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-Cℓ 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)

• Ari Cukierman
• Dominic Beck