Collaborative Research: An Archaeological Survey for Substructure in the Stellar Halos of the Nearest Massive Galaxies

我们的银河系周围环绕着围绕我们银河系运行的“矮小”星系，偶尔还会与我们的星系发生碰撞。我们是大型星系“局部群”的一部分，每个星系都有自己的矮星系群。天文学中一个重要的悬而未决的问题是，这些星系是如何形成的，它们是如何随时间变化的。我们目前对宇宙结构的理解表明，像银河系这样的大星系实际上应该拥有比我们观察到的更多数量的矮星。为了检验这是普遍现象，还是仅仅是我们当地群体的财产，该计划将对我们最近的两个银河系邻居周围的地区进行详细的普查。他们将调查两种类型的星系--螺旋星系(如银河系)和大型椭圆星系--然后测量这些新发现的星系的基本性质。这涉及三个机构之间的合作努力，并将使用一些最大和最好的地面望远镜。这三个私人助理都积极参与教育和公众宣传活动。皮桑德的机构，德克萨斯理工大学，有一个新的天体物理学研究小组和本科生集中精力。这项建议中的科学将有助于建立TTU的天体物理计划，并接触到更大的Lubbock社区。特别值得一提的是，两名天体物理学本科生将在加州度过暑假，为该项目做研究，让他们能够与更大的天体物理学社区互动。Pi Guhathakurta非常积极地参与了几个为高中生提供指导和研究经验的项目。这三个PI与一名博士后研究人员和学生一起，将解决与银河系和M31相关的观测到的缺乏暗矮星系的问题(比较了Lambda-CDM对小规模结构形成的预测)。他们将使用麦哲伦和凯克望远镜进行全景成像研究，以测量NGC253和NGC5128中的恒星流和矮星系内容。NGC253是一个丝状环境中的类似银河系的螺旋星系，NGC5128是一个大质量的中央椭圆星系。他们还将使用Keck Diemos和新开发的共加技术来获得潮汐流和矮星系的光谱。如果成功，这将使运动学和金属丰度研究首次在当地集团之外进行。

Our Milky Way galaxy is surrounded by "dwarf" galaxies that orbit and occasionally collide with our galaxy. We are part of a "local group" of large galaxies, each with its own swarm of dwarf galaxies. One of the important unanswered questions in astronomy is how these galaxies formed and how they change in time. Our current understanding of structure in the universe suggests that a large galaxy like the Milky Way should actually host a larger number of dwarf satellites than we observe. To examine whether this is universal or merely a property of our local group, this program will conduct a detailed census of the regions surrounding two of our nearest galactic neighbors. They will survey two types of galaxy - spiral, like the Milky Way, and a large elliptical galaxy - and then measure the basic properties of these newly discovered systems. This involves a collaborative effort between three institutions and will use some of the largest and best ground-based telescopes. All three PIs are active in education and public outreach. PI Sand's institution, Texas Tech University, has a new astrophysics research group and undergraduate concentration. The science in this proposal will help establish TTU's astrophysics program and reach out to the larger Lubbock community. In particular, two undergraduate astrophysics students will spend summers in California doing research for the program, allowing them to interact with the larger astrophysics community. PI Guhathakurta is very actively involved with several programs that provide mentoring and research experiences for high-school students. The three PIs, along with a postdoctoral researcher and students, will address the observed lack of faint dwarf galaxies associated with the Milky Way and M31 (compared Lambda-CDM predictions for small-scale structure formation). Using the Magellan and Keck telescopes, they will conduct a panoramic imaging study to measure the stellar stream and dwarf galaxy content in NGC 253, a Milky Way-like spiral in a filamentary environment, and NGC 5128, a massive central elliptical galaxy. They will also use Keck+Diemos and newly-developed coaddition techniques to obtain spectra of tidal streams and dwarf galaxies. If successful, this would enable kinematic and metallicity studies for the first time outside the local group.