THE STRUCTURE OF THE SUPER-STAR CLUSTERS IN NGC-1569 FROM HUBBLE-SPACE-TELESCOPE WFPC2 IMAGES

We present high-resolution observations of the super-star clusters in the nearby irregular galaxy NGC 1569, obtained with the WFPC2 on board the Hubble Space Telescope. Our analysis shows that the brightest of these clusters, NGC 1569A, results from the superposition of two clust ers with an angular separation of similar to 0.'' 2 Recent ground-base d spectroscopy revealed that both red supergiant and Wolf-Rayet stars are associated with NGC 1569A. According to current evolutionary model s, this finding requires the coexistence of two noncoeval stellar popu lations within the same cluster. Our discovery that NGC 1569A is doubl e simplifies the interpretation, since red supergiants and Wolf-Rayet stars may belong to different clusters. We derive for the three cluste rs half-light radii of similar to 1.6-1.8 pc, smaller than indicated b y previous HST observations. The size, mass, and luminosity of the bri ghtest of these superclusters confirm that these objects could be youn g globulars, reinforcing previous conclusions.