Orateur
Description
Type Ia Supernova (SNIa) distance measurement for cosmology is based on a well-established observational paradigm that two main effects explain their variabilities in luminosity: stretch (link to intrinsic properties), and color (link mainly to dust extinction). However, after correcting the luminosity of both stretch and color, an intrinsic scatter in luminosity and a correlation of Hubble residuals with host properties are observed. It indicates that the standard scheme lacks some ingredients and could potentially bias cosmological contraints.
The approach presented here, is to revisit the spectral diversity of the SNIa with the help of the Nearby Supernova Factory data consisting of hundreds of spectrophotometric time series, and to build a new SED model, SUGAR (SUpernovae Generator and Reconstructor) extending the principles of the current model used:SALT2. Our principal findings are that the spectral diversity exhibits 2 new intrinsic components, and that the color law is confirmed to be compatible with extinction by dust. Taking these new variabilities into account, we are able to derive a SED model which matches closer the observed spectra than SALT2 does, and which improves the distance measurement. We will present the derivation of this model, its applicability for photometric time series, and its consequences for cosmology.
