The Milky Way in 3D Velocity Space: A View from the Southern Hemisphere

卡塞蒂博士和她的团队将继续进行耶鲁/圣胡安南方固有运动（SPM）调查，该调查测量了几十年来恒星在天空中的微小运动，以测试银河系形成的模型。在目前的项目中，他们将测量从人马座矮星系中分离出来的恒星的绝对固有运动，测量在大犬座天空中密度过大区域的恒星，以及15个球状星团，以确定它们围绕银河系中心的轨道。为了提高精度，在调查早期（第一历元）拍摄的照相板将使用耶鲁大学PDS微密度计重新测量，以提高精度。第二历元CCD观测将覆盖大犬座的过度密度和人马座矮星系的前后尾，并扩大球状星团的样本。新的观测总计约8000个点，或在埃尔莱昂西托天文台用Cesco双占星仪观察了2.5年。该团队还将通过结合测量的固有运动和径向速度来探测银河系的厚盘，以找到恒星在太空中运动的所有三个组成部分。智利大学的一名博士生对银河系南极附近1160颗红巨星的样本进行了调查，并利用RAVE对银河系中纬度的恒星进行了测量。RAVE是一项利用澳大利亚的望远镜对恒星径向速度进行的调查。将这些运动与动力学模型预测的结果进行比较，研究小组将探索垂直于银河系中间平面的这些恒星所受的力，以及引力势的平坦程度。由1100万颗恒星组成的SPM3.3星表的测量固有运动、位置和照相光度现在可以从耶鲁大学的网站上通过ftp获得，第四颗SPM4星表将很快发布。阿根廷圣胡安大学、科尔多瓦大学和拉普拉塔大学的本科生将在为该项目进行观测时接受培训。该组织为El Leoncito天文台非常活跃的游客中心提供材料。该奖项是根据2009年美国复苏和再投资法案（公法111-5）资助的。

Dr. Casetti and her team will continue work on the Yale/San Juan Southern Proper Motion (SPM) survey, which measures the tiny motions of stars across the sky over multiple decades, to test models for the Milky Way's formation. In the present project they will measure absolute proper motions for stars torn off the Sagittarius dwarf galaxy, for stars in an over-dense region of the sky in the constellation of Canis Major, and for 15 globular star clusters, to determine their orbits around the Galactic center. To improve accuracy, photographic plates taken early in the survey (the first epoch) will be re-measured using the Yale PDS microdensitometer, to improve the precision. Second-epoch CCD observations will be made to cover the Canis Major overdensity and both the leading and trailing tails of the Sagittarius dwarf, and to enlarge the sample of globular clusters. The new observations amount to about 8000 pointings, or 2.5 years observing at El Leoncito observatory with the Cesco double astrograph.The team will also probe the Milky Way's thick disk by combining their measured proper motions with radial velocities to find all 3 components of a star's motion through space. They will do this for a sample of 1160 red giants near the South Galactic Pole surveyed by a PhD student at the University of Chile, and with measurements of stars at intermediate Galactic latitudes from RAVE, a survey of stellar radial velocities using a telescope in Australia. Comparing these motions to what is predicted by dynamical models, the group will explore the force on these stars perpendicular to the mid-plane of the Milky Way, and hence the degree of flattening in the gravitational potential.The measured proper motions, positions and photographic photometry for the SPM3.3 catalog with 11 million stars is now available by ftp from Yale's website, and the fourth catalog SPM4 will be released shortly. Undergraduates at the Universities of San Juan, Cordoba and La Plata in Argentina will be trained as they obtain observations for the project. The group provides materials for the very active visitor center at El Leoncito observatory.This award is funded under the American Recovery and Reinvestment Act of 2009 (Public Law 111-5).