Probability distribution of z_sat, the redshift at which a blue principal galaxy at z = 0.9 becomes a satellite. The upper x-axis shows the cosmological time spanned since z = 0.9. The solid vertical line shows the redshift at which half of the initial sources have become a satellite. The dashed line marks T_Q = 1.8 Gyr after z = 0.9. The arrow marks the redshift at which we estimate the infall rate.