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Title: No evidence for dust B -mode decorrelation in Planck data

Constraints on inflationary B modes using cosmic microwave background polarization data commonly rely on either template cleaning or cross-spectra between maps at different frequencies to disentangle Galactic foregrounds from the cosmological signal. Assumptions about how the foregrounds scale with frequency are therefore crucial to interpreting the data. Recent results from the Planck satellite collaboration claim significant evidence for a decorrelation in the polarization signal of the spatial pattern of Galactic dust between 217 and 353 GHz. Such a decorrelation would suppress power in the cross-spectrum between high-frequency maps, where the dust is strong, and lower-frequency maps, where the sensitivity to cosmological B modes is strongest. Alternatively, it would leave residuals in lower-frequency maps cleaned with a template derived from the higher-frequency maps. If not accounted for, both situations would result in an underestimate of the dust contribution and thus an upward bias on measurements of the tensor-to-scalar ratio, r. In this paper, we revisit this measurement and find that the no-decorrelation hypothesis cannot be excluded with the Planck data. There are three main reasons for this: (i) There is significant noise bias in cross-spectra between Planck data splits that needs to be accounted for. (ii) There is strong evidence formore » unknown instrumental systematics, the amplitude of which we estimate using alternative Planck data splits. (iii) There are significant correlations between measurements in different sky patches that need to be taken into account when assessing the statistical significance. Finally, between ℓ = 55-90 and over 72% of the sky, the dust BB correlation between 217 and 353 GHz is 1.001 +.004/.021 -.004/.000 (68% stat/syst.) and shows no significant trend with the sky fraction.« less
Authors:
 [1] ;  [1]
  1. Brookhaven National Lab. (BNL), Upton, NY (United States). Physics Dept.
Publication Date:
Report Number(s):
BNL-203365-2018-JAAM
Journal ID: ISSN 2470-0010
Grant/Contract Number:
SC0012704
Type:
Accepted Manuscript
Journal Name:
Physical Review D
Additional Journal Information:
Journal Volume: 97; Journal Issue: 4; Journal ID: ISSN 2470-0010
Publisher:
American Physical Society (APS)
Research Org:
Brookhaven National Lab. (BNL), Upton, NY (United States)
Sponsoring Org:
USDOE; BNL Laboratory Directed Research and Development (LDRD) Program
Country of Publication:
United States
Language:
English
Subject:
79 ASTRONOMY AND ASTROPHYSICS; cosmic microwave background; inflation; radio, microwave, & sub-mm astronomy
OSTI Identifier:
1430840

Sheehy, Christopher, and Slosar, Anze. No evidence for dust B -mode decorrelation in Planck data. United States: N. p., Web. doi:10.1103/PhysRevD.97.043522.
Sheehy, Christopher, & Slosar, Anze. No evidence for dust B -mode decorrelation in Planck data. United States. doi:10.1103/PhysRevD.97.043522.
Sheehy, Christopher, and Slosar, Anze. 2018. "No evidence for dust B -mode decorrelation in Planck data". United States. doi:10.1103/PhysRevD.97.043522.
@article{osti_1430840,
title = {No evidence for dust B -mode decorrelation in Planck data},
author = {Sheehy, Christopher and Slosar, Anze},
abstractNote = {Constraints on inflationary B modes using cosmic microwave background polarization data commonly rely on either template cleaning or cross-spectra between maps at different frequencies to disentangle Galactic foregrounds from the cosmological signal. Assumptions about how the foregrounds scale with frequency are therefore crucial to interpreting the data. Recent results from the Planck satellite collaboration claim significant evidence for a decorrelation in the polarization signal of the spatial pattern of Galactic dust between 217 and 353 GHz. Such a decorrelation would suppress power in the cross-spectrum between high-frequency maps, where the dust is strong, and lower-frequency maps, where the sensitivity to cosmological B modes is strongest. Alternatively, it would leave residuals in lower-frequency maps cleaned with a template derived from the higher-frequency maps. If not accounted for, both situations would result in an underestimate of the dust contribution and thus an upward bias on measurements of the tensor-to-scalar ratio, r. In this paper, we revisit this measurement and find that the no-decorrelation hypothesis cannot be excluded with the Planck data. There are three main reasons for this: (i) There is significant noise bias in cross-spectra between Planck data splits that needs to be accounted for. (ii) There is strong evidence for unknown instrumental systematics, the amplitude of which we estimate using alternative Planck data splits. (iii) There are significant correlations between measurements in different sky patches that need to be taken into account when assessing the statistical significance. Finally, between ℓ = 55-90 and over 72% of the sky, the dust BB correlation between 217 and 353 GHz is 1.001 +.004/.021-.004/.000 (68% stat/syst.) and shows no significant trend with the sky fraction.},
doi = {10.1103/PhysRevD.97.043522},
journal = {Physical Review D},
number = 4,
volume = 97,
place = {United States},
year = {2018},
month = {2}
}