Relative mass fraction of baryons which are accreted smoothly. The fraction is plotted as a function of both the dark-matter virial mass and redshift. The redshift of each curve is colour coded by the colour bar on the right. Each curve, starting at z = 0.0, is separated by Δz = 0.1. For z >  z_reion = 7.0, we set . The grey vertical bar indicates the minimum halo mass in our dark-matter model. The grey horizontal line indicates f = 0.5.