False colour image from 2MASS (blue channel for J band, green for H, and red for K_S), covering approx. 13′ × 20′, with the sources under study marked. Labels follow the notation in Table 1. Yellow circles denote the photometric candidates, while spectroscopically confirmed RSGs are marked with a red plus. Blue crosses left for those stars that are late type giants. North is up, east to the left.