Extended Data Fig. 1: Contour image of [O iii] emission in NGC 6240.

The blue curves show linear contours for the HST/F502N observations. The contours are set at 7.5%, 15%, 30%, 45%, 60%, 75% and 90% of the peak of emission. The extended [O iii] emission is traced by the contour representing 7.5% of the peak of emission. The other contours (15–90% of the peak of emission) are located mostly around the two nuclei. A geometric model of the [O iii] cone is shown in light blue. The model was created using the software Shape⁴⁸. We constrained the model (size and opening angle) to follow the outer contours (7.5% of the peak of emission) of the wedge-shaped structure in region 1. Interestingly, a regular cone (a cone with a sharp apex) does not provide a good fit to the wedge-shaped structure. The best fit is obtained for a truncated cone. If we had used a regular cone, the apex would be located exactly at the position of the southwestern nucleus. This is consistent with our interpretation that the [O iii] cone is probably produced by the two AGNs, with a larger contribution from the southwestern nucleus. For the [O iii] cone, we obtained a size of 3.7 ± 0.2 kpc and an opening angle of 50.2 ± 3.1°. The red-shaded rectangles indicate the spatial coverage of the long slits of the DIS. PA₁ = 22° is oriented along the major axis of the galaxy disk, and PA₂ = 56° covers the region where the [O iii] cone is observed (region 1). Both slits were centred between the nuclei. The dashed rectangle represents the SINFONI field of view. North is up and east is to the left.