Treffer: Deep learning approach for identification of H II regions during reionization in 21-cm observations - III. Image recovery

The low-frequency component of the upcoming Square Kilometre Array Observatory (SKA-Low) will be sensitive enough to construct 3D tomographic images of the 21-cm signal distribution during reionization. However, foreground contamination poses challenges for detecting this signal, and image recovery will heavily rely on effective mitigation methods. We introduce SERENEt, a deep-learning framework designed to recover the 21-cm signal from SKA-Low's foreground-contaminated observations, enabling the detection of ionized ( H II ) and neutral (HI) regions during reionization. SERENEt can recover the signal distribution with an average accuracy of 75 per cent at the early stages (x(HI )similar or equal to 0 . 9) and up to 90 per cent at the late stages of reionization (x(HI) similar or equal to 0 . 1). Conversely, HI region detection starts at 92 per cent accuracy, decreasing to 73 per cent as reionization progresses. Beyond improving image recovery, SERENEt provides cylindrical power spectra with an average accuracy exceeding 93 per cent throughout the reionization period. We tested SERENEt on a 10-deg field-of-view simulation, consistently achieving better and more stable results when prior maps were provided. Notably, including prior information about H II region locations improved 21-cm signal recovery by approximately 10 per cent. This capability was demonstrated by supplying SERENEt with ionizing source distribution measurements, showing that high-redshift galaxy surveys of similar observation fields can optimize foreground mitigation and enhance 21-cm image construction.