The table stores all the friend-of-friends (FOF) groups extracted from the raw output from Millennium
simulation. These FOF groups form the basis that the SUBFIND algorithm uses to detect the subhalos.
| column | type | UCD | unit | description |
|---|
| fofId |
long |
meta.id;meta.main |
|
The id of this FOF group, unique within the full simulation.
|
| snapNum |
int |
time |
|
The snapshot number where this FOF group was identified.
This column corresponds to the snapnum column in
the Snapshots table in MField.
|
| redshift |
float |
time |
|
The redshift of the snapshot to which this halo belongs.
|
| np |
int |
meta.number |
|
Number of simulation particles in this FOF group.
|
| numSubGroups |
int |
meta.number |
|
The number of sub halos found in this FOF group with the SUBFIND algorithm.
These subhalos are stord in the FofSubHalo table in this same database.
|
| firstSubHaloId |
long |
|
meta.id.assoc |
The identifier of the most massive subhalo in this FOF group.
NB This is not equivalent to the fofID in MPAGalxies..DeLucia2006a or the firstHaloInFOFGroupId in MPAHalotrees..MHalo! |
| m_Mean200 |
float |
phys.mass |
1010 Msun/h |
The mass within the radius where the FOF group has an overdensity 200 times the mean density of the simulation.
|
| r_mean200 |
float |
phys.mass |
Mpc/h |
The (comoving) radius within which the FOF group has an overdensity 200 times the mean density of the simulation.
|
| m_Crit200 |
float |
phys.mass |
1010 Msun/h |
The mass within the radius where the FOF group has an overdensity 200 times the critical density of the simulation.
|
| r_crit200 |
float |
phys.mass |
Mpc/h |
The (comoving) radius within which the FOF group has an overdensity 200 times the critical density of the simulation.
|
| m_tophat200 |
float |
phys.mass |
1010 Msun/h |
The mass within the radius where the FOF group has an overdensity corresponding to the value at virialisation in the top-hat collapse model for this cosmology.
|
| r_tophat200 |
float |
phys.mass |
Mpc/h |
The (comoving) radius within which the FOF group has an overdensity corresponding to the value at virialisation in the top-hat collapse model for this cosmology.
|
| x |
float |
pos.cartesian.x |
Mpc/h |
The X-coordinate of the position in comoving coordinates.
|
| y |
float |
pos.cartesian.y |
Mpc/h |
The Y-coordinate of the position in comoving coordinates.
|
| z |
float |
pos.cartesian.z |
Mpc/h |
The Z-coordinate of the position in comoving coordinates.
|
| phKey |
int |
|
|
The Peano-Hilbert index for the position of this FOF group.
See the text on spatial indexes.
|
| zIndex |
long |
|
|
The "bit-interleaved" or "Z-curve" index, same resolution as phKey.
See the text on spatial indexes.
|
| ix |
integer |
pos.cartesian.x |
|
Zone index along x-direction, based on 50 bins
See the text on spatial indexes.
|
| iy |
integer |
pos.cartesian.x |
|
Zone index along y-direction, based on 50 bins
See the text on spatial indexes.
|
| iz |
integer |
pos.cartesian.x |
|
Zone index along z-direction, based on 50 bins
See the text on spatial indexes.
|
| random |
integer |
|
|
Random number between 0 and 1000000 (using java.lang.Math.random()).
See the page on random sampling.
|
