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Halo Catalogs and Centers

FOF/SUBFIND catalogs identify candidate structures, but the analysis center and spherical-overdensity quantities should be recomputed consistently for each snapshot.

halo_utils.py provides the shared FOF association, periodic centering, shrinking-sphere refinement, and M200c/R200c calculation. The 12-halo suite additionally uses zoom_halo_utils.py and the target metadata produced during candidate selection.

Required catalog quantities

For every halo and redshift, retain:

  • target identifier and matching method;
  • center and bulk velocity;
  • M200c and R200c;
  • distance to any low-resolution contaminant;
  • particle counts by type inside R200c; and
  • the aperture used for galaxy-integrated quantities.

Mstar, Mgas, SFR, metallicity, Mdust, D/G, and D/Z must not be labeled simply "halo properties" without an aperture. Use R200c for halo-wide budgets and an explicitly declared physical or scaled radius for the galaxy.

Tracking through time

Do not assume a fixed coordinate center. Match the target between catalogs and refine the center at each output. Likewise, raw dust displacement from BirthPos includes halo bulk motion; subtract the evolving halo trajectory before interpreting it as transport or outflow.