QUBIC: the Q & U Bolometric Interferometer for Cosmology

C. G. SCOCCOLA; AND THE QUBIC COLLABORATION

Buenos Aires

Congreso; Workshop "Dark Side of the Universe"; 2019

Remnant radiation from the early universe, known as the Cosmic Microwave Background (CMB), has been redshifted and cooled, and today has a blackbody spectrum peaking in the THz region. One of the major challenges of modern cosmology is the detection of B-mode polarization anisotropies in the CMB. These originates from tensor fluctuations of the metric produced during the inflationary phase. The expected level of these anisotropies is however so small that it requires a new generation of instruments with high sensitivity and extremely good control of systematic effects. The QUBIC (Q&U Bolometric Interferometer for Cosmology) instrument is designed to map the very faint polarization structure in the CMB. QUBIC is based on the novel concept of bolometric interferometry in conjunction with synthetic imaging. It will have a large array of input feedhorns, which creates a large number of interferometric baselines. The later enable a precise control of the systematics of the  instrument. The bolometers are TES (Transition Edge Sensors) sensors, which are a type of cryogenic energy sensor that exploits the strongly temperature-dependent resistance of a superconducting phase transition. They reach an  excellent level of sensitivity. All these characteristics make QUBIC a promising instrument to put strong constraints on the primordial B modes. Moreover, the synthesized beam has a non trivial structure, with a primary peak and secondary peaks. The separation between peaks has a frequency dependence, which complicates the map-making process, but at the same time, it allows for doing spectro-imaging with the QUBIC maps, obtaining maps at different frequencies. In this way, the separation of foregrounds can be done with better accuracy. In this talk I review the concept of the QUBIC instrument, and I focus on the component separation of the maps using the spectro-imaging characteristics of the instrument. Using simulations, and different dust models, I show how the use of spectro-imaging help to separate the signal into different maps, and study how well we can reconstruct the CMB polarization signal, in particular, the B modes polarization.