DORCHA simulations: halo catalogues and merger trees

These are the halo catalogues and merger trees associated with the DORCHA suite of dark-matter-only N-body zoom simulations of Milky Way analogues (MWAs). A parent simulation, DORCHA_00, was run and from this 25 MWAs were selected. The suite comprises: 15 isolated systems (DORCHA_01–15) and 10 systems forming five interacting pairs similar to the MW-M31 system (DORCHA_16–20). The simulations were run with AREPO (Springel 2010, Weinberger+20), and the outputs were post-processed using Subfind-HBT (part of GADGET-4; Springel+21) to generate the halo catalogues and merger trees. This dataset was used in Balu et al 2025 (arXiv:2506.14016; DOI: 10.48550/arXiv.2506.14016).

The simulations contain 123 snapshots spanning redshifts z = 30 to z = 0, distributed as follows:





50 snapshots evenly spaced in $\rm{ln}(a)$, where $a$ is the scale factor, between $z = 30$ and $z = 5$.




73 snapshots between $z = 5$ and $z = 0$.



The file a_list.txt lists the corresponding scale factors for all snapshots.

After decompressing, the dataset has the following structure:

├── fof_subhalo_tab_000.hdf5 (halo catalogues at snapshot_000)
├── fof_subhalo_tab_001.hdf5
├── ...
├── fof_subhalo_tab_122.hdf5
└── trees.hdf5 (the full merger tree)

For further information, see solas-sims.github.io.