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Washington photometry of five star clusters in the Large Magellanic Cloud

Published online by Cambridge University Press:  18 January 2010

Andrés E. Piatti ,
Doug Geisler ,
Ata Sarajedini  and
Carme Gallart
Andrés E. Piatti
Affiliation:
Instituto de Astronomía y Física del Espacio, CC 67, Suc. 28, 1428, Ciudad de Buenos Aires, Argentina email: andres@iafe.uba.ar
Doug Geisler
Affiliation:
Grupo de Astronomía, Departamento de Astronomía, Universidad de Concepción, Casilla 160-C, Concepción, Chile email: dgeisler@astro-udec.cl
Ata Sarajedini
Affiliation:
Department of Astronomy, University of Florida, PO Box 112055, Gainesville, FL 32611, USA email: ata@astro.ufl.edu
Carme Gallart
Affiliation:
Instituto de Astrofísica de Canarias, Calle Vía Láctea, E-38200, La Laguna, Tenerife, Spain email: carme@iac.es
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Abstract

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We present CCD photometry in the Washington-system C and T1 passbands down to T1 ~ 22.5 mag in the fields of NGC 1697, SL 133, NGC 1997, SL 663, and OHSC 28, five mostly unstudied star clusters in the LMC. Cluster radii were estimated from star counts in appropriately sized boxes distributed throughout the entire observed fields. We perform a detailed analysis of field-star contamination and derive cluster colour–magnitude diagrams (CMDs). Based on the best fits of isochrones computed by the Padova group to the (C − T1, T1) CMDs, the δ(T1) index and the ‘standard giant-branch’ procedure, we derive metallicities and ages for the five clusters. With the exception of NGC 1697 (age = 0.7 Gyr, [Fe/H] = 0.0 dex), the remaining four clusters are of intermediate age (from 2.2 to 3.0 Gyr) and relatively metal poor ([Fe/H] = −0.7 dex). We combine our sample with clusters with ages and metallicities on a similar scale and examine relationships between position in the LMC, age and metallicity. We confirm previous results that clusters younger than ~ 1 Gyr were formed during an outside-in process; this occurred after a burst of cluster formation that took place mainly in the outer disk and peaked ~ 2 Gyr ago. Finally, the cluster and field age–metallicity relations (AMRs) show evidence for a metallicity offset but do overlap, particularly on the upper-envelope side of the cluster AMR.

Keywords

galaxies: individual (Large Magellanic Cloud)galaxies: star clusterstechniques: photometric
Type
Contributed Papers
Information
Proceedings of the International Astronomical Union , Volume 5 , Symposium S266: Star clusters: basic galactic building blocks throughout time and space , August 2009 , pp. 500 - 503
Copyright
Copyright © International Astronomical Union 2010

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