Surface brightness due to emission from oxygen ions for: (a) Run L1 at 20 kyr; (b) Run L1 at 60 kyr; (c) Run H1 at 20 kyr and (d) Run H1 at 60 kyr. The ions are (left-hand panels) O vi, (middle panels) O vii and (right-hand panels) O viii. The tick marks indicate projected distances of 10 pc. Because the distribution of O vi emitting gas originates from a very narrow shell, the image shows striations that arise from the pixellation of this boundary in the simulations. The colour scale is the logarithm of the surface brightness in erg s⁻¹ cm⁻² sr⁻¹.