Rockstar

Rockstar tables store the halo catalogues created using the ROCKSTAR halo finder (see Bitbucket-Rockstar for the code). The table contains also consistent merger tree information in the form of links (Ids) to progenitors and descendants, see Merger trees for merger tree documentation.

Further, the catalogue includes substructure-information as links to the least massive (pId) and most massive (upId) host halo. Distinct halos can thus be found by searching for halos with no least massive halo, i.e. with pId = -1.

Please be aware that the Rockstar catalogue aims to provide a smooth history for each halo, and therefore halo’s properties were interpolated if a halo went missing at a timestep. These interpolated “phantom” halos are marked with the flag phantom being non-zero.

The table below gives a summary of all possible columns in our Rockstar-tables in the database. Depending on the version of Rockstar, some columns may be missing (marked with *).

Column Type UCD Unit Description
dbId bigint meta.id; meta.main unique database id for the halo
rockstarId bigint meta.id; meta.main unique id for the halo, same as in Rockstar catalogue
scale float time.epoch scale factor, same as aexp in Redshifts-table
desc_scale float time.epoch scale factor of the descendant halo, if there is one
descId bigint meta.id.assoc rockstarId of the descendant
nprog int meta.number number of progenitors
pId bigint meta.id.assoc rockstarId of least massive host halo, -1 if it is a distinct halo
upId bigint meta.id.assoc rockstarId of most massive host halo, only different from pid, if halo lies within two or more larger halos
desc_pId bigint meta.id.assoc pId of the descendant halo, if applicable
phantom smallint meta.code flag for phantom halos, non-zero if the halo is interpolated across timesteps
Mvir_SAM float phys.mass 1/h Msun halo mass, smoothed across accretion history; always greater than the sum of halo masses of contributing progenitors; only for use with selected semi-analytic models
Mvir float phys.mass 1/h Msun halo mass (within virial radius)
Rvir float phys.size.radius kpc/h halo radius (comoving)
Rs float phys.size.radius kpc/h scale radius (comoving)
Vrms float phys.veloc.dispMeasure km/s velocity dispersion (physical)
mmp smallint flag indicating if the halo is the most massive progenitor or not
lastMM_scale float scale factor of the last major merger (mass ratio > 0.3)
Vmax float phys.veloc km/s maximum circular velocity (physical)
x float pos.cartesian.x 1/h Mpc halo position, comoving
y float pos.cartesian.y 1/h Mpc halo position, comoving
z float pos.cartesian.z 1/h Mpc halo position, comoving
vx float phys.veloc; pos.cartesian.x km/s halo velocity, physical, just “a \dot{x}”, i.e. no Hubble flow
vy float phys.veloc; pos.cartesian.y km/s halo velocity, physical, just “a \dot{y}”, i.e. no Hubble flow
vz float phys.veloc; pos.cartesian.z km/s halo velocity, physical, just “a \dot{z}”, i.e. no Hubble flow
angMom_x float phys.angMomentum; pos.cartesian.x (Msun/h) * (Mpc/h) * km/s halo angular momentum
angMom_y float phys.angMomentum; pos.cartesian.y (Msun/h) * (Mpc/h) * km/s halo angular momentum
angMom_z float phys.angMomentum; pos.cartesian.z (Msun/h) * (Mpc/h) * km/s halo angular momentum
spin float halo spin parameter
breadthFirstId bigint meta.id Id for breadth-first ordering of halos within a tree
depthFirstId bigint meta.id Id for depth-first ordering of halos within a tree
treeRootId bigint meta.id.assoc rockstarId of forest to which the halo with the given treeRootId belongs
forestId bigint meta.id.assoc forestId of the halo at the last timestep in the tree; also see this blog entry for usage examples
origHaloId bigint meta.id.cross original halo Id from halo finder
rockstar_snapnum int time.epoch consequent snapshot number (from which the halo originated) for Rockstar
snapnum int time.epoch (original) snapshot number as used in other catalogues (e.g. FOF, BDM)
nextCoprog_depthFirstId bigint meta.id.assoc depthFirstId of next coprogenitor
mainLeaf_depthFirstId bigint meta.id.assoc depthFirstId of last leaf on the main branch, determined additionally using the database for convenience. If this value is ‘-1’, this value was not yet updated.
lastProg_depthFirstId bigint meta.id.assoc depthFirstId of last progenitor
Rs_Klypin float phys.size.radius Scale radius determined using Vmax and Mvir (see Rockstar paper)
Mvir_all float phys.mass 1/h Msun Mass enclosed within the specified overdensity, including unbound particles
M200b float phys.mass 1/h Msun Mass enclosed within overdensity 200*rho_b
M200c float phys.mass 1/h Msun Mass enclosed within overdensity 200*rho_crit
M500c float phys.mass 1/h Msun Mass enclosed within overdensity 500*rho_crit
M2500c float phys.mass 1/h Msun Mass enclosed within overdensity 2500*rho_crit
Xoff float phys.distance 1/h kpc Offset of density peak from average particle position, comoving
Voff float phys.veloc;arith.diff km/s Offset of density peak from average particle velocity, comoving
spin_Bullock float Bullock spin parameter (J/(sqrt(2)*GMVR))
axisratio_2_1 float ratio of second largest shape ellipsoid axes to largest shape ellipsoid axis; shapes determined by method in Allgood et al. (2006)
axisratio_3_1 float ratio of smallest shape ellipsoid axes to largest shape ellipsoid axis
axis1_x float 1/h kpc coordinate of largest shape ellipsoid axis, comoving
axis1_y float 1/h kpc coordinate of largest shape ellipsoid axis, comoving
axis1_z float 1/h kpc coordinate of largest shape ellipsoid axis, comoving
axisratio_2_1_500c * float ratio of second largest shape ellipsoid axes to largest shape ellipsoid axis, for particles within overdensity 500*rho_crit
axisratio_3_1_500c * float ratio of smallest shape ellipsoid axes to largest shape ellipsoid axis, for particles within overdensity 500*rho_crit
axis1_x_500c * float 1/h kpc coordinate of largest shape ellipsoid axis, for particles within overdensity 500*rho_crit, comoving
axis1_y_500c * float 1/h kpc coordinate of largest shape ellipsoid axis, for particles within overdensity 500*rho_crit, comoving
axis1_z_500c * float 1/h kpc coordinate of largest shape ellipsoid axis, for particles within overdensity 500*rho_crit, comoving
T_U float phys.energy;arith.ratio ratio of kinetic to potential energies
M_pe_Behroozi * float phys.mass 1/h Msun Pseudo-evolution corrected masses (very experimental)
M_pe_Diemer * float phys.mass 1/h Msun Pseudo-evolution corrected masses (very experimental)
Rhalfmass * float phys.radius 1/h kpc Radius within which 1/2 of Mvir is enclosed
Macc float phys.mass 1/h Msun halo mass at accretion of the halo to its host
Mpeak float phys.mass 1/h Msun peak mass over accretion history
Vacc float phys.veloc Vmax at accretion
Vpeak float phys.veloc peak Vmax over accretion history
halfmass_scale float time.epoch scale factor at which the most massive progenitor (mmp) reaches 0.5*Mpeak
accRate_Inst float 1/h Msun/yr instantaneous halo mass accretion rate
accRate_100Myr float 1/h Msun/yr halo mass accretion rate averaged over passt 100 Myr
accRate_1Tdyn float 1/h Msun/yr halo mass accretion rate averaged over past 1*virial dynamical time
accRate_2Tdyn float 1/h Msun/yr halo mass accretion rate averaged over past 2*virial dynamical time
accRate_Mpeak * float 1/h Msun/yr growth rate of Mpeak, averaged from current z to z+0.5
Mpeak_scale * float time.epoch scale factor at which Mpeak was reached
Acc_scale * float time.epoch scale factor at which satellites were accreted
First_Acc_scale * float time.epoch scale factor at which current and former satellites first passed through a larger halo
First_Acc_Mvir * float phys.mass h-1.solMass Mvir at First_Acc_scale
First_Acc_Vmax * float phys.veloc km/s Vmax at First_Acc_scale
Vmax_Mpeak * float phys.veloc km/s halo Vmax at the scale at which Mpeak was reached
ix int pos.cartesian.x spatial grid index, x-direction
iy int pos.cartesian.y spatial grid index, y-direction
iz int pos.cartesian.z spatial grid index, z-direction
phkey int Peano-Hilbert key index of space-filling curve

Examples

Get 10 rows from the ROCKSTAR table

SELECT * FROM SMDPL.Rockstar 
LIMIT 10

This query retrieves ten records (arbitrarily) from the Rockstar-table.

Get the 10 most massive ROCKSTAR-halos at z=0

SELECT rockstarId, x, y, z, Mvir, Rvir FROM SMDPL.Rockstar WHERE snapnum = 116
ORDER BY Mvir DESC
LIMIT 10

This query retrieves the first ten Rockstar-halos for redshift 0 (snapshot number 116) after sorting them by decreasing mass and hence returns the ten most massive objects.

Get all progenitors of a halo

SELECT p.* FROM MDPL2.Rockstar AS p, 
(SELECT depthFirstId, lastProg_depthFirstId FROM MDPL2.Rockstar WHERE rockstarId=...) AS r WHERE p.depthFirstId BETWEEN r.depthFirstId AND r.lastProg_depthFirstId 
ORDER BY p.snapnum

This query makes use of the properties of depthFirstIds: all halos with ids between the current halos id and its last progenitor id (lastProg_depthFirstId) must be progenitors.

Get the main branch, i.e. the most massive progenitors for each timestep, for e.g. extracting mass accretion history, for a halo with given rockstarId

SELECT p.* FROM MDPL2.Rockstar AS p, 
(SELECT depthFirstId, mainLeaf_depthFirstId FROM MDPL2.Rockstar WHERE rockstarId=...) AS mycl WHERE p.depthFirstId BETWEEN mycl.depthFirstId AND mycl.mainLeaf_depthFirstId 
ORDER BY p.snapnum

This uses the mainLeaf_depthFirstId which is the depthFirstId of the last leaf on the main branch, i.e. it’s the earliest found main progenitor (with mmp-flag = 1).

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