  The next generation of submillimetre/millimetre instruments will provide us
with a deeper insight into the mechanisms that rule galaxy formation. As the
brightest starbursts are thought to be heavily obscured at optical wavelengths,
the opening of this new window will complement the present observations, and
enable a detailed investigation of the hierarchical merging of galaxies at
remote epochs. In this context, we will present preliminary results of
simulations currently developed for deep galaxy surveys with FIRST.
  N-body simulations of galaxy mergers are being developed to produce realistic
morphologies and star formation histories. A Schmidt law is used to account for
the evolution of the stellar and gas content of each particle. These
simulations will be gathered in a library, including the temporal information
with a timestep of 10 Myr. We then build consistent spectra accounting for this
star formation history at each resolution element of the simulations. These
morphologies will be included in the framework of the GalICS hybrid model of
hierarchical galaxy formation, which reproduces the main observational
constraints. We intend to present synthetic maps with the characteristics of
the FIRST PACS/SPIRE instruments and discuss the optimal strategy for deep
surveys complemented with the ground-based ALMA project.
