The rates of type Ia supernovae - II. Diversity of events at low and high redshifts

This paper investigates the possible systematic difference of type Ia supernovae (SNe Ia) properties related to the age and masses of the progenitors that could introduce a systematic bias between low- and high-redshift SNe Ia. The relation between the main features of the distribution of delay times and the masses of the progenitors is illustrated for the single (SD) and double degenerate (DD) models. Mixed models, which assume contributions from both the SD and DD channels, are also presented and tested versus the observed correlations between the SN Ia rates and the parent galaxy properties. It is shown that these correlations can be accounted for with both single-channel and mixed models, and that the rate in S0 and E galaxies may effectively provide clues on the contribution of SD progenitors to late epoch explosions. A wide range of masses for the CO white dwarf at the start of accretion is expected in almost all galaxy types; only in galaxies of the earliest types are the properties of the progenitors expected to be more uniform. For mixed models, late-type galaxies should host SD and DD explosions in comparable fractions, while in early-type galaxies DD explosions should largely prevail. Events hosted by star-forming galaxies span a wide range of delay times; prompt events could dominate only in the presence of a strong starburst. It is concluded that nearby SN Ia samples should well include the young, massive and hot progenitors that necessarily dominate at high redshift.