Multi-Wavelength, Multi-Epoch Integral Field Spectrograph Extraction for the Nearby Supernova Factory
Résumé
The SuperNova Integral Field Spectrograph (SNIFS), operated by the Nearby Supernova Factory since 2004, is a fully-integrated instrument optimized for automated observation of point sources on structured background over the full optical window at moderate spectral resolution. We have developed a forward fitting technique for separating supernova spectra from their host galaxy background, capitalizing on the multi-wavelength, multi-epoch nature of SNIFS supernova observations. With a well-sampled point spread function from simultaneous photometric observations with SNIFS, we reconstruct the host galaxy spectro-spatial shape and extract the supernova spectra. This approach takes avantage of all exposures from each supernova time serie. This bias-free optimal extraction enables not only the spectrophotometry of the SNfactory data set, but also host galaxy studies based on extracted hosts. In addition, we discuss an alternative technique based on a subtraction of a spectro-spatial galaxy reconstruction. In this approach we reconstruct a host galaxy spectro-spatial shape using a SNIFS final reference observation with constraints from earlier epoch observations. We then subtract this reconstructed host galaxy datacube from the previous epochs, and can then use either PSF or aperture-based extraction as we see fit.