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转变为我们今天所看到的星系分布的事件顺序？我的研究项目是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第一批形成的恒星，这些古老恒星的系统为我们提供了独特的详细观测窗口，让我们了解到恒星形成和结构形成最迅速的早期关键时期。****这种工作（有时被称为“近场宇宙学”）利用了我们可以在逐星的基础上非常详细地研究附近星系的事实。它与其他类型的观测宇宙学完全互补，这些观测宇宙学寻找极其遥远、微弱的高红移星系——在这些星系中，我们可以直接看到很久以前的星系，但很少或根本没有内部结构细节。高红移巡天告诉我们星系形成的大致特征，包括它们的全球恒星形成速率和它们在空间中的分布；然而，对附近星系的深入研究告诉我们有关恒星年龄分布和化学富集历史的所有细节。我提出的计划的目标是将建模和观测数据分析相结合(a)球状星团，球状星团是质量最大的星团，也是年轻星系中密度最大、质量最大、最剧烈的有效恒星形成地点的遗迹；(b)附近巨大星系的场晕星群。************

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.************