Purity of the sample extracted from the simulated map above the 5σ_conf threshold in intensity (blue) and polarization (dark red). The solid lines correspond to definition A of purity (see Sect. 3.5), where a source is considered “true” if the brightest galaxy in the beam is at least half of the measured flux. The dashed and dash-dotted lines are corresponding to definition B with and without clustering, respectively. In this second definition, we lower the minimal flux density to consider a source to be true by the flux density excess factor measured in Sect. 4.1. We discuss the intensity in Sect. 4.3 and the polarization in Sect. 5.3.