Galaxy Formation and the Oldest Stellar Systems

当今天体物理学最突出的前沿领域之一是了解星系形成和早期演化的过程：我们如何揭示将大爆炸产生的原始气体改变为我们今天看到的周围星系分布的一系列事件？我的研究计划旨在研究大型星系中最古老的恒星系统：球状星团和最古老的晕星。作为星系形成历史上形成的第一批恒星，这些古老恒星系统为我们提供了独特的详细观察窗口，让我们了解恒星形成和结构形成最快的关键早期。 这类工作(有时被称为近场宇宙学)利用了这样一个事实，即我们可以在逐个恒星的基础上非常详细地研究附近的星系。它完全是对其他类型的观测宇宙学的补充，这些宇宙学搜索极远、微弱的高红移星系--在这种星系中，我们可以直接看到很久以前的星系，但几乎没有内部结构细节。高红移测量告诉我们星系形成的概括性特征，包括它们的全球恒星形成速度和它们在太空中的分布；而对附近星系的深入研究告诉我们关于它们的恒星的年龄分布和它们的化学富集史的所有细节。在我提议的计划中，目标是针对(A)球状星团的建模和观测数据分析的组合，球状星团是最大质量的星团，以及年轻星系中最密集、最大质量和最猛烈的高效恒星形成地点的残留物；以及(B)附近巨型星系中的场晕星群。

One of the most prominent frontier areas in astrophysics today is to understand the process of galaxy formation and early evolution: how do we uncover the sequence of events that changed the primordial gas emerging from the Big Bang into the distribution of galaxies we see around us today? My research program is directed at investigating the oldest stellar systems in large galaxies: globular star clusters and the oldest halo stars. As the first populations of stars to form during the history of galaxy formation, these systems of old stars give us uniquely detailed observational windows into that critical early era during which star formation and structure formation was the most rapid. This kind of work (sometimes referred to as "near-field cosmology") takes advantage of the fact that we can study nearby galaxies in great detail on a star-by-star basis. It is entirely complementary to other types of observational cosmology that search for extremely distant, faint high-redshift galaxies -- where we can see the galaxies directly as they were long ago, but with little or no internal structural detail. The high-redshift surveys tell us the broad-brush features of galaxy formation including their global rates of star formation and their distributions in space; whereas the deep studies of nearby galaxies tell us all the detail about the age distribution of their stars and their chemical enrichment histories. The Objectives in my proposed program are directed at a combination of modelling and observational data analysis of (a) globular clusters, which are the most massive clusters of stars and the remnants of the densest, most massive, and most violent sites of efficient star formation in young galaxies; and (b) the field-halo-star populations in nearby giant galaxies.