Sussing Merger Trees: Stability and Convergence
  Merger trees are routinely used to follow the growth and merging history of
dark matter haloes and subhaloes in simulations of cosmic structure formation.
Srisawat et al. (2013) compared a wide range of merger-tree-building codes.
Here we test the influence of output strategies and mass resolution on
tree-building. We find that, somewhat surprisingly, building the tree from more
snapshots does not generally produce more complete trees; instead, it tends to
short- en them. Significant improvements are seen for patching schemes which
attempt to bridge over occasional dropouts in the underlying halo catalogues or
schemes which combine the halo-finding and tree-building steps seamlessly. The
adopted output strategy does not affec- t the average number of branches
(bushiness) of the resultant merger trees. However, mass resolution has an
influence on both main branch length and the bushiness. As the resolution
increases, a halo with the same mass can be traced back further in time and
will encounter more small progenitors during its evolutionary history. Given
these results, we recommend that, for simulations intended as precursors for
galaxy formation models where of order 100 or more snapshots are analysed, the
tree-building routine should be integrated with the halo finder, or at the very
least be able to patch over multiple adjacent snapshots.
