Emission-line models

Recipes

Each emission complex is an immutable recipe containing its fit window, components, line IDs, roles, profile multiplicities, kinematic bounds, coverage rules, and QA labels. Dedicated adapters implement Hβ/[O III], Mg II, Hα, and Lyα/N V; generic variable projection handles the remaining recipes.

Profiles and roles

  • Broad components represent the summed broad-line profile used for flux, centroid, dispersion, numerical FWHM, and EW.

  • Narrow components use narrower FWHM and velocity bounds.

  • Wing components are optional outflow-like profiles selected only when the relevant recipe supports them.

  • Fixed ratios and shared kinematics are encoded in recipe metadata.

For [O III], the default wing candidate must improve BIC by at least 20, have flux S/N of at least 5, be at least twice as broad as the narrow core, and have a centroid separated from the core by at least 150 km/s. The candidate diagnostics and rejection reasons are retained in result metadata.

Current UV defaults

  • Lyα: two broad Gaussians; N V: one broad effective 1240.14 Å blend.

  • C IV: three broad Gaussians at the unresolved 1549.06 Å blend, with velocities from -5000 to +3000 km/s.

  • C III]: two broad Gaussians at 1908.73 Å with velocities within \(\pm2000\) km/s.

  • No narrow UV components are included by default.

Current optical/NIR defaults

Dedicated recipes fit Mg II, Hβ/[O III], and Hα/[N II]/[S II]. The optical-blue and Paschen/NIR recipes are component-adaptive after the full window passes its minimum coverage requirement.

See Recipe reference for exact windows and components.