Simons Observatory: Constraining inflationary gravitational waves with multitracer B-mode delensing

Journal Article · 09 January 2022 · Physical Review D

DOI: https://doi.org/10.1103/physrevd.105.023511 · OSTI ID:1856230

Namikawa, Toshiya  ^[1]; Lizancos, Anton Baleato ^[2]; Robertson, Naomi ^[3]; Sherwin, Blake D. ^[4]; Challinor, Anthony ^[5]; Alonso, David ^[6]; Azzoni, Susanna ^[7]; Baccigalupi, Carlo ^[8]; Calabrese, Erminia ^[9]; Carron, Julien ^[10]; Chinone, Yuji ^[11]; Chluba, Jens ^[12]; Coppi, Gabriele ^[13]; Errard, Josquin ^[14]; Fabbian, Giulio ^[15]; Ferraro, Simone ^[16]; Kalaja, Alba ^[17]; Lewis, Antony ^[18]; Madhavacheril, Mathew S. ^[19]; Meerburg, P. Daniel ^[17] ; Meyers, Joel ^[20]; Nati, Federico ^[13]; Orlando, Giorgio ^[17]; Poletti, Davide ^[21]; Puglisi, Giuseppe ^[22]; Remazeilles, Mathieu ^[12]; Sehgal, Neelima ^[23]; Tajima, Osamu ^[24]; Teply, Grant ^[25]; van Engelen, Alexander ^[26]; Wollack, Edward J. ^[27]; Xu, Zhilei ^[28]; Yu, Byeonghee ^[29]; Zhu, Ningfeng ^[30]; Zonca, Andrea ^[25]

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1. Univ. of Tokyo (Japan). Kavli Institute for the Physics and Mathematics of the Universe (WPI); Univ. of Cambridge (United Kingdom)
2. Institute of Astronomy, Cambridge (United Kingdom); Kavli Institute for Cosmology Cambridge (United Kingdom); Univ. of California, Berkeley, CA (United States); Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)
3. Institute of Astronomy, Cambridge (United Kingdom)
4. Univ. of Cambridge (United Kingdom); Kavli Institute for Cosmology Cambridge (United Kingdom)
5. Institute of Astronomy, Cambridge (United Kingdom); Univ. of Cambridge (United Kingdom); Kavli Institute for Cosmology Cambridge (United Kingdom)
6. Univ. of Oxford (United Kingdom)
7. Univ. of Oxford (United Kingdom); Univ. of Tokyo (Japan). Kavli Institute for the Physics and Mathematics of the Universe (WPI)
8. International School for Advanced Studies (SISSA), Trieste (Italy); Institute for Fundamental Physics of the Universe (IFPU), Grignano (Italy); Istituto Nazionale di Fisica Nucleare (INFN), Trieste (Italy)
9. Cardiff Univ., Wales (United Kingdom)
10. Univ. of Geneva (Switzerland)
11. Univ. of Tokyo (Japan). Research Center for the Early Universe; Univ. of Tokyo (Japan). Kavli Institute for the Physics and Mathematics of the Universe (WPI)
12. Univ. of Manchester (United Kingdom)
13. Univ. of Milano-Bicocca (Italy)
14. Univ. of Paris (France)
15. Flatiron Institute, New York, NY (United States); Cardiff Univ., Wales (United Kingdom)
16. Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)
17. Univ. of Groningen (Netherlands). Van Swinderen Institute for Particle Physics and Gravity
18. Univ. of Sussex, Brighton (United Kingdom)
19. Perimeter Inst. for Theoretical Physics, Waterloo, ON (Canada). Centre for the Universe
20. Southern Methodist Univ., Dallas, TX (United States)
21. Univ. of Milano-Bicocca (Italy); INFN sezione di Milano-Bicocca, Milano (Italy)
22. Tor Vergata Univ. of Rome (Italy); Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)
23. Stony Brook Univ., NY (United States)
24. Kyoto Univ. (Japan)
25. Univ. of California, San Diego, CA (United States)
26. Arizona State Univ., Tempe, AZ (United States)
27. NASA Goddard Space Flight Center (GSFC), Greenbelt, MD (United States)
28. Massachusetts Inst. of Technology (MIT), Cambridge, MA (United States)
29. Univ. of California, Berkeley, CA (United States)
30. Univ. of Pennsylvania, Philadelphia, PA (United States)

We introduce and validate a delensing framework for the Simons Observatory (SO), which will be used to improve constraints on inflationary gravitational waves by reducing the lensing noise in measurements of the B modes in CMB polarization. SO will initially observe CMB by using three small aperture telescopes and one large-aperture telescope. While polarization maps from small-aperture telescopes will be used to constrain inflationary gravitational waves, the internal CMB lensing maps used to delens will be reconstructed from data from the large-aperture telescope. Since lensing maps obtained from the SO data will be noise dominated on subdegree scales, the SO lensing framework constructs a template for lensing-induced B modes by combining internal CMB lensing maps with maps of the cosmic infrared background from Planck as well as galaxy density maps from the LSST survey. We construct a likelihood for constraining the tensor-to-scalar ratio r that contains auto and cross spectra between observed B modes and the lensing B-mode template. We test our delensing analysis pipeline on map-based simulations containing survey nonidealities, but that, for this initial exploration, does not include contamination from Galactic and extragalactic foregrounds. We find that the SO survey masking and inhomogeneous and atmospheric noise have very little impact on the delensing performance, and the r constraint becomes σ(r)≈0.0015 which is close to that obtained from the idealized forecasts in the absence of the Galactic foreground and is nearly a factor of 2 tighter than without delensing. We also find that uncertainties in the external large-scale structure tracers used in our multitracer delensing pipeline lead to bias much smaller than the 1σ statistical uncertainties.

• Research Organization: Lawrence Berkeley National Laboratory (LBNL), Berkeley, CA (United States); Southern Methodist Univ., Dallas, TX (United States); Stony Brook University, NY (United States)
• Sponsoring Organization: European Research Council (ERC); Isaac Newton Trust Early Career Grant; JSPS KAKENHI; National Science Foundation (NSF); UK Science and Technology Facilities Council (STFC); USDOE; USDOE Office of Science (SC); World Premier International Research Center Initiative (WPI)
• Grant/Contract Number: AC02-05CH11231; SC0010129; SC0020441
• OSTI ID: 1856230
• Journal Information: Physical Review D, Journal Name: Physical Review D Journal Issue: 2 Vol. 105; ISSN 2470-0010
• Publisher: American Physical Society (APS)Copyright Statement
• Country of Publication: United States
• Language: English