On the Effects of Bursts of Massive Star Formation During the Evolution   of Elliptical Galaxies
  We consider the hypothesis that the formation of elliptical galaxies includes a phase in which star formation is mostly restricted to massive stars, with the bias towards high mass stars increasing with elliptical galaxy mass. The mass fraction of stars in this top-heavy mode of star formation is constrained by requiring the resulting stellar remnants to account for the observed increase in the mass-to-light ratio of ellipticals with increasing galaxy mass. We then consider the implications of this population of massive stars for the intracluster medium and the extragalactic background at various wavelengths. The mass and abundance ratios of metals produced by our proposed population of massive stars are consistent with the observations of the mass and abundance ratios of metals in the hot gas of galaxy clusters for most of the standard range of IMF slopes and SN II yields. The predicted energy density produced by this stellar population approaches current limits on the extragalactic background at both optical wavelengths, into which the ultraviolet radiation of the massive stars is likely to be redshifted, and far-infared wavelengths, at which starlight reprocessed by dust associated with the starburst will be observed. In either case, the background is predicted to be significantly clustered since massive ellipticals are clustered. 
Stephen E. Zepf and Joseph Silk (UC Berkeley)