Improved Constraints on Primordial Gravitational Waves using Planck, WMAP, and BICEP/Keck Observations through the 2018 Observing Season

P. A.R. Ade, Z. Ahmed, M. Amiri, D. Barkats, R. Basu Thakur, C. A. Bischoff, D. Beck, J. J. Bock, H. Boenish, E. Bullock, V. Buza, J. R. Cheshire, J. Connors, J. Cornelison, M. Crumrine, A. Cukierman, E. V. Denison, M. Dierickx, L. Duband, M. EibenS. Fatigoni, J. P. Filippini, S. Fliescher, N. Goeckner-Wald, D. C. Goldfinger, J. Grayson, P. Grimes, G. Hall, G. Halal, M. Halpern, E. Hand, S. Harrison, S. Henderson, S. R. Hildebrandt, G. C. Hilton, J. Hubmayr, H. Hui, K. D. Irwin, J. Kang, K. S. Karkare, E. Karpel, S. Kefeli, S. A. Kernasovskiy, J. M. Kovac, C. L. Kuo, K. Lau, E. M. Leitch, A. Lennox, K. G. Megerian, L. Minutolo, L. Moncelsi, Y. Nakato, T. Namikawa, H. T. Nguyen, R. O’Brient, R. W. Ogburn, S. Palladino, T. Prouve, C. Pryke, B. Racine, C. D. Reintsema, S. Richter, A. Schillaci, R. Schwarz, B. L. Schmitt, C. D. Sheehy, A. Soliman, T. ST Germaine, B. Steinbach, R. V. Sudiwala, G. P. Teply, K. L. Thompson, J. E. Tolan, C. Tucker, A. D. Turner, C. Umiltà, C. Vergès, A. G. Vieregg, A. Wandui, A. C. Weber, D. V. Wiebe, J. Willmert, C. L. Wong, W. L.K. Wu, H. Yang, K. W. Yoon, E. Young, C. Yu, L. Zeng, C. Zhang, S. Zhang

Research output: Contribution to journalArticlepeer-review

177 Scopus citations


We present results from an analysis of all data taken by the BICEP2, Keck Array, and BICEP3 CMB polarization experiments up to and including the 2018 observing season. We add additional Keck Array observations at 220 GHz and BICEP3 observations at 95 GHz to the previous dataset. The maps now reach depths of 2.8, 2.8, and at 95, 150, and 220 GHz, respectively, over an effective area of square degrees at 95 GHz and square degrees at 150 and 220 GHz. The 220 GHz maps now achieve a signal-to-noise ratio on polarized dust emission exceeding that of Planck at 353 GHz. We take auto- and cross-spectra between these maps and publicly available WMAP and Planck maps at frequencies from 23 to 353 GHz and evaluate the joint likelihood of the spectra versus a multicomponent model of lensed . The foreground model has seven parameters, and no longer requires a prior on the frequency spectral index of the dust emission taken from measurements on other regions of the sky. This model is an adequate description of the data at the current noise levels. The likelihood analysis yields the constraint at 95% confidence. Running maximum likelihood search on simulations we obtain unbiased results and find that . These are the strongest constraints to date on primordial gravitational waves.

Original languageEnglish (US)
Article number151301
JournalPhysical review letters
Issue number15
StatePublished - Oct 8 2021

Bibliographical note

Funding Information:
The BICEP/Keck projects have been made possible through a series of grants from the National Science Foundation including Grants No. 0742818, No. 0742592, No. 1044978, No. 1110087, No. 1145172, No. 1145143, No. 1145248, No. 1639040, No. 1638957, No. 1638978, and No. 1638970, and by the Keck Foundation. The development of antenna-coupled detector technology was supported by the JPL Research and Technology Development Fund, and by NASA Grants No. 06-ARPA206-0040, No. 10-SAT10-0017, No. 12-SAT12-0031, No. 14-SAT14-0009, and No. 16-SAT-16-0002. The development and testing of focal planes were supported by the Gordon and Betty Moore Foundation at Caltech. Readout electronics were supported by a Canada Foundation for Innovation grant to UBC. Support for quasioptical filtering was provided by UK STFC Grant No. ST/N000706/1. The computations in this Letter were run on the Odyssey/Cannon cluster supported by the FAS Science Division Research Computing Group at Harvard University. The analysis effort at Stanford and S. L. A. C. is partially supported by the U.S. DOE Office of Science. We thank the staff of the U.S. Antarctic Program and in particular the South Pole Station without whose help this research would not have been possible. Most special thanks go to our heroic winter-overs Robert Schwarz, Steffen Richter, Sam Harrison, Grantland Hall, and Hans Boenish. We thank all those who have contributed past efforts to the BICEP/Keck series of experiments, including the BICEP1 team. We also thank the Planck and WMAP teams for the use of their data, and are grateful to the Planck team for helpful discussions.

Funding Information:
National Science Foundation W.?M. Keck Foundation Jet Propulsion Laboratory National Aeronautics and Space Administration Gordon and Betty Moore Foundation Canada Foundation for Innovation University of British Columbia Science and Technology Facilities Council Faculty of Arts and Sciences, Harvard University U.S. Department of Energy Office of Science

Publisher Copyright:
© 2021 American Physical Society


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