A Demonstration of Improved Constraints on Primordial Gravitational Waves with Delensing. (arXiv:2011.08163v1 [astro-ph.CO])

A Demonstration of Improved Constraints on Primordial Gravitational Waves with Delensing. (arXiv:2011.08163v1 [astro-ph.CO])
<a href="http://arxiv.org/find/astro-ph/1/au:+BICEP/Keck/0/1/0/all/0/1">BICEP/Keck</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Collaboration_SPTpol/0/1/0/all/0/1">SPTpol Collaborations</a>: <a href="http://arxiv.org/find/astro-ph/1/au:+Ade_P/0/1/0/all/0/1">P. A. R. Ade</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Ahmed_Z/0/1/0/all/0/1">Z. Ahmed</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Amiri_M/0/1/0/all/0/1">M. Amiri</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Anderson_A/0/1/0/all/0/1">A. J. Anderson</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Austermann_J/0/1/0/all/0/1">J. E. Austermann</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Avva_J/0/1/0/all/0/1">J. S. Avva</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Barkats_D/0/1/0/all/0/1">D. Barkats</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Thakur_R/0/1/0/all/0/1">R. Basu Thakur</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Beall_J/0/1/0/all/0/1">J. A. 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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 data set collected through 2014
using the same parametric foreground modelling as in the previous analysis.
From simulations, we find that the uncertainty on $r$ is reduced by $sim10%$,
from $sigma(r)$= 0.024 to 0.022, which can be compared with a $sim26%$
reduction obtained when using a perfect lensing template. 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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