It is noted immediately that the supernova spectra is embedded in the galaxy spectra. The line of silicon towards 6100A is definitely perceptible on this document. A difficulty comes due to the fact that the spectrum of the supernova is spread out over the diffuse and intense background spectrum of the galaxy. Note that before carrying out these profiles the natural sky background was withdrawn. It is thus imperative to elimitate very carefully the galaxy spectrum before being able to interpret the spectrum of the supernova correctly.
Blue wavelength is on the left and the red is on the right.
At top left, the spectrum of the supernova after the subtraction of the background signal of the galaxy. At top right, reduction of the noise in the supernova spectrum by a wavelet-type processing . At bottom right, the final result after division of the uncalibrated photometric spectrum by the response of the instrument. Processed with Iris and VisualSpec . The principal features characteristic of an Ia supernova are quite identifiable.