Theoretical and Observational Cosmology

物理宇宙学是研究宇宙大尺度结构和演化的学科。这可以分为两个主要分支：详细研究星系如何形成和聚集在一起;以及确定描述整个宇宙的参数。我的研究涉及这两个分支的几个不同部分。在过去的几十年里，我们对宇宙学了解到的最不寻常的事实是，宇宙的大尺度性质直接适用于观测。这些观测量的测量精度越来越高，导致了宇宙学中的“标准模型”。这幅图基于一些简单的假设，提供了一个称为LambdaCDM模型的框架。目前，测量只需要一组六个参数，随着我们收集更多的数据，其不确定性将继续降低。我们知道，宇宙具有接近平坦的几何形状，并由一种神秘的暗能量主导，大部分物质也由某种未知的形式组成。早期宇宙非常平滑，具有低振幅、随机相位的密度扰动，就像早期宇宙暴胀图像中产生的那种。我们知道这些微扰通过引力不稳定性的增长，形成了我们今天在宇宙中看到的所有结构。星系是这种结构的基本组成部分，但星系形成的细节还不清楚，因为这涉及各种长度尺度和时间尺度上的大量物理过程。如果不测量取决于星系形成和演化的量，通常就无法测量六个或更多宇宙学参数。因此，宇宙学的两个主要分支的研究总是密切相关的。随着参数被测量得越来越精确，星系形成的物理学被越来越详细地剖析，我们仍然有许多未解之谜。特别是：为什么参数具有它们所具有的值？什么是暗物质和暗能量？通货膨胀真的发生了吗？我们能从中学到什么吗？标准宇宙学模型中是否缺少了一些基本要素？第一颗恒星的形成结束了宇宙的黑暗时代宇宙时间中恒星形成的历史是怎样的？星系究竟是如何形成暗物质晕的超大质量黑洞和它们内部形成的星系之间的关系是什么？宇宙和我们这一小部分的未来命运会是什么？宇宙结构的发展是一个复杂而多方面的话题。解决星系和星系团形成和演化中的最大问题需要结合观测和理论方法，涵盖电磁波谱的全部范围。亚毫米波段是一个关键的发展窗口，人们可以很容易地研究早期的恒星形成星系，以及星系团中的气体和最极端的引力透镜。正因为如此，我已经参与了几个项目和仪器，重点是使用这些波长，以进行雄心勃勃的，深河外调查。

Physical Cosmology is the study of the structure and evolution of large scales in the Universe. This can be split into two major branches: the detailed study of how galaxies formed and clustered together; and the determination of the parameters which describe the entire Cosmos. My research involves several different parts of both of these branches. The most extraordinary fact that we have learned about cosmology over the last few decades is that the large scale nature of the Universe is directly amenable to observations. These observables have been measured with increasing precision, leading to a "standard model" in cosmology. This picture is based on a few simple assumptions, providing a framework called the LambdaCDM model. Right now the measurements require a set of only six parameters, whose uncertainties continue to decrease as we gather more data. We know that the Universe has close to flat geometry, and is dominated by a mysterious dark energy, with most of the matter also made of some as yet unknown form. The early Universe was very smooth, with low amplitude, random-phase density perturbations, of the sort generated in the inflationary picture of the early Universe. And we know that those perturbations grew through gravitational instability to make all the structure that we seee in the Universe today. Galaxies are the fundamental building blocks of this structure, but the details of galaxy formation are not yet understood, because this involves a huge range of physical processes on a variety of length scales and time scales. Measuring the six or more cosmological parameters cannot typically be done without also measuring quantities that depend on galaxy formation and evolution. Hence the study of the two main branches of cosmology are always intimately connected. With the parameters being measured to greater and greater precision, and the physics of galaxy formation being dissected in ever increasing detail, we are still left with many unsolved puzzles. In particular: why do the parameters have the values that they do? what are the dark matter and the dark energy? did inflation really happen and can we learn anything about it? are some basic ingredients currently missing from the standard cosmological model? when exactly did the first stars form to end the cosmic dark ages? what is the history of star-formation over cosmic time? how exactly do galaxies populate the halos of dark matter? what is the relationship between supermassive black holes and the galaxies that they form inside? what will be the far future fate of the Universe and of our small part of it? The development of structure in the Universe is a complex and multi-faceted topic. Tackling the biggest questions in the formation and evolution of galaxies and clusters of galaxies requires a combination of observational and theoretical approaches, covering the full range of the electromagnetic spectrum. A crucial and developing window is in the sub-millimetre band, where one can readily study star-forming galaxies at very early times, as well as the gas in clusters, and the most extreme gravitational lenses. Because of this I have become involved in several projects and instruments which focus on using these wavelengths in order to conduct ambitious, deep extragalactic surveys.