2010PASP..122.1171S

The presence of abundance inhomogeneities in the CNO elements in globular clusters indicates that these objects sustained extended eras of star formation combined with chemical enrichment. Nonetheless, most globular clusters in the Milky Way are homogeneous in iron-peak elements and the heavier alpha elements. If globular clusters were sites of chemical evolution, then it seems to have occurred at constant iron-peak abundance. This might imply that only nonsupernova stars contributed to the chemical evolution. In this article another scenario is explored, one in which supernovae did participate, but in which the chemical evolution occurred in such a way as to maintain a constant iron-peak abundance, while at the same time establishing CNO and related element inhomogeneities. In order to keep the [Fe/H] abundance homogeneous, a scenario is studied that requires the net protocluster mass (gas plus stars) to be specifically related to the number of supernovae that occur. By comparing models from the literature for element production in metal-poor supernovae and intermediate-mass asymptotic giant branch (IM-AGB) stars, it is found that iron homogeneity plus a pattern of CNO-Na abundance inhomogeneities that reasonably match Milky Way globular clusters can be obtained by combining very low mass supernovae with relatively high mass IM-AGB stars. Nucleosynthesis within metal-poor stars in the mass range of could prove useful to understanding the abundances of globular cluster stars.