Uchuu DR1 Merger Trees We constructed merger trees using the consistent-trees code (Behroozi et al. 2013). Because the current version of the consistent-trees code can not run in parallel on distributed memory environment, we can not use as it is to construct merger trees for huge simulations such Uchuu. To overcome the most significant obstacle, we split the entire Uchuu box into smaller regularly spaced sub-volumes and run consistent-trees code for each sub-volume separately. See Ishiyama et al. 2020 for the details of the adopted algorithm. Note2: For a small number of corrupted halos in additional 77 files of the Uchuu merger trees listed here, their properties were mistakenly filled with zero due to a bug of HDF5 conversion. Differently from the previous problem, corrupted halos exist somewhere in the file. Please replace those 77 files with new ones if you downloaded the trees before April 21, 2021. Sorry for the inconvenience. Note3: For Shin-Uchuu the merger tree data is provided in the original ascii format, HDF5 conversion will be done soon. Halos/subhalos in twenty tree files match with a single halo catalogue file in file number order. For example, corresponding trees of halos/subhalos in "halolist_z[0p00-13p96]_0.h5" exist in "mergertree_[0-19].h5" files. The other columns in the The halos within each forest are stored contiguously and can be easily accessed using the
The generated ascii catalogues were then converted using the customuchuutools package. The halo catalogues were converted using the scriptconvert_halocat_to_h5while the tree catalogues were converted using theconvert_ctrees_to_h5.
•How to download the data
Note1: For a small number of corrupted halos at the end of 20 files of the Uchuu merger trees listed here, their properties were mistakenly filled with zero due to a bug of HDF5 conversion. Please replace those 20 files with new ones if you downloaded the trees before March 22, 2021. Sorry for the inconvenience.
Mergertree Data Format
The Uchuu HDF5 merger trees are split into 2,000 files. When you find a tree in a file, you can always find in the same file all trees that have past interactions with that tree.
Most of the properties in the tree catalogues are already found in the halo catalogues. Please refer to the documentation in thehalo catalogues pagefor details such columns. The new columns that have been added to the tree catalogues areFofID, FirstHaloInFOFgroup, NextHaloInFOFgroup, PrevHaloInFOFgroup, FirstProgenitor, NextProgenitor, PrevProgenitor, Descendant. With the exception ofFofID, the remaining fields are indices that refer to another halo within the same forest. These indices are forest-local (i.e., range from[0, nforests-1]and follow theLHaloTreeconvention (see figure below; Credits). TheFofIDis thehaloIDfor the host halo that contains the (sub-) subhalo. ThePrevProgenitorandPrevHaloInFOFgrouphave been added to allow more flexible tree-walking.
We have added two additional datasets that contain forest-level and tree-level information:
(ForestID, np.int64), contains the ForestID (taken directly from Consistent-Trees)(ForestHalosOffset, np.int64), contains the offset at which the halos belonging to that forest start(ForestNhalos, np.int64), contains the total number of halos within this forest(ForestNtrees, np.int64), contains the total number of trees within this forest
(ForestID, np.int64), contains the ForestID (taken directly from Consistent-Trees)(TreeRootID, np.int64), contains the TreeRootID (taken directly from Consistent-Trees)(TreeHalosOffset, np.int64), contains the offset at which the halos belonging to that tree start(TreeNhalos, np.int64), contains the total number of halos within this tree
For details on the fields carried across from the Consistent-Trees catalogue, we have preserved the header information from the ascii Consistent-Trees catalogue. This information is available under the root dataset as themetadataattribute (i.e.,hf.attrs['Consistent Trees_metadata']from the example above). The cosmological parameters and the boxsize are available as attributes under the grouphf['simulation_params'].Reading and Analysing the trees
2.cd yt
3.python -m pip install -e . (--user)
Afterytis installed, then installytreewith the following steps:
Onceytreeis installed, you can useytreeto load and visualise the hdf5 files Note that within ytree, you can either load single trees (default) or load single forests through theaccess='tree'oraccess='forest'keyword toytree.load. Please refer to thedocumentation of ytreefor further details aboutloadingandvisualisingmergertrees.
