Supernova Legacy Survey: Using Spectral Signatures To Improve Type Ia Supernovae As Distance Indicators
Abstract
GMOS optical long-slit spectroscopy at the Gemini-North telescope was used to classify targets from the Supernova Legacy Survey (SNLS) from July 2005 and May 2006 - May 2008. During this time, 95 objects were observed. Where possible the objects' redshifts (z) were measured from narrow emission or absorption features in the host galaxy spectrum, otherwise they were measured from the broader supernova features. We present spectra of 68 confirmed or probable SNe Ia from SNLS with redshifts in the range 0.17 \leq z \leq 1.02. In combination with earlier SNLS Gemini and VLT spectra, we used these new observations to measure pseudo-equivalent widths (EWs) of three spectral features - CaII H&K, SiII and MgII - in 144 objects and compared them to the EWs of low-redshift SNe Ia from a sample drawn from the literature. No signs of changes with z are seen for the CaII H&K and MgII features. Systematically lower EW SiII is seen at high redshift, but this can be explained by a change in demographics of the SNe Ia population within a two-component model combined with an observed correlation between EW SiII and photometric lightcurve stretch.
Keywords
Cite
@article{arxiv.1008.2308,
title = {Supernova Legacy Survey: Using Spectral Signatures To Improve Type Ia Supernovae As Distance Indicators},
author = {E. S. Walker and I. M. Hook and M. Sullivan and D. A. Howell and P. Astier and C. Balland and S. Basa and T. J. Bronder and R. Carlberg and A. Conley and D. Fouchez and J. Guy and D. Hardin and R. Pain and K. Perrett and C. Pritchet and N. Regnault and J. Rich and G. Aldering and H. K. Fakhouri and T. Kronborg and N. Palanque-Delabrouille and S. Perlmutter and V. Ruhlmann-Kleider and T. Zhang},
journal= {arXiv preprint arXiv:1008.2308},
year = {2015}
}
Comments
49 pages including 2 online-only appendices, accepted for publication in MNRAS