Collaborative Research: Probing Phase-Space Structure in the Galaxy - Kapteyn's Selected Areas

合作研究：探测星系中的相空间结构 - Kapteyn 的选定区域

• 批准号: 0407207
• 负责人: Steven Majewski
• 金额: $ 22.84万
• 依托单位: University of Virginia Main Campus
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2004
• 资助国家: 美国
• 起止时间: 2004-07-01 至 2008-06-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0407207&HistoricalAwards=false
• 关键词: Collaborative; Research; Probing; Phase; Space

Recent results from large-area photometric surveys have shown that the Milky Way outer halo contains accretion-driven substructure. These structures of known or assumed remnants of satellite accretion, have long-lived, coherent tidal features that can be used to accurately model the Galactic gravitational potential, as well as the characteristics of the original satellite. However, such modeling studies have been limited by the meager available kinematical data over large angles along the tidal features. While radial-velocity programs have just recently begun to address this problem for the few known Galactic tidal tails, no systemic survey has begun to address the transverse (tangential) velocities (i.e., absolute proper motions), which contain twice as much dynamical information. Without this information, dynamical models remain poorly constrained, and therefore limited to describing merely a range of possible events, rather than providing an accurate description of the real event. In this collaborative project, Dr. Dana Dinescu at Yale University and Dr. Steven Majewski, at the University of Virginia, will undertake a deep, high-precision absolute and relative proper-motion survey that will sample more than 50 lines of sight in the Selected Areas designated by Kapteyn for Galactic structure studies in 1906; indeed, the photographic plates taken at that time by Kapteyn and colleagues will be used as first epoch material. Current proper-motion programs do not achieve this precision at a similar magnitude limit, and are thus limited in detecting and characterizing distant halo substructure. The combination of proper-motion precision, depth, and sky coverage of this project will not be surpassed until the upcoming astrometric satellite missions GAIA and SIM. The data from these missions may be available in 2015 and 2020 respectively, while results from this project will be available in the next 3-4 years. The proper motions will be complemented by radial velocities, distance and metallicity estimates from photometric and spectroscopic work as well as from overlapping surveys like 2MASS, QUEST, SDSS and RAVE. Examples of intended applications of the data include: 1) Determining the extent and orbital motion of the highly obscured Monoceros, anticenter structure both above and below the Galactic plane, 2) Characterizing the transverse motion of the Sagittarius tidal streams. 3) Detecting and characterizing additional substructures in the halo of the Milky Way. 4) Determining the kinematical properties of the numerous thick disk and halo stars in the fields as a function of Galacto-centric distance. There are only a few deep, precise (pencil-beam-type) proper-motion data-sets that are centered on Galactic field stars rather than on a globular cluster or a dwarf spheroidal. This project will substantially increase the number of pencil-beam-type data-sets and therefore systematically probe our Galaxy in more than 50 distinct lines-of-sight. What makes the project possible is the combination of original 60-inch Mt. Wilson telescope plates taken in 1909 with matching Du Pont 2.5-m plates, thus yielding a 90 year baseline of excellent plate scale material. This research will contribute to an accurate model of the interaction of our Galaxy with its former satellites, and help characterize the Galaxy's satellite system. Also, the kinematical data of debris stars have the potential of measuring the lumpiness of the dark matter halo. These two issues are relevant for cold dark matter simulations that currently overpredict, by two orders of magnitude, the number of dark matter halos relative to the number of observed satellites of the Milky Way. ***

最近大面积光度测量的结果表明，银河系外晕包含吸积驱动的子结构。这些已知或假定的卫星吸积残余物的结构具有长期的、相干的潮汐特征，可用于精确模拟银河引力势以及原始卫星的特征。然而，此类建模研究受到沿潮汐特征的大角度可用运动学数据很少的限制。虽然径向速度计划最近才开始解决少数已知的银河潮汐尾的问题，但还没有系统调查开始解决横向（切向）速度（即绝对自行），其中包含两倍的动力学信息。如果没有这些信息，动力学模型的约束仍然很差，因此仅限于描述一系列可能的事件，而不是提供对真实事件的准确描述。在这个合作项目中，耶鲁大学的 Dana Dinescu 博士和弗吉尼亚大学的 Steven Majewski 博士将进行一项深入、高精度的绝对和相对自行调查，将对区域内 50 多条视线进行采样。 1906 年 Kapteyn 指定用于银河系结构研究的选定区域；事实上，卡普坦及其同事当时拍摄的摄影底片将被用作第一个时代的材料。目前的自行程序无法在类似的幅度限制下达到这种精度，因此在检测和表征遥远的晕子结构方面受到限制。在即将到来的天体测量卫星任务 GAIA 和 SIM 之前，该项目的自行精度、深度和天空覆盖范围将不会被超越。这些任务的数据可能分别于 2015 年和 2020 年提供，而该项目的结果将在未来 3-4 年内提供。自行运动将得到来自光度和光谱工作以及 2MASS、QUEST、SDSS 和 RAVE 等重叠调查的径向速度、距离和金属丰度估计的补充。数据的预期应用示例包括：1) 确定高度模糊的麒麟座、银道面上方和下方的反中心结构的范围和轨道运动，2) 表征人马座潮汐流的横向运动。 3) 检测并表征银河系光晕中的其他子结构。 4) 确定场中众多厚盘和晕恒星的运动学特性，作为银河系中心距离的函数。只有少数深度、精确（铅笔束型）自行数据集以银河场恒星为中心，而不是以球状星团或矮椭球体为中心。该项目将大幅增加笔形光束类型数据集的数量，从而在 50 多个不同的视线范围内系统地探测我们的银河系。该项目之所以成为可能，是因为将 1909 年拍摄的原始 60 英寸威尔逊山望远镜片与匹配的杜邦 2.5 米片相结合，从而产生了 90 年的优质片刻度材料基线。这项研究将有助于建立银河系与其以前的卫星相互作用的精确模型，并有助于描述银河系卫星系统的特征。此外，碎片恒星的运动学数据有可能测量暗物质晕的块度。这两个问题与冷暗物质模拟相关，目前冷暗物质模拟相对于银河系观测到的卫星数量高估了暗物质晕的数量两个数量级。 ***