IRAS F13451+1232 images from MUSE observations with TOT = 2.04 h. Left: colour-composite optical image, showing [O III] (green, from the wavelength range 4975 − 5047 Å rest-frame), Hα (red, 6554 − 6576 Å), and stellar continuum (blue, 4410 − 4490 Å). Centre: red (7590 − 7665 Å) continuum image from MUSE with contours from HST/F160W. Right: continuum colour map obtained from MUSE by dividing the red continuum image (central panel) by a blue image obtained by collapsing the stellar emission in the range 4410 − 4490 Å; contours from HST/F160W. In all panels, the top part of the ULIRG shows an almost horizontal feature that is due to the removal of a satellite trail.