Exploring the early evolution of galaxies

我们对宇宙的理解的中心是星系演化的话题。这些由恒星、气体、尘埃和暗物质组成的大型系统是如何从大爆炸产生的近乎均匀的物质分布中形成和演化的，这些细节影响了宇宙其余部分的特性是如何演化的。虽然关于星系是如何形成的有相当详细的理论观点，这些理论观点为多种不同的、经常相互竞争/矛盾的星系形成模型提供了依据，但对早期星系的观测测量，可以用来约束和测试这些模型，目前还很少。要验证这些模型，特别重要的是对宇宙年轻时所见星系的观测。我们看到的星系应该是相对原始的组成部分，构成了今天我们看到的更成熟、更大的星系。考虑到这些系统演化的时间有限，它们的演化不应该特别复杂，因此它们的特性应该直接告知和测试我们对星系演化早期阶段的理解。在过去的几年中，我们通过最大的光学和近红外敏感望远镜的深度观测，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，这些星系是在宇宙年龄不超过10亿年（现在是137亿年）的时候看到的，并且已经确定了更早时候看到的星系的候选星系。我们目前对它们的性质几乎没有任何细节的了解，主要集中在它们的发现和测量最简单的性质和统计上。我们掌握的关于这些系统的几乎所有信息都来自于它们正在进行的恒星形成事件，这些事件导致了短寿命大质量恒星强烈的紫外线辐射。这些星系中的大部分物质，无论是重子（普通物质）还是暗物质，在静止坐标系下都是不亮的，也无法探测到。因此，我们对这些星系内部和周围的大部分物质知之甚少，严重限制了它们用于开发和测试早期星系演化模型的能力。新一代的仪器即将问世，这些仪器将改变我们探索星系特性及其环境细节的能力。使用KMOS， VLT上的多目标近红外光谱仪，ALMA和其他毫米/亚毫米波望远镜，我们将确定精确的红移，星系的动力学和质量，确定它们是否包含相当数量的第一代恒星（尚未被发现），并寻找任何物质作为星系演化的一部分落入星系的迹象。我们将探索冷气体和冷气体的性质，原子气体和分子气体，如果它们要形成我们今天在宇宙中看到的最大的星系，它们必须在星系内部和周围环境中。通过将所有这些观测研究的结果与同一星系的现有数据相结合，我们将对早期星系的演化过程有一个更完整的了解，这一了解将直接告知和挑战导致像我们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.