healpy.sphtfunc.blm_gauss

healpy.sphtfunc.blm_gauss(fwhm, lmax, pol=False)

Computes spherical harmonic coefficients of a circular Gaussian beam pointing towards the North Pole

The beam window function computed from these coefficients is consistent with the output of gauss_beam(), following the formalism described in Challinor et al. 2000 (astro-ph/0008228).

Changed in version 1.19.0: The formula was changed from exp(-0.5 * l^2 * sigma^2) to exp(-0.5 * l*(l+1) * sigma^2) to be consistent with gauss_beam() and the Challinor et al. 2000 paper. This is a breaking change that affects the computed spherical harmonic coefficients.

See an example of usage in the documentation

Parameters:

fwhmfloat, scalar

desired FWHM of the beam, in radians

lmaxint, scalar

maximum l multipole moment to compute

polbool, scalar

if True, E and B coefficients will also be computed

Returns:

blmarray with dtype numpy.complex128

lmax will be as specified mmax is 0 for pol==False, else 2