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Astronomy & Astrophysics

Resolved Stellar Populations of Super-Metal-Rich Star Clusters in the Bulge of M31

P. Jablonka1, F. Courbin2, G. Meylan3, A. Sarajedini4, T.J. Bridges5 and P. Magain6

1 DAEC-URA 8631, Observatoire de Paris-Meudon, Place Jules Janssen, 92195 Meudon, France
2 Universidad Católica de Chile, Departamento de Astronomía y Astrofísica, Av. Vicuña Mackena 4860, Casilla 306, Santiago 22, Chile
3 European Southern Observatory, Karl-Schwarzschild-Strasse 2, D-85748 Garching-bei-München, Germany
4 Astronomy Department, Wesleyan University, Middletown, CT 06459 USA
5 Anglo-Australian Observatory, P.O. Box 296, Epping, NSW, 1710, Australia
6 Institut d'Astrophysique et de Géophysique - Université de Liège, Avenue de Cointe 5, 4000 Liège, Belgium


     We have applied the MCS image deconvolution algorithm (Magain, Courbin & Sohy 1998) to HST/WFPC2 V, I data of three M31 bulge globular clusters (G170, G177, and G198) and control fields near each cluster. All three clusters are clearly detected, with an increase in stellar density with decreasing radius from the cluster centers; this is the first time that stars have been resolved in bulge clusters in the inner regions of another galaxy. From the RGB slopes of the clusters and the difference in I magnitude between the HB and the top of the RGB, we conclude that these three clusters all have roughly solar metallicity, in agreement with earlier integrated-light spectroscopic measurements. Our data support a picture whereby the M31 bulge clusters and field stars were born from the same metal-rich gas, early in the galaxy formation.

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