Diversity of supernovae Ia determined using equivalent widths of Si II 4000
Abstract
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 wavelet transformed spectra in which one can easily measure spectral features. We investigate the Si II 4000 equivalent width (EWw{Si II}). The ability and, especially, the ease in extending the method to SNe at high-z is demonstrated. We applied the method to 110 SNe Ia and found correlations between EWw{Si II} and parameters related to the light-curve shape for 88 supernovae with available photometry. No evidence for evolution of EWw{Si II} with redshift is seen. Three sub-classes of SNe Ia were confirmed using an independent cluster analysis with only light-curve shape, colour, and EWw{Si II}. SNe from high-z samples seem to follow a similar grouping to nearby objects. The EWw{Si II} value measured on a single spectrum may point towards SN Ia sub-classification, avoiding the need for expansion velocity gradient calculations.
- Publication:
-
Astronomy and Astrophysics
- Pub Date:
- December 2008
- DOI:
- 10.1051/0004-6361:200810675
- arXiv:
- arXiv:0809.3133
- Bibcode:
- 2008A&A...492..535A
- Keywords:
-
- supernovae: general;
- methods: data analysis;
- Astrophysics
- E-Print:
- 12 pages, 5 figures