Constraining the reionization era and inflation with the CMB polarization

par Anna Mangilli (Institut d'Astrophysique Spatiale, Orsay)

jeudi 19 nov. 2015, 11:00 → 12:00 Europe/Paris

Petit Amphi (Annecy-le-Vieux)

The accurate measurement of the CMB polarization at large angular scales is one of the key challenges left for the current and future CMB experiments. The large scale enhancement of the CMB polarization power spectra due to the reionization of the Universe in fact encodes unique informations about the reionization history and the inflationary epoch. In this talk I will go through a brief introduction about the CMB polarization, highlighting the scientific goals related to the analysis of the CMB data at large angular scales. I will show how the Planck 2015 release represented a first step towards the accurate characterization of the CMB polarization on the full sky. I will then present the new and improved -yet preliminary- results of the Planck data analysis at large angular scales. In particular I will present the latest tightest constraints on cosmic reionization extracted from the CMB polarization at low multipole by Planck. I will show that the reionization optical depth parameter τ measured by Planck is significantly smaller than previous estimations from CMB polarization data. This result reduces the tension between CMB based analyses and constraints from other astrophysical sources. Finally I will discuss the improvement on the estimation of the tensor-to-scalar ratio parameter r when the B-modes data at large scales are included and I will present the theoretical implications of the results and the future prospects for forthcoming CMB experiments like CoRE+/LiteBird.