Collaborative Research: M31 Satellites Past and Present

合作研究：M31 卫星的过去和现在

• 批准号: 1010039
• 负责人: Puragra Guha Thakurta
• 金额: $ 31.62万
• 依托单位: University of California-Santa Cruz
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2010
• 资助国家: 美国
• 起止时间: 2010-09-15 至 2016-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1010039&HistoricalAwards=false
• 关键词: Collaborative; Research; M31; Satellites; Past

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.

合作研究：M31 卫星的过去和现在AST 1010039，Puragra Guhathakurta，加州大学圣克鲁斯分校（领导）AST-1009882，Steven R. Majewski，弗吉尼亚大学主校区AST-1009973，James Bullock，加州大学欧文分校这是一项综合性研究矮椭球体（dSph）卫星的形成和演化研究仙女座 (M31)。本星系群内的这些卫星包括已知最不发光的星系，可以对它们进行探索，以测试有关在最小暗物质晕和最早时间恒星形成的想法。 M31 卫星已解析恒星群的大量数据集与最先进的星系模型相结合，以便了解当前和未来的动力学、合并、组装、恒星形成和化学浓缩历史。过去的 M31 卫星系统在分层星系形成的一般范式的背景下组合在一起。 M31 的数据与研究人员之前研究过的银河系卫星和光环群进行了比较。银河系和 M31 都是螺旋星系，但拥有不同的卫星星系群，需要对其进行解释。 M31 的附加数据对于评估“卫星失踪问题”的解决方案非常重要。在 Lambda-冷暗物质 (CDM) 模拟中，预计子晕的数量将高于观测到的卫星数量。到目前为止，银河系是唯一可以与模型进行比较的系统，当这项研究的结果出来时，模型将会发生变化。三位主要研究人员有长期合作，他们发起了 SPLASH（光谱和光度景观）仙女座的恒星光环）调查先前得到了美国国家科学基金会的支持。这里使用的方法和技术在这次合作中得到了很好的确立。 SPLASH 调查使用了凯克 II 望远镜上的深部成像多目标摄谱仪 (DEIMOS) 和基特峰国家天文台配备马赛克 CCD 宽视场成像仪的 4 米望远镜。该调查范围扩大到研究仙女座系统更多卫星星系中的红巨星分支恒星。该小组已经拥有 139 个 DEIMOS 掩模（约 20,000 个光谱）以及从成像数据中选出的 M31 红巨星候选者的光谱。目标是观测另外 135 个 DEIMOS 掩模，以获得 M31 的每颗已知和任何新发现的 dSph 卫星中超过 100 颗红巨星成员的光谱。 M33 是一颗与 M31 相互作用的低光度圆盘卫星，其中约 3,000 颗恒星的进一步光谱被认为是存在的； NE 架上有约 1,000 颗恒星，这些恒星是过去一颗 M31 卫星的潮汐碎片，与 M31 中的巨型南流有关。这项工作的一部分结合了光谱和光度诊断，以有效地隔离 M31 红巨星。此外，还有对精确恒星速度的测量，以得出矮星系和潮汐流中的速度色散，这两者都是运动学冷子系统。使用中等分辨率共同添加光谱来测量元素丰度来限制 M31 卫星的化学富集/恒星形成历史。理论模型用于确定 M31 中每个矮卫星星系的暗物质质量，以便将观测结果置于宇宙学框架内。这将提供更多数据来破译如何在 Lambda-CDM 宇宙学背景下描述银河系和 M31 的演化。这项工作为星系系统提供了另一个数据集来测试 Lambda-CDM 宇宙学。这将对其他领域产生广泛的影响。 DEIMOS 衍生的化学丰度引起了恒星种群研究界的兴趣。这里开发的新分析方法为其他恒星系统中解析恒星的类似研究奠定了基础，包括下一代望远镜瞄准的更遥远的星系。本科生正在参与研究活动，研究生正在研究其中的部分内容他们的论文项目。这将有助于培养下一代科学家。研究人员努力在 K-12 课堂上进行演讲，并接触到代表性不足的高中生和本科生。关于著名的大型螺旋星系仙女座的研究成果非常适合纳入团队成员定期进行的公开讲座和演示中。