B-sure. Part II. Scattering transforms as robustness test for tensor-to-scalar ratio detection from CMB observations
Abstract
Galactic foregrounds represent a major contamination to the measurement of primordial B-modes from observations of the Cosmic Microwave Background polarisation. Even after the application of component separation algorithms, foreground residuals may potentially still bias the estimate of the tensor-to-scalar ratio r, causing a false detection. In this work, we present the methodology of a robustness test for the validation of an eventual detection of primordial B-modes, as obtained by a future, LiteBIRD-like satellite experiment. The goal of the test is to identify the foreground residuals contamination by looking for non-Gaussian properties in the CMB B-modes map, recovered through blind component separation algorithms. We adopt scattering transforms (ST) as our summary statistics sensitive to the non-Gaussian features of foreground residuals and to their correlation with foregrounds tracer maps. We characterise and validate the methodology on realistic sky simulations with different levels of foregrounds complexity. The proposed test is able to identify a bias on the tensor-to-scalar ratio of ≳ 10−3 in ∼ 90% of our simulations, with this bias value being of the same order of the accuracy targeted by LiteBIRD. Additionally, for our particular experimental configuration, the test is passed when the bias is lower than the sensitivity on the r parameter, and no warning is raised. These results provide an important step forward in the development of statistical tools for validating future measurement of cosmological parameters, against foregrounds contamination.
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BibTeX
@misc{ranucci2026bsure,
title = {{$B$-sure. Part II. Scattering transforms as robustness test for tensor-to-scalar ratio detection from CMB observations}},
author = {Claudio Ranucci and Sébastien Pierre and Léo Vacher and Alessandro Carones and Nicoletta Krachmalnicoff and Erwan Allys and Jean-Marc Delouis and Paolo Campeti and Giuseppe Puglisi and Carlo Baccigalupi},
howpublished = {HAL},
year = {2026},
month = sep,
doi = {10.48550/arxiv.2609.17531},
eprint = {2609.17531},
archivePrefix = {arXiv},
url = {https://hal.science/hal-05769632v1},
note = {CC BY-NC-SA 4.0},
}
RIS
TY - UNPB
TI - B-sure. Part II. Scattering transforms as robustness test for tensor-to-scalar ratio detection from CMB observations
AU - Claudio Ranucci
AU - Sébastien Pierre
AU - Léo Vacher
AU - Alessandro Carones
AU - Nicoletta Krachmalnicoff
AU - Erwan Allys
AU - Jean-Marc Delouis
AU - Paolo Campeti
AU - Giuseppe Puglisi
AU - Carlo Baccigalupi
PY - 2026
DA - 2026/09/15
PB - HAL
DO - 10.48550/arxiv.2609.17531
UR - https://hal.science/hal-05769632v1
AB - Galactic foregrounds represent a major contamination to the measurement of primordial B-modes from observations of the Cosmic Microwave Background polarisation. Even after the application of component separation algorithms, foreground residuals may potentially still bias the estimate of the tensor-to-scalar ratio r, causing a false detection. In this work, we present the methodology of a robustness test for the validation of an eventual detection of primordial B-modes, as obtained by a future, LiteBIRD-like satellite experiment. The goal of the test is to identify the foreground residuals contamination by looking for non-Gaussian properties in the CMB B-modes map, recovered through blind component separation algorithms. We adopt scattering transforms (ST) as our summary statistics sensitive to the non-Gaussian features of foreground residuals and to their correlation with foregrounds tracer maps. We characterise and validate the methodology on realistic sky simulations with different levels of foregrounds complexity. The proposed test is able to identify a bias on the tensor-to-scalar ratio of ≳ 10^−3 in ∼ 90% of our simulations, with this bias value being of the same order of the accuracy targeted by LiteBIRD. Additionally, for our particular experimental configuration, the test is passed when the bias is lower than the sensitivity on the r parameter, and no warning is raised. These results provide an important step forward in the development of statistical tools for validating future measurement of cosmological parameters, against foregrounds contamination.
ER -