Ionisation profile of O²⁺ to O⁷⁺ ions from a two-dimensional simulation of the interaction between the WR wind and the remnant RSG wind, shown 23.36 kyr after the onset of the WR wind. The panels illustrate the ionisation fraction, Y_O, i on a linear scale, with white representing a oxygen completely in this ionisation state (Y_O, i = 1) and black denoting the zero abundance (Y_O, i = 0). The colour scale is shown at the far right of the plot.