Florent MERTENS (OBSPM)

Unveiling the Physics of the EoR and Cosmic Dawn with LOFAR and NenUFAR

Resume by AI: This presentation explores the study of the Cosmic Dawn and the Epoch of Reionization (EoR) through 21-cm line observations using LOFAR and NenuFAR radio telescopes. It highlights the challenges of detecting the faint 21-cm signal, which is buried under strong astrophysical foregrounds and instrumental effects, and presents various mitigation strategies, including sky model optimization, point-source subtraction, and advanced machine learning techniques such as Gaussian Process Regression (GPR) and Variational Autoencoders. The LOFAR-EoR project has established new multi-redshift upper limits on the 21-cm power spectrum, rejecting cold IGM scenarios, while NenuFAR achieved the deepest upper limits at z ~ 20 using newly identified dark sky regions. The presentation culminates with results from the SKA Data Challenge 3a, where the DOTSS-21 team demonstrated a complete pipeline for extracting the 21-cm signal by combining compact source subtraction, galactic foreground modeling, and ML-GPR, setting the stage for future breakthroughs in 21-cm cosmology.