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/圣胡安南方自然运动(SPM)调查，以测试银河系形成的模型。SPM调查测量几十年来恒星在天空中的微小运动。在目前的项目中，他们将测量从人马座矮星系撕裂出来的恒星的绝对自行，测量位于大犬座过密区域的恒星，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(第一个纪元)拍摄的照相底片将使用耶鲁PDS显微密度计重新测量，以提高精度。第二个纪元的ccd观测将覆盖大犬座超密度和射手座矮星的前尾和尾部，并扩大球状星团的样本。新的观测总计约8000个点，相当于在埃尔莱昂西托天文台使用Cesco双星相图观测了2.5年。研究小组还将通过将测量到的自身运动与径向速度相结合来探测银河系的厚盘，以找出恒星在太空中运动的所有三个分量。他们将对南银河系极点附近的1160颗红巨星样本进行这项研究，该样本是由智利大学的一名博士生调查的，并通过RAVE对银河系中纬度的恒星进行测量，RAVE是一项使用澳大利亚望远镜测量恒星径向速度的项目。将这些运动与动力学模型的预测进行比较，该小组将探索垂直于银河系中面的这些恒星所受的力，从而探索引力势的扁平化程度。拥有1100万颗恒星的SPM3.3星表的测量自行、位置和摄影光度现在可以通过耶鲁大学网站上的ftp获得，第四个星表SPM4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获得观察时接受培训。该组织为埃尔莱昂西托天文台非常活跃的游客中心提供材料。该奖项由2009年美国复苏和再投资法案(公法111-5)资助。

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).