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Using inpainting to construct accurate cut-sky CMB estimators

Accepted version
Peer-reviewed

Type

Article

Change log

Authors

Gruetjen, HF 
Fergusson, JR 
Liguori, M 
Shellard, EPS 

Abstract

The direct evaluation of manifestly optimal, cut-sky cosmic microwave background (CMB) power spectrum and bispectrum estimators is numerically very costly, due to the presence of inverse-covariance filtering operations. This justifies the investigation of alternative approaches. In this work, we mostly focus on an inpainting algorithm that was introduced in recent CMB analyses to cure cut-sky suboptimalities of bispectrum estimators. First, we show that inpainting can equally be applied to the problem of unbiased estimation of power spectra. We then compare the performance of a novel inpainted CMB temperature power spectrum estimator to the popular apodized pseudo-Cl (PCL) method and demonstrate, both numerically and with analytic arguments, that inpainted power spectrum estimates significantly outperform PCL estimates. Finally, we study the case of cut-sky bispectrum estimators, comparing the performance of three different approaches: inpainting, apodization and a novel low-l leaning scheme. Providing an analytic argument of why the local shape is typically most affected we mainly focus on local-type non-Gaussianity. Our results show that inpainting allows us to achieve optimality also for bispectrum estimation, but interestingly also demonstrate that appropriate apodization, in conjunction with low-l cleaning, can lead to comparable accuracy.

Description

Keywords

astro-ph.CO, astro-ph.CO, astro-ph.IM

Journal Title

Physical Review D - Particles, Fields, Gravitation and Cosmology

Conference Name

Journal ISSN

2470-0010
2470-0029

Volume Title

95

Publisher

American Physical Society
Sponsorship
Science and Technology Facilities Council (ST/L000636/1)
Science and Technology Facilities Council (ST/J005673/1)
Science and Technology Facilities Council (ST/K00333X/1)
Science and Technology Facilities Council (ST/M007065/1)
Science and Technology Facilities Council (ST/P000673/1)
Science and Technology Facilities Council (ST/H008586/1)
H. F. G. gratefully acknowledges the support of the Studienstiftung des deutschen Volkes, an Science and Technology Funding Council (STFC) studentship and a studentship of the Centre for Theoretical Cosmology (CTC), Department for Applied Mathematics and Theoretical Physics (DAMTP). This work was supported by an STFC consolidated Grant No. ST/L000636/1. It was undertaken on the COSMOS Shared Memory system at DAMTP, University of Cambridge, operated on behalf of the STFC Distributed Research utilising Advanced Computing (DiRAC) High Performance Computing (HPC) Facility. This equipment is funded by Business Innovation and Skills (BIS) National E-infrastructure capital Grant No. ST/J005673/1 and STFC Grants No. ST/H008586/1 and No. ST/K00333X/1.