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: 0406884
• 负责人: Dana Casetti
• 金额: --
• 依托单位: Yale University
• 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 2009-06-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0406884&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 satellitemissions 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. ***

最近来自大面积光度测量的结果表明，银河系外晕包含吸积驱动的亚结构。这些已知的或假定的卫星吸积残余物的结构，具有长期存在的、连贯的潮汐特征，可以用来精确地模拟银河系的引力势，以及原始卫星的特征。然而，这种建模研究受到沿潮汐特征的大角度运动数据贫乏的限制。虽然径向速度计划最近才开始为少数已知的银河潮尾解决这个问题，但还没有系统的调查开始解决横向（切向）速度（即绝对固有运动），这包含了两倍的动力学信息。如果没有这些信息，动力学模型仍然很不受约束，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博士将在Kapteyn于1906年为银河系结构研究指定的选定区域对50多个视线进行深入、高精度的绝对和相对自动调查；事实上，Kapteyn和他的同事在那个时候拍摄的照片将被用作第一个时代的材料。目前的自运动程序不能在类似的星等限制下达到这种精度，因此在探测和表征遥远的光晕子结构方面受到限制。在即将发射的天体测量卫星GAIA和SIM之前，这个项目的运动精度、深度和天空覆盖的组合将不会被超越。这些任务的数据可能分别在2015年和2020年可用，而这个项目的结果将在未来3-4年内可用。适当的运动将由径向速度、距离和金属丰度估算来补充，这些估算来自光度和光谱工作，以及像2MASS、QUEST、SDSS和RAVE这样的重叠调查。这些数据的预期应用示例包括：1)确定高度模糊的单角星的范围和轨道运动，银面上下的反中心结构；2)表征人马座潮汐流的横向运动。3)探测和表征银河系光晕中的附加子结构。4)确定视场中众多厚盘和光晕恒星的运动特性与银河系中心距离的关系。只有少数深度、精确（铅笔束式）的运动数据集以银河系野星为中心，而不是以球状星团或矮球体为中心。这个项目将大大增加铅笔束型数据集的数量，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。使该项目成为可能的是将1909年拍摄的原始60英寸威尔逊山望远镜板与匹配的杜邦2.5米板结合在一起，从而产生了90年的优秀板尺度材料基线。这项研究将有助于建立银河系与其前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，碎片恒星的运动数据有可能测量暗物质晕的块状。这两个问题与冷暗物质模拟有关，目前，暗物质晕的数量相对于观测到的银河系卫星的数量，被高估了两个数量级。＊＊＊