Comparison between the [O III] and Lyα line maps. a, [O III] surface brightness map overlaid with the Lyα contours (cyan; Li et al. 2019). The Lyα contour levels correspond to +2, 3, 5, 10, and 15 σ_SB (Appendix B). The yellow boxes mark the same line emitting features as shown in Fig. D.1. b, [O III] map smoothed to the same resolution as the Lyα image for comparison, overlaid with the Lyα contours (cyan). c, Lyα surface brightness map. d, [O III]-to-Lyα surface brightness ratio map overlaid with the Lyα contours (cyan). Only the pixels with the surface brightness larger than the 2 σ_SB for both Lyα and the smoothed [O III] are plotted.