Bridging the Gap between Intermediate and Massive Stars II: $M_\text{mas}$ for the most metal-rich stars and implications for Fe CCSNe rates

TL;DR

This study investigates the minimum initial stellar mass for Fe core collapse supernovae at super metal-rich metallicities, revealing a reversal in the trend of ignition mass with increasing metallicity and implications for galactic chemical evolution models.

Contribution

It provides new models for the minimum mass threshold for supernovae at metallicities up to Z=0.10, extending previous studies to super metal-rich stars.

Findings

Fe core collapse occurs at lower masses for Z > 0.05.

Metallicity influences the Fe ignition threshold non-linearly.

Results inform more accurate supernova rate models in metal-rich galaxies.

Abstract

The minimum initial mass required for a star to explode as an Fe core collapse supernova, typically denoted $M_\text{mas}$, is an important quantity in stellar evolution because it defines the border between intermediate mass and massive stellar evolutionary paths. The precise value of $M_\text{mas}$ 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 $2.5\times 10^{-3} \leq Z \leq 0.10$. Although an increase in initial $Z$ corresponds to an increase in the Fe ignition threshold for $Z \approx 1\times 10^{-3}$ to $Z\approx0.04$, 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 utilised 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.