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. compared a wide range of merger-tree-building codes. Here we test the influence of output strategies and mass resolution on tree-...

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Published in:Monthly notices of the Royal Astronomical Society 2016-06, Vol.459 (2), p.1554-1568
Main Authors: Wang, Yang, Pearce, Frazer R., Knebe, Alexander, Schneider, Aurel, Srisawat, Chaichalit, Tweed, Dylan, Jung, Intae, Han, Jiaxin, Helly, John, Onions, Julian, Elahi, Pascal J., Thomas, Peter A., Behroozi, Peter, Yi, Sukyoung K., Rodriguez-Gomez, Vicente, Mao, Yao-Yuan, Jing, Yipeng, Lin, Weipeng
Format: Article
Language:English
Subjects:
Astronomical models
Computer simulation
Dark matter
Encounters
Evolutionary
Galactic halos
Halos
Simulation
Star & galaxy formation
Strategy
Trees
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Summary: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. 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 shorten them. Significant improvements are seen for patching schemes that attempt to bridge over occasional dropouts in the underlying halo catalogues or schemes that combine the halo-finding and tree-building steps seamlessly. The adopted output strategy does not affect 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 the order of 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.
ISSN:0035-8711
1365-2966
DOI:10.1093/mnras/stw726