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Astron. Astrophys. 333, 117-124 (1998)

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Globular clusters within 5o of the Galactic center *

B. Barbuy 1, E. Bica 2 and S. Ortolani 3

1 Universidade de São Paulo, CP 3386, Departamento de Astronomia, São Paulo 01060-970, Brazil
2 Universidade Federal do Rio Grande do Sul, Departamento de Astronomia, CP 15051, Porto Alegre 91500-970, Brazil
3 Università di Padova, Dipartimento di Astronomia, Vicolo dell'Osservatorio 5, I-35122 Padova, Italy

Received 1 April 1997 / Accepted 28 November 1997


In the recent years we have concentrated efforts to collect Colour-Magnitude Diagrams of the globular clusters projected in the central parts of the Galaxy. So far we were able to gather photometric data in the V, I and Gunn z bandpasses, for 16 out of the 17 known clusters in the central [FORMULA] radius, most of them severely reddened. Reddening, distance and metallicity are estimated from the horizontal and red giant branches.

We study the resulting cluster spatial distribution and conclude that essentially no cluster is detected beyond the Galactic Center distance. The results favour a flattened bulge extending from the Galactic Center to 4.5 kpc from the Sun. The density distribution of the clusters follows the current models for bulge field stars. We estimate that missing clusters on the opposite side of the Galaxy bulge may amount [FORMULA] 15 clusters similar to those detected on our side. The projected distribution of clusters is asymmetrical, with higher absorption in the southern Galactic hemisphere. The metallicity distribution of our sample clusters results similar to that of bulge field stars.

The present ground-based results coupled to main sequence data of two genuine bulge clusters using the Hubble Space Telescope, point to a scenario of an old flat bulge with common origin for the stellar populations in both globular clusters and field.

Key words: globular clusters: general – Galaxy: center – Galaxy: formation – Hertzsprung – Russel (HR) and C-M diagrams

* Observations collected at the European Southern Observatory - ESO, Chile

© European Southern Observatory (ESO) 1998

Online publication: April 15, 1998