# Simulation output¶

## Particle data¶

Arepo supports various formats for in- and output, which are essentially the same as in Gadget-2. Format 1 and format 2 are binary outputs and the main reason why they are still supported is to allow the use of initial conditions from well-tested initial condition codes that write one of these formats. For output (or when creating new initial condition generating code), the authors recommend the format 3, which is an HDF5 format. Many of the examples create the initial conditions in HDF5 with the examples/*/create.py python script.

Fields for the particle data output

Field name

Block ID

Units

Description

Coordinates

POS

$$\text{UnitLength}$$ $$a \, h^{-1}$$

Comoving position; for cells: position of mesh-generating point

Velocities

VEL

$$\text{UnitVelocity}$$ $$a^{0.5}$$

Velocity

ParticleIDs

ID

Unique ID of particle

Masses

MASS

$$\text{UnitMass}$$ $$h^{-1}$$

Potential

POT

$$\text{UnitVelocity}^2$$ $$a^{-1}$$

Gravitational potential energy (OUTPUTPOTENTIAL)

InternalEnergy

U

$$\text{UnitVelocity}^2$$

Specific internal energy

Density

RHO

$$\text{UnitMass}$$ $$\text{UnitLength}^{-3}$$ $$a^{-3} \, h^2$$

Density of gas

Pressure

PRES

$$\text{UnitLength}^{-3}$$ $$\text{UnitMass}^1$$ $$\text{UnitVelocity}^2$$ $$a^{-3} \, h^2$$

Thermal pressure of gas (OUTPUT_PRESSURE)

SoundSpeed

CSND

$$\text{UnitVelocity}$$

Effective sound speed of both thermal and magnetic component (note different a scaling compared to VEL!) (OUTPUT_CSND)

ElectronAbundance

NE

Electron number density relative to hydrogen (COOLING)

NeutralHydrogenAbundance

NH

Neutral hydrogen fraction (COOLING)

StarFormationRate

SFR

$$\text{Msun} \, \text{yr}^{-1}$$

Star formation rate (USE_SFR)

VelocityDivergence

DIVV

$$\text{UnitVelocity}$$ $$\text{UnitLength}^{-1}$$ $$h$$

Velocity divergence (OUTPUT_DIVVEL)

VelocityCurl

ROTV

$$\text{UnitVelocity}$$ $$\text{UnitLength}^{-1}$$ $$h$$

Rotation of velocity (OUTPUT_CURLVEL)

CoolingHeatingEnergy

COHE

$$\text{UnitLength}^{-1}$$ $$\text{UnitVelocity}^3$$ $$\text{UnitMass}$$

Actual cooling rate, differing from nominal cooling rate in star forming cells (OUTPUT_COOLHEAT)

SurfaceArea

AREA

$$\text{UnitLength}^2$$ $$a^2 \, h^{-2}$$

Surface area of a Voronoi cell (OUTPUT_SURFACE_AREA)

NumFacesCell

NFAC

Number of faces of a Voronoi cell (OUTPUT_SURFACE_AREA)

CoolingRate

COOR

$$\text{erg} \, \text{cm}^3 \, \text{s}^{-1}$$

The cooling rate of a gas cell (e.g. Lambda_net/n_H^2). (OUTPUTCOOLRATE)

Vorticity

VORT

$$\text{UnitVelocity}$$ $$\text{UnitLength}^{-1}$$ $$h$$

Vorticity of a cell (OUTPUT_VORTICITY)

GRAP

$$\text{UnitLength}^{-4}$$ $$\text{UnitMass}$$ $$\text{UnitVelocity}^2$$ $$a^{-4} \, h^3$$

Gradient of the pressure (limited) (OUTPUT_PRESSURE_GRADIENT)

GRAR

$$\text{UnitLength}^{-4}$$ $$\text{UnitMass}$$ $$a^{-4} \, h^3$$

Gradient of the density (limited) (OUTPUT_DENSITY_GRADIENT)

GRAV

$$\text{UnitLength}^{-1}$$ $$\text{UnitVelocity}^1$$ $$h$$

Gradient of the velocity (limited) (OUTPUT_VELOCITY_GRADIENT)

GRAB

$$\text{UnitMass}^{0.5}$$ $$\text{UnitVelocity}$$ $$\text{UnitLength}^{-5/2}$$ $$h^2 \, a^{-3}$$

Gradient of the magnetic field (limited) (OUTPUT_BFIELD_GRADIENT)

Volume

VOL

$$\text{UnitLength}^3$$ $$a^3 \, h^{-3}$$

(comoving) volume of gas cell. Can be calculated by Masses / Density. (OUTPUT_VOLUME)

VertexVelocity

VEVE

$$\text{UnitVelocity}$$ $$a^1$$

velocity of the mesh-generating point (OUTPUT_VERTEX_VELOCITY)

MaxFaceAngle

FACA

Maximum face angle of cell, quantifies roundness (OUTPUT_MESH_FACE_ANGLE)

CenterOfMass

CMCE

$$\text{UnitLength}$$ $$a^1 \, h^{-1}$$

Center of mass of cell. Generally not equal to position of mesh generating point POS (OUTPUT_CENTER_OF_MASS)

MPI task this particle is at (OUTPUT_TASK)

TimebinHydro

TBH

Time bin the cell is at (OUTPUT_TIMEBIN_HYDRO)

TimeStep

TSTP

$$\text{UnitLength}$$ $$\text{UnitVelocity}^{-1}$$ $$h^{-1}$$

Timestep in code units (OUTPUTTIMESTEP)

Acceleration

ACCE

$$\text{UnitVelocity}^2$$ $$\text{UnitLength}^{-1}$$ $$a^{-1} \, h$$

Acceleration due to gravitational forces, including external potential; different a scaling than internally!(OUTPUTACCELERATION)

Softenings

SOFT

$$\text{UnitLength}$$ $$a \, h^{-1}$$

Gravitational softening length of particle/cell (OUTPUT_SOFTENINGS)

GravityInteractions

GINT

Number of force calculations in tree (OUTPUTGRAVINTERACTIONS)

MagneticField

BFLD

$$\text{UnitLength}^{-1.5}$$ $$\text{UnitMass}^{0.5}$$ $$\text{UnitVelocity}$$ $$h \, a^{-2}$$

Magnetic field (in code units but Gauss system; note that internally, the Heaviside-Lorentz system is used) (MHD)

MagneticFieldDivergence

DIVB

$$\text{UnitLength}^{-2.5}$$ $$\text{UnitMass}^{0.5}$$ $$\text{UnitVelocity}$$ $$h^2 \, a^{-3}$$

Divergence of magnetic field (MHD)

PassiveScalars

PASS

Mass fraction of passive scalar quantity in cell (PASSIVE_SCALARS)

SubfindDensity

SFDE

$$\text{UnitLength}^{-3}$$ $$\text{UnitMass}$$ $$a^{-3} \, h^2$$

density around particle (SPH like estimate) (SAVE_HSML_IN_SNAPSHOT)

SubfindDMDensity

SFDD

$$\text{UnitLength}^{-3}$$ $$\text{UnitMass}$$ $$a^{-3} \, h^2$$

dark matter density around particle (SPH like estimate) (SAVE_HSML_IN_SNAPSHOT)

SubfindHsml

SFHS

$$\text{UnitLength}$$ $$a \, h^{-1}$$

SPH smoothing length for density estimate (SAVE_HSML_IN_SNAPSHOT)

SubfindVelDisp

SFVD

$$\text{UnitVelocity}$$

SPH averaged velocity dispersion around particle (SAVE_HSML_IN_SNAPSHOT)

GroupNr

GROU

Number of nearest group (FOF_FUZZ_SORT_BY_NEAREST_GROUP=1)

HighResGasMass

HRGM

$$\text{UnitMass}$$ $$h^{-1}$$

Conserved scalar quantity flaging the high-res region of a cosmological zoom simulation (REFINEMENT_HIGH_RES_GAS)

AllowRefinement

REF

Is refinement allowed in gas cell. 0 for low-resolution region gas cells in zoom simulations (REFINEMENT_HIGH_RES_GAS)

### Format 1¶

Format 1 is organized in blocks, each holding information about all particles for a specific property. The first block is the header, containing global information about the particle set. Within the other blocks, particles are ordered according to their particle type.

For a more detailed description of this file format, see the Gadget-2 user guide (https://wwwmpa.mpa-garching.mpg.de/gadget/users-guide.pdf).

### Format 2¶

Format 2 is a variant of format 1, but containing an additional 4-character string at the beginning of each block (called Block ID in table). This way, it is possible to read the snapshot without having detailed information about all settings that were active in the code that produced this output.

### Format 3 / HDF5¶

Format 3 is the by now recommended format, based on the hdf5 library. The particle data output consists of hdf5 groups called PartTypeX where X runs from 0 to NTYPES-1 (NTYPES=6 if not set in Config-file). Each of these hdf5 groups has a number of datasets with properties belonging to this particular particle type, e.g. Coordinates for the position of particles. These are in general 2d arrays, where the first dimension represents the different particles, while the second dimension is the dimensionality of the specific property (e.g. for Coordinates, every particle has 3 entries, its x, y and z coordinate). Consequently, for scalar quantities, the array is just one dimensional.

In addition to the particle types, each file has an hdf5 group called Header, with general information about the simulation and this file in particular. These informations are stored in hdf5 attributes within the header group.

To facilitate the use of the snapshot, the compile time settings are also stored in the snapshots, saved as attributes in the group Config, as well as the parameter settings in the group Parameters. To be sure it is however advisable to check the ./build/arepoconfig.h and the ./output/parameters-usedvalues files for the compile time and run-time variables of a given simulation.

## FOF/Subfind¶

The halo and subhalo finder produces a separate output file, summarizing the properties determined by the on the fly analysis. These run immediately before every simulation output, and also sort the particles in the particle data output according to group membership, subhalo membership and binding energy.

The (sub)halo output files have two hdf5 groups containing halo data, called Group, for the properties of groups (identified by the Friend-of-Friends algorithm), and Subhalo, for substructures in groups.

Halo fields in group catalogue files

Group field name

Block ID

Units

Description

GroupLen

FLEN

Number of particles/cells in group

GroupMass

FMAS

$$\text{UnitMass}$$ $$h^{-1}$$

Sum of masses of all particles in group

GroupPos

FPOS

$$\text{UnitLength}$$ $$a \, h^{-1}$$

Position of the most bound particle in group

GroupCM

FGCM

$$\text{UnitLength}$$ $$a \, h^{-1}$$

Position of center of mass of group

GroupVel

FVEL

$$\text{UnitVelocity}$$ $$a^{-1}$$

Velocity of the group, computed as the sum of the mass weighted velocities of all particles/cells in this group, of all types.

GroupLenType

FLTY

Number of particles of given type in group

GroupMassType

FMTY

$$\text{UnitMass}$$ $$h^{-1}$$

Sum of particle masses of given type

GroupSFR

FSFR

$$\text{Msun}$$ $$\text{yr}^{-1}$$

Cumulative star formation rate of all gas cells in group

Group_M_Mean200

FMM2

$$\text{UnitMass}$$ $$h^{-1}$$

Total mass within a sphere with mean density of 200 times the mean density of the Universe.

Group_R_Mean200

FRM2

$$\text{UnitLength}$$ $$a \, h^{-1}$$

Radius of sphere corresponding to Group_M_Mean200

Group_M_Crit200

FMC2

$$\text{UnitMass}$$ $$h^{-1}$$

Total mass within a sphere around GroupPos with mean density of 200 times the critical density of the Universe.

Group_R_Crit200

FRC2

$$\text{UnitLength}$$ $$a \, h^{-1}$$

Radius of sphere corresponding to Group_M_Crit200

Group_M_Crit500

FMC5

$$\text{UnitMass}$$ $$h^{-1}$$

Total mass within a sphere around GroupPos with mean density of 500 times the critical density of the Universe.

Group_R_Crit500

FRC5

$$\text{UnitLength}$$ $$a \, h^{-1}$$

Radius of sphere corresponding to Group_M_Crit500

Group_M_TopHat200

FMT2

$$\text{UnitMass}$$ $$h^{-1}$$

Total mass within a sphere around GroupPos with mean density having a specific fraction of the mean density of the Universe.

Group_R_TopHat200

FRT2

$$\text{UnitLength}$$ $$a \, h^{-1}$$

Radius of sphere corresponding to Group_M_TopHat200

GroupNsubs

FNSH

Number of subhalos identified in this group

GroupFirstSub

FFSH

(Global) index of first subhalo in this group. -1 if there are none.

GroupFuzzOffsetType

FUOF

Particle offset (for each type) of fuzzy particles.

Subhalo fields in group catalogue files

Subhalo field name

Block-ID

Units

Description

SubhaloLen

SLEN

Total number of particles/cells in this subhalo

SubhaloMass

SMAS

$$\text{UnitMass}$$ $$h^{-1}$$

Total mass of all particles in this subhalo, child subhalos not included

SubhaloPos

SPOS

$$\text{UnitLength}$$ $$a \, h^{-1}$$

Position of most bound particle in subhalo

SubhaloVel

SVEL

$$\text{UnitVelocity}$$

Physical velocity of subhalo

SubhaloLenType

SLTY

Number of particle of each type in a subhalo

SubhaloMassType

SMTY

$$\text{UnitMass}$$ $$h^{-1}$$

Mass of each particle type in a subhalo

SubhaloCM

SCMP

$$\text{UnitLength}$$ $$a \, h^{-1}$$

Center of mass of subhalo

SubhaloSpin

SSPI

$$\text{UnitLength}$$ $$\text{UnitVelocity}$$ $$h^{-1}$$

Total spin in each coordinate axis from all subhalo particles/cells

SubhaloVelDisp

SVDI

$$\text{UnitVelocity}$$

1d velocity dispersion

SubhaloVmax

SVMX

$$\text{UnitVelocity}$$

Maximum circular velocity

SVRX

$$\text{UnitLength}$$ $$a$$ $$h^{-1}$$

SHMR

$$\text{UnitLength}$$ $$a$$ $$h^{-1}$$

Radius containing half the mass of the subhalo

SHMT

$$\text{UnitLength}$$ $$a$$ $$h^{-1}$$

Radius containing half the mass of a given type of particles in the subhalo

SMIR

$$\text{UnitMass}$$ $$h^{-1}$$

Sum of all particle masses enclosed in a sphere with twice the part4 (i.e. stellar) half mass radius

SMIH

$$\text{UnitMass}$$ $$h^{-1}$$

Sum of all particle masses enclosed in a sphere with the part4 (i.e. stellar) half mass radius

SMIM

$$\text{UnitMass}$$ $$h^{-1}$$

Sum of all particle masses enclosed in a sphere with radius SubhaloVmaxRad

SMIT

$$\text{UnitMass}$$ $$h^{-1}$$

Sum of particle masses of specific type particles enclosed in a sphere with twice the part4 (i.e. stellar) half mass radius

SMHT

$$\text{UnitMass}$$ $$h^{-1}$$

Sum of particle masses of specific type particles enclosed in a sphere with the part4 (i.e. stellar) half mass radius

SMMT

$$\text{UnitMass}$$ $$h^{-1}$$

Sum of particle masses of specific type particles enclosed in a sphere with radius SubhaloVmaxRad

SubhaloIDMostbound

SIDM

The ID of the most bound particle

SubhaloGrNr

SGNR

Global index of the (FoF) group this subhalo belongs to

SubhaloParent

SPRT

Index of a potential parent subhalo this subhalo is part of

SubhaloBfldHalo

BFDH

$$\text{UnitMass}^{0.5}$$ $$\text{UnitVelocity}$$ $$\text{UnitLength}^{-1.5}$$ $$h \, a^{-2}$$

Volume averaged magnetic field strength in subhalo (Gauss unit system, not Heaviside-Lorentz)

SubhaloBfldDisk

BFDD

$$\text{UnitMass}^{0.5}$$ $$\text{UnitVelocity}$$ $$\text{UnitLength}^{-1.5}$$ $$h \, a^{-2}$$

Volume averaged magnetic field strength within twice the stellar half mass radius (Gauss unit system, not Heaviside-Lorentz)

SubhaloSFR

SSFR

$$\text{Msun} \, \text{yr}^{-1}$$

Sum of star formation rates of all gas cells in the subhalo

SSFI

$$\text{Msun} \, \text{yr}^{-1}$$

Sum of star formation rates of all gas cells within twice the stellar half mass radius

SSFH

$$\text{Msun} \, \text{yr}^{-1}$$

Sum of star formation rates of all gas cells within the stellar half mass radius

SSFM

$$\text{Msun} \, \text{yr}^{-1}$$

Sum of star formation rates of all gas cells within a sphere with radius SubhaloVmaxRad

ID

PIDS

Particle IDs in subhalo

Additional group fields that are calculated when SUBFIND_EXTENDED_PROPERTIES is set

Group field name

Block ID

Units

Description

Group_J_Mean200

FJM2

$$\text{UnitMass}$$ $$\text{UnitLength}$$ $$\text{UnitVelocity}$$ $$h^{-2}$$

Total angular momentum of all particles in group within Group_R_Mean200

Group_Jdm_Mean200

JDM2

$$\text{UnitMass}$$ $$\text{UnitLength}$$ $$\text{UnitVelocity}$$ $$h^{-2}$$

Total angular momentum of dark matter particles in group within Group_R_Mean200

Group_Jgas_Mean200

JGM2

$$\text{UnitMass}$$ $$\text{UnitLength}$$ $$\text{UnitVelocity}$$ $$h^{-2}$$

Total angular momentum of gas particles in group within Group_R_Mean200

Group_Jstars_Mean200

JSM2

$$\text{UnitMass}$$ $$\text{UnitLength}$$ $$\text{UnitVelocity}$$ $$h^{-2}$$

Total angular momentum of star matter particles in group within Group_R_Mean200

Group_MassType_Mean200

MTM2

$$\text{UnitMass}$$ $$h^{-1}$$

Total mass of group for each particle type within Group_R_Mean200

Group_LenType_Mean200

LTM2

Total number of particles for each particle type within Group_R_Mean200

Group_CMFrac_Mean200

CFM2

Mass fraction of counter-rotating particles within Group_R_Mean200

Group_CMFracType_Mean200

FTM2

Mass fraction of counter-rotating particles within Group_R_Mean200 for each type

Group_J_Crit200

FJC2

$$\text{UnitMass}$$ $$\text{UnitLength}$$ $$\text{UnitVelocity}$$ $$h^{-2}$$

Total angular momentum of all particles in group within Group_R_Crit200

Group_Jdm_Crit200

JDC2

$$\text{UnitMass}$$ $$\text{UnitLength}$$ $$\text{UnitVelocity}$$ $$h^{-2}$$

Total angular momentum of dark matter particles in group within Group_R_Crit200

Group_Jgas_Crit200

JGC2

$$\text{UnitMass}$$ $$\text{UnitLength}$$ $$\text{UnitVelocity}$$ $$h^{-2}$$

Total angular momentum of gas particles in group within Group_R_Crit200

Group_Jstars_Crit200

JSC2

$$\text{UnitMass}$$ $$\text{UnitLength}$$ $$\text{UnitVelocity}$$ $$h^{-2}$$

Total angular momentum of star particles in group within Group_R_Crit200

Group_MassType_Crit200

MTC2

$$\text{UnitMass}$$ $$h^{-1}$$

Total mass of group for each particle type within Group_R_Crit200

Group_LenType_Crit200

LTC2

Total number of particles for each particle type within Group_R_Crit200

Group_CMFrac_Crit200

CFC2

Mass fraction of counter-rotating particles within Group_R_Crit200

Group_CMFracType_Crit200

FTC2

Mass fraction of counter-rotating particles within Group_R_Crit200 for each type

Group_J_Crit500

FJC5

$$\text{UnitMass}$$ $$\text{UnitLength}$$ $$\text{UnitVelocity}$$ $$h^{-2}$$

Total angular momentum of all particles in group within Group_R_Crit500

Group_Jdm_Crit500

JDC5

$$\text{UnitMass}$$ $$\text{UnitLength}$$ $$\text{UnitVelocity}$$ $$h^{-2}$$

Total angular momentum of dark matter particles in group within Group_R_Crit500

Group_Jgas_Crit500

JGC5

$$\text{UnitMass}$$ $$\text{UnitLength}$$ $$\text{UnitVelocity}$$ $$h^{-2}$$

Total angular momentum of gas particles in group within Group_R_Crit500

Group_Jstars_Crit500

JSC5

$$\text{UnitMass}$$ $$\text{UnitLength}$$ $$\text{UnitVelocity}$$ $$h^{-2}$$

Total angular momentum of star particles in group within Group_R_Crit500

Group_MassType_Crit500

MTC5

$$\text{UnitMass}$$ $$h^{-1}$$

Total mass of group for each particle type within Group_R_Crit500

Group_LenType_Crit500

LTC5

Total number of particles for each particle type within Group_R_Crit500

Group_CMFrac_Crit500

CFC5

Mass fraction of counter-rotating particles within Group_R_Crit500

Group_CMFracType_Crit500

FTC5

Mass fraction of counter-rotating particles within Group_R_Crit500 for each type

Group_J_TopHat200

FJT2

$$\text{UnitMass}$$ $$\text{UnitLength}$$ $$\text{UnitVelocity}$$ $$h^{-2}$$

Total angular momentum of all particles in group within Group_R_TopHat200

Group_Jdm_TopHat200

JDT2

$$\text{UnitMass}$$ $$\text{UnitLength}$$ $$\text{UnitVelocity}$$ $$h^{-2}$$

Total angular momentum of dark matter particles in group within Group_R_TopHat200

Group_Jgas_TopHat200

JGT2

$$\text{UnitMass}$$ $$\text{UnitLength}$$ $$\text{UnitVelocity}$$ $$h^{-2}$$

Total angular momentum of gas particles in group within Group_R_TopHat200

Group_Jstars_TopHat200

JST2

$$\text{UnitMass}$$ $$\text{UnitLength}$$ $$\text{UnitVelocity}$$ $$h^{-2}$$

Total angular momentum of star particles in group within Group_R_TopHat200

Group_MassType_TopHat200

MTT2

$$\text{UnitMass}$$ $$h^{-1}$$

Total mass of group for each particle type within Group_R_TopHat200

Group_LenType_TopHat200

LTT2

Total number of particles for each particle type within Group_R_TopHat200

Group_CMFrac_TopHat200

CFT2

Mass fraction of counter-rotating particles within Group_R_TopHat200

Group_CMFracType_TopHat200

FTT2

Mass fraction of counter-rotating particles within Group_R_TopHat200 for each type

Group_Epot_Crit200

EPO1

$$\text{UnitMass}$$ $$\text{UnitVelocity}$$ $$a^{-2} \, h^{-1}$$

Total potential energy of particles within Group_R_Crit200

Group_Ekin_Crit200

EKI1

$$\text{UnitMass}$$ $$\text{UnitVelocity}$$ $$a^{-2} \, h^{-1}$$

Total kinetic energy of particles within Group_R_Crit200

Group_Ethr_Crit200

ETH1

$$\text{UnitMass}$$ $$\text{UnitVelocity}$$ $$a^{-2} \, h^{-1}$$

Total thermal energy of particles within Group_R_Crit200

Group_Epot_Mean200

EPO2

$$\text{UnitMass}$$ $$\text{UnitVelocity}$$ $$a^{-2} \, h^{-1}$$

Total potential energy of particles within Group_R_Mean200

Group_Ekin_Mean200

EKI2

$$\text{UnitMass}$$ $$\text{UnitVelocity}$$ $$a^{-2} \, h^{-1}$$

Total kinetic energy of particles within Group_R_Mean200

Group_Ethr_Mean200

ETH2

$$\text{UnitMass}$$ $$\text{UnitVelocity}$$ $$a^{-2} \, h^{-1}$$

Total thermal energy of particles within Group_R_Mean200

Group_Epot_TopHat200

EPO3

$$\text{UnitMass}$$ $$\text{UnitVelocity}$$ $$a^{-2} \, h^{-1}$$

Total potential energy of particles within Group_R_TopHat200

Group_Ekin_TopHat200

EKI3

$$\text{UnitMass}$$ $$\text{UnitVelocity}$$ $$a^{-2} \, h^{-1}$$

Total kinetic energy of particles within Group_R_TopHat200

Group_Ethr_TopHat200

ETH3

$$\text{UnitMass}$$ $$\text{UnitVelocity}$$ $$a^{-2} \, h^{-1}$$

Total thermal energy of particles within Group_R_TopHat200

Group_Epot_Crit500

EPO4

$$\text{UnitMass}$$ $$\text{UnitVelocity}$$ $$a^{-2} \, h^{-1}$$

Total potential energy of particles within Group_R_Crit500

Group_Ekin_Crit500

EKI4

$$\text{UnitMass}$$ $$\text{UnitVelocity}$$ $$a^{-2} \, h^{-1}$$

Total kinetic energy of particles within Group_R_Crit500

Group_Ethr_Crit500

ETH4

$$\text{UnitMass}$$ $$\text{UnitVelocity}$$ $$a^{-2} \, h^{-1}$$

Total thermal energy of particles within Group_R_Crit500

Group_J

FOFJ

$$\text{UnitMass}$$ $$\text{UnitLength}$$ $$\text{UnitVelocity} \, h^{-2}$$

Total angular momentum of all particles in fof-group

Group_Jdm

FOJD

$$\text{UnitMass}$$ $$\text{UnitLength}$$ $$\text{UnitVelocity} \, h^{-2}$$

Total angular momentum of all dark matter particles in fof-group

Group_Jgas

FOJG

$$\text{UnitMass}$$ $$\text{UnitLength}$$ $$\text{UnitVelocity} h^{-2}$$

Total angular momentum of all gas cells in fof-group

Group_Jstars

FOJS

$$\text{UnitMass}$$ $$\text{UnitLength}$$ $$\text{UnitVelocity} \, h^{-2}$$

Total angular momentum of all stars in fof-group

Group_CMFrac

FOCF

Mass fraction of counter-rotating particles in fof-group

Group_CMFracType

FOFT

Mass fraction of counter-rotating particles in fof-group for each type

GroupEkin

EKIN

$$\text{UnitMass}$$ $$\text{UnitVelocity}$$ $$a^{-2} \, h^{-1}$$

Total kinetic energy of all particles in fof-group

GroupEthr

ETHR

$$\text{UnitMass}$$ $$\text{UnitVelocity}$$ $$a^{-2} \, h^{-1}$$

Total thermal energy of all particles in fof-group

GroupEpot

EPOT

$$\text{UnitMass}$$ $$\text{UnitVelocity}$$ $$a^{-2} \, h^{-1}$$

Total potential energy of all particles in fof-group

Additional subhalo fields that are calculated when SUBFIND_EXTENDED_PROPERTIES is set

Subhalo field name

Block ID

Units

Description

SubhaloEkin

SEKN

$$\text{UnitMass}$$ $$\text{UnitVelocity}$$ $$a^{-2} \, h^{-1}$$

Total kinetic energy of all particles in subhalo

SubhaloEthr

SETH

$$\text{UnitMass}$$ $$\text{UnitVelocity}$$ $$a^{-2} \, h^{-1}$$

Total thermal energy of all particles in subhalo

SubhaloEpot

SEPT

$$\text{UnitMass}$$ $$\text{UnitVelocity}$$ $$a^{-2} \, h^{-1}$$

Total potential energy of all particles in subhalo

Subhalo_J

SUBJ

$$\text{UnitMass}$$ $$\text{UnitLength}$$ $$\text{UnitVelocity}$$ $$h^{-2}$$

Total angular momentum of all particles in subhalo

Subhalo_Jdm

SJDM

$$\text{UnitMass}$$ $$\text{UnitLength}$$ $$\text{UnitVelocity}$$ $$h^{-2}$$

Total angular momentum of dark matter particles in subhalo

Subhalo_Jgas

SJGS

$$\text{UnitMass}$$ $$\text{UnitLength}$$ $$\text{UnitVelocity}$$ $$h^{-2}$$

Total angular momentum of gas cells in subhalo

Subhalo_Jstars

SJST

$$\text{UnitMass}$$ $$\text{UnitLength}$$ $$\text{UnitVelocity}$$ $$h^{-2}$$

Total angular momentum of star particles in subhalo

SJHR

$$\text{UnitMass}$$ $$\text{UnitLength}$$ $$\text{UnitVelocity}$$ $$h^{-2}$$

Total angular momentum of all particles in stellar half mass radius

SJDH

$$\text{UnitMass}$$ $$\text{UnitLength}$$ $$\text{UnitVelocity}$$ $$h^{-2}$$

Total angular momentum of dark matter particles within stellar half mass radius

SJGH

$$\text{UnitMass}$$ $$\text{UnitLength}$$ $$\text{UnitVelocity}$$ $$h^{-2}$$

Total angular momentum of gas cells within stellar half mass radius

SJSH

$$\text{UnitMass}$$ $$\text{UnitLength}$$ $$\text{UnitVelocity}$$ $$h^{-2}$$

Total angular momentum of star particles within stellar half mass radius

SJMR

$$\text{UnitMass}$$ $$\text{UnitLength}$$ $$\text{UnitVelocity}$$ $$h^{-2}$$

Total angular momentum of all particles in sphere with radius twice the stellar half mass radius

SJDR

$$\text{UnitMass}$$ $$\text{UnitLength}$$ $$\text{UnitVelocity}$$ $$h^{-2}$$

Total angular momentum of dark matter particles within twice the stellar half mass radius

SJGR

$$\text{UnitMass}$$ $$\text{UnitLength}$$ $$\text{UnitVelocity}$$ $$h^{-2}$$

Total angular momentum of gas cells within twice the stellar half mass radius

SJSR

$$\text{UnitMass}$$ $$\text{UnitLength}$$ $$\text{UnitVelocity}$$ $$h^{-2}$$

Total angular momentum of star particles within twice the stellar half mass radius

Subhalo_CMFrac

SCMF

Mass fraction of counter-rotating particles in subhalo

Subhalo_CMFracType

SCMT

Mass fraction of counter-rotating particles in subhalo for each type

SCMH

Mass fraction of counter-rotating particles within stellar half mass radius

SCTH

Mass fraction of counter-rotating particles within stellar half mass radius for each type