Particle Types and HDF5 Layout

CosmicGrain is compiled with NTYPES=7. Six-element GADGET headers are not valid for a dust-enabled build even when no dust exists initially.

Type	Role in the current zoom workflow
0	Gas
1	High-resolution dark matter
2	Coarser dark matter in the zoom hierarchy
3	Reserved/unused in the accepted IC suite
4	Stars formed during the simulation
5	Reserved for black holes or other configured GADGET use; unused here
6	Live CosmicGrain dust superparticles

Initial conditions

MUSIC2 initially writes the conventional six-type layout. The suite runner extends NumPart_ThisFile, NumPart_Total, NumPart_Total_HighWord, and MassTable to seven elements and creates an empty PartType6 group with:

Coordinates   (0, 3)
Velocities    (0, 3)
ParticleIDs   (0,)
Masses        (0,)

The empty group and zero header count are intentional. Stellar feedback later creates PartType6 particles.

Evolved dust particles

Every live dust superparticle carries dynamical fields plus Masses, GrainRadius, CarbonMassFraction, DustTemperature, DustSource, formation-time information, and birth position. DustSource uses 0=SNII, 1=AGB, and 2=LRN. Carbon and silicate masses must sum to total dust mass within floating-point tolerance.

Particle IDs are globally unique across all types and must use 64-bit storage for dust-enabled production runs.