QUBIC II: Spectro-Polarimetry with Bolometric Interferometry

TL;DR

This paper introduces bolometric interferometry as a spectral imaging technique for CMB studies, demonstrating its effectiveness with the QUBIC instrument in reconstructing sky maps and separating foregrounds.

Contribution

It presents a novel methodology for spectral imaging with bolometric interferometers, specifically applied to the QUBIC instrument for improved CMB polarization measurements.

Findings

Spectral imaging with QUBIC is nearly optimal up to five sub-bands.

The method effectively reconstructs point sources and Galactic dust maps.

Noise properties and sub-band correlations are well-characterized through simulations.

Abstract

Bolometric interferometry is a novel technique that has the ability to perform spectral imaging. A bolometric interferometer observes the sky in a wide frequency band and can reconstruct sky maps in several sub-bands within the physical band in post-processing of the data. This provides a powerful spectral method to discriminate between the cosmic microwave background (CMB) and astrophysical foregrounds. In this paper, the methodology is illustrated with examples based on the Q \& U Bolometric Interferometer for Cosmology (QUBIC) which is a ground-based instrument designed to measure the B-mode polarization of the sky at millimeter wavelengths. We consider the specific cases of point source reconstruction and Galactic dust mapping and we characterize the point spread function as a function of frequency. We study the noise properties of spectral imaging, especially the correlations between sub-bands, using end-to-end simulations together with a fast noise simulator. We conclude showing that spectral imaging performance are nearly optimal up to five sub-bands in the case of QUBIC.