kinextract.gauss_hermite_losvd_model_ho

kinextract.gauss_hermite_losvd_model_ho(v: ndarray, amp: float, vel: float, sig: float, *hn: float) → ndarray[source]

Higher-order Gauss-Hermite LOSVD model, van der Marel & Franx (1993) convention.

Evaluates amp * exp(-w^2/2) / (sqrt(2*pi)*sig) * (1 + sum_i hn[i] * H_{i+3}(w)) where w = (v - vel) / sig and H_n are the vdM1993-normalized Gauss-Hermite polynomials (see _gh_poly_vdm()). Unlike gauss_hermite_losvd_model(), this supports an arbitrary number of higher-order moments (h3, h4, h5, h6, …) passed positionally via *hn, enabling a more flexible characterization of non-Gaussian LOSVD wings. Uses the same polynomial normalization as pPXF, which is numerically distinct from the legacy fortran convention used by gauss_hermite_losvd_model() — do not compare h3/h4 values between the two model functions directly.

Parameters:

  • v (ndarray) – Velocities (km/s) at which to evaluate the model.

  • amp (float) – Overall normalization (total flux/area under the LOSVD).

  • vel (float) – Mean velocity V (km/s).

  • sig (float) – Velocity dispersion sigma (km/s). Must be positive and finite; if not, the model returns an array of NaN with the same shape as v.

  • *hn (float) – Higher-order Gauss-Hermite moments h3, h4, h5, … (dimensionless), in ascending order starting at h3.

Returns:

Model LOSVD amplitude evaluated at each v, same shape as v. All-NaN if sig is non-positive or non-finite.

Return type:

ndarray