Ionizing flux vs. radial distance from 9 Sgr, shown separately for the eastward and westward directions (negative and positive distances, respectively). Black (gray) dots refer to pure-sky (faint star) fibres. The blue, green, and red solid lines refer to normal distances of 1.46, 1.09, and 0.73 pc, respectively. The blue dashed line refers to a distance of 1.46 pc, adopting a different maximum flux.