Detection of Wolf-Rayet stars of WN and WC subtype in Super Star Clusters of NGC 5253

Abstract

We present spectroscopic observations of the central star clusters in NGC 5253 the aim of which is to search for WC stars. Our observations show the presence of Wolf-Rayet (WR) stars not only of WN but also of WC subtype in two star forming regions corresponding to the maximum optical and UV emission. The massive star population we derive is consistent with young bursts of ~3 and 4 Myr. The region of maximum optical emission is found to provide the dominant contribution of the ionizing flux as opposed to the less extinguished region of maximum UV brightness. The presence of WR stars near the N-enriched regions found by Walsh & Roy (1987, 1989) and Kobulnicky et al. (1997) suggests they are a possible source of N. It is presently unclear whether or not our detection of WC stars is compatible with the normal observed He/O and C/O abundance ratios.

Accepted by ApJ Letters. 10 pages, including 2 Figures. LaTeX using aas2pp4 and psfig macros. Also available at http://www.stsci.edu/ftp/science/starburst/