The Dynamical evolution of galaxies

这项提议描述了一项利用数值模拟探索星系动力学演化的研究计划。在被称为Lambda-CDM的主流宇宙膨胀理论中，星系起源于由于引力不稳定而在暗物质集中的重子(星际气体)凝聚。通过这种方式，宇宙中炽热、密集和几乎均匀的等离子体转变成了我们今天在可观察到的宇宙中看到的1000亿个星系的动物园。人们对了解这一过程的细节非常感兴趣，对附近星系和星系系统的性质的研究，加上对星系形成和星系动力学的超级计算机模拟，使我们能够解开许多谜团。一项被称为泛仙女座考古调查(PANAS)的观测研究正在调查附近旋涡星系仙女座周围微弱的恒星分布。这种被称为恒星晕的分布揭示了许多奇妙的新特征，它们以恒星流和星壳的形式出现，被解释为引力湮没卫星星系的残余物。因此，我们看到了仙女座星系形成的最后阶段，因为卫星像雨点一样落下，被更大的星系吸收。我们将在包含仙女座星系、银河系和较小的三角星系的局部星系群的详细动力学模型的背景下详细研究这些过程，并了解该系统的过去和未来历史及其基本结构特征。我们还计划进行补充的数值研究，以了解在存在数百颗暗物质卫星的情况下盘星系的更复杂的动力学，这是Lambda-CDM模型所预测的特征。利用建立螺旋星系模型的新技术，我们还在探索通过星系群合并将螺旋形态转变为椭圆形态的过程。

This proposal describes a research programme to explore the dynamical evolution of galaxies using numerical simulations. In the prevailing theory of the expanding universe known as Lambda-CDM, galaxies originate in the condensation of baryons (interstellar gas) within concentrations of dark matter due to gravitational instability. In this way, the hot dense and nearly uniform plasma of the universe transforms into a zoo of 100 billion galaxies that we see in the observable universe today. There is great interest in understanding the details of this process and studies of the properties of nearby galaxies and galactic systems complemented with supercomputer simulations of galaxy formation and galactic dynamics are allowing us to solve many puzzles. One observational study known as the Pan-Andromeda Archaeological Survey (PAndAS) is surveying the faint stellar distribution around the nearby spiral galaxy Andromeda. This distribution known as the stellar halo is revealing many wonderful new features which show up as stellar streams and shells that are interpreted as the remnants of gravitationally obliterated satellite galaxies. We are therefore seeing the last phases of galaxy formation in Andromeda as satellites rain down and are absorbed by the larger galaxy. We will study these processes in detail in the context of a detailed dynamical model of the Local Group of galaxies that contains Andromeda, the Milky Way and the smaller Triangulum galaxy and learn about the past and future history of this system along with its essential structural characteristics. We are also planning complementary numerical studies to understand the more complex dynamics of disk galaxies in the presence of hundreds of dark matter satellites a feature predicted by the Lambda-CDM model. Using new techniques for setting up models of spiral galaxies, we are also exploring the process of transformation of spiral to elliptical morphology through mergers in galaxy groups.