Canonical schema¶

All readers convert their native fields into a single in-memory schema before the writer emits HDF5. Sticking to this contract is what makes new readers cheap to add.

Units¶

Quantity	Units
length	Mpc/h (comoving)
mass	M_sun/h
velocity	km/s (peculiar; no Hubble flow)
spin	dimensionless (Bullock)
expansion `a`	dimensionless scale factor

`Halo` dtype¶

HALO_DTYPE = np.dtype([
    ("nodeIndex",        "<i8"),
    ("descendantIndex",  "<i8"),
    ("hostIndex",        "<i8"),
    ("expansionFactor",  "<f8"),
    ("nodeMass",         "<f8"),
    ("scaleRadius",      "<f8"),
    ("halfMassRadius",   "<f8"),
    ("position",         "<f8", (3,)),
    ("velocity",         "<f8", (3,)),
    ("angularMomentum",  "<f8", (3,)),
    ("spin",             "<f8"),
])

scaleRadius is the NFW scale radius. halfMassRadius is the radius enclosing half the halo’s mass. Galacticus accepts either (or both); readers that have only one of the two leave the other at NaN, which the writer faithfully emits.

`Forest`¶

A astrosylva.Forest packages one self-contained merger tree:

@dataclass(frozen=True)
class Forest:
    forest_id: int
    halos: np.ndarray   # dtype = HALO_DTYPE
    weight: float = 1.0

Galacticus conventions¶

Halos with no host have hostIndex == nodeIndex (never -1).
Halos with no descendant have descendantIndex == -1.
Per-forest indices in /forestIndex are written in the order forests are yielded by the reader.

Metadata¶

The astrosylva.Metadata dataclass mirrors the Galacticus HDF5 group layout. Reader-introspected values win over config-supplied values; conflicts emit a astrosylva.MetadataConflictWarning.