Images showing the color-magnitude and color-color diagrams of the 2MASS and UKIDSS point sources. Top left: K vs. H − K color-magnitude diagram of the 2MASS near-infrared point sources within a circle of radius 4′ centered at G19.68-0.13. The reddening vectors of the massive stars (O3-B9) are plotted on the color-magnitude diagram. Top right: J − H vs. H − K color-color diagram of the 2MASS point sources with spectral type earlier than B9 in the color-magnitude diagram. The solid black and red lines represent the loci of Class V (main sequence stars) and Class III (giant stars) objects respectively (Bessell & Brett 1988; Cox 2000). The black long-dashed line represents the locus of the T-Tauri stars (Meyer et al. 1997). The reddening vectors corresponding to the different classes are also shown using dotted lines with crosses placed at an increasing interval of A_V = 5. The candidate ionizing stars are shown using red ‘*’ with respective error bars. Bottom row: same as the top row but for the point sources detected in the UKIDSS survey.