The Chemical Evolution of Iron-Peak Elements with Hypernovae
  We calculate the mean evolution of the iron-peak abundance ratios
[(Cr,Mn,Co,Zn)/Fe] in the Galaxy, using modern supernova and hypernova chemical
yields and a Galactic Chemical Evolution code that assumes homogeneous chemical
evolution. We investigate a range of hypernova occurrence rates and are able to
produce a chemical composition that is a reasonable fit to the observed values
in metal-poor stars. This requires a hypernova occurence rate that is large
(50%) in the early Universe, decreasing throughout evolution to a value that is
within present day observational constraints (>~ 1%). A large hypernova
occurence rate is beneficial to matching the high [Zn/Fe] observed in the most
metal-poor stars, although including hypernovae with progenitor mass >= 60
solar masses is detrimental to matching the observed [(Mn,Co)/Fe] evolution at
low [Fe/H]. A significant contribution from HNe seems to be critical for
producing supersolar [(Co,Zn)/Fe] at low metallicity, though more work will
need to be done in order to match the most extreme values. We also emphasise
the need to update models for the enrichment sources at higher metallicity, as
the satisfactory recovery of the solar values of [(Cr,Mn,Co,Zn)/Fe] still
presents a challenge.
