Module beam 

Radio astronomy beam (PSF) represented as a 2D elliptical Gaussian.

All stored values use FITS conventions: major/minor FWHM in degrees, PA in degrees East of North.

The beam algebra (convolution, deconvolution, and the Jy/beam flux-scaling factor) is implemented here from the standard second-moment / covariance formulation of an elliptical Gaussian:

• An elliptical Gaussian is described by a symmetric 2×2 covariance matrix C in (East, North) axes. Its eigenvalues are the squared axis lengths and its eigenvectors give the orientation.
• Convolving two Gaussians adds their covariance matrices; deconvolving subtracts them (valid only while the residual stays positive-definite).
• The integral of a 2D Gaussian is proportional to sqrt(det C), which yields the peak-amplitude / flux-rescaling factor as a ratio of determinants.

These are textbook results for combining Gaussian point-spread functions (see Wild 1970, Aust. J. Phys. 23, 113, for the radio-astronomy form). The same standard formulae underpin radio_beam and RACS-tools; this module is an independent implementation in terms of the covariance matrix and its eigendecomposition.

Structs

Beam

A 2D elliptical Gaussian beam in FITS conventions.

Enums

BeamError

Functions

gauss_factor

Flux-scaling factor for Jy/beam images after convolution to a larger beam.