Year: 2021
Type: article
Abstract: A crucial problem for partial sky analysis of CMB polarization is the E - B leakage problem. Such leakage arises from the presence of `ambiguous' modes that satisfy properties of both E and B modes. Solving this problem is critical for primordial polarization B mode detection in partial sky CMB polarization experiments. In this work we introduce a new method for reducing the leakage. We demonstrate that if we complement the E -mode information outside the observation patch with ancillary data from full-sky CMB observations, we can reduce and even effectively remove the E -to- B leakage. For this objective, we produce E -mode Stokes QU maps from Wiener filtered full-sky intensity and polarization CMB observations. We use these maps to fill the sky region that is not observed by the ground-based experiment of interest, and thus complement the partial sky Stokes QU maps. Since the E -mode information is now available on the full sky we see a significant reduction in the E -to- B leakage. We evaluate on simulated data sets the performance of our method for a `shallow' f sky = 8%, and a `deep' f sky = 2% northern hemisphere sky patch, with AliCPT-like properties, and a LSPE-like f sky = 30% sky patch, by combining those observations with Planck-like full sky polarization maps. We find that our method outperforms the standard and the pure- B method pseudo- C ℓ estimators for all of our simulations. Our new method gives unbiased estimates of the B -mode power spectrum through-out the entire multipole range with near-optimal pseudo- C ℓ errors for ℓ > 20. We also study the application of our method to the CMB-S4 experiment combined with LiteBIRD-like full sky data, and show that using signal-dominated full sky E -mode data we can eliminate the E -to- B leakage problem.
Authors: Shamik Ghosh, Jacques Delabrouille, Wen Zhao, Larissa Santos
Institutions: University of Science and Technology of China, Chinese Academy of Sciences, Centre National de la Recherche Scientifique, Commissariat à l'Énergie Atomique et aux Énergies Alternatives, Université Paris-Saclay, Observatoire de Paris, Laboratoire AstroParticule et Cosmologie, Sorbonne Paris Cité, Institut National de Physique Nucléaire et de Physique des Particules, Université Paris Diderot, Shanghai Jiao Tong University, Yangzhou University
Language: English
Subfield: Astronomy and Astrophysics
Field: Physics and Astronomy
Domain: Physical Sciences
Open Access status: bronze
OpenAlex ID: W3043772155