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Sussing merger trees: stability and convergence

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


Yang Wang

Frazer R. Pearce

Alexander Knebe

Aurel Schneider

Chaichalit Srisawat

Dylan Tweed

Intae Jung

Jiaxin Han

John Helly

Julian Onions

Pascal J. Elahi

Peter A. Thomas

Peter Behroozi

Sukyoung K. Yi

Vicente Rodriguez-Gomez

Yao-Yuan Mao

Yipeng Jing

Weipeng Lin


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.


Wang, Y., Pearce, F. R., Knebe, A., Schneider, A., Srisawat, C., Tweed, D., …Lin, W. (2016). Sussing merger trees: stability and convergence. Monthly Notices of the Royal Astronomical Society, 459(2),

Journal Article Type Article
Acceptance Date Mar 23, 2016
Publication Date Mar 30, 2016
Deposit Date May 3, 2017
Publicly Available Date May 3, 2017
Journal Monthly Notices of the Royal Astronomical Society
Print ISSN 0035-8711
Electronic ISSN 1365-2966
Publisher Oxford University Press
Peer Reviewed Peer Reviewed
Volume 459
Issue 2
Keywords methods: numerical, galaxies: haloes– galaxies: evolution, dark matter
Public URL
Publisher URL


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