The Dynamics of Galaxy Evolution

温伯格博士和他的团队将通过星系盘、球体和暗物质晕之间的集体相互作用，研究星系在数十亿年里是如何进化的。在这些大尺度上起作用的主要力量是恒星和暗物质之间的相互引力。星系被认为是由许多较小的单位合并而成；在这段时间里，引力变化很大。在宇宙历史早期看到的星系通常有非常大的条形；该小组将探索这些大棒子是如何在早期的暴力阶段产生的。然后，他们将研究在银河系较安静的后期，这些大棒子是如何缩小成今天看到的更短、更快旋转的棒子的。他们还将研究恒星盘是如何弯曲和变厚的，以及中央凸起是如何在宇宙历史中慢慢形成的。在这项研究中，他们将结合摄动理论、恒星轨道的直接积分和几种n体模拟。为了研究圆盘中的气体如何影响星系的发展，他们将把他们的n体代码与跟踪气体动力学的代码结合起来，并将实现一个多时间步长算法，该算法将使模拟吞吐量提高30倍。其结果将是对当今星系中恒星和气体运动的详细预测。该奖项将支持一名研究生，该小组将为本科生提供研究项目，包括其所在机构计算机动画小组的研究项目。这些学生将接受数值和可视化技术方面的培训。该小组将为他们的模拟代码分发测试套件和工具，以及参考解决方案，以使该领域的其他研究人员能够比较他们自己的代码在相同测试问题上的详细结果。他们还将根据他们的计算制作可视化和其他外联材料。

Dr Weinberg and his group will examine how galaxies evolve over billions of years, by the collective interactions between their disk, spheroid, and dark-matter halo. The main force acting on these large scales is the mutual gravitational pull of the stars and the dark matter. Galaxies are believed to form by the merger of many smaller units; during this time, gravitational forces vary wildly. Galaxies seen early in cosmic history often have very large bars; the group will explore how these large bars could be produced in this early violent phase. They will then examine how, in the quieter later life of the galaxy, such large bars could shrink to become the shorter and faster-rotating bars seen today. They will also investigate how the disk of stars could become warped and thickened, and how the central bulge might be built up, slowly over cosmic history. In this investigation they will use a combination of perturbation theory, direct integration of stellar orbits, and N-body simulations of several types. To study how gas in the disk affects the galaxy's development, they will combine their N-body code with a code to follow gas dynamics, and will implement a multiple time step algorithm that should increase the simulation throughput by 30 times. The result will be detailed predictions for the motions of stars and gas in present-day galaxies.This award will support a graduate student, and the group will offer research projects to undergraduates, including those in their institution's computer animation group. These students will be trained in numerical and visualization techniques. The group will distribute test suites and tools for their simulation codes, together with reference solutions, to enable other researchers in the field to compare the detailed results of their own codes on the same test problems. They will also produce visualizations and other outreach material from their computations.