Left panel: probability distribution of all stars in our sample which do not have a null probability of being chemically compatible with ω Cen, according to the GMMChem model. Middle panel: [Fe/H] distribution of all stars with a probability P > 0 (grey), P ≥ 0.7 (magenta), and P ≥ 0.99 (yellow) to be chemically compatible with ω Cen (black). Right panel: distribution in the [Mg∕Fe]-[Fe∕H] plane of ω Centauri stars (black points), and of stars chemically compatible to it, coloured-coded by the probability of their compatibility P. Outliers, defined as stars with a probability density below the 10th percentile threshold, are shown as empty black circles for ω Cen and as contours for field stars. Stars 0 < P < 0.7 mostly distribute in the region occupied by α-enhanced thick disc stars; these are interpreted as contaminants from the disc.