Collaborative Research: M31 Satellites Past and Present

合作研究：M31 Saintly Past and PresentAST 1010039，Puragra Guhathakurta，University of California-Santa Cruz（lead）AST-1009882，Steven R. Mauriski，弗吉尼亚大学主校区AST-1009973，James布洛克，加利福尼亚大学欧文分校这是对仙女座（M31）矮球状（dSph）卫星形成和演化的综合研究。本星系群中的这些卫星包括已知的最不明亮的星系，可以对它们进行探索，以测试关于最小暗物质晕和最早时期星星形成的想法。M31卫星解析恒星种群的大量数据集与最先进的星系模型相结合，以了解动力学、合并、组装、星星形成、和化学富集的历史，目前和过去的M31卫星系统配合在一起的一般范式的层次星系的形成。M31的数据与研究人员先前研究的银河系的卫星和晕群进行了比较。银河系和M31都是螺旋星系，但有不同的人口的卫星星系的解释需要found. The额外的数据M31是重要的评估解决方案？卫星失踪问题？在拉姆达冷暗物质（CDM）模拟，其中subhalos的数量预计将高于观测到的卫星的数量。到目前为止，银河系是唯一一个可以与模型进行比较的系统，当这项研究的结果可用时，它将发生变化。三位主要研究人员有一个长期的合作，他们已经在NSF的支持下启动了SPLASH（仙女座恒星晕的光谱和光度景观）调查。这里使用的方法和技术在这种合作中得到了很好的确立。SPLASH调查使用凯克II望远镜上的深度成像多目标摄谱仪和基特峰国家天文台的4米望远镜，该望远镜配备马赛克CCD宽视场成像仪。该调查延伸到研究仙女座系统更多卫星星系中的红巨星分支恒星。该小组已经有139个DEIMOS掩模（大约20，000个光谱）和从成像数据中选择的M31红巨星候选者的光谱。目标是观察另外135个DEIMOS掩模，以获得M31的每个已知和任何新发现的dSph卫星中100多个成员红巨星的光谱。进一步的光谱被认为是M33中大约3,000颗恒星的光谱，M33是一颗与M31相互作用的低光度盘状卫星;东北大陆架中大约1,000颗恒星是过去M31卫星的潮汐碎片，与M31中的巨大南流有关。此外，还有精确的恒星速度测量，以获得矮星系和潮汐流的速度色散，这两者都是运动学上冷的子系统。从中等分辨率共加光谱测量元素丰度，用于限制M31卫星的化学富集/星星形成历史。理论模型用于确定M31中每个矮卫星星系的暗物质质量，以将观测结果置于宇宙学框架内。这将提供更多的数据来破译银河系和M31的演化如何在Lambda-CDM宇宙学的背景下进行描述。这项工作提供了另一个数据集的星系系统来测试Lambda-CDM宇宙学。这将对其他领域产生广泛影响。DEIMOS衍生的化学丰度是恒星种群研究界感兴趣的。在此开发的新分析方法为其他恒星系统中的类似研究提供了基础，包括下一代望远镜瞄准的更遥远的星系。本科生参加了研究活动，研究生为论文工作完成了该项目的一部分。这将有助于培养下一代科学家。研究人员努力在K-12教室发言，并接触到代表性不足的高中和本科生。关于著名的大螺旋星系仙女座的研究成果非常适合纳入小组成员定期举行的公开讲座和演讲。

Collaborative Research: M31 Satellites Past and PresentAST 1010039, Puragra Guhathakurta, University of California-Santa Cruz (lead)AST-1009882, Steven R. Majewski, University of Virginia Main CampusAST-1009973, James Bullock, University of California-IrvineThis is a comprehensive study of the formation and evolution of the dwarf spheroidal (dSph) satellites of Andromeda (M31). These satellites within the Local Group include the least luminous galaxies known and they can be explored to test ideas about star formation in the smallest dark matter halos and at the earliest times.Extensive data sets on the resolved stellar populations of M31 satellites are combined with state-of-the-art galaxy models in order to learn how the dynamical -, merger -, assembly -, star formation -, and chemical enrichment histories of the current and past M31 satellite systems fit together in the context of the general paradigm of hierarchical galaxy formation. The data for M31 are compared to the satellites and halo population of the Milky Way galaxy for which were previously studied by the investigators. The Milky Way and M31 are both spiral galaxies but have different populations of satellite galaxies for which an explanations needs to be found. The additional data for M31 are important for evaluating solutions to the ?missing satellites problem? in Lambda-Cold Dark Matter (CDM) simulations, where the number of subhalos is predicted to be higher than the number of observed satellites. So far the Milky Way is the only system for which the comparison to models can be made which will change when the results of this study are available.The three principal investigators have a standing collaboration and they have initiated the SPLASH (Spectroscopic and Photometric Landscape of Andromeda's Stellar Halo) survey with previous support from the NSF. The methods and techniques used here are well established in this collaboration. The SPLASH survey uses the DEep Imaging Multi-Object Spectrograph (DEIMOS) on the Keck II telescope and the 4-m telescope with Mosaic CCD wide field Imager at Kitt Peak National Observatory. The survey extends to study red giant branch stars in more satellite galaxies of the Andromeda system. The group has already 139 DEIMOS masks (about 20,000 spectra) and spectroscopy of M31 red giant candidates selected from the imaging data. The goal is to observe another 135 DEIMOS masks to obtain spectra of more than 100 member red giant stars in each of the known and any newly found dSph satellites of M31. Further spectra are thought for about 3,000 stars in M33, a low-luminosity disk satellite interacting with M31; and about 1,000 stars in the NE shelf which is tidal debris from a past M31 satellite associated with the Giant Southern Stream in M31.One part of the work combines spectral and photometric diagnostics to isolate M31 red giants efficiently. Further there are measurements of precision stellar velocities to derive velocity dispersions in dwarf galaxies and tidal streams, which are both kinematically cold subsystems. Measurements of elemental abundances from moderate resolution co-added spectra tare used o constrain the chemical enrichment/star formation histories of M31 satellites. Theoretical models are used to determine the dark matter mass of each dwarf satellite galaxy in M31 to place the observations within a cosmological framework. This will give more data to decipher how the evolution of the Milky Way and M31 can be described in the context of Lambda-CDM cosmology.This work provides another data set for a galaxy system to test Lambda-CDM cosmologies. This will have a broad impact on other fields. The DEIMOS-derived chemical abundances are of interest for stellar population studies community. The new analytical methods developed here provide a foundation for similar studies of resolved stars in other stellar systems, including more distant galaxies to be targeted with the next generation of telescopes.Undergraduate students are participating in the research activities and graduate students work on parts of this project for their theses. This will help to train the next generation of scientists. The researchers make efforts to speak in K-12 classrooms and to reach out to underrepresented high-school and undergraduate students. Research results about the well-known large spiral galaxy Andromeda are well suited to be incorporated into public lectures and presentations which are given by the team members on a regular basis.