Disk galaxies in a cosmological context

星系是宇宙的基石。我们的太阳(一颗恒星)围绕着一个由大约4000亿颗恒星组成的大圆盘状系统运行--一个被称为银河系的螺旋星系。我们的银河系只是我们可以在可观测的宇宙中计数的1000亿中的一个。了解星系的起源以及它们是如何出现和演化的，是宇宙学研究的主要目标。这一提议的重点是在兰姆达-冷-暗物质宇宙学模型的背景下理解盘状星系的演化--这是解释宇宙结构起源的当前范式。在这个模型中，星系是由恒星和气体组成的有组织的系统--我们可以看到的东西--以及由一种名为暗物质的神秘物质组成的无形组件，称为光晕。暗物质晕解释了星系的自转运动，是宇宙学理论的重要组成部分。盘状星系占整个银河系人口的大多数。当它们的形态被详细量化时，它们以螺旋图案、条形(细长的中心结构)和边缘微妙的翘曲的形式显示出奇妙的结构。这些结构的特征似乎也随着时间的推移而变化，在过去，条状星系较少，扰动较多的螺旋图案。大多数这些特征的物理机制是重力驱动和激发它们的形成。恒星盘和带有暗晕的气体之间的引力相互作用是主要的驱动力。在这个方案中，我们使用并行超级计算机上的数值实验来模拟这些物理过程。我们使用粒子建立逼真的星系模型，并根据已知的引力定律计算它们的运动方程，以模拟恒星和暗物质的相互作用。在这个数值实验室中，我们可以检验与周围暗物质晕相互作用的螺旋结构和棒状结构起源的各种假设，从而探索宇宙学范式与观测到的星系性质的一致性。这些过程的计算机动画将数十亿年的动力学过程转化为星系演化的直观呈现。

Galaxies are the building blocks of the universe. Our sun (a star) is in orbit around a large disk-shaped system of about four hundred billion stars - a spiral galaxy known as the Milky Way. Our Milky Way is just one in a 100 billion that we can count in the observable universe. Understanding the origin of galaxies and how they emerge and evolve is a primary goal in cosmological research. This proposal focuses on understanding the evolution of disk galaxies within the context of the Lambda-Cold-Dark-Matter cosmological model - the current paradigm for explaining the origin of structure in the universe. In this model, galaxies are organized systems of stars and gas - stuff we can see - and an invisible component called the halo made of a mysterious substance called the dark matter. The dark matter halo explains the rotational motion of galaxies and is an essential component of cosmology theory. Disk galaxies represent the majority of the total galactic population. When their morphology is quantified in detail, they show wonderful structure in the form of spiral patterns, bars (elongated central structures) and subtle warping at the edges. The character of these structures also seems to be varying with time with fewer barred galaxies and more disturbed spiral patterns in the past. The physical mechanism responsible for most of these features is gravity that drives and excites their formation. The gravitational interaction between the disk of stars and gas with the dark halo is the primary driver. In this proposal, we model these physical processes using numerical experiments on parallel supercomputers. We build realistic models of galaxies using particles and compute their equations of motion to simulate the interaction of the stars and dark matter according to the known laws of gravity. In this numerical laboratory, we can test various hypotheses for the origin of spiral structure and bars as the result of the interaction with surrounding dark matter halo and so explore the consistency of the cosmological paradigm with the observed properties of galaxies. Computer animations of these processes translate billions of years of dynamical processes into an intuitive presentation of galaxy evolution.