Achieving Convergence in Galaxy Formation Models by Augmenting N-body
  Merger Trees
  Accurate modeling of galaxy formation in a hierarchical, cold dark matter
universe requires the use of sufficiently high-resolution merger trees to
obtain convergence in the predicted properties of galaxies. When semi-analytic
galaxy formation models are applied to cosmological N-body simulation merger
trees, it is often the case that those trees have insufficient resolution to
give converged galaxy properties. We demonstrate a method to augment the
resolution of N-body merger trees by grafting in branches of Monte Carlo merger
trees with higher resolution, but which are consistent with the pre-existing
branches in the N-body tree. We show that this approach leads to converged
galaxy properties.
