Nordin, J. and Östman, L. and Goobar, A. and Amanullah, R. and Nichol, R. C. and Smith, M. and Sollerman, J. and Bassett, B. A. and Frieman, J. and Garnavich, P. M. and Leloudas, G. and Sako, M. and Schneider, D. P. (2011) Spectral properties of type Ia supernovae up to z ~ 0.3. Astronomy & Astrophysics, 526: A119. ISSN 1432-0746
Full text not available from this repository.Abstract
Aims: Spectroscopic observations of type Ia supernovae obtained at the New Technology Telescope (NTT) and the Nordic Optical Telescope (NOT), in conjunction with the SDSS-II Supernova Survey, are analysed. We use spectral indicators measured up to a month after the lightcurve peak luminosity to characterise the supernova properties, and examine these for potential correlations with host galaxy type, lightcurve shape, colour excess, and redshift. Methods: Our analysis is based on 89 type Ia supernovae at a redshift interval z = 0.05-0.3, for which multiband SDSS photometry is available. A lower-z spectroscopy reference sample was used for comparisons over cosmic time. We present measurements of time series of pseudo equivalent widths and line velocities of the main spectral features in type Ia supernovae. Results: Supernovae with shallower features are found predominantly among the intrinsically brighter slow declining supernovae. We detect the strongest correlation between lightcurve stretch and the Si ii λ4000 absorption feature, which also correlates with the estimated mass and star formation rate of the host galaxy. We also report a tentative correlation between colour excess and spectral properties. If confirmed, this would suggest that moderate reddening of type Ia supernovae is dominated by effects in the explosion or its immediate environment, as opposed to extinction by interstellar dust. Based on observations collected at the European Organisation for Astronomical Research in the Southern Hemisphere, Chile, in the ESO programmes 077.A-0437, 078.A-0325, 079.A-0715 and 080.A-0024. Also based on observations with the Nordic Optical Telescope acquired in the programmes with proposal numbers 34-004, 35-023 and 36-010.Appendices are only available in electronic form at http://www.aanda.org