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Challenges for the forthcoming CMB polarization experiments

Sede A. Riccò Via Santa Sofia 78, Catania

One of the major challenges in the context of the Cosmic Microwave Background (CMB) radiation is to detect a polarization pattern, the so called B-modes of CMB polarization, that are thought to be directly linked to the space-time fluctuations present in the Universe at the very first instants of life. To date, several challenges have prevented to detect the B-modes partly because of the lower sensitivity of the detectors. Our own Galaxy is observed in this context as a foreground contamination. However the awareness of improving the modeling of its polarized emission has been constantly increase not only to assess the cosmological signals but also to provide new insights onto the Galactic magnetic field probed with the Galactic polarized emissions, e.g. synchrotron and thermal dust. This is particularly relevant in order to better characterize the foreground contamination for future CMB experiments (e.g. SO, LiteBIRD, CMB-S4 ), where unprecedented polarization sensitivities are expected to be achieved in the coming decades.

Non-standard signatures from CMB polarisation with an insight into the new technological challenges

Sede A. Riccò Via Santa Sofia 78, Catania

In this seminar, I will focus on non-standard signatures from CMB polarisation that may indicate the existence of new phenomena beyond the standard models of cosmology and particle physics, from both theoretical and observational perspectives. ESA's Planck mission has observed CMB temperature anisotropies at the cosmic variance limit, but polarisation remains to be further investigated. CMB polarisation data are important not only because they contribute to provide tighter constraints on cosmological parameters but also because they allow the study of physical processes that would be excluded if only the CMB temperature maps were considered. I use polarisation data into account to assess the statistical significance of the anomalies currently observed only in the CMB temperature map, and to constrain the Cosmic Birefringence (CB) effect, which is expected in parity-violating extensions of the standard electromagnetism.
Measuring CMB polarisation is technically challenging because the polarised signal is much fainter than the temperature signal, and accurate polarisation estimates require exquisite control of systematic effects. To investigate the impact of spurious signals in upcoming CMB polarisation experiments, I present a study of the interplay between half-wave plate (HWP) non-idealities and the beams of the instrument for the next generation of CMB experiments, with an insight into how this instrumental contamination affects the measurement of the cosmic birefringence effect.

Precision Meter-wavelength Polarimetry with the Very Large Array

Sede A. Riccò Via Santa Sofia 78, Catania

Accurate imaging polarimetry at meter wavelengths requires removal of the highly variable ionospheric Faraday rotation (IFRM) with an accuracy of 0.1 rad/m^2 or better. Models to estimate the VTEC using GNSS timing data, combined with global terrestrial magnetic field models have been developed over the past 25 years. Estimating the accuracy of these models requires observations of a source of known intrinsic electric vector position angle (EVPA) over a wide rage of ionospheric conditions.