A search for old star clusters in the large magellanic cloud

GEISLER, DOUG; BICA, EDUARDO; DOTTORI, HORACIO; PIATTI, ANDRÉS E.; CLARIA OLMEDO, JUAN JOSÉ

Estados Unidos

Congreso; 190th Meeting of the American Astronomical Society; 1997

There are only a handful of known star clusters in the LMC that are genuinely old, i.e. of similar age to the globular star clusters in the Milky Way. Recently, Bica et al. (1996, ApJS, 102, 57) have uncovered a large number of old star cluster candidates in the LMC from integrated UBV photometry. There are also several clusters from the study of Olszewski et al. (1991, AJ, 101, 515) which have low metallicities based on Ca triplet spectroscopy and therefore also are good candidates for old LMC clusters. We have obtained Washington C,T_1 photometry for nearly all of these candidates using the CTIO 0.9m telescope. From the T_1 vs. (C-T_1) color-magnitude diagram, we can determine the cluster ages as well as their metal abundance and reddening. We present preliminary results from this study. One of our major findings is that no new old LMC clusters were found (although we cannot rule out old age for 2 of the very crowded bar clusters). All of the other candidates turn out to be intermediate age clusters. We discuss several reasons why integrated photometry can confuse intermediate age clusters with genuine old clusters.