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Astron. Astrophys. 335, 867-875 (1998)


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Metallicity distribution of bulge globular clusters in M 31

P. Jablonka 1, E. Bica 2, C. Bonatto 2, T.J. Bridges * 3, M. Langlois 1 and D. Carter 4

1 URA 173 CNRS, DAEC, Observatoire de Paris, F-92195 Meudon Principal Cedex, France
2 Universidade Federal do Rio Grande do Sul, IF, Dept. de Astronomia, CP 15051, Porto Alegre 91501-970, RS, Brazil
3 Royal Greenwich Observatory, Madingley Road, Cambridge, UK
4 Astrophysics Group, Liverpool John Moores University, Byrom Street, Liverpool, L3 3AF, UK

Received 17 July 1997 / Accepted 27 January 1998

Abstract

This paper presents 3600-5400 Å integrated spectra of 19 globular clusters (or candidates) projected on the central regions of M 31, [FORMULA]´ ([FORMULA]1.2 kpc). We check the cluster nature of these objects, and derive their ages, metallicities and reddenings. From the initial sample, 16 objects turn out to be true star clusters, two are Galactic dwarf stars, and one is a high redshift background galaxy. Only two clusters are found to be super metal-rich, suggesting that this phenomenon is not very common. For some clusters, we cannot rule out the possibility that they are of intermediate age; this requires confirmation by observations at the calcium triplet. We also present the metallicity histogram of this central bulge sample and discuss possible scenarios to explain its properties.

Key words: galaxies: formation – galaxies: individual: M 31 – galaxies: star clusters

* Visiting Astronomer, William Herschel Telescope. The WHT is operated on the island of La Palma by the Royal Greenwich Observatory at the Spanish Observatorio del Roque de los Muchachos of the Instituto de Astrofisica de Canarias.

Send offprint requests to: P. Jablonka

© European Southern Observatory (ESO) 1998

Online publication: June 26, 1998

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