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Session 98 - Globular Clusters.
Oral session, Friday, January 09

[98.03] Kinematics of Globular Clusters from Tangential Velocities and Constraints on Formation Scenarios of the Galaxy

D. I. Dinescu, W. F. van Altena, T. M. Girard (Yale Univ.), C. E. López (YSO - Univ. of San Juan, Argentina)

Tangential velocities of globular clusters derived from absolute proper motions tied directly to galaxies allow one to determine the orbit-type of the cluster, which contributes to a substantial improvement for studies of cluster origins and destruction processes. Also the full kinematics of globular clusters interpreted in combination with metallicities, horizontal branch morphologies and ages, provide strong constraints on formation scenarios of the Galaxy. We present here results for fifteen southern globular clusters for which absolute proper motions were determined with precisions between 0.4 and 1.0 mas yr^-1; this sample represents a third of the total number of clusters which have absolute proper motions determinations. To date, work in this field covers mostly inner (R_GC < 8 kpc), metal-poor ([Fe/H]< -0.8) clusters. For these clusters, our results together with previous work, show significant overlap in metallicity for two kinematically distinct populations: cold, rotationally-supported clusters, and hot, pressure-supported ones. Also, our results indicate that, the most metal-poor clusters ([Fe/H] < -1.8) in the inner parts of the Galaxy are essentially a pressure-supported system with a large velocity dispersion. Other - more cluster-specific results - will also be discussed.

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Program listing for Friday