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P. Hoeflich, J.C. Wheeler (Department of Astronomy, U of Texas at Austin), I. Dominguez (Dept. of Astronomy, University of Granada, Granada, Spain)
Evolutionary effects of Type Ia with redshift have been studied to evaluate their size on cosmological time scales, how the effects can be recognized and how one may be able to correct for them. Based on a given white dwarf and the delayed detonation scenario which gives a good account of the optical and IR light curves and of the spectral evolution, detailed model calculations have been performed. Using our elaborated numerical schemes, the hydrodynamical explosion, the light curves and spectra are calculated consistently. This allows to address directly the influence of the initial metallicity and the C/O ratio on the nucleosynthesis, light curves and spectra. The C/O ratio of the typical progenitor must be expected to change with redshift because it depends on the mass and, consequently, on the lifetime of the progenitor. In a second part, detailed stellar evolution calculations have been performed to quantify the influence of Main Sequence mass of the progenitor and its metallicity on the structure of the exploding WD. It is shown that both the change of the metallicity and the C/O ratio are correlated We find that evolutionary effects are small and may be of the order of \approx 0.2m both due to changes in the spectra and the light curve shape/absolute brigthness relation. However, these variations are comparable to the effect of changes of \OmegaM and \Lambda at redshifts of 0.5 to 1.
With proper account of evolutionary corrections, supernovae will provide a valuable tool to determine the cosmological parameters and they will provide new insight into the chemical evolution of the universe. In combination with NGST, the relation between life time of the progenitor system and the properties of light curves and spectra can studied directly.