AHF-tables contain halo catalogues produced with the Amiga Halo Finder. Its documentation can be found here: AHF Documentation, an overview is also given in our Halo finders section.

Only halos with at least 20 bound particles are included in the AHF catalogues.

For simulations including gas physics and star formation, additional properties are stored in tables AHFGas for the gas particles and AHFStars for the stellar component.

The column fMhires indicates the pollution by massive low resolution particles. Please only use halos with fMhires >= 0.99 or similar if you want to avoid contaminated halos.

Such massive low resolution particles are used in resimulations of cosmological boxes in order to represent the full box with lower resolution, outside of the of the high resolution region. But it can happen that these particles wander into the high resolution area and pollute the halos and their properties.

These halos are nevertheless included here, so that each user can decide for him/herself to what extend he/she wants to use them.

Column Type UCD Unit Description
ahfId bigint meta.id; meta.main unique id for AHF-halo, e.g.

ahfId = ( snapnum*106 + (original number in AHF catalogue) )

The power of 10 can be different for each simulation database.

snapnum smallint time.epoch number of snapshot
NInFile int meta.id number of halo in AHF catalogue file (= “ID” in file, starts with 0)
hostId bigint meta.id ahfId of the direct host halo; it is -1, if there is no host (distinct halo). The host halo itself can also be a subhalo of another halo (see AHF-substructures).
numSubStruct int meta.number number of subhalos inside the halo
Mvir float phys.mass 1/h Msun halo mass – mass of bound particles within Rvir
np bigint meta.number number of particles in the halo (all components)
x float pos.cartesian.x 1/h kpc (comoving) position of the halo (density center), x-component
y float pos.cartesian.y 1/h kpc (comoving) position, y-component
z float pos.cartesian.z 1/h kpc (comoving) position, z-component
vx float phys.veloc; pos.cartesian.x km/s (peculiar) velocity of the halo, x-component
vy float phys.veloc; pos.cartesian.y km/s (peculiar) velocity, y-component
vz float phys.veloc; pos.cartesian.z km/s (peculiar) velocity, z-component
Rvir float phys.size.radius 1/h kpc virial radius
Rmax float phys.size.radius 1/h kpc position of rotation curve maximum, i.e. distance from center at which the rotation curve has its maximum
r2 float pos.distance 1/h kpc position where rho * r2 peaks, r = distance from center, rho = density at this distance
mbp_offset float pos; arith.diff 1/h kpc offset between most bound particle and halo center
com_offset float pos; arith.diff 1/h kpc offset between center-of-mass and halo center
Vmax float phys.veloc km/s maximum circular velocity in the halo
Vesc float phys.veloc km/s escape velocity at Rvir
sigV float phys.veloc.dispersion km/s 3D velocity dispersion
lambda float spin parameter (Bullock et al. 2001 definition)
lambdaE float classical spin parameter (Peebles’ definition)
Lx float phys.angMomentum; pos.cartesian.x x-component of the angular momentum vector; normalized, i.e. |L| = 1
Ly float phys.angMomentum; pos.cartesian.y y-component of the angular momentum vector
Lz float phys.angMomentum; pos.cartesian.z z-component of the angular momentum vector
b float arith.ratio ratio of intermediate to major axis; derived from 2. eigenvalue of the inertia tensor
c float arith.ratio ratio of minor to major axis
Eax float x-component of the major axis (normalized)
Eay float y-component of the major axis (normalized)
Eaz float z-component of the major axis (normalized)
Ebx float x-component of the intermediate axis (normalized)
Eby float y-component of the intermediate axis (normalized)
Ebz float z-component of the intermediate axis (normalized)
Ecx float x-component of the minor axis (normalized)
Ecy float y-component of the minor axis (normalized)
Ecz float z-component of the minor axis (normalized)
ovdens float phys.density; arith.ratio overdensity at virial radius
nbins int meta.number number of bins in profiles-table
fMhires float arith.ratio mass fraction in high resolution particles for zoomed simulations (should be >= 0.9)
Ekin float phys.energy Msun/h (km/s)2 kinetic energy
Epot float phys.energy Msun/h (km/s)2 potential energy
SurfP float Msun/h (km/s)2 surface pressure (Shaw et al. 2006 definition)
Phi0 float phys.energy (km/s)2 normalisation of gravitational potential used during unbinding procedure (cf. Eq.(A9) in Knollmann & Knebe 2009)
cNFW float NFW concentration estimated using Eq. (9) from Prada et al. (2012)
ix int pos.cartesian.x spatial index, x-direction
iy int pos.cartesian.y spatial index, y-direction
iz int pos.cartesian.z spatial index, z-direction
phkey int Peano-Hilbert key


Mass function of AHF halos at redshift z=0

SELECT 0.25*(0.5+FLOOR(LOG10(Mvir)/0.25)) AS log_mass, COUNT(*) AS num
WHERE snapnum=496
AND fMhires > 0.99
GROUP BY FLOOR(LOG10(Mvir)/0.25)
ORDER BY FLOOR(LOG10(Mvir)/0.25)

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