On the relative frequencies of core-collapse supernovae sub-types: the role of progenitor metallicity

We show that the observed ratio NIb,c/NII of the subtypes Ib,c and II core-collapse supernovae depends on the metallicity of the host galaxy, as expected on theoretical grounds. However, the observed relation differs considerably from expectations based on non-rotating models of single stars with mass loss. We argue that the predictions of recent models with rotation offer a much better agreement with observations, at least for progenitor stars with solar metallicity; calculations of models with higher and lower metallicities are required in order to substantiate these conclusions. We also suggest that systematic surveys of core collapse supernovae up to redshift z ∼1 with the SNAP satellite would allow to probe the effect of metallicity on supernovae properties during the past history of the universe.