Analysis

CosmicGrain analysis must preserve three distinctions:

1. halo versus galaxy apertures — R200c is not interchangeable with a fixed physical ISM aperture;
2. gas-phase versus total metals — D/Z depends on which metal reservoir is used; and
3. numerical validation versus scientific inference — a conserved whole-box budget does not imply a converged galaxy.

The shared analysis modules are halo_utils.py and zoom_halo_utils.py. They centralize periodic coordinates, halo centers, spherical-overdensity quantities, unit conversion, and target matching. New scripts should use these utilities rather than reimplementing centering or units.

Recommended analysis order:

1. audit the complete snapshot;
2. identify and center the target halo;
3. measure M200c and R200c;
4. define and record the galaxy/ISM aperture;
5. compute baryonic and dust budgets;
6. examine grain size, composition, and source tags;
7. construct spatial/radial diagnostics; and
8. export selected snapshots to SKIRT.