Making maps of cosmic microwave background polarization for B-mode studies: The POLARBEAR example

Davide Poletti, Giulio Fabbian, Maude Le Jeune, Julien Peloton, Kam Arnold, Carlo Baccigalupi, Darcy Barron, Shawn Beckman, Julian Borrill, Scott Chapman, Yuji Chinone, Ari Cukierman, Anne Ducout, Tucker Elleflot, Josquin Errard, Stephen Feeney, Neil Goeckner-Wald, John Groh, Grantland Hall, Masaya HasegawaMasashi Hazumi, Charles Hill, Logan Howe, Yuki Inoue, Andrew H. Jaffe, Oliver Jeong, Nobuhiko Katayama, Brian Keating, Reijo Keskitalo, Theodore Kisner, Akito Kusaka, Adrian T. Lee, David Leon, Eric Linder, Lindsay Lowry, Frederick Matsuda, Martin Navaroli, Hans Paar, Giuseppe Puglisi, Christian L. Reichardt, Colin Ross, Praween Siritanasak, Nathan Stebor, Bryan Steinbach, Radek Stompor, Aritoki Suzuki, Osamu Tajima, Grant Teply, Nathan Whitehorn

Research output: Contribution to journalArticlepeer-review

13 Scopus citations


Analysis of cosmic microwave background (CMB) datasets typically requires some filtering of the raw time-ordered data. For instance, in the context of ground-based observations, filtering is frequently used to minimize the impact of low frequency noise, atmospheric contributions and/or scan synchronous signals on the resulting maps. In this work we have explicitly constructed a general filtering operator, which can unambiguously remove any set of unwanted modes in the data, and then amend the map-making procedure in order to incorporate and correct for it. We show that such an approach is mathematically equivalent to the solution of a problem in which the sky signal and unwanted modes are estimated simultaneously and the latter are marginalized over. We investigated the conditions under which this amended map-making procedure can render an unbiased estimate of the sky signal in realistic circumstances. We then discuss the potential implications of these observations on the choice of map-making and power spectrum estimation approaches in the context of B-mode polarization studies. Specifically, we have studied the effects of time-domain filtering on the noise correlation structure in the map domain, as well as impact it may haveon the performance of the popular pseudo-spectrum estimators. We conclude that although maps produced by the proposed estimators arguably provide the most faithful representation of the sky possible given the data, they may not straightforwardly lead to the best constraints on the power spectra of the underlying sky signal and special care may need to be taken to ensure this is the case. By contrast, simplified map-makers which do not explicitly correct for time-domain filtering, but leave it to subsequent steps in the data analysis, may perform equally well and be easier and faster to implement. We focused on polarization-sensitive measurements targeting the B-mode component of the CMB signal and apply the proposed methods to realistic simulations based on characteristics of an actual CMB polarization experiment, POLARBEAR. Our analysis and conclusions are however more generally applicable.

Original languageEnglish
Article numberA60
JournalAstronomy and Astrophysics
StatePublished - 1 Apr 2017


  • Cosmic background radiation
  • Cosmology: Observations


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