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Astro Seminar

Detecting the CMB B-mode through foregrounds: a hybrid component separation approach.

Speaker: Susanna Azzoni (University of Oxford)
Date: Wednesday 5 October 2022
Time: 14:00
Venue: N3.28/Zoom

Detecting the imprint of inflationary gravitational waves on the B-mode polarization of the Cosmic Microwave Background (CMB) is currently one of the most compelling fundamental science cases for cosmology. Arguably the largest source of systematic uncertainty for both space and ground experiments will be contamination by the astrophysical foreground signal from the Milky Way. The separation of CMB radiation and foregrounds can be performed either in real space or in Fourier space. Different CMB experiments have followed either approach, revealing their advantages and caveats. The effects of the different approaches will become crucial at the sensitivity of the forthcoming CMB experiments (e.g. CMB-S4, LiteBIRD). In this talk I will compare different foreground cleaning methods, including a novel two-step self-consistent hybrid method. This method combines the advantages of both approaches, by cleaning out the spatially-constant part of the foregrounds at the map level, assuming nothing about the scale dependence of foregrounds, and modelling the residual frequency maps at power-spectrum level. We validate the method using Simons-Observatory-like simulated observations, recovering an unbiased estimate of the tensor-to-scalar ratio r for a wide range of realistic foreground scenarios.eaning out the spatially-constant part of the foregrounds at the map level, assuming nothing about the scale dependence of foregrounds, and modelling the residual frequency maps at power-spectrum level.