Recovering the initial conditions of our local Universe from NOG and PSCz catalogues

We apply the ztrace algorithm to the optical NOG and infrared PSCz galaxy catalogues to reconstruct the pattern of primordial fluctuations that have generated our local Universe. We check that the density fields traced by the two catalogues are well correlated, and consistent with a linear relation [either in delta or in log (1 +delta)] with relative bias (of NOG with respect to PSCz ) b (rel) = 1.1 +/- 0.1. The relative bias relation is used to fill the optical zone of avoidance at \b \ < 20degrees using the PSCz galaxy density field. We perform extensive testing on simulated galaxy catalogues to optimize the reconstruction. The quality of the reconstruction is predicted to be good at large scales, up to a limiting wavenumber k (lim) similar or equal to 0.4 h Mpc(-1) beyond which all information is lost. We find that the improvement arising from the denser sampling of the optical catalogue is compensated by the uncertainties connected to the larger zone of avoidance. The initial conditions reconstructed from the NOG catalogue are found (analogously to those from the PSCz ) to be consistent with a Gaussian paradigm. We use the reconstructions to produce sets of initial conditions ready to be used for constrained simulations of our local Universe.