Point Spread Functions

GalPaK provides the two most common PSF : Gaussian and Moffat.

You may use them as the psf argument of the Instrument, as described here.

Gaussian

All instruments use this PSF model by default, with their own configuration :

class galpak.GaussianPointSpreadFunction(fwhm=None, pa=0, ba=1.0)[source]

The default Gaussian Point Spread Function.

fwhm: float
Full Width Half Maximum in arcsec, aka. “seeing”.
pa: float [default is 0.]
Position Angle, clockwise rotation from Y of ellipse, in angular degrees.
ba: float [default is 1.0]
Axis ratio of the ellipsis, b/a ratio (y/x).

Moffat

class galpak.MoffatPointSpreadFunction(fwhm=None, alpha=None, beta=None, pa=None, ba=None)[source]

The Moffat Point Spread Function

fwhm if alpha is None: float [in arcsec]
Moffat’s distribution fwhm variable : http://en.wikipedia.org/wiki/Moffat_distribution
alpha if fwhm is None: float [in arcsec]
Moffat’s distribution alpha variable : http://en.wikipedia.org/wiki/Moffat_distribution
beta: float
Moffat’s distribution beta variable : http://en.wikipedia.org/wiki/Moffat_distribution
pa: float [default is 0.]
Position Angle, the clockwise rotation from Y of ellipse, in angular degrees.
ba: float [default is 1.0]
Axis ratio of the ellipsis, b/a ratio (y/x).

Interface

In order to furthermore customize the PSF you want to use, you can create your own PSF class and use it in the instrument, it simply needs to implement the following interface :

class galpak.PointSpreadFunction[source]

This is the interface all Point Spread Functions (PSF) should implement.

as_image(for_cube)[source]

Should return this PSF as a 2D image shaped [for_cube].

for_cube: HyperspectralCube
Has additional properties computed and attributed by GalPaK :
  • xy_step (in ”)
  • z_step (in µm)
  • z_central (in µm)
Return type:ndarray