R23−O32 diagram for the GS_4891 system in comparison with other works. Spatially binned regions are shown as red dots, whereas integrated values are shown as red polygons and empty and filled magenta circles. As a reference, we have added the stacks of galaxies at z ∼ 2.5, 3.5 from Kriek et al. (2015, light and dark blue points, respectively), the stacks in different redshift bins from Sanders et al. (2023, yellow symbols), and the individual galaxies at z ∼ 6, 8 from Cameron et al. (2023, purple and brown pluses, respectively). Shaded contours demarcate the regions in the diagram encompassed by 70, 80, and 90% of the local SDSS sample (Abazajian et al. 2009).