The table stores subhalos from the mini-Millennium-II Simulation in a
representation that allows efficient querying for merger histories.
For a description of how merger trees were constructed for the mini-Millennium-II Simulation,
see Boylan-Kolchin et al. 2009.
| column | type | UCD | unit | description |
| haloId |
long |
meta.id;meta.main |
|
The identifier of this subhalo in the merger tree, unique within the full simulation.
See the documentation on merger trees for further
details on the structure of merger trees in the database.
|
| subhaloId |
long |
meta.id; |
|
The identifier of this subhalo based on its rank within its parent FOF halo. This column is a foreign key ("pointer")
to the entry for this subhalo in the SubHalo table.
|
| fofId |
long |
meta.id; |
|
The id of FOF group this subhalo belongs to.
This column is a foreign key ("pointer") to the entry for this FOF group in the
FOF table.
That row will have the same value for its fofIId column. |
| treeRootId |
long |
meta.id.parent |
|
The haloId of the subhalo at the root of this merger tree. This is especially useful for improving the performance
of queries that aim to retrieve descendants of known progenitors. Note that this root halo is not necessarily at z=0,
there are some trees in the database that do not extend down to the last snapshot.
See the documentation on merger trees for further
details on querying merger trees.
|
| descendantId |
long |
meta.id.assoc |
|
The haloId of the unique descendant of this subhalo in the merger tree. -1 if there is no descendant.
This is the case for all halos at z=0, and for some halos at earlier times (see treeRootId).
|
| lastProgenitorId |
long |
meta.id.assoc |
|
The last progenitor in the subhalo merger tree rooted in this subhalo.
All subhalos with haloId between haloId and lastProgenitorId from the merger tree rooted in this subhalo. |
See the documentation on merger trees for further
details on the structure of merger trees in the database.
| mainLeafId |
long |
meta.id.assoc |
|
The last progenitor along the main branch in the subhalo merger tree for this subhalo.
All subhalos with haloId between this halo's haloId and mainLeafId make up the main progenitor branch for this subhalo.
|
| firstProgenitorId |
long |
meta.id.assoc |
|
The haloId of the main progenitor of this subhalo.
|
| nextProgenitorId |
long |
meta.id.assoc |
|
The haloId of the "next progenitor" in the subhalo merger trees (the "next progenitor" of a subhalo S is the next most massive subhalo that has the same descendant as subhalo S).
|
| firstHaloInFOFgroupId |
long |
meta.id.assoc |
|
haloId of the dominant subhalo of the friend-of-friends group to which this subhalo belongs.
|
| nextHaloInFOFgroupId |
long |
meta.id.assoc |
|
Id of the next most massive halo within the same FOF group.
|
| snapNum |
int |
time |
|
The snapshot number where this subhalo was identified.
This column corresponds to the snapnum column in
the Snapshots table in the Millennium-II database.
|
| redshift |
float |
time |
|
The redshift of the snapshot to which this subhalo belongs.
|
| np |
int |
meta.number |
|
Number of simulation particles in this subhalo.
|
| m_crit200 |
float |
phys.mass |
1010 Msun/h |
The mass within the radius where the subhalo has an overdensity 200 times the critical density of the simulation.
Note: this value is only defined for subhalos with haloId=firstHaloInFOFgroupId. |
| m_mean200 |
float |
phys.mass |
1010 Msun/h |
The mass within the radius where the subhalo has an overdensity 200 times the mean density of the simulation.
Note: this value is only defined for subhalos with haloId=firstHaloInFOFgroupId. |
| m_tophat |
float |
phys.mass |
1010 Msun/h |
The mass within the radius where the subhalo has an overdensity corresponding to the value at virialisation in the
top-hat collapse model for this cosmology.
Note: this value is only defined for subhalos with haloId=firstHaloInFOFgroupId. |
| x |
float |
pos.cartesian.x |
Mpc/h |
The X-coordinate of the subhalo's position in comoving coordinates.
|
| y |
float |
pos.cartesian.y |
Mpc/h |
The Y-coordinate of the subhalo's position in comoving coordinates.
|
| z |
float |
pos.cartesian.z |
Mpc/h |
The Z-coordinate of the subhalo's position in comoving coordinates.
|
| ix |
integer |
pos.cartesian.x |
|
Zone index along x-direction, based on 20 bins
See the text on spatial indexes.
|
| iy |
integer |
pos.cartesian.x |
|
Zone index along y-direction, based on 20 bins
See the text on spatial indexes.
|
| iz |
integer |
pos.cartesian.x |
|
Zone index along z-direction, based on 20 bins
See the text on spatial indexes.
|
| phKey |
int |
|
|
The Peano-Hilbert index for the position of this subhalo.
|
| velX |
float |
phys.veloc |
km/sec |
The X-component of the subhalo's peculiar velocity.
|
| velY |
float |
phys.veloc |
km/sec |
The Y-component of the subhalo's peculiar velocity.
|
| velZ |
float |
phys.veloc |
km/sec |
The Z-component of the subhalo's peculiar velocity.
|
| vDisp |
float |
phys.veloc.dispersion |
km/sec |
The 1-D velocity dispersion of the subhalo, computed from all of the subhalo particles.
|
| vMax |
float |
phys.veloc.rotat |
km/sec |
Maximum of the circular velocity curve vCirc, where
vCirc2=G M(< r)/r
|
| vMaxRad |
float |
|
Mpc/h |
The radius at which the circular velocity maximum vMax is attained
|
| spinX |
float |
phys.veloc.ang |
(Mpc/h) (km/sec) |
The X-component of the spin of the subhalo.
|
| spinY |
float |
phys.veloc.ang |
(Mpc/h) (km/sec) |
The Y-component of the spin of the subhalo.
|
| spinZ |
float |
phys.veloc.ang |
(Mpc/h) (km/sec) |
The Z-component of the spin of the subhalo.
|
| mostBoundID |
long |
meta.id.assoc |
|
The id of the most bound particle of this subhalo.
|
| fileNr |
int |
meta.file;meta.id |
|
Original file number in which the subhalo was defined.
See the documentation on identifiers for its
role in defining the haloId.
|
| subhaloIndex |
int |
meta.id.assoc |
|
Index of this subhalo in the file identified by fileNr.
|
| subhaloFileId |
long |
meta.id; |
|
This column corresponds to the subhaloFileId in the SubHalo table and gives an alternative way of identifying that halo.
This is an older way of identifying that subhalo, it is better to use the subhaloId column instead.
|
| halfmassRadius |
float |
phys.size.radius |
Mpc/h |
Radius containing half of the mass of the subhalo.
|
| random |
integer |
|
|
Random number between 0 and 1000000 using java.lang.Math.random().
See the page on random sampling.
|
| treeId |
long |
meta.id.parent |
|
The unique identifier of the L-Galaxies galaxy formation "tree" to which this subhalo belongs.
See the page on the MPA trees |
