A series of optical and one near-infrared nebular spectra covering the first\nyear of the Type Ia supernova SN 2011fe are presented and modelled. The density\nprofile that proved best for the early optical/ultraviolet spectra, "rho-11fe",\nwas extended to lower velocities to include the regions that emit at nebular\nepochs. Model rho-11fe is intermediate between the fast deflagration model W7\nand a low-energy delayed-detonation. Good fits to the nebular spectra are\nobtained if the innermost ejecta are dominated by neutron-rich, stable Fe-group\nspecies, which contribute to cooling but not to heating. The correct thermal\nbalance can thus be reached for the strongest [FeII] and [FeIII] lines to be\nreproduced with the observed ratio. The 56Ni mass thus obtained is 0.47 +/-\n0.05 Mo. The bulk of 56Ni has an outermost velocity of ~8500 km/s. The mass of\nstable iron is 0.23 +/- 0.03 Mo. Stable Ni has low abundance, ~10^{-2} Mo. This\nis sufficient to reproduce an observed emission line near 7400 A. A\nsub-Chandrasekhar explosion model with mass 1.02 Mo and no central stable Fe\ndoes not reproduce the observed line ratios. A mock model where neutron-rich\nFe-group species are located above 56Ni following recent suggestions is also\nshown to yield spectra that are less compatible with the observations. The\ndensities and abundances in the inner layers obtained from the nebular\nanalysis, combined with those of the outer layers previously obtained, are used\nto compute a synthetic bolometric light curve, which compares favourably with\nthe light curve of SN 2011fe.\n
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