healpy.sphtfunc.map2alm

healpy.sphtfunc.map2alm(maps, lmax=None, mmax=None, iter=3, pol=True, use_weights=False, datapath=None)

Computes the alm of an Healpix map.

Parameters:

maps : array-like, shape (Npix,) or (n, Npix)

The input map or a list of n input maps.

lmax : int, scalar, optional

Maximum l of the power spectrum. Default: 3*nside-1

mmax : int, scalar, optional

Maximum m of the alm. Default: lmax

iter : int, scalar, optional

Number of iteration (default: 3)

pol : bool, optional

If True, assumes input maps are TQU. Output will be TEB alm’s. (input must be 1 or 3 maps) If False, apply spin 0 harmonic transform to each map. (input can be any number of maps) If there is only one input map, it has no effect. Default: True.

use_weights: bool, scalar, optional

If True, use the ring weighting. Default: False.

datapath : None or str, optional

If given, the directory where to find the weights data.

Returns:

alms : array or tuple of array

alm or a tuple of 3 alm (almT, almE, almB) if polarized input.

Notes

The pixels which have the special UNSEEN value are replaced by zeros before spherical harmonic transform. They are converted back to UNSEEN value, so that the input maps are not modified. Each map have its own, independent mask.