Superposition of all [O III] lines from each pixel, colour-coded by the position of the pixel (as shown in the left panel). Bottom left: SDSS g-band image (black contours). The hexagon is the field of view of MaNGA. Top: Spectra of the whole map. Middle right: Top half of the field (i.e. the field above the dotted white line in the bottom-left panel), emphasising regions where galaxies b and c are present. Bottom right: Bottom half of the field, highlighting areas where galaxies a₁ and a₂ are situated.