Investigations of Star Clusters

对星团的调查。耶克斯天文台的星团研究主要涉及球状星团、矮小球状星系和少数疏散星团的天体测量(自行)和光度学研究。自然运动被用来得出星系团的成员资格，研究较近的星系团的内部动力学，以及得出空间速度。高质量的光度测量通常与天文测量一起获得，以产生非常干净的颜色-星等图。在一些球状星系团中，自行与库德沃斯博士和其他人获得的径向速度相结合，以进一步约束动力学模型，并以足够的精度推导距离，以提供一个有用的球状星团距离标度的新校准，而不依赖于“标准蜡烛”假设。球状星系和一些矮小的球状星系的绝对自行和空间速度正在被确定。通过重点研究非常遥远的球状星体和矮小类星体的空间速度，库德沃斯博士将能够对银河系的质量施加更好的约束。

Investigations of Star Clusters. Star cluster research at Yerkes Observatory primarily involves astrometric (proper motions) and photometric studies of globular clusters, dwarf spheroidal galaxies, and a few open clusters. Proper motions are used to derive cluster membership, study the internal dynamics of the nearer clusters, and derive space velocities. High quality photometry is normally obtained along with the astrometry to produce very clean color-magnitude diagrams. In some globular clusters the proper motions are combined with radial velocities obtained by Dr. Cudworth and others to further constrain dynamical models and to derive distances with sufficient precision to provide a useful new calibration of the globular cluster distance scale independent of "standard candle" assumptions. Absolute proper motions and hence space velocities are being determined for globulars and some dwarf spheroidal galaxies. With an emphasis on space velocity derivations for very distant globulars and dwarf speroidals, Dr. Cudworth will be able to place better constrains on the mass of the Milky Way.