The Star Clusters in the Starburst Irregular Galaxy NGC 1569

We examine star clusters in the irregular, starburst galaxy NGC 1569 from HSTimages. In addition to the two known super star clusters, we identify 45 otherclusters that are compact but resolved. Integrated UVI colors of the clustersspan a large range, and suggest that ages range from 3 Myrs to 1 Gyr. However,most of the clusters were formed at the tail end of the recent starburst.Numerous clusters in addition to the know super star clusters are similar inluminosity to a small globular cluster. We examined the radial surfacebrightness of four of the clusters. Their half-light radii and core radii arein the range observed in present-day globular clusters. Therefore, conditionsthat produced the recent starburst have also been those necessary for producingcompact, bright star clusters. We examine resolved stars in the outer parts of the two super star clusters.Cluster A is dominated by bright blue stars with a small population of redsupergiants. Sub-components A1 and A2 have similar colors and a two-dimensionalcolor map does not offer evidence that one component is dominated by redsupergiants and the other not. The contradiction of the presence of red super-giants with Wolf-Rayet stars may instead not be a contradiction at all sincethere coexistence in a coeval population is not inconsistent with the evolutionof massive stars. Cluster B is dominated by red supergiants, and this isconfirmed by the presence of the stellar CO absorption feature in an integratedspectrum. The various age indicators are consistent with a picture in whichcluster B is of order 10--20 Myrs old, and cluster A is >4-5 Myrs old.Comment: To be published in AJ, November 200