciting because it opens a new observational window into the Universe and can push the boundaries of our understanding of astrophysics and cosmology.In the next few years, HI surveys of exquisite sensitivity will be performed using radio telescopes, and part of the proposed research is working on new techniques in order to maximise their science output. I have pioneered a new observational method that does not require the -difficult and expensive- detection of individual galaxies but maps the entire HI flux coming from many galaxies together in large 3D pixels (across the sky and along time). I aim to use this technique to provide a 3D map of the Universe using HI intensity mapping data from the MeerKAT and SKA arrays. MeerKAT is a radio telescope located in Karoo, South Africa, and it is a pathfinder for the Square Kilometre Array (SKA), which is going to be the largest radio telescope in the world.My main goal is to build a complete pipeline for the cosmological analysis of the HI intensity mapping signal from instruments like MeerKAT and the SKA. This pipeline will also account for the possibility of powerful synergies between HI and traditional optical galaxy surveys, by including cross-correlations data analysis tools. This is useful in order to obtain measurements that are free of systematic contaminations that often plague individual surveys (but drop out when combining them), and therefore more robust. I aim to perform the first ever measurements of HI and cosmological parameters in the radio wavelength using the intensity mapping technique, exploit multi-wavelength synergies, and revolutionarise our understanding of galaxy evolution and dark energy. I am also working on two of the largest and best optical galaxy surveys of the next decade, the Euclid satellite mission and the ground-based Large Synoptic Survey telescope, whose main goals are to measure dark energy and understand the initial conditions of the Universe. In Euclid, I am working on various projects including building the software tools that are going to be used for the analysis of the data as soon as they become available. I am also working on the very challenging task of modelling the way galaxies cluster on small scales, in order to extract useful information for cosmology. I am also using tailored simulations to assess how well Euclid will measure the largest cosmological scales in order to characterise the initial conditions of the Universe. In both Euclid and LSST, I am working on synergies with radio experiments. My goal is to find innovative ways to optimally combine optical and radio surveys, in order to maximise their joint scientific output. Another exciting part of working with these surveys is the huge amount of data that are going to be available. For example, the Phase 1 of the SKA is expected to generate 300 petabytes of data products every year. My research includes developing modernised and innovative data processing and analysis pipelines, which is required for the success of these amazing surveys.