3.3.11  :  FoFTrees

FoFHalo

This table contains merger trees for the Millennium Run (MR) constructed using the friends of friends (FoF) group catalogues. The merger trees are stored in the same format as the DHalo trees. Each FoFHalo contains zero or more subhalos, and the FoFSubhalo table can be used to find all the subhalos that belong to a FoFHalo.

columntypeUCDunitdescription
FoFHaloID long meta.id;meta.main The ID of this FoFHalo, unique within the full simulation.
DescendantId long meta.id.assoc The ID of the descendant of this FoFHalo in the merger tree.
LastProgenitorId long meta.id.assoc Indicator of the last progenitor in the FoFHalo merger tree rooted in this FoFHalo.
All FoFHalos with id between ID and LastProgenitorId form the merger tree rooted in this FoFHalo.
TreeId long meta.id.parent The unique id of the FoFHalo merger tree to which this FoFHalo belongs.
FirstSubhaloID long meta.id.assoc The unique id of the most massive subhalo in this FoFHalo. This corresponds to the SubhaloID column in the Subhalo table.
np int meta.number Number of simulation particles in this FoFHalo. This is equal to the total number of particles in the constituent subhalos of the FoFHalo.
NSubhalos int meta.number Number of subhalos in this FoFHalo.
SnapNum int time The snapshot number where this FoFHalo was identified.
Redshift float time The redshift of the snapshot to which this FoFHalo belongs.
FirstProgenitorID long meta.id.assoc The ID of the most massive progenitor of the FoFHalo
EndMainBranchID long meta.id.assoc The ID of the halo at the end of the main progenitor branch of this halo.
phKey integer Peano-Hilbert key, (bits=5), for position in 62.5/h Mpc box. See the text on spatial indexes.
zIndex integer The "bit-interleaved" or "Z-curve" index, corresponding to this halo's position. Same resolution as phKey. See the text on spatial indexes.
ix integer pos.cartesian.x Zone index along x-direction, based on 7 bins. See the text on spatial indexes.
iy integer pos.cartesian.y Zone index along y-direction, based on 7 bins. See the text on spatial indexes.
iz integer pos.cartesian.y Zone index along z-direction, based on 7 bins. See the text on spatial indexes.
random float A random number between 0 and 1000000. See the section on random sampling.
x float pos.cartesian.x 1/h Mpc x-component position
y float pos.cartesian.y 1/h Mpc y-component position
z float pos.cartesian.z 1/h Mpc z-component position
vx float phys.veloc km/s x-component of peculiar velocity
vy float phys.veloc km/s y-component of peculiar velocity
vz float phys.veloc km/s z-component of peculiar velocity

DSubhalo

The FoFSubhalo table specifies the parent FoFHalo for each subhalo. It may be used to determine which subhalos belong to each FoFHalo. The SubhaloID column corresponds to the subHaloID column in the MHalo and Subhalo tables, so additional information about a subhalo may be obtained by finding the entry in the MHalo table such that MHalo.subHaloID = FoFSubhalo.SubhaloID.

columntypeUCDunitdescription
SubhaloID long meta.id The unique ID of a subhalo.
FoFHaloID long meta.id The ID of the FoFHalo to which this subhalo belongs