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首页> 外文学位 >Dynamical studies of two common features in spiral galaxies: Bars and warps.
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Dynamical studies of two common features in spiral galaxies: Bars and warps.

机译：旋涡星系中两个常见特征的动力学研究：条和扭曲。

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摘要

This thesis presents two new studies of different aspects of disk galaxy dynamics using high-quality N-body simulations.; The first part of the thesis is a systematic study of the effects of central mass concentrations (CMCs) on bars. We find that bars are more robust than previously thought; the central mass has to be as large as several percent of the disk mass to completely destroy the bar on a short timescale. For a given mass, dense objects cause the greatest reduction in bar amplitude, while significantly more diffuse objects have a lesser effect. The bar is generally weakened by a CMC in two phases---the first phase of bar-weakening is due to the destruction by the CMC of lower-energy, bar-supporting orbits, while the second phase is a consequence of secular changes to the global potential which further diminish the number of bar-supporting orbits. We provide detailed phase-space and orbit analysis to support this suggestion. Our findings show that neither typical supermassive black holes in spirals nor typical central molecular gas concentrations should weaken the bar significantly within a Hubble time.; In the second part of the thesis, we study galactic warps formed through an idealized form of cosmic infall onto a disk galaxy. We find warps that closely resemble those observed and are in agreement with Briggs (1990)'s rules. The inner disk tilts remarkably rigidly, indicating strong cohesion due to self-gravity. The line of nodes of the warp inside R 26.5 ∼ 4.5Rd is straight, while that beyond R26.5 generally forms a loosely-wound, leading spiral in agreement with Briggs's rules. We focus on the mechanism of the warp and show that the leading spiral arises from the torques from the misaligned inner disk and its associated inner oblate halo. The warp is not strongly damped by the halo because the precession rate of the inner disk is slow and the inner halo generally remains aligned with the inner disk. Thus warps formed this way can persist for a few Gyrs, by which time another infall event can be expected.
机译：本文利用高质量的N体模拟对圆盘星系动力学的不同方面进行了两项新的研究。本文的第一部分是对中央质量浓度（CMC）对条形的影响的系统研究。我们发现酒吧比以前认为的更坚固。中心质量必须大到磁盘质量的百分之几，才能在短时间内完全破坏磁条。对于给定的质量，稠密的物体会导致最大幅度的条幅减小，而明显更多的弥散物体的影响较小。棒通常在两个阶段被CMC削弱-第一阶段的弱化是由于CMC破坏了能量较低的棒支撑轨道，而第二阶段是长期变化的结果。全球潜力，这进一步减少了酒吧支撑轨道的数量。我们提供详细的相空间和轨道分析以支持该建议。我们的发现表明，在哈勃时间内，典型的螺旋形超大质量黑洞或典型的中心分子气体浓度均不会显着削弱该棒。在论文的第二部分中，我们研究了通过理想形式的宇宙进入盘状星系形成的银河扭曲。我们发现翘曲与观察到的翘曲非常相似，并且与Briggs（1990）的规则一致。内圆盘明显倾斜，表明由于自重而产生的强大内聚力。 R 26.5〜4.5Rd内部的经线节点线是直的，而超出R26.5的节点线通常形成松散缠绕的螺旋，与Briggs规则一致。我们关注于翘曲的机理，并表明超前螺旋是由未对准的内盘及其相关的内扁圆形光晕产生的扭矩引起的。由于内圆盘的进动速度很慢，并且内圆环通常保持与内圆盘对齐，因此翘曲不会被光晕强烈衰减。因此，以这种方式形成的翘曲可能会持续数个Gyrs，届时可能会发生另一个下坠事件。

著录项

  • 作者

    Shen, Juntai.;

  • 作者单位

    Rutgers The State University of New Jersey - New Brunswick.;

  • 授予单位 Rutgers The State University of New Jersey - New Brunswick.;
  • 学科 Physics Astronomy and Astrophysics.
  • 学位 Ph.D.
  • 年度 2005
  • 页码 118 p.
  • 总页数 118
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类 天文学;
  • 关键词

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