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Abstract: We have measured the absolute proper motions of globular clusters NGC 2808,3201, 4372, 4833, 5927 and 5986. The proper motions are on the Hipparcos systemand they are the first determinations ever made for these low Galactic latitudeclusters. The proper motion uncertainties range from 0.3 to 0.5 mas-yr. Theinferred orbits indicate that 1) the single metal rich cluster in our sample,NGC 5927, dynamically belongs to the thick disk, 2) the remaining metal poorclusters have rather low-energy orbits of high eccentricity; among these, thereappear to be two -pairs- of dynamically associated clusters, 3) the mostenergetic cluster in our sample, NGC 3201 is on a highly retrograde orbit -which had already been surmised from its radial velocity alone - with anapocentric distance of 22 kpc, and 4) none of the metal poor clusters appear tobe associated with the recently detected SDSS streams, or with the Monocerosstructure.These are the first results of the Southern Proper-Motion Program (SPM) wherethe second-epoch observations are taken with the CCD camera system recentlyinstalled on the double astrograph at El Leoncito, Argentina.



Author: D. I. Casetti-Dinescu, T. M. Girard, D. Herrera, W. F. van Altena, C. E. López, D. J. Castillo

Source: https://arxiv.org/



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