Example of fitting processing and foreground removal in NGC 2403. Top panel: Gaia sources where green ellipse defines boundary selected for galaxy. Middle panel: fitting parallax data for all sources within NGC 2403. The foreground contribution (dotted dark gray line) is scaled according to the densities of sources inside and outside the galaxy, while the dashed purple line shows the (Gaussian) contribution of galactic sources, and the blue line indicates the total fit. The vertical dashed black lines show the 3σ limits defined by the Gaussian properties of the galactic sources. Bottom panel: similar to parallax, but for proper motion in declination (see Sect. 2.3 for more details).