Exploring the early evolution of galaxies

我们理解宇宙的核心是星系演化的主题。这些由恒星、气体、尘埃和暗物质组成的大型系统如何从大爆炸产生的近乎均匀的物质分布中形成和演变的细节，影响了宇宙其余部分的性质如何演变。虽然关于星系如何形成的理论观点相当详细，但这些理论观点与星系形成的多个不同且往往相互竞争/矛盾的模型有关，但目前很少有早期星系的观测测量可用于约束和测试这些模型。对测试这些模型特别重要的是对宇宙年轻时看到的星系的观测。所看到的星系应该是今天所看到的更成熟、更大的星系的相对原始的组成部分。鉴于这些系统演化的时间有限，它们的演化应该不会特别复杂，因此它们的性质应该直接告知和测试我们对星系演化早期阶段的理解。在过去几年中，我们通过使用最大的光学和近红外敏感望远镜进行深层观测，在识别遥远星系方面取得了很大进展。我们已经确定了100多个星系，这些星系是在宇宙不超过10亿岁时看到的（现在是137亿岁），并且已经确定了在更早的时间看到的星系的候选者。目前，我们对它们的性质几乎没有任何详细的了解，主要集中在它们的发现和测量它们最简单的性质和统计数据上。几乎所有的信息，我们对这些系统来自他们正在进行的星星形成插曲，导致强烈的紫外线辐射从短命的大质量恒星。这些系统中的大部分物质，无论是重子（普通物质）还是暗物质，在静止坐标系的紫外线下都不明亮或不可检测。因此，我们对这些星系内部和周围的大部分物质几乎没有任何信息，严重限制了它们在开发和测试早期星系演化模型方面的用途。新一代的仪器刚刚问世，这些仪器将改变我们探索星系及其环境的能力。使用KMOS，一个多目标近红外光谱仪，这将是在VLT，和阿尔马和其他毫米/亚毫米波望远镜，我们将确定准确的红移，动力学和星系的质量，确定它们是否包含相当数量的第一代恒星（尚未检测到）和搜索的迹象，任何物质落入星系作为其演变的一部分。我们将探索冷和冷气体的性质，包括原子和分子，如果它们要继续形成我们今天在宇宙中看到的最大的星系，它们必须在星系及其周围。通过将所有这些观测研究的结果与相同星系的现有数据沿着，我们将开发一个更完整的早期星系演化过程的图片，这张图片将直接告知并挑战导致像我们自己的银河系这样的星系形成的关键过程的模型。

Central to our understanding of the the Universe is the topic of galaxy evolution. The details of how these large systems of stars, gas, dust and dark matter formed and evolved from the near-uniform matter distribution created by the Big Bang impact on how the properties of the rest of the Universe evolved. While there are quite detailed theoretical ideas about how galaxies form which feed in to multiple different and often competing/contradicting models of galaxy formation, observational measurements of early galaxies that can be used to constrain and test these models are currently rare. Particularly important to testing these models are observations of galaxies seen when the Universe was young. The galaxies seen should be the comparatively primitive building blocks of the much more mature and bigger galaxies seen today. Given the limited time available for such systems to evolve, their evolution should not be particularly complex and consequently their properties should directly inform and test our understanding of the early stages of galaxy evolution. In the past few years we have made great progress in identifying distant galaxies through deep observations with the largest optical and near-infra-red sensitive telescopes. We have identified with certainty over 100 galaxies which are seen when the Universe was no older than about 1 billion years old ( it is now 13.7 billion years old), and have identified candidates for galaxies seen at even earlier times. We currently have little understanding of their properties in any detail, having concentrated on their discovery and measuring the simplest of their properties and statistics. Almost all of the information we have on these systems comes from their ongoing star formation episodes which result in strong UV emission from short-lived massive stars. The bulk of the matter in these systems, whether baryons (ordinary matter) or dark matter, is not bright or detectable in the rest-frame ultra violet. Consequently, we have little or no information on the bulk of the material in and around these galaxies, severely limiting their use to develop and test models of early galaxy evolution. A new generation of instrumentation is just becoming available, instruments that will transform our ability to explore the properties of the galaxies and their environments in some detail. Using KMOS, a multi-object near-IR spectrograph which will be available on the VLT, and ALMA and other mm/sub-mm wave telescopes, we will determine accurate redshifts, dynamics and masses for the galaxies, determine whether they contain an appreciable number of the first generation of stars (as yet undetected) and search for signs of any material infalling onto the galaxies as part of their evolution. We will probe the properties of cool and cold gas, both atomic and molecular, that must be within the galaxies and in their surroundings if they are going to go on to form the largest galaxies that we see in the Universe today. By combining the results of all of these observational studies along with existing data on the same galaxies, we will develop a much more complete picture of how early galaxy evolution proceeds, a picture that will directly inform and challenge models of the key processes that leads to the formation of galaxies like our own Milky Way.