Distributions of the D4000 break and the EW of some notable lines. In each panel we show the distributions at S/N ≥ 1 (light grey) and S/N ≥ 3 (green). For the lines from the 'Gaussian fit' catalogues, the cut is in S/N flux. Top left: Lya EW (direct integration). Top right: D4000 (direct integration). Middle left: CIII]λ909 Å EW (Gaussian fit). Middle right: [OII]λ3727 Å EW (Gaussian fit). Bottom left: OI+SiIIλ303 Å EW (direct integration). Bottom right: OI+SiIIλ1303 A EW (Gaussian fit). In the last two panels, we also show the distribution at S/N > 2 (dark grey).