Halo Substructure and the Dynamics of Disk Galaxies

星系是由什么组成的？银河系(MW)或仙女座(M31)等大型螺旋星系的常见图像显示了一个由恒星、气体、尘埃、旋臂和中央凸起组成的旋转圆盘。**但从20世纪70年代的S开始，随着我们积累了星系嵌入扩展的暗物质光环的证据，我们对银河系的图像变得越来越大。最近，对MW和M31外围的观测揭示了丰富的恒星结构，其形式为卫星星系和从卫星上剥离的恒星流。最后，结构形成的宇宙学模拟表明，光晕中的暗物质是成团的，甚至可能比恒星更成团。**我的研究将集中在卫星和光晕下种群的关键方面。这项研究在很大程度上是由观测和计算天体物理学的显著进步推动的，并将对星系动力学、宇宙结构形成和暗物质探测领域产生影响。**最近，我和我的合作者分析了恒星在太阳附近的分布及其运动，以揭示微波盘中似乎存在的垂直波。我们将这一发现解释为微波与其一颗卫星最近在附近相遇的证据。我对这些浪潮的调查将在多个方面进行。我已经获得了更多的数据，这些数据正在被我所在团队的研究生分析。其他学生正在使用理论分析和数值模拟来研究卫星星系和恒星盘的相互作用。**泛仙女座考古调查获得了前所未有的M31和它的同伴M33的全景照片。我们的观察表明，M31正在蚕食它的卫星，而M33可能在最近与M31发生了近距离接触。这些想法得到了我和Dubinski(多伦多)进行的N体模拟的支持，有助于促进我们对宇宙结构形成和暗物质在局部群中的分布的理解。

What constitutes a galaxy? The usual image of a large spiral galaxy such as the Milky Way (MW) or Andromeda (M31) shows a rotating disk of stars, gas, dust, spiral arms, and a central bulge. **But beginning in the 1970's, our image of the galaxy swelled as we amassed evidence that galaxies are embedded in extended halos of dark matter. More recently, observations of the outskirt of the MW and M31 have revealed a wealth of stellar structure in the form of satellite galaxies and streams of stars that were tidally stripped from satellites. Finally cosmological simulations of structure formation indicate that dark matter in halos is clumpy, perhaps even more so than the stars.** My research will focus on key aspects of the satellite and subhalo populations. The research is driven, in large part, by the remarkable advances in observations and computational astrophysics and will have implications for the fields of galactic dynamics, cosmological structure formation, and dark matter detection.** Recently, my collaborators and I analysed the distribution of stars in the solar neighbourhood and their motions to reveal what appear to be vertical waves in the MW's disk. We have interpreted this discovery as evidence for a recent and nearby encounter between the MW and one of its satellites. My investigations of these waves will proceed on a variety of fronts. I have obtained additional data, which is being analyzed by graduate students in my group. Other students are using theoretical analysis and numerical simulations to study the interaction of satellite galaxies and stellar disks.** The Pan-Andromeda Archaeological Survey has obtained an unprecedented panoramic picture of M31 and its companion, M33. Our observations suggest that M31 is cannibalizing its satellites while M33 may have had a close encounter with M31 in the recent past. These ideas, bolstered by N-body simulations performed by me and Dubinski (Toronto), help advance our understanding of cosmological structure formation and the distribution of dark matter in the Local Group.********************