Enhancing the detectability of ionized regions during the Epoch of Reionization

Abstract We present an improved matched filter method for detecting large ionized regions in 21 cm observations of the Epoch of Reionization. In addition to detection, the method constrains the properties of these regions, offering insights into the underlying source populations. Extending a previously developed Bayesian framework, we replace the spherical filter with an eight-parameter spheroidal filter, enabling a more flexible characterization of ionized bubbles. This enhancement significantly improves both detectability and recovery of bubble orientations. For a representative reionization scenario with a mean ionization fraction of 0.4 at z = 7, we find that a 10σ detection of the largest ionized region can be achieved with ∼ 1 h of observation using the SKA-low AA4 and AA ★ layouts. Our method can help identify regions in the observed field that host large ionized bubbles, making them prime targets for deeper follow-up observations.