Continuum and preprocessing model

Galactic foreground

File workflows query a two-dimensional foreground map and evaluate the Fitzpatrick (1999) Milky Way law in the observed frame:

\[f_{\lambda,\mathrm{corrected}} = f_{\lambda,\mathrm{observed}}\,10^{0.4 A_\lambda}.\]

Planck GNILC is the default. SFD values are multiplied by 0.86 following Schlafly & Finkbeiner (2011).

Power law and Fe II

The AGN continuum includes a pivoted power law. mode="single" uses one slope. mode="double" uses a continuous broken law with independent slopes on either side of a configurable 4661 Å break. mode="auto" compares both models on a shared accepted-pixel mask and selects the broken law only for a default \(\Delta\mathrm{BIC}\ge10\).

\[f_\lambda = N\left(\frac{\lambda}{\lambda_\mathrm{pivot}}\right)^\alpha,\]

plus independently broadened UV and optical Fe II templates when the spectrum and template overlap sufficiently.

Balmer pseudo-continuum

The production Balmer component is continuous at the 3646 Å edge. Above the edge it uses the velocity-shifted, velocity-broadened high-order Balmer series \(H(\lambda)\). Below the edge, the bound-free shape \(C(\lambda)\) is normalized by the high-order blend at the edge:

\[\begin{split}F(\lambda)=A \begin{cases} H(3646)\,C(\lambda)/C(3646), & \lambda \le 3646\\ H(\lambda), & \lambda > 3646. \end{cases}\end{split}\]

The default series uses \(n=6\)–400, fixed \(T_e=15000\,\mathrm{K}\) and \(\tau_{3646}=1\), with fitted amplitude, FWHM, and velocity. Diagnostic outputs retain separate balmer_bound_free and balmer_high_order_series arrays.

Continuum masks

Only configured continuum windows contribute to the fit. Additional mask windows remove known line contamination. Blue-side pixels below the initial continuum by more than three spectral uncertainties are rejected once below 3500 Å.

See Configuration reference for configurable behavior.