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Symposium 241

Abstract details

Detailed Properties of Populous Clusters in the Large Magellanic Cloud
A. J. Grocholski, A. Sarajedini, A. A. Cole, D. Geisler, K. A. G. Olsen, G. P. Tiede, V. V. Smith, C. L. Mancone

We present results from a series of projects aimed at better understanding the ages, velocities, metallicities and distances of populous clusters in the LMC. In an effort to update previous [Fe/H] determinations, we have utilized FORS2 on the VLT to obtain infrared spectra for more than 200 stars in 28 LMC clusters. The absorption lines of the calcium II triplet were then used to calculate radial velocities and [Fe/H] for a sample of clusters spanning a large range of ages (~ 1-13 Gyr) and metallicities (-0.3 > [Fe/H] > -2.0). To calculate cluster ages, we have compiled deep optical photometry for 30 LMC clusters using a combination of published photometry, VLT/FORS2 images and archival HST/WFPC2 images. These data, in conjunction with our derived metallicities, have allowed us to determine accurate cluster ages via main sequence fitting with theoretical isochrones that include treatment for core overshoot. Finally, we have utilized the K-band luminosity of core helium burning red clump (RC) stars to determine distances for 17 of these LMC clusters. Using ISPI on the CTIO 4m, we obtained JK photometry down to K ~ 18.5, allowing us to measure the apparent K-band RC magnitude of each cluster. Additionally, age and [Fe/H] can be used to predict the absolute K-band RC magnitude of a given cluster; thus, we have combined the apparent and absolute magnitudes, along with cluster reddenings, to calculate the distance to each individual cluster. These distances are used to probe the structure of the LMC as traced by its star cluster population.

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