# The advantage of Bolometric Interferometry for controlling Galactic foreground contamination in CMB primordial B-modes measurements

**Authors:** E. Manzan, M. Regnier, J-Ch. Hamilton, A. Mennella, J. Errard, L. Zapelli, S. A. Torchinsky, S. Paradiso, E. Battistelli, M. Bersanelli, P. De Bernardis, M. De Petris, G. D'Alessandro, M. Gervasi, S. Masi, M. Piat, E. Rasztocky, G. E Romero, C. G. Scoccola, M. Zannoni  
**arXiv:** [2311.01814](https://arxiv.org/abs/2311.01814)  
**Date:** 2023-11-03  
**Summary page:** https://www.summarizepaper.com/en/paper/2311.01814v1/

## Key points

- Bolometric Interferometry (BI) offers advantages in controlling Galactic foreground contamination in measurements of the faint primordial B-mode polarization of the Cosmic Microwave Background (CMB)
- Three key requirements for present or future experiments in this field: utmost sensitivity, control over instrumental systematic effects, and control over Galactic foreground contamination
- BI combines bolometric detectors' sensitivity, interferometry's control over instrumental systematics, and software-based, tunable, in-band spectral resolution
- BI's spectral imaging capability allows for band-splitting during data analysis
- Study investigates how BI's spectral imaging capability can help detect residual contamination when an oversimplified model of foreground emission is assumed
- Comparison between CMB-S4 and hypothetical version based on BI called CMB-S4/BI in terms of sensitivities, frequency coverage, and sky coverage
- Analysis assumes line-of-sight (LOS) frequency decorrelation is present in dust emission but not accounted for during component separation
- Monte Carlo analysis using parametric component separation method FGBuster demonstrates how BI can diagnose presence of foreground residuals in estimates of tensor-to-scalar ratio r when unaccounted Galactic dust LOS frequency decorrelation occurs
- Overall study highlights how BI can provide better control over Galactic foreground contamination and improve measurements of primordial B-mode polarization in future experiments like CMB-S4.

## Summary

This paper explores the advantages of Bolometric Interferometry (BI) in controlling Galactic foreground contamination in measurements of the faint primordial B-mode polarization of the Cosmic Microwave Background (CMB). The authors highlight three key requirements for any present or future experiment in this field: utmost sensitivity, excellent control over instrumental systematic effects, and control over Galactic foreground contamination. BI is a novel technique that combines the sensitivity of bolometric detectors, the control of instrumental systematics from interferometry, and a software-based, tunable, in-band spectral resolution. This spectral imaging capability allows BI to perform band-splitting during data analysis. In this study, the authors investigate how BI's spectral imaging capability can help detect residual contamination when an oversimplified model of foreground emission is assumed in the analysis. To mimic this situation, they focus on CMB-S4 which is the next generation ground-based CMB experiment. They compare its anticipated sensitivities, frequency coverage and sky coverage with a hypothetical version of the same experiment based on BI called CMB-S4/BI. In their analysis they assume that line-of-sight (LOS) frequency decorrelation is present in dust emission but not accounted for during component separation. The authors present results from a Monte Carlo analysis based on a parametric component separation method called FGBuster. They demonstrate how BI has the potential to diagnose the presence of foreground residuals in estimates of the tensor-to-scalar ratio r when unaccounted Galactic dust LOS frequency decorrelation occurs. Overall this study highlights how BI can address one of the key challenges in CMB research by providing better control over Galactic foreground contamination. By combining bolometric detectors' sensitivity with interferometry's control over instrumental systematics and spectral imaging capabilities BI offers promising opportunities for improving measurements of primordial B-mode polarization in future experiments like CMB-S4.