Exploring metallicity-dependent rates of Type Ia supernovae and their impact on galaxy formation

Type la supernovae are critical for feedback and elemental enrichment in galaxies. Recent surveys like the All-Sky Automated Survey for Supernova (ASAS-SN) and the Dark Energy Survey (DES) find that the specific supernova Ia rate at z similar to 0 may be less than or similar to 20-50x higher in lower mass galaxies than at Milky Way-mass. Independently, observations show that the close-binary fraction of solar-type Milky Way stars is higher at lower metallicity. Motivated by these observations, we use the FIRE-2 cosmological zoom-in simulations to explore the impact of metallicity-dependent rate models on galaxies of M-* similar to 10(7)-10(11) M-circle dot. First, we benchmark our simulated star formation histories against observations, and show that the assumed stellar mass functions play a major role in determining the degree of tension between observations and metallicity-independent rate models, potentially causing ASAS-SN and DES observations to agree more than might appear. Models in which the supernova Ia rate increases with decreasing metallicity (proportional to Z(-0.5 to -1)) provide significantly better agreement with observations. Encouragingly, these rate increases (greater than or similar to 10x in low-mass galaxies) do not significantly impact galaxy masses and morphologies, which remain largely unaffected except for our most extreme models. We explore implications for both [Fe/H] and [alpha/Fe] enrichment; metallicity-dependent rate models can improve agreement with the observed stellar mass-metallicity relations in low-mass galaxies. Our results demonstrate that a range of metallicity-dependent rate models are viable for galaxy formation and motivate future work.

Automated summary

Type la supernovae play a crucial role in feedback and elemental enrichment in galaxies. Recent surveys have found that the rate of supernova la in lower mass galaxies may be higher than in the Milky Way. The study suggests that models in which the supernova la rate increases with decreasing metallicity provide better agreement with observations. These findings are important for understanding galaxy formation.