Evolution of disk galaxies

旋涡图案是盘状星系动力学演化最重要的因素之一。它们重新分配角动量，导致恒星的随机速度随着时间的推移而上升，引起径向混合和大范围湍流，将恒星添加到厚厚的圆盘中，并使旋转曲线变平。这个项目是对螺旋图案对圆盘演化的影响的计算研究。这位Pricpal Investigator(PI)有几个开发得很好的引力N体代码，他将在两个项目中与支持的研究生使用这些代码：(1)银河系的厚盘是由旧恒星组成的，这与该组件形成的“螺旋搅动”模型相冲突。PI假设，内银河系中一个条状星云的出现可能通过“搅拌”阻止了厚盘的生长。他计划进行模拟来测试这一想法，比较有或没有形成棒状物的相似圆盘的演化。(2)螺旋星系如何管理所谓的“盘-晕阴谋”仍不明确，在这种阴谋中，盘和暗晕引力场的不同贡献，在可观测的恒星和气体中产生了一条平坦的观测旋转曲线。PI和合作者的简单模型表明，螺旋波可以导致圆盘中的质量分布重新排列，直到旋转曲线变得平坦；他计划进行进一步的模拟，包括“活的”光晕，以验证这种行为的普遍性。最后，PI将继续研究重复出现的螺旋图案及其在本地恒星群中的可观测后果。PI计划以前所未有的质量进行仔细的N体模拟，以进行深入研究，以揭示简化模型中复发机制的细节。研究生将协助项目，以证明当简化假设放松时，这种行为仍然存在。国际宣讲团将通过公开讲座向更广泛的社区传播这项工作的成果。他将让本科生、研究生和博士后参与研究，为他们提供研究过程中的经验和培训。

Spiral patterns are one of the most important agents of dynamical evolution in disk galaxies. They redistribute angular momentum, cause the random speeds of stars to rise over time, cause radial mixing and large-scale turbulence, add stars to the thick disk, and flatten rotation curves. This project is a computational study of the effects of spiral patterns on disk evolution. The Prinicpal Investigator (PI) has several well-developed gravitational N-body codes that he will use with supported graduate students in two projects: (1) The Milky Way's thick disk is composed of old stars, in conflict with the "spiral churning" model for the formation of this component. The PI hypothesizes that the appearance of a bar in the inner Milky Way may have shut off thick disk growth by "churning." He plans simulations to test this idea, comparing the evolution of similar disks in which bars are or are not formed. (2) It is still ambiguous how spiral galaxies manage the so-called "disk-halo conspiracy," in which the different contributions of the disk and dark halo gravitational fields produce a flat observed rotation curve in the observable stars and gas. Simple models by the PI and collaborators showed that spiral waves could cause the mass distribution in a disk to rearrange itself until the rotation curve became flat; he plans further simulations including "live" halos to verify the generality of this behavior. Finally, the PI will continue work on recurring spiral patterns and their observable consequences in local stellar population. The PI plans careful N-body simulations of unprecedented quality for an in-depth study that will uncover the details of the recurrence mechanism in simplified models. Graduate students will assist with projects to show that the behavior persists when simplifying assumptions are relaxed. The PI will disseminate results of this work to the broader community through public lectures. He will involve undergraduate and graduate students, and postdocs, in the research, providing them with experience and training in the research process.