Abundances in the [Al/Fe]-[Mg/Fe] plane, showing the background stars (gray color-coded density map) and the full P-rich candidates sample (black circles) described in Sect. 2.2. Empty black circles represent upper limits in [P/Fe]. Outliers identified in this or the plane shown in Fig. 3 are highlighted with orange, green, and blue stars. The red star corresponds to the P-rich GC (M4) member 2M16231729-2624578. Violet crosses indicate outliers in the background sample with GC characteristics, two of which (dark violet crosses; 2M12155306+1431114, 2M 17350460-2856477) have a high [O/Fe] abundance ratio. As defined in Sect. 3.3, the error bar represents the typical standard deviation of the elements listed in Table D.2.