Spatial distributions of star subsamples in the studied region. The background image is a two-dimensional density histogram of stars in VPHAS+ DR2 (and sources in our NIR catalog in the bottom right panel). The dashed squares are the Chandra FOVs. Top left: M_gri stars (red) selected from Fig. 4a. Top right: M_riJ stars (red) from Fig. 4b. Bottom left: M_riH stars (red) from Fig. 4c. Bottom right: dark-red points, orange circles, and larger purple crosses are stars with Hα emission, optical-NIR excesses, and UV-excesses, respectively, as in Fig. 4; big blue dots are O or B stars from SIMBAD. The green rectangle is the field studied by Kalari et al. (2015). The green and blue asterisks are the stars 7 Sgr (F2II-III) and HD 164536 (O7.5V), respectively.