ON THE EFFECTS OF BURSTS OF MASSIVE STAR-FORMATION DURING THE EVOLUTION OF ELLIPTIC GALAXIES

We consider the hypothesis that the formation of elliptical galaxies i ncludes a phase in which star formation is mostly restricted to massiv e stars, with the bias toward high-mass stars increasing with elliptic al galaxy mass. The mass fraction of stars in this top-heavy mode of s tar formation is constrained by requiring the resulting stellar remnan ts to account for the observed increase in the mass-to-light ratio of ellipticals with increasing galaxy mass. We then consider the implicat ions of this population of massive stars for the intracluster medium a nd the extragalactic background at various wavelengths. The mass and a bundance ratios of metals produced by our proposed population of massi ve stars are consistent with the observations of the mass and abundanc e ratios of metals in the hot gas of galaxy dusters for most of the st andard range of initial mass function slopes and Type II supernova yie lds. The predicted energy density produced by this stellar population approaches current limits on the extragalactic background at both opti cal wavelengths, into which the ultraviolet radiation of the massive s tars is likely to be redshifted, and far-infrared wavelengths, at whic h starlight reprocessed by dust associated with the starburst will be observed. In either case, the background is predicted to be significan tly clustered since massive ellipticals are clustered.