Flowchart describing the first two stages of the automated selection procedure, detailed in Sect. 2.2. We list up all selection criteria and note the number of galaxies at each selection step. In stage 1 we select preliminary candidates and a control sample (CS) using emission line properties and χ² ratios from emission line fitting computed by Chilingarian et al. (2017). We visualise the stacking and fitting procedure and all selection criteria described in Sect. 2.2.2. In stage 2 we describe the individual fitting of each emission line and list up all criteria for the DP flag detailed in Sect. 2.2.4. We finally select 7479 DP candidates and 89 412 galaxies for the CS.