Upper panels: distributions of impact parameters and absolute B-band magnitudes for galaxies that are located within | Δv | = 1000 km s^-1 of the absorbers (galaxy/absorber samples). On the left-hand side we show the distribtions for all sightlines that exhibit Si iii absorption, while on the right-hand side only the bias-corrected set of sightlines is considered (see Sect. 4.2). Galaxies tend to cluster around the LOS in velocity regions where intervening absorption is observed. Lower panels: the same distributions for galaxies that have no absorption systems within | Δv | = 1000 km s^-1 (composite control samples; see Sect. 6.2 for details). No clustering is observed in this case.