Friday 10/02/2023 @ 11:30, Sala riunioni quarto piano e on-line (meet.google.com/sue-bwvk-axf)
Tiziana Trombetti (INAF-IRA Bologna), "CMB low frequency spectral distortions: absolute vs differential methods"
The Cosmic Microwave Background (CMB) frequency spectrum has been shown to be a blackbody to a precision of 50 part per million. CMB spectral distortions result from an out-of-equilibrium energy-photon exchange between matter and radiation in different phases of Universe evolution. I will describe the main unavoidable physical mechanisms leading to these spectral features, the theoretical and observational framework, and the evolution of the photon occupation number. I will go deeper in the low frequency spectral distortions, in particular on the free-free process and the amplification of its signal induced by the clumping factor, discussing the impact of extragalactic foregrounds. Then, I will present an innovative method which describes how the peculiar motion of the observer with respect to the CMB impacts the spectrum of the different multipoles with emphasis to dipole analysis, showing the corresponding CMB maps and angular power spectra. Finally, I will describe the observational feasibility of this approach.