Bridging the gap between intermediate and massive stars II: M_mas for the most metal-rich stars and implications for Fe CCSNe rates

The minimum initial mass required for a star to explode as an Fe core collapse supernova, typically denoted M mas, is an important quantity in stellar evolution because it defines the border between intermediate mass and massive stellar evolutionary paths. The precise value of M mas carries implications for models of galactic chemical evolution and the calculation of star formation rates. Despite the fact that stars with super-solar metallicities are commonplace within spiral and some giant elliptical galaxies, there are currently no studies of this mass threshold in super metal-rich models with Z > 0.05. Here, we study the minimum mass necessary for a star to undergo an Fe core collapse supernova when its initial metal content falls in the range 2.5 x10(-3) = Z = 0.10. Although an increase in initial Z corresponds to an increase in the Fe ignition threshold for Z approximate to 1 x10(-3) to Z approximate to 0.04, we find that there is a steady reversal in trend that occurs for Z > 0.05. Our super metal-rich models thus undergo Fe core collapse at lower initial masses than those required at solar metallicity. Our results indicate that metallicity-dependent curves extending to Z = 0.10 for the minimum Fe ignition mass should be utilized in galactic chemical evolution simulations to accurately model supernovae rates as a function of metallicity, particularly for simulations of metal-rich spiral and elliptical galaxies.