CaltechAUTHORS
Published March 1, 2026 | Version Published
Journal Article Open

BICEP/Keck. XX. Component-separated Maps of the Polarized Cosmic Microwave Background and Thermal Dust Emission Using Planck and BICEP/Keck Observations through the 2018 Observing Season

Creators

  • 1. ROR icon Cardiff University
  • 2. ROR icon Kavli Institute for Particle Astrophysics and Cosmology
  • 3. ROR icon SLAC National Accelerator Laboratory
  • 4. ROR icon University of British Columbia
  • 5. ROR icon Harvard-Smithsonian Center for Astrophysics
  • 6. ROR icon California Institute of Technology
  • 7. ROR icon University of Cincinnati
  • 8. ROR icon Stanford University
  • 9. ROR icon Jet Propulsion Lab
  • 10. ROR icon University of Chicago
  • 11. ROR icon National Institute of Standards and Technology
  • 12. ROR icon Argonne National Laboratory
  • 13. ROR icon University of Minnesota
  • 14. ROR icon CEA Grenoble
  • 15. ROR icon Harvard University
  • 16. ROR icon University of Illinois Urbana-Champaign
  • 17. ROR icon University of Cambridge
  • 18. ROR icon Boston University
  • 19. ROR icon Lawrence Berkeley National Laboratory

Abstract

We present component-separated polarization maps of the cosmic microwave background (CMB) and Galactic thermal dust emission, derived using data from the BICEP/Keck experiments through the 2018 observing season and Planck. By employing a maximum-likelihood method that utilizes observing matrices, we produce unbiased maps of the CMB and dust signals. We outline the computational challenges and demonstrate an efficient implementation of the component map estimator. We show methods to compute and characterize power spectra of these maps, opening up an alternative way to infer the tensor-to-scalar ratio from our data. We compare the results of this map-based separation method with the baseline BICEP/Keck analysis. Our analysis demonstrates consistency between the two methods, finding an 84% correlation between the pipelines.

Copyright and License

© 2026. The Author(s). Published by the American Astronomical Society. Original content from this work may be used under the terms of the Creative Commons Attribution 4.0 licence. Any further distribution of this work must maintain attribution to the author(s) and the title of the work, journal citation and DOI.

Acknowledgement

The BICEP/Keck projects have been made possible through a series of grants from the National Science Foundation, most recently including 2220444-2220448, 2216223, 1836010, and 1726917. The development of antenna-coupled detector technology was supported by the JPL Research and Technology Development Fund and by NASA grants 06-ARPA206-0040, 10-SAT10-0017, 12-SAT12-0031, 14-SAT14-0009, and 16-SAT-16-0002. The development and testing of focal planes was 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 quasi-optical filtering was provided by UK STFC grant ST/N000706/1. The computations in this paper 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 SLAC 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 during the observing seasons up until 2018: 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 BICEPone team. We also thank the Planck and WMAP teams for the use of their data.

We are grateful to Federico Bianchini and Radek Stompor for insightful discussions and to Josquin Errard for valuable comments on the manuscript.

Files

Ade_2026_ApJ_999_89.pdf

Files (17.9 MB)

Name Size
md5:a862832662ffbfd943b7454d803a10ec
17.9 MB Preview Download

Additional details

Related works

Is new version of
Discussion Paper: arXiv:2509.21648 (arXiv)

Funding

National Science Foundation
2220444-2220448
National Science Foundation
2216223
National Science Foundation
1836010
National Science Foundation
1726917
Jet Propulsion Laboratory
JPL Research and Technology Development Fund -
National Aeronautics and Space Administration
06-ARPA206-0040
National Aeronautics and Space Administration
10-SAT10-0017
National Aeronautics and Space Administration
12-SAT12-0031
National Aeronautics and Space Administration
14-SAT14-0009
National Aeronautics and Space Administration
16-SAT-16-0002
Gordon and Betty Moore Foundation
Canada Foundation for Innovation
Science and Technology Facilities Council
ST/N000706/1
Harvard University
United States Department of Energy

Dates

Submitted
2025-10-14
Accepted
2026-01-25
Available
2026-02-25
Published

Caltech Custom Metadata

Caltech groups
Astronomy Department , Physics Department , Division of Physics, Mathematics and Astronomy (PMA)
Publication Status
Published