PI: Imants Platais, The Johns Hopkins University, email@example.com
Address: Physics Department, 3400 N. Charles Street, Baltimore, MD 21218, USA
CoI: Terrence M. Girard, Yale University
CoI: William F. van Altena, Yale University
Title: Deep Astrometry of Old Open Clusters
Abstract: We propose to complete the determination of cluster membership to very faint magnitudes (V=20-22) for a set of five rich and old open clusters as defined by the NSF-supported WIYN Open Cluster Study (WOCS). For each cluster the proper-motion measurements will provide excellent kinematic membership determinations for the entire cluster out to the tidal radius or exceeding it. This astrometric study is a precursor to the coordinated radial velocity survey of the same clusters conducted by R. Mathieu (UW), which ultimately will provide three-dimensional kinematic membership determination for the entire evolved cluster population including a new class of the so-called sub-subgiants. With ages from 2 Gyr to 8 Gyr, this set of clusters will allow us to examine the evolution of the Present Day Mass Function toward the depletion of low-mass stars and the evolution of binary populations. The new absolute proper motions for these clusters in conjunction with other space-phase coordinates will lead to a reliable determination of cluster orbits in the Galaxy. Finally, the proposed BV photometry at the low- mass end of the main sequence will provide additional leverage for calibrating the theoretical temperature-color transformation over this difficult range.
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