Halo Substructure and the Dynamics of Disk Galaxies

星系是由什么组成的？像银河系（MW）或仙女座星系（M31）这样的大型螺旋星系的通常图像显示了一个由恒星、气体、尘埃、旋臂和中心凸起组成的旋转盘。**但从20世纪70年代开始，随着我们积累的证据表明星系嵌入在暗物质的延伸光晕中，我们对银河系的印象不断膨胀。最近，对MW和M31外围的观测揭示了卫星星系和从卫星中潮汐剥离的恒星流形式的丰富恒星结构。最后，对结构形成的宇宙学模拟表明，晕中的暗物质是块状的，甚至可能比恒星更块状。**我的研究将集中在卫星和亚光晕人口的关键方面。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等领域产生影响。**最近，我和我的合作者分析了太阳附近恒星的分布和它们的运动，揭示了MW圆盘上似乎是垂直波的东西。我们把这一发现解释为最近和附近的一次宇宙微波与它的一颗卫星相遇的证据。我对这些波浪的研究将从多方面展开。我获得了额外的数据，正在由我组的研究生进行分析。其他学生则利用理论分析和数值模拟来研究卫星星系和星盘之间的相互作用。**泛仙女座考古调查获得了前所未有的M31及其伴星M33的全景照片。我们的观察表明，M31正在蚕食它的卫星，而M33可能在最近的过去与M31有过近距离接触。这些想法得到了我和杜宾斯基（多伦多）进行的n体模拟的支持，有助于提高我们对宇宙结构形成和暗物质在本星系群中的分布的理解。********************

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.********************