Using Globular Clusters as Tracers of Galaxy Formation

星系的成长有两种途径：扩散气体和暗物质通过细丝的吸积，以及与其他星系的合并。与其他星系的合并可以以大合并的形式出现：两个质量相似的星系相撞，可能会改变星系的形态类型。然而，较小的合并更为常见，这是一个质量较低的星系被吸积到一个质量较大的星系上。这两种合并的特征在今天的宇宙中都可以观察到。较小的合并事件可以留下恒星流的痕迹，这些恒星流被引力从低质量星系中剥离出来。在我们自己的星系中有证据表明，人马座矮星系正被银河系潮汐地扭曲。研究发现，在空间上与这个矮星系相关的球状星团（GCs）的性质与其他银河系GC群具有不同的化学成分和潜在的年龄。球状星团（GCs）是建立星系形成图景的有力工具：它们的空间分布和化学成分反映了其宿主星系的合并和恒星形成历史。然而，以前的工作主要是在自然界的观测，在我们对GC种群及其形成的理论认识上留下了空白。E-MOSAICS（在EAGLE的宇宙学模拟中模拟星团系统组装）是第一个将星团形成和演化实现为流体动力学、宇宙学模拟的工作，将用于追溯星系的GC系统，以调查每个GC形成的位置。这使我们能够将GC系统的属性与各种宿主星系的属性联系起来，并最终使用星系的GC系统来构建其形成的图像。

Galaxies grow through two channels: accretion of diffuse gas and dark matter via filaments and mergers with other galaxies. Mergers with other galaxies can be in the form of a major merger: where two galaxies of similar mass collide, potentially changing the morphological type of the galaxy. Minor mergers, however, are far more common, this is where a galaxy of lower mass is accreted onto a more massive galaxy.Signatures of both types of merger can be observed in the universe today. The minor merger events can leave their trace in the form of streams of stars which have been gravitationally stripped from the lower mass galaxy. There is evidence of this in our own galaxy in the form of the Sagittarius dwarf galaxy which is being tidally distorted by the Milky Way. It has been found that the properties of the globular clusters (GCs) which are spatially associated with this dwarf galaxy have a different chemical composition and potentially age than the rest of the Galactic GC population.Globular clusters (GCs) are a powerful tool for building up a picture of the formation of a galaxy: their spatial distribution and chemical composition reflect the merger and star formation histories of their host galaxy. However, previous work has mainly been observational in nature, leaving a gap in our theoretical understanding of GC populations and their formation. E-MOSAICS (MOdelling Star cluster system Assembly in Cosmological Simulations within EAGLE)- the first work to implement star cluster formation and evolution into hydrodynamical, cosmological simulations- will be used to trace a galaxy's GC system back through time to investigate where each GC was formed. This allows us to relate the properties of a GC system to various host galaxy properties and ultimately use a galaxy's GC system to build up a picture of its formation.