EWs of He II, O III]λ1666, [Si III]λ1883, and [C III]λ1907 for the different subsamples of MUSE HUDF LAEs (x-axis). The symbols refer to different emission lines, as labeled in the legend. Smaller and larger symbol sizes indicate the subsample of LAEs whose properties are lower and higher than the median value, respectively. Empty symbols with downward arrows indicate upper limits, while non-detections are shown by the black dash. Red symbols show the EWs for all 220 LAEs in the sample.