lightweight pure pseudo-Cl estimator for HEALPix
Use with caution - not tested!
pip install . [--user]
Compute pure E- and B-mode spherical harmonic coefficients
import pur
alm=pur.map2alm_pure(map,mask)
cl=hp.alm2cl(alm)
Compute mode-coupling matrix corresponding to these pseudeo-power spectra
import healpy
mcl=healpy.anafast(mask)
mcm=pur.compute_mcm(mcl,lmax=500,pe1=False,pe2=False,pb1=True,pb2=True) # This assumes non-pure E-modes and pure B-modes in the mode-coupling matrix
That's it!
The framework of E- and B-purification and mode-coupling-matrix computation is outlined in
- K. Smith, Pseudo-Cโ estimators which do not mix E and B modes (2006)
- J. Grain et al, Polarized CMB power spectrum estimation using the pure pseudo-cross-spectrum approach (2009)
Parts of this package evolved from code provided in
- NaMaster (https://github.com/LSSTDESC/NaMaster)
- pspy (https://github.com/simonsobs/pspy)
- healpy (https://github.com/healpy/healpy)