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Ages and Metallicities of LMC Clusters and Their Surrounding Fields

Published online by Cambridge University Press:  25 May 2016

Doug Geisler ,
Eduardo Bica ,
Horacio Dottori ,
Juan J. Clariá ,
Andrés E. Piatti  and
João F.C. Santos Jr.
Doug Geisler
Affiliation:
Kitt Peak National Observatory, NOAO, Tucson AZ, 85719 USA
Eduardo Bica
Affiliation:
Instituto de Física, UFRGS, Porto Alegre, RS, BRAZIL
Horacio Dottori
Affiliation:
Instituto de Física, UFRGS, Porto Alegre, RS, BRAZIL
Juan J. Clariá
Affiliation:
Observatorio Astronómico, Córdoba, ARGENTINA
Andrés E. Piatti
Affiliation:
Observatorio Astronómico, Córdoba, ARGENTINA
João F.C. Santos Jr.
Affiliation:
Dpto. de Física, UFMG, Belo Horizonte, MG, BRAZIL

Abstract

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We report on a survey of 25 candidate old LMC clusters. Washington photometry was obtained on the CTIO 0.9m in < 1h, reaching below the turnoff. Ages based on the magnitude difference δT1 between the giant branch clump and the turnoff revealed that no new old clusters were found. The candidates all turned out to be of intermediate age (1–3 Gyr). We confirm that there was apparently no cluster formation in the LMC from 3–9 Gyr ago, and that there was a pronounced epoch of cluster formation beginning 3 Gyrs ago that peaked at ~1.5 Gyrs ago. We also determine ages for the surrounding fields, as well as metallicities for both the clusters and fields from the color of the giant branch. In most cases the stellar population of each cluster is quite similar to that of its field. The mean metallicity for the intermediate age outer disk clusters is −0.65. A few clusters stand out in the age-metallicity relation in the sense that they are intermediate age clusters at relatively low metallicity. In the northern part of the LMC disk 3 fields all have a secondary clump ~0.45 mag fainter than the dominant clump, suggesting a component located behind the LMC at a distance comparable to that of the SMC.

Type
Part 6. Stellar Clusters
Information
Symposium - International Astronomical Union , Volume 190: New Views of the Magellanic Clouds , 1999 , pp. 431 - 433
Copyright
Copyright © Astronomical Society of the Pacific 1999 

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