INVESTIGADORES
PIATTI Andres Eduardo
congresos y reuniones científicas
Título:
Edades y metalicidades de cúmulos estelares de la Nube Mayor de Magallanes y de sus campos estelares circundantes
Autor/es:
BICA, EDUARDO; GEISLER, DOUG; DOTTORI, HORACIO; PIATTI, ANDRÉS E.; CLARIA OLMEDO, JUAN JOSÉ; SANTOS JR, JOÂO F.C.
Lugar:
La Plata
Reunión:
Congreso; Reunión Anual de la Asoc. Argentina de Astronomía; 1998
Resumen:
We report the results of a CMD survey of 25 candidate old LMC clusters
uncovered by previous investigations. Washington system C,T1
photometry was obtained on the CTIO 0.9m. Ages based on the magnitude
difference δT1 between the giant branch clump and the
turnoff revealed that no new old clusters were found. The candidates
turned out to be of intermediate age (1-3 Gyr). We also study the age
distribution of intermediate age and old clusters using both our data
and CMDs from the literature. We confirm previous indications that there
was apparently no cluster formation in the LMC during the period from
3-9 Gyr ago, and there was a pronounced epoch of cluster formation
beginning 3 Gyrs ago that peaked at ~ 1.5 Gyrs ago. Our results suggest
that there are few, if any, genuine old clusters in the LMC left to be
found. We also determine ages for the surrounding fields, as well as
metallicities for both the clusters and fields from the color of the
giant branch compared to fiducial clusters. In most cases the stellar
population of each cluster is quite similar to that of the field where
it is embedded. In the northern part of the LMC disk the fields of
SL388, SL509 and NGC1997 have a secondary clump ~0.45 mag fainter than
the dominant clump, suggesting a component located behind the LMC at a
distance comparable to that of the SMC. The mean metallicity for the
intermediate age outer disk clusters is somewhat lower than found by
Olszewski et. al (1991, AJ, 101, 515) for a sample of clusters of
similar age, but is in good agreement with several recent studies. A few
clusters stand out in the age-metallicity relation in the sense that are
intermediate age clusters at relatively low metallicity ([Fe/H]~ -1.).