# Data Fields of the HBT Subhalo Catalogs
### The released HBT+ catalogs are stripped from the original HBT outputs.
#### Each file has attributes: "Cosmology", "SnapshotId" and a dataset named "Subhalos".
# References:
#### Link to the [HBT+ wiki](https://github.com/Kambrian/HBTplus/wiki) for descriptions of HBT codes and outputs.
#### Some more detailed documentation may be found on the website of [HBT-HERONS](https://hbt-herons.strw.leidenuniv.nl/), which is a fork of the original HBT+ code with further developments for hydro simulations.
| Field | Unit | Description |
| :------------------------------------ | :-------------------- | :---------- |
| **TrackId** | — | The unique ID of the subhalo in this simulation. Persistent over time. |
| **Nbound** | — | The number of dark matter particles bound to the subhalo. |
| **Mbound** | 1010 M⊙/h | The bound mass of the subhalo, equal to Nbound multiplied by the particle mass. |
| **HostHaloId** | — | The index of the host halo in the FoF catalog. |
| **Rank** | — | The rank of the subhalo within its host group, sorted by mass, with rank=0 indicating the most massive subhalo in each group (i.e., the main/central subhalo), and rank>0 for satellites. |
| **Depth** | — | The hierarchical level of the subhalo in its host according to the merger tree, with central=0, sub=1, sub-sub=2... |
| **LastMaxMass** | 1010 M⊙/h | The maximum `Mbound` of the subhalo in current and all preceding snapshots. |
| **SnapshotIndexOfLastMaxMass** | — | The snapshot number at which the subhalo attained its maximum `Mbound`. |
| **SnapshotIndexOfLastIsolation** | — | The snapshot number of the most recent time the subhalo is/was a central. |
| **SnapshotIndexOfBirth** | — | The snapshot number at which the subhalo first became resolved. |
| **SnapshotIndexOfDeath** | — | The snapshot number at which the subhalo first became unresolved; this value is only set if the current snapshot >= `SnapshotIndexOfDeath`, and is -1 otherwise. |
| **SnapshotIndexOfSink** | — | The snapshot number of the subhalo when it sinks into another subhalo. |
| **RmaxComoving** | Mpc/h | The comoving radius at which the circular velocity reaches `VmaxPhysical`, centred on the `ComovingMostBoundPosition`. |
| **VmaxPhysical** | km/s | The maximum value of the circular velocity of the subhalo, centred on the `ComovingMostBoundPosition`. |
| **LastMaxVmaxPhysical** | km/s | The maximum `VmaxPhysical` of the subhalo in current and preceding snapshots. |
| **SnapshotIndexOfLastMaxVmax** | — | The snapshot number of the subhalo at which it has maximum `VmaxPhysical`. |
| **R2SigmaComoving** | Mpc/h | The comoving radius within which 95.5% of the bound particles are contained. |
| **RHalfComoving** | Mpc/h | The half `Mbound` radius in comoving distance. |
| **BoundR200CritComoving** | Mpc/h | The R200c of the subhalo calculated using its bound particles. |
| **BoundM200Crit** | 1010 M⊙/h | The M200c of the subhalo calculated using its bound particles. |
| **SpecificSelfPotentialEnergy** | — | The average specific potential energy per particle, \phi/m. The total potential energy of the system is 0.5 × (\phi/m) × Mbound, where the factor of 0.5 corrects for the double counting of mutual potential energy. |
| **SpecificSelfKineticEnergy** | (km/s)2 | The average specific kinetic energy per particle, in the center of mass reference frame of the subhalo. |
| **SpecificAngularMomentum** | Mpc/h · km/s | The specific angular momentum of the subhalo. It is equal to [r × v] for the particles in the subhalo (where r is position vector and v is velocity vector), calculated in the center of mass reference frame of the subhalo. |
| **InertialEigenVector** | — | The inertial eigenvectors of the `InertialTensor` matrix of the subhalo, with amplitudes equal to eigenvalues. |
| **InertialEigenVectorWeighted** | — | Eigenvectors of the `InertialTensorWeighted`. |
| **InertialTensor** | (Mpc/h)2 | Flattened representation of the inertia tensor of the subhalo, (Ixx, Ixy, Ixz, Iyy, Iyz, Izz), with Iij=\Sigmak mk xk,i xk,j / \Sigmak mk, where xk,i is the i-th component of the coordinate of particle k in the reference frame of the most bound particle, and mk is the particle mass. |
| **InertialTensorWeighted** | — | The inverse distance-weighted InertialTensor, with xk replaced by xk/rk, where rk is the distance of particle k from the most bound particle. |
| **ComovingAveragePosition** | Mpc/h | The average position of the bound particles in this subhalo. |
| **PhysicalAverageVelocity** | km/s | The average velocity of the bound particles in this subhalo. |
| **ComovingMostBoundPosition** | Mpc/h | Position of the most bound particle of this subhalo. |
| **PhysicalMostBoundVelocity** | km/s | Velocity of the most bound particle of this subhalo. |
| **MostBoundParticleId** | — | ID of the most bound particle of this subhalo. |
| **SinkTrackId** | — | The TrackId of the subhalo that this subhalo has sunk into. -1 if it has not sunk. |
| **Group_mass** | 1010 M⊙/h | The sum of the masses of all particles in the host FoF halo. |
| **Group_M_200crit** | 1010 M⊙/h | The M200c of the host FoF halo, calculated using all the particles within the corresponding sphere enclosing an average density of 200 times the critical density. |
| **Group_R_200crit** | Mpc/h | The R200c of the host halo. |
| **Group_M_200mean** | 1010 M⊙/h | The M200mean of the host halo, calculated using all the particles within the corresponding sphere enclosing an average density of 200 times the mean density of the universe. |
| **Group_R_200mean** | Mpc/h | The R200mean of the host halo. |
| **Group_M_200tophat** | 1010 M⊙/h | The M200tophat of the host halo, calculated using all the particles within the corresponding sphere enclosing an average density predicted by the tophat spherical collapse model. |
| **Group_R_200tophat** | Mpc/h | The R200tophat of the host halo. |