Massive stars embedded in GMC’s in the southern galaxy

Regions of massive star formation can be identified as IRAS point‐like sources with characteristic FIR colors in the Galactic plane. The close association of these sources with molecular clouds provides a way of determining their kinematic distances and therefore luminosities. The mean radial distribution of the FIR luminosity generated by embedded massive stars in the IV Galactic quadrant is strongly peaked at the position of the molecular annulus. The FIR surface luminosity appears to be proportional to the 2nd power of the H2 surface density in the Galactic disk. At least 13% of the total FIR emission from massive star forming molecular clouds is produced in their dense cores, with typical sizes of 1–2 pc, in the close neighborhood of embedded OB stars. We present here a CS (2‐1) map and near‐infrared images of one of such regions, at 5.7 kpc of the Sun, associated with a strongly self‐absorbed CO (1‐0) profile.