Ionization Stratification and Stellar Feedback in the Galactic H ii Region Sh2-124 from Deep Narrowband Imaging

Abstract I present deep narrowband imaging of the Galactic H ii region Sh2-124 obtained with a total integration time of 79 hr using 2.5 nm S ii , H α , and O iii filters. The observations reveal a well-defined shell morphology with clear ionization stratification, dense compression fronts, and photo-eroded dust structures. Comparison with known stellar content and molecular gas distributions suggests that Sh2-124 is shaped by ongoing stellar feedback operating within a non-uniform interstellar medium. The data also reveal faint extended emission beyond the bright shell, indicating partial leakage of ionizing radiation not readily apparent in existing survey data.