Metal enrichment in spheroidal star systems

Summary

Observations and theoretical expectations indicate that metal enrichment in spheroidal star systems has taken place in their early evolutionary phases through continuous star formation from the ambient gas polluted by supernova explosions, until the remaining gas was ejected from the system. Star populations and mean star metallicity are determined practically by the time of the gas ejection, since the accumulation of matter subsequently lost by the stars (and expelled by supernovae) may only lead to some sporadic episodes of star formation. We discuss the implications of a global wind driven by supernova explosions in the framework of the closed one-zone models for star systems ranging from globular clusters to giant elliptical galaxies. Difficulties with these simple models are pointed out especially with regard to the choice of the protogalactic radius. Possible implementations are mentioned and a self-consistent determination of the initial radius is outlined; that is, the final (i.e. at the present age) galactic masses and binding energies of the models are required to fulfil the relationship obtained from observations of present-epoch star systems.