Top row. Spatial distribution of the central portion of our image for UGC 8638 and CMDs of the stars contained in the two highlighted regions (cyan boxes); the gray background points are all the stars in this central field. Bottom row. Map of the whole field (with an empty rectangle corresponding to the central area in the top panel, where the galaxy is); the background gray points are the same as before, as a reference, while the red points show the stars contained in the two control fields (cyan boxes).