Selection probability for sources with a RUWE higher than the threshold represented in Fig. 3. The regions with a higher selection probability, e.g., cores of globular clusters, the Galactic plane, and the Magellanic Clouds, contain sources with an increased RUWE due to a combination of binarity, source crowding, and other effects. These regions may indicate a higher contamination rate if binaries are selected solely based on RUWE. The dark halos around the Magellanic Clouds are due to an excess of faint sources with low RUWE in that region.