Type Ia Supernova Progenitors, Environmental Effects, and Cosmic Supernova Rates

摘要

Relatively uniform light curves and spectral evolution of Type Ia supernovae(SNe Ia) have led to the use of SNe Ia as a ``standard candle'' to determinecosmological parameters, such as the Hubble constant, the density parameter,and the cosmological constant. Whether a statistically significant value of thecosmological constant can be obtained depends on whether the peak luminositiesof SNe Ia are sufficiently free from the effects of cosmic and galacticevolutions. Here we first review the single degenerate scenario for theChandrasekhar mass white dwarf (WD) models of SNe Ia. We identify theprogenitor's evolution and population with two channels: (1) the WD+RG(red-giant) and (2) the WD+MS (near main-sequence He-rich star) channels. Inthese channels, the strong wind from accreting white dwarfs plays a key role,which yields important age and metallicity effects on the evolution. We thenaddress the questions whether the nature of SNe Ia depends systematically onenvironmental properties such as metallicity and age of the progenitor systemand whether significant evolutionary effects exist. We suggest that thevariation of the carbon mass fraction $X$(C) in the C+O WD (or the variation ofthe initial WD mass) causes the diversity of the brightness of SNe Ia. Thismodel can explain the observed dependence of SNe Ia brighness on the galaxytypes. Finally, applying the metallicity effect on the evolution of SN Iaprogenitors, we make a prediction of the cosmic supernova rate history as acomposite of the supernova rates in different types of galaxies.