A demonstration of improved constraints on primordial gravitational waves with delensing
We present a constraint on the tensor-to-scalar ratio, r , derived from measurements of cosmic microwave background (CMB) polarization B -modes with “delensing,” whereby the uncertainty on r contributed by the sample variance of the gravitational lensing B -modes is reduced by cross-correlating agai...
Published in: | Physical Review D |
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Main Authors: | , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , |
Format: | Article in Journal/Newspaper |
Language: | English |
Published: |
American Physical Society
2021
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Subjects: | |
Online Access: | https://orca.cardiff.ac.uk/id/eprint/138655/ https://doi.org/10.1103/PhysRevD.103.022004 https://orca.cardiff.ac.uk/id/eprint/138655/1/PhysRevD.103.022004.pdf |
Summary: | We present a constraint on the tensor-to-scalar ratio, r , derived from measurements of cosmic microwave background (CMB) polarization B -modes with “delensing,” whereby the uncertainty on r contributed by the sample variance of the gravitational lensing B -modes is reduced by cross-correlating against a lensing B -mode template. This template is constructed by combining an estimate of the polarized CMB with a tracer of the projected large-scale structure. The large-scale-structure tracer used is a map of the cosmic infrared background derived from Planck satellite data, while the polarized CMB map comes from a combination of South Pole Telescope, bicep/Keck, and Planck data. We expand the bicep/Keck likelihood analysis framework to accept a lensing template and apply it to the bicep/Keck dataset collected through 2014 using the same parametric foreground modeling as in the previous analysis. From simulations, we find that the uncertainty on r is reduced by ∼ 10 % , from σ ( r ) = 0.024 to 0.022, which can be compared with a ∼ 26 % reduction obtained when using a perfect lensing template or if there were zero lensing B -modes. Applying the technique to the real data, the constraint on r is improved from r 0.05 < 0.090 to r 0.05 < 0.082 (95% C.L.). This is the first demonstration of improvement in an r constraint through delensing. |
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