Washington photometry of five star clusters in the Large Magellanic Cloud

PIATTI, ANDRÉS E.; GEISLER, DOUG; SARAJEDINI, A.; GALLART, C.

Proc. IAU Symp. "Star Clusters - Basic Galactic Building Blocks throughout Time and Space"

Cambridge Univ Press

Año: 2010 vol. 266 p. 500 - 503

1743–9213

Abstract. We present CCD photometry in the Washington-system C and T1 passbands down toT1 ∼ 22.5 mag in the fields of NGC 1697, SL 133, NGC 1997, SL 663, and OHSC 28, five mostlyunstudied star clusters in the LMC. Cluster radii were estimated from star counts in appropri-ately sized boxes distributed throughout the entire observed fields. We perform a detailed anal-ysis of field-star contamination and derive cluster colour–magnitude diagrams (CMDs). Basedon the best fits of isochrones computed by the Padova group to the (C − T1 ,T1 ) CMDs, the δ(T1 )index and the ‘standard giant-branchÂ’ procedure, we derive metallicities and ages for the fiveclusters. With the exception of NGC 1697 (age = 0.7 Gyr, [Fe/H] = 0.0 dex), the remaining fourclusters are of intermediate- age (from 2.2 to 3.0 Gyr) and relatively metal poor ([Fe/H] = -0.7dex). We combine our sample with clusters with ages and metallicities on a similar scale andexamine relationships between position in the LMC, age and metallicity. We confirm previousresults that clusters younger than ∼ 1 Gyr were formed during an outside-in process; this oc-curred after a burst of cluster formation that took place mainly in the outer disk and peaked at∼ 2 Gyr ago. Finally, the cluster and field age–metallicity relations (AMRs) show evidence fora metallicity offset but do overlap, particularly on the upper-envelope side of the cluster AMR.