Coffee talks
Friday 10/11/2023 @ 11:30, Sala riunioni quarto piano e on-line (meet.google.com/sue-bwvk-axf)
Emilio Ceccotti (Kapteyn Astronomical Institute, University of Groningen), "Improved spectral modelling of Cygnus A using a novel radio imaging method: impact on the LOFAR 21-cm power spectrum"
Recent studies by the LOFAR 'Epoch of Reionization' collaboration have highlighted the need to refine models of A-team sources, such as Cygnus A, to reduce their contamination in the North Celestial Pole field. In fact, Cygnus A has complex spectral features that are not taken into account in the low-resolution model used in the current 21-cm power spectrum analysis pipeline. In this talk, I introduce a new, high-resolution, physical model of Cygnus A obtained by extracting spectral index and curvature maps from LOFAR-HBA observations. Such spectral information is transferred to the model components directly during a multi-frequency deconvolution, using the new 'forced-spectrum fitting' method of WSClean. This improves upon current common deconvolution fitting methods, which often produce inaccurate spectra. I will describe how the forced-spectrum fitting works, showing results from both simulations and observations. The impact of the new Cygnus A model on the cosmological 21-cm power spectrum is then evaluated by comparing the results with those obtained using the current low-resolution model, showing important improvements especially at k > 0.2 h/Mpc.