Email:
This e-mail address is being protected from spambots. You need JavaScript enabled to view it
URL:
Spectroscopic and photometric properties of low and high-z supernovae Ia (SNe Ia) have been analyzed in order to achieve a better understanding of their diversity and to identify possible SN Ia sub-types. We use a wavelet based approach to obtain wavelet transformed spectra on which one can easily measure spectral features. We exemplify it with the Si II 4000 equivalent width. The ability and, especially, the facility to extend the method to SNe at high-z is demonstrated. We applied the method to 110 SNe Ia and found correlations between $EW_w lbrace rm{Si II}rbrace$ and parameters related with the light-curve shape for 88 supernovae with available photometry. No evidence for evolution of $EW_w lbrace rm{Si II}rbrace$ with redshift is seen. The three sub-classes of SNe Ia were confirmed using an independent cluster analysis with only light-curve shape, colour, and $EW_w lbrace rm{Si II}rbrace$. SNe from high-$z$ sample seem to follow a similar grouping as nearby objects. The $EW_w lbrace rm{Si II}rbrace$ value measured on a single spectrum may point towards SN Ia sub-classification, avoiding the need for the expansion velocity gradient calculations as is commonly used. Further implications for SNe Ia cosmology are discussed.
