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On the self-consistent physical parameters of LMC intermediate-age clusters

Published online by Cambridge University Press:  01 July 2008

Leandro O. Kerber  and
Basílio X. Santiago
Leandro O. Kerber
Affiliation:
IAG/USP, São Paulo, Brazil email: kerber@astro.iag.usp.br INAF-OAPd, Padova, Italy
Basílio X. Santiago
Affiliation:
IF/UFRGS, Porto Alegre, Brazil
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Abstract

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The LMC clusters with similar ages to the Milky Way open clusters are in general more metal-poor and more populous than the latter, being located close enough to allow their stellar content to be well resolved. Therefore, they are unique templates of simple stellar population (SSP), being crucial to calibrate models describing the integral light as well as to test the stellar evolution theory. With this in mind we analyzed HST/WFPC2 (V, B − V) colour-magnitude diagrams (CMDs) of 15 populous LMC clusters with ages between ~0.3 Gyr and ~4 Gyr using different stellar evolutionary models. Following the approach described by Kerber, Santiago & Brocato (2007), we determined accurate and self-consistent physical parameters (age, metallicity, distance modulus and reddening) for each cluster by comparing the observed CMDs with synthetic ones generated using isochrones from the PEL and BaSTI libraries. These determinations were made by means of simultaneous statistical comparison of the main-sequence fiducial line and the red clump position, offering objective and robust criteria to select the best models. We compared these results with the ones obtained by Kerber, Santiago & Brocato (2007) using the Padova isochrones. This revealed that there are significant trends in the physical parameters due to the choice of stellar evolutionary model and treatment of convective core overshooting. In general, models that incorporate overshooting presented more reliable results than those that do not. Furthermore, the Padova models fitted better the data than the PEL and BaSTI models. Comparisons with the results found in the literature demonstrated that our derived metallicities are in good agreement with the ones from the spectroscopy of red giants. We also confirmed that, independent of the adopted stellar evolutionary library, the recovered 3D distribution for these clusters is consistent with a thick disk roughly aligned with the LMC disk as defined by field stars. Finally, we also provide new estimates of distance modulus to the LMC center, that are marginally consistent with the canonical value of 18.50 mag.

Keywords

Hertzsprung-Russell diagramgalaxies: individual (LMC)Magellanic Cloudsgalaxies: star clusters
Type
Contributed Papers
Information
Proceedings of the International Astronomical Union , Volume 4 , Symposium S256: The Magellanic System: Stars, Gas, and Galaxies , July 2008 , pp. 391 - 396
Copyright
Copyright © International Astronomical Union 2009

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