Extended Data Fig. 1: [O III] ionized gas profile.

Left and right panels show the spectrum of J2230 + 0032 and J1512 + 4422, respectively (black). The best-fit models for the continuum, iron, and Hβ line emissions are subtracted for illustration purposes. The core and broad wing components modeled as Gaussian profiles are shown with blue and orange lines, respectively. The total profiles of the best-fit emission line models are shown with red lines. The rest-frame wavelengths indicated at the top, as well as the expected locations of each doublet line (grey dashed lines) are based on redshifts estimated from the Balmer absorption lines. In the bottom panels, the residuals are shown in black lines, and the ± 1σ flux uncertainty at each pixel is indicated as grey shades.