Quantitative comparison between type Ia supernova spectra at low and high redshifts: a case study

G. Garavini, G. Folatelli, S. Nobili, G. Aldering, R. Amanullah, P. Antilogus, P. Astier, G. Blanc, T. Bronder, M. S. Burns, A. Conley, S. E. Deustua (+35 others)
2007 Astronomy and Astrophysics  
We develop a method to measure the strength of the absorption features in Type Ia supernova (SN Ia) spectra and use it to make a quantitative comparison between the spectra of Type Ia supernovae at low and high redshifts. In this case study, we apply the method to 12 high-redshift (0.212 < z < 0.912) SNe Ia observed by the Supernova Cosmology Project . Through measurements of the strengths of these features and of the blueshift of the absorption minimum in Ca II H&K, we show that the spectra of
more » ... that the spectra of the high-redshift SNe Ia are quantitatively similar to spectra of nearby SNe Ia (z < 0.15). One supernova in our high redshift sample, SN 2002fd at z=0.279, is found to have spectral characteristics that are associated with peculiar SN 1991T/SN 1999aa-like supernovae.
doi:10.1051/0004-6361:20065400 fatcat:ppfcmxl2sfczxnzphhi6kkobra