pS²HAT // `"pure S²HAT"` // - S²HAT-based pure E/B harmonic transforms

Features & functionality

The routines allow efficient, parallel calculation of the so-called 'pure' polarized multipoles (see Smith (2006)). The computed multipole coefficients are equal to the standard pseudo-multipoles calculated for the apodized sky maps of the Stokes parameters Q and U subsequently corrected by so-called counterterms. If the applied apodizations fullfill certain boundary conditions, these multipoles correspond to the pure multipoles. Pure multipoles of one type, i.e., either E or B, are ensured not to contain contributions from the other one, at least to within numerical artifacts. They can be therefore further used in the estimation of the sky power spectra via the pseudo power spectrum technique, which has to however correctly account for the applied apodization on the one hand, and the presence of the counterterms, on the other.

In addition, the package contains the routines permitting calculation of the spin-weighted apodizations, given an input scalar, i.e., spin-0 window. The former are needed to compute the counterterms. It also provides routines for maps and window manipulations.

The package implements the formalism as described in the paper by Grain, Tristram and Stompor, Physical Review D, 79, 123515, (2009) (also available as arXiv:0903.2350).

The routines are written in C and based on the S²HAT library, which is used to perform all required spherical harmonic transforms as well as all inter-processor communication. They are therefore parallelized using MPI and follow the distributed-memory computational model. The data distribution patterns, pixelization choices, conventions etc are all as those assumed/allowed by the S²HAT library.

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Software

The current version of the package is a version v1.10 beta and can be downloaded from here. (The last update: June, 15, 2009 and the log file of the recent changes (since the version 1.00) is here.) The software is distributed as is with the hope that it will be found useful but with all the caveats as implied by the GNU public license.

The on-line documentation is available here.

Please quote this website: http://www.apc.univ-paris7.fr/APC_CS/Recherche/Adamis/MIDAS09/software.html and the paper: Grain, J., Tristram, M., Stompor, R., Phys. Rev. D. 79, 123515, (2009), whenever using this package.

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Contact info/bug tracker

This package has been developed by J. Grain (APC, Paris/IAS, Orsay), R. Stompor (APC, Paris), and M. Tristram (LAL, Orsay).

Please report any issues, comments, suggestions via our bug tracking site (an external link).

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Acknowledgments

This work has been supported in part by:

the European Community Marie Curie International Reintergration grant (FP6) (2006-2008);
the Agence National de Recherche grant MIDAS awarded under the ANR-Calcul Intensif programme (2010-2012).
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Relevant links

This package requires the S²HAT library to be ported on your platform. It can be found here.

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Centre National de la Recherche Scientifique
Laboratoire Astroparticule et Cosmologie
Equipe de Traitement des Données et Simulations (ADAMIS)