Upper panel: cumulative number density of intervening Si iii absorbers for different equivalent-width limits predicted by a simulation run from the OverWhelmingly Large Simulations (OWLS; Schaye et al. 2010), as presented in Tepper-García et al. (2012). The measured value from this study and from Tilton et al. (2012; T12) and Danforth et al. (2016; D16) are indicated with filled circles. Lower panel: phase diagram of intervening Si iii absorbers in the temperature-density plane, as predicted by OWLS.