Left: 2D histogram comparing the integrated absorbed luminosity per dust cell including all stellar components with the same quantity, but as the sum of separate simulations including only evolved, young and ionising stellar populations. Middle: distribution of the bolometric absorption fraction of unevolved stellar emission per dust cell: . The histogram is weighted by mass fraction of each dust cell and normalised. The red line indicates the median . Right: 2D histogram showing the radial distribution of . The bins are weighted by the mass fraction of the dust cells. Red indicates a high number of data points, blue a low number. The spread at a fixed radius is a combination of dust cells at the same radius and with different vertical location in the disk. The white line is the weighted mean heating fraction per radius.