Color composite image of the massive star-forming region NGC 6357 combining UKIRT Ks-band (blue) with Spitzer-IRAC 4.5 μm (green) and Spitzer-IRAC 8.0 μm (red) data. The small colored points show the location of the XUE sources with respect to the massive stars (T_eff > 25 000 K) in the region which are shown with the stars. The color bar indicates the temperature of the massive stars. The white circles show the location of the three subclusters: Pis 24 containing XUE 1, 2, 3, and 4, G353.1+0.6 containing XUE 5, 6, 7, and 8, and G353.1+0.7 containing XUE 9, 10, 11, and 12.