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

Abstract

We calculate nucleosynthesis in core collapse explosions of massive Population III stars and compare the results with abundances of metal-poor halo stars to constrain the parameters of Population 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 fallback in Type II supernovae. Furthermore, large explosion energies ( E 51 ≳ 2 for M ~ 13 M ☉ and E 51 ≳ 20 for M ≳ 20 M ☉ ) are required to reproduce [Zn/Fe] ~ 0.5. The observed trends of the abundance ratios among the iron peak elements are better explained with this high-energy ("hypernova") model than with 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 ≃ 130-300 M ☉ stars and discuss that the abundance features of very metal-poor stars cannot be explained by pair instability supernovae.