Ages of LMC Star Clusters using ASAD$_2$

Abstract

We use ASAD$_2$, the new version of ASAD (Analyzer of Spectra for Age Determination), to obtain the age and reddening of 27 LMC clusters from full fitting of integrated spectra using different statistical methods ($\chi^{2}$ and K-S test) and a set of stellar population models including GALAXEV and MILES. We show that our results are in good agreement with the CMD ages for both models, and that metallicity does not affect the age determination for the full spectrum fitting method regardless of the model used for ages with log (age/year) $<$ 9. We discuss the results obtained by the two statistical results for both GALAXEV and MILES versus three factors: age, S/N and resolution (FWHM). The predicted reddening values when using the $\chi^{2}$ minimization method are within the range found in the literature for resolved clusters (i.e: $<$ 0.35), however the K-S test can predict E(B$-$V) higher values. The sharp spectrum transition originated at ages around the supergiants contribution, at either side of the AGB peak around log (age/year) 9.0 and log (age/year) 7.8 are limiting our ability to provide values in agreement with the CMD estimates and as a result the reddening determination is not accurate. We provide the detailed results of four clusters spanning a wide range of ages. ASAD$_2$ is a user-friendly program available for download on the Web and can be immediately used at $http://randaasad.wordpress.com/asad-package/$.Comment: Accepted for publication in MNRA