Panel (a) shows the Hα emission map of J0921, with each region coloured according to its radial velocity (not inclination-corrected due to the unknown inclination of the system). Red indicates regions moving away from us, and blue indicates regions moving towards us. Here we can see evidence that J0921 is rotating as a large body, as discussed in J20 and also illustrated in Marasco et al. (2023). Panel (b): Similar to (a), but regions are instead coloured by their oxygen abundance (using the S calibration) to indicate the spatial distribution of metals in J0921. Also plotted are the various galactic centres tested in this work, as listed in the text.