SUPER-NOVA REMNANTS AND CONTENT IN HIGH MASS STARS OF THE GIANT H II REGION NGC-604

An optical survey of NGC 604, the brightest HII complex in M33, has lead to the discovery of a single supernova remnant, in agreement with the predominantly thermal radio spectrum of the region. For the same NGC 604, we have derived from the Hβ flux and the evolutionary tracks of the stars, the population and the birth-rates of Main Sequence, high-mass stars. The computation is in agreement with the observations of the upper part of the stellar luminosity function. From the stellar population one predicts in the region a number of remnants significantly larger than 1. To explain this discrepancy, it is suggested the presence in NGC 604 of at least one overluminous, hot star (MB≃9), which contributes to a large fraction of the ionizations. © 1979 D. Reidel Publishing Co.