A HYPERSPECTRAL VIEW OF THE CRAB NEBULA

We have obtained spatially resolved spectra of the Crab nebula in the spectral ranges 450-520 nm and 650-680 nm, encompassing the H beta, [OIII] lambda 4959, lambda 5007, H alpha, [NII] lambda 6548, lambda 6584, and [SII] lambda 6717, lambda 6731 emission lines, with the imaging Fourier transform spectrometer SpIOMM at the Observatoire du Mont-Megantic's 1.6 m telescope. We first compare our data with published observations obtained either from a Fabry-Perot interferometer or from a long-slit spectrograph. Using a spectral deconvolution technique similar to the one developed by Cadez. et al., we identify and resolve multiple emission lines separated by large Doppler shifts and contained within the rapidly expanding filamentary structure of the Crab. This allows us to measure important line ratios, such as [NII]/H alpha, [SII]/H alpha, and [SII] lambda 6717/[SII] lambda 6731 of individual filaments, providing a new insight on the SE-NW asymmetry in the Crab. From our analysis of the spatial distribution of the electronic density and of the respective shocked versus photoionized gas components, we deduce that the skin-less NW region must have evolved faster than the rest of the nebula. Assuming a very simple expansion model for the ejecta material, our data provide us with a complete tridimensional view of the Crab.