Alongside the full particle snapshots, we have retained partial snapshots for all of the original outputs (see :doc:`snapshot_redshifts` for the list). There are two kinds of partial snapshots. Both kinds have the same file format as the original snapshots, and can be opened using swiftsimio.
For the downsampled snapshots at each output we select a random 1% of particles to keep (not the same 1% for each output). All black hole particles have been retained. The following fields are available for each particle type, with the description for each the same as in the :doc:`full snapshots <snapshot_particle_properties>`.
Note
Masses (except for black hole masses) have been rescaled by a factor of 100 to conserve the total mass within the snapshot.
| Particle Type | Included Fields |
|---|---|
| Gas | ComptonYParameters, Coordinates, Masses, Velocities |
| Dark matter | Coordinates, Masses, Velocities |
| Stars | Coordinates, Masses, Velocities |
| Black holes | Coordinates, DynamicalMasses, SubgridMasses, Velocities |
| Neutrinos | Coordinates, Masses, SampledSpeeds, Velocities, Weights |
TODO: Add a link to an example downsampled snapshot directory
The reduced snapshots contains all the particles within the R_{100c} radius of a selection of massive halos. Within the SOAP catalogues each subhalo has a flag SOAP/IncludedInReducedSnapshot which indicates whether its particles are included in the reduced snapshot. To pick these halos we define a set of M_{200c} halo mass bins of width 0.05 dex, with the lowest mass bin starting at M_{200c}=10^{13} M_\odot. If a bin has less than 200 halos then we include all of them in the reduced snapshot, if not then we include a random 200.
All of the properties available in the :doc:`full snapshots <snapshot_particle_properties>` are present in the reduced snapshots.
TODO: Add a link to an example reduced snapshot directory