The effect of metallicity on the delay-time distribution of type Ia supernova

Measuring the delay-time distribution (DTD) of type Ia supernova(SNe Ia) is an important way to constrain the progenitor nature of SNe Ia. Recently, Strolger et al. (2010) obtained a very delayed DTD, which is much different from other measurements. They suggested that metallicity could be the origin of their delayed DTD. In this paper, we show the effect of metallicity on the DTD of SNe Ia from single-degenerate models (including WD + MS and WD+RG channels). Via a binary population synthesis approach, we find that the DTD from a low metallicity population is significantly delayed compared with that from a high metallicity one. In addition, we also find that a substantial fraction of SNe Ia have a delay time shorter than 1 Gyr, and the fraction of SNe Ia with short delay times increases with metallicity, i.e. about 35% for Z=0.001, while more than 70% for Z=0.02. These results would help to qualitatively explain the result of Strolger et al. (2010). Furthermore, we noticed that the contribution of WD + RG channel from the low metallicity population is higher than that from the high metallicity one. However, we can not quantitatively obtain a DTD consistent with the results of Strolger et al. (2010) by changing metallicity. As a consequence, metallicity may partly contribute to the DTD of SNe Ia and should therefore be checked carefully when one derives the DTD of SNe Ia from observations.