Nucleosynthesis of Zinc and Iron-Peak Elements in Pop III Type II Supernovae: Comparison with Abundances of Very Metal-Poor Halo Stars

We calculate nucleosynthesis in core-collapse explosions of massive Pop III stars, and compare the results with abundances of metal-poor halo stars to constrain the parameters of Pop III supernovae. We focus on iron-peak elements and, in particular, we try to reproduce the large [Zn/Fe] observed in extremely metal-poor stars. The interesting trends of the observed ratios [Zn, Co, Mn, Cr, V/Fe] can be related to the variation of the relative mass of the complete and incomplete Si-burning regions in supernova ejecta. We find that [Zn/Fe] is larger for deeper mass-cuts, smaller neutron excess, and larger explosion energies. The large [Zn/Fe] and [O/Fe] observed in the very metal-poor halo stars suggest deep mixing of complete Si-burning material and a significant amount of fall-back in Type II supernovae. Furthermore, large explosion energies (E51 ∼ > 2 for M ∼ 13M⊙ and E51 ∼ > 20 for M ∼ > 20M⊙) are required to reproduce [Zn/Fe] ∼ 0.5. The observed trends of the abundance ratios among the ironpeak elements are better explained with this high energy (“Hypernova”) models rather than the simple “deep” mass-cut effect, because the overabundance of Ni can be avoided in the hypernova models. We also present the yields of pair-instability supernova explosions of M ≃ 130 − 300M⊙ stars, and discuss that the abundance features of very metal-poor stars cannot be explained by pair-instability supernovae. Subject headings: Galaxy: halo — nucleosynthesis — stars: abundances — stars: Population III — supernovae: general