Spectral imaging with QUBIC: building astrophysical components from Time-Ordered-Data using Bolometric Interferometry

Abstract The detection of B-modes in the CMB polarization pattern is a major issue in modern cosmology and must therefore be handled with analytical methods that produce reliable results. We describe a method that uses the frequency dependence of the QUBIC synthesized beam to perform component separation at the map-making stage, to obtain more precise results. We aim to demonstrate the feasibility of component separation during the map-making stage in time domain space. This new technique leads to a more accurate description of the data and reduces the biases in cosmological analyses. The method uses a library for highly parallel computation which facilitates the programming and allows the description of experiments as easily manipulated operators. These operators can be combined to obtain a joint analysis using several experiments to maximize precision. The results show that the method works well and permits end-to-end analysis for the CMB experiments, and in particular, for QUBIC. The method includes astrophysical foregrounds, and also systematic effects like gain variation in the detectors. We developed a software pipeline that produces uncertainties on the tensor-to-scalar ratio at the level of σ(r) ∼ 0.023 using only QUBIC simulated data.