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dc.contributor.authorGeisler, Dougpt_BR
dc.contributor.authorBica, Eduardo Luiz Damianipt_BR
dc.contributor.authorDottori, Horacio Albertopt_BR
dc.contributor.authorClaria Olmedo, Juan Josept_BR
dc.contributor.authorPiatti, Andres E.pt_BR
dc.contributor.authorSantos Junior, Joao Francisco Coelho dospt_BR
dc.date.accessioned2014-12-04T02:13:46Zpt_BR
dc.date.issued1997pt_BR
dc.identifier.issn0004-6256pt_BR
dc.identifier.urihttp://hdl.handle.net/10183/107735pt_BR
dc.description.abstractThere 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. We report the first results of a color-magnitude diagram survey of 25 candidate old LMC clusters, which were uncovered by means of integrated UBV photometry and Ca II triplet spectroscopy during previous investigations. The photometry was carried out with the Washington system C,T 1 filters on the Cerro Tololo 0.9 m telescope. For almost all of the sample, it was possible to reach the tumoff region, and in many clusters we have several magnitudes of the main sequence. The efficiency and efficacy of the technique are demonstrated by our deep CMD for ESO 121-SC03 (used as a control and calibrator), which clearly shows a magnitude of main sequence for this =9 Gyr old object in a total of <1 hour of integration time. Age estimates based on the magnitude difference 8T 1 between the giant branch clump and the tumoff, calibrated using standard clusters, revealed that no new old clusters were found. The candidates tumed out to be of intermediate age (1-3 Gyr) (we cannot role out old ages for NGC 1928 and NGC 1939 since the turnoff was not reached for these compact clusters in crowded bar fields). We show that the apparently old ages as inferred from integrated UBV colors can be explained by a combination of stochastic effects produced by bright stars and by photometric errors for faint clusters lying in crowded fields. The relatively metal poor ([Fe/H]- -1.0) candidates from the Ca II triplet spectroscopy also turned out to be of intermediate age. This, combined with the fact that they Iie far out in the disk, yields interesting constraints regarding the formation and evolution of the LMC disk. We also study the age distribution of intermediate age and old clusters considering not only the present 8T 1 parameter, but also 8V and 8R measured in CMDs from the literature. This homogeneous set of accurate relative ages allows us to make an improved study of the history of cluster formationldestruction for ages > 1 Gyr. We confirrn previous indications that there was apparently no cluster formation in the LMC during the period from 3-8 Gyr ago, and that there was a pronounced epoch of cluster formation beginning 3 Gyr ago that peaked at about 1.5 Gyr ago. Our results suggest that there are few, if any, genuine old clusters in the LMC Ieft to be found. © 1997 American Astronomical Society. [50004-6256(97)03711-4]en
dc.format.mimetypeapplication/pdf
dc.language.isoengpt_BR
dc.relation.ispartofThe Astronomical Journal. New York. Vol. 114, no. 5 (nov. 1997), p. 1920-1932pt_BR
dc.rightsOpen Accessen
dc.subjectAstrofisica extragalaticapt_BR
dc.subjectNuvens de magalhaespt_BR
dc.subjectAglomerados estelares e associacoespt_BR
dc.subjectGaláxiaspt_BR
dc.titleA search for old star clusters in the large magellanic cloudpt_BR
dc.typeArtigo de periódicopt_BR
dc.identifier.nrb000152529pt_BR
dc.type.originEstrangeiropt_BR


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