Search

We search for the signature of parity-violating physics in the cosmic microwave background, called cosmic birefringence, using the Planck data release 4. We initially find a birefringence angle of β=0.30°±0.11° (68% C.L.) for nearly full-sky data. The values of β decrease as we enlarge the Galactic mask, which can be interpreted as the effect of polarized foreground emission. Two independent ways to model this effect are used to mitigate the systematic impact on β for different sky fractions. We choose not to assign cosmological significance to the measured value of β until we improve our knowledge of the foreground polarization., Open access publication funded by the Max Planck Society., Planck is a project of the European Space Agency (ESA) with instruments provided by two scientific consortia funded by ESA member states and led by Principal Investigators from France and Italy, telescope reflectors provided through a collaboration between ESA and a scientific consortium led and funded by Denmark, and additional contributions from NASA (USA). Some of the results in this Letter have been derived using the HEALPix package. This research used resources of the National Energy Research Scientific Computing Center (NERSC), a U.S. Department of Energy Office of Science User Facility operated under Contract No. DE-AC02-05CH11231. Part of the research was carried out at the Jet Propulsion Laboratory, California Institute of Technology, under a contract with the National Aeronautics and Space Administration (80NM0018D0004). J. R. E., H. K. E., and I.W. acknowledge funding from the European Research Council (ERC) under the Horizon 2020 Research and Innovation Programme (Grant Agreement No. 819478). The work of Y. M. was supported in part by the Japan Society for the Promotion of Science (JSPS) KAKENHI, Grants No. JP20K14497. R. S. and D. S. acknowledge the support of the Natural Sciences and Engineering Research Council of Canada. P. D.-P. acknowledges financial support from the Formación del Profesorado Universitario (FPU) Programme of the Spanish Ministerio de Ciencia, Innovación y Universidades, and thanks the Max Planck Institute for Astrophysics for hospitality when this work was being finalized. P. D.-P., B. B., E.M.-G., and P. V. thank the Spanish Agencia Estatal de Investigación (AEI, MICIU) for the financial support provided under the projects with references PID2019-110610RB-C21, ESP2017-83921-C2-1-R and AYA2017-90675-REDC, co-funded with EU FEDER funds, and acknowledge supports from Universidad de Cantabria and Consejería de Universidades, Igualdad, Cultura y Deporte del Gobierno de Cantabria via the “Instrumentación y ciencia de datos para sondear la naturaleza del universo” project, as well as from Unidad de Excelencia María de Maeztu (MDM-2017-0765). The work of E. K. was supported in part by JSPS KAKENHI Grants No. JP20H05850 and No. JP20H05859, and the Deutsche Forschungsgemeinschaft (DFG, German Research Foundation) under Germany’s Excellence Strategy—EXC-2094–390783311. The Kavli I. P. M. U. is supported by World Premier International Research Center Initiative (WPI), MEXT, Japan.

The BeyondPlanck and Cosmoglobe collaborations have implemented the first integrated Bayesian end-to-end analysis pipeline for CMB experiments. The primary long-term motivation for this work is to develop a common analysis platform that supports efficient global joint analysis of complementary radio, microwave, and sub-millimeter experiments. A strict prerequisite for this to succeed is broad participation from the CMB community, and two foundational aspects of the program are therefore reproducibility and Open Science. In this paper, we discuss our efforts toward this aim. We also discuss measures toward facilitating easy code and data distribution, community-based code documentation, user-friendly compilation procedures, etc. This work represents the first publicly released end-to-end CMB analysis pipeline that includes raw data, source code, parameter files, and documentation. We argue that such a complete pipeline release should be a requirement for all major future and publicly-funded CMB experiments, noting that a full public release significantly increases data longevity by ensuring that the data quality can be improved whenever better processing techniques, complementary datasets, or more computing power become available, and thereby also taxpayers' value for money; providing only raw data and final products is not sufficient to guarantee full reproducibility in the future.