Proper motions and kinematics of selected bulge globular clusters

Abstract

We computed proper motions of a selected sample of globular clusters projected on the central bulge, employing CCD images gathered along the last 25 years at the ESO-NTT, ESO-Danish and HST telescopes. We presented a method to derive their proper motions, and a set of coordinate transformations to obtain 3D Galactic velocity vectors of the clusters. We analysed 10 globular clusters, namely Terzan 1, Terzan 2, Terzan 4, Terzan 9, NGC 6522, NGC 6558, NGC 6540, AL~3,ESO456--SC38 and Palomar 6. For comparison purposes we also studied the outer bulge cluster NGC 6652. We discuss the general properties of the proper-motion-cleaned Colour-Magnitude Diagrams, derived for the first time for most of them. A general conclusion is that the inner bulge globular clusters have clearly lower transverse motions (and spatial velocities) than halo clusters, and appear to be trapped in the bulge bar.

22 pages, 26 figures accepted on 2 April 2015. in MNRAS 2015

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• Bayesian Mass Estimates of the Milky Way II: The dark and light sides of parameter assumptions
• A Deep View of a Fossil Relic in the Galactic Bulge: The Globular Cluster HP1
• Globular clusters in the inner Galaxy classified from dynamical orbital criteria
• Another relic bulge globular cluster: ESO 456-SC38 (Djorgovski~2)
• The Chemical Composition of Red Giant Branch Stars in the Galactic Globular Clusters NGC 6342 and NGC 6366
• Halo intruders in the Galactic bulge revealed by HST and Gaia: the globular clusters Terzan 10 and Djorgovski 1
• Galactic Orbits of Globular Clusters in the Region of the Galactic Bulge
• Gemini/Phoenix H-band analysis of the globular cluster AL3
• Variable stars in the bulge globular cluster NGC 6401
• A MUSE study of the inner bulge globular cluster Terzan 9: a fossil record in the Galaxy
• Search for possibly evolutionary linked globular and open clusters