Orbits of Milky Way Globular Clusters and Satellite Galaxies

AST 0098687货车Altena耶鲁南方天文台的William货车阿尔特纳博士将获得这个奖项，确定大约20个银河系球状星团和几个银河系卫星星系的绝对自行和切向速度。切向速度结合它们的测量距离和径向速度，以及假设的银河系质量模型，将使货车阿尔特纳博士能够计算它们的轨道，并将它们的轨道向后投影，以研究它们与现有或新发现的残余流的关联。特别是，目标球状星团的分布是这样的，它将提供一个很好的探测银河系内部，使研究人员能够从运动学上解开它的各个组成部分。切向速度和银心轨道将被确定为大麦哲伦云，小麦哲伦云，云间区域，人马座矮星系，和众多的银河系球状星团在第一个时代的南方自行计划（SPM）板块的十进制和星等限制，在这三年的奖励期间。绝对自行将通过第谷-2恒星锚定在国际天体参考系（ICRS）上，这将形成这个自行参考系。对于大多数球状星团，推导出的切向速度的预期精度范围为10至20 km/s，对于其余的星团以及人马座矮椭球体，大约为35 km/s，从70公里到90公里，这一奖项获得的整套数据应先于计划中的天体测量卫星的结果任务，如FAME和SIM。事实上，FAME仪器测量高密度场的能力有限，使得大多数这些拟议目标无法接近它。SIM将为大多数（如果不是所有）这些目标提供明确的测量，但要到2015年。通过使用SPM材料，货车阿尔特纳博士将在2004年之前提供相当准确的测定结果。在将来某个日期，当SPM完成时，将有可能把目前正在建设的施密特巡天星表减少到SPM系统中，并利用这些经过转换的施密特数据进一步提高切向速度的准确性。

AST 0098687Van AltenaWith this award Dr. William Van Altena of Yale Southern Observatory will determine the absolute proper motions, and hence tangential velocities, for approximately twenty Galactic globular clusters and several Milky Way satellite galaxies. The tangential velocities in combination with their measured distances and radial velocities, and assumed Galactic mass models, will enable Dr. Van Altena to calculate their orbits and project their trajectories backwards in time to study their association with existing or newly identified remnant streams. In particular, the distribution of target globular clusters is such that it will provide an excellent probe of the inner Galaxy, allowing the researchers to kinematically disentangle its various components.Tangential velocities and Galactocentric orbits will be determined for the Large Magellanic Cloud, the Small Magellanic Cloud, an Intercloud region, the Sagittarius dwarf galaxy, and numerous Galactic globular clusters within the declination and magnitude limits of the first-epoch Southern Proper Motion program (SPM) plates, during this three-year award period. The absolute proper motions will be anchored to the International Celestial Reference System (ICRS), via Tycho-2 stars, which will serve to form this proper- motion reference frame. The anticipated accuracy of the derived tangential velocities ranges from 10 to 20 km/s for the majority of the globular clusters, roughly 35 km/s for the remaining clusters as well as for the Sagittarius dwarf spheroidal, and from 70 to 90 km/s for the three separate Magellanic Cloud fields.The entire set of data obtained with this award should be available prior to the results from planned astrometric satellite missions, such as FAME and SIM. In fact, limitations in the ability of the FAME instrumentation to measure high-density fields, renders most of these proposed targets inaccessible to it. SIM will provide definitive measures for most if not all of these targets, but not until 2015. With the use of the SPM material, Dr. Van Altena will provide reasonably accurate determinations by 2004. At some future date, when the SPM has been completed, it will be possible to reduce the currently under-construction Schmidt sky survey catalogs into the SPM system and use those transformed Schmidt data to improve the accuracy of the tangential velocities further.***