Bound fraction of star formation, evaluated for Q_eff = 1.0, as a function of angular frequency and cold gas surface density. Solid blue and dashed grey contours give the smoothed distribution (with a standard deviation of 1 dex) of all annuli of all galaxies running L-Galaxies tree-files 0-9 and 40-79 on the Millennium and Millennium-II simulations, respectively. The location of the solar neighbourhood (see Figure 2 for details) is marked with a cross.