Radial velocity semi-amplitude K induced by stellar activity (K of activity signal defined as the slope of the RV_i vs. RV_m correlation times the RV semi-amplitude observed in the RV_m) as a function of the line depth for our four selection of lines: correlated lines (red dots), unblended (blue dots), symmetric (green dots), and symmetric-unblended (black dots). The colour encodes the Pearson coefficient . The different curves, from bottom to top, represent the lower envelope of the correlated lines (left bottom panel) taking as threshold and 0.4, respectively.Top: Fe I lines. Bottom: all species.