AHF
AHFtables 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.
IMPORTANT
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 AHFhalo, e.g.
ahfId = ( snapnum*10^{6} + (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 AHFsubstructures).  
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), xcomponent 
y  float  pos.cartesian.y  1/h kpc  (comoving) position, ycomponent 
z  float  pos.cartesian.z  1/h kpc  (comoving) position, zcomponent 
vx  float  phys.veloc; pos.cartesian.x  km/s  (peculiar) velocity of the halo, xcomponent 
vy  float  phys.veloc; pos.cartesian.y  km/s  (peculiar) velocity, ycomponent 
vz  float  phys.veloc; pos.cartesian.z  km/s  (peculiar) velocity, zcomponent 
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 * r^{2} 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 centerofmass 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  xcomponent of the angular momentum vector; normalized, i.e. L = 1  
Ly  float  phys.angMomentum; pos.cartesian.y  ycomponent of the angular momentum vector  
Lz  float  phys.angMomentum; pos.cartesian.z  zcomponent 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  xcomponent of the major axis (normalized)  
Eay  float  ycomponent of the major axis (normalized)  
Eaz  float  zcomponent of the major axis (normalized)  
Ebx  float  xcomponent of the intermediate axis (normalized)  
Eby  float  ycomponent of the intermediate axis (normalized)  
Ebz  float  zcomponent of the intermediate axis (normalized)  
Ecx  float  xcomponent of the minor axis (normalized)  
Ecy  float  ycomponent of the minor axis (normalized)  
Ecz  float  zcomponent of the minor axis (normalized)  
ovdens  float  phys.density; arith.ratio  overdensity at virial radius  
nbins  int  meta.number  number of bins in profilestable  
fMhires  float  arith.ratio  mass fraction in high resolution particles for zoomed simulations (should be >= 0.9)  
Ekin  float  phys.energy  M_{sun}/h (km/s)^{2}  kinetic energy 
Epot  float  phys.energy  M_{sun}/h (km/s)^{2}  potential energy 
SurfP  float  M_{sun}/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, xdirection  
iy  int  pos.cartesian.y  spatial index, ydirection  
iz  int  pos.cartesian.z  spatial index, zdirection  
phkey  int  PeanoHilbert key 
Example
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 FROM Clues3_LGGas.AHF WHERE snapnum=496 AND fMhires > 0.99 GROUP BY FLOOR(LOG10(Mvir)/0.25) ORDER BY FLOOR(LOG10(Mvir)/0.25)