Evidence for short-lived SN Ia progenitors

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Abstract
The standardization of SNIa as standard candles is still largely empirical and may be affected by as-yet unexplored effects evolving with redshift. A systematic effect of 1-2% in the peak luminosity correlated with redshift is not excluded by current observations, and could be degenerate with cosmological parameters jeopardizing the measurement of the equation of state parameters of the estimate of dark energy as planned by Joint Dark Energy Mission (JDEM). A crucial issue is of course metallicity, which evolves with redshift. There have also been indications for a diversity of delay times between epochs of star formation in the host galaxy and the supernova explosion itself, which would imply a progenitor population evolution between high and low redshift supernovae. As a first step toward modeling the effect of progenitor properties on the SNIa luminosities and the stellar evolution paths leading to a supernova explosion, we determine, by modeling the host spectra with stellar population models, delay times from a sample of 257 SNIa host galaxies with spectra in the SDSS-DR5. We show evidence (at more than 5 sigma significance) for a short (less than 70 Myr) delay time component in the SNIa population, which is distinct from a long delay time of a few Gyr.

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