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Astron. Astrophys. 319, 394-396 (1997)

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Age and metallicity effects in single stellar populations: application to M 31 clusters

J.A. de Freitas Pacheco

Observatoire de la Côte d'Azur, B.P. 229, F-06304 Nice Cedex 4, France

Received 8 January 1996 / Accepted 30 July 1996


We have recently calculated (Borges et al. 1995) integrated metallicity indices for single stellar populations (SSP). Effects of age, metallicity and abundances were taken into account. In particular, the explicit dependence of the indices [FORMULA] and NaD respectively on the ratios [Mg/Fe] and [Na/Fe] was included in the calibration. We report in this work an application of those models to a sample of 12 globular clusters in M 31. A fitting procedure was used to obtain age, metallicity and the [Mg/Fe] ratio for each object, which best reproduce the data. The mean age of the sample is 15 [FORMULA] 2.8 Gyr and the mean [Mg/Fe] ratio is 0.35 [FORMULA] 0.10. These values and the derived metallicity spread are comparable to those found in galactic counterparts.

Key words: galaxies: M 31 – galaxies: abundances – galaxies: star clusters – globular clusters: general

Send offprint requests to: J.A. de Freitas Pacheco

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© European Southern Observatory (ESO) 1997

Online publication: July 3, 1998