Warm dense gas in luminous protostellar regions - A submillimeter and far-infrared CO line study

The authors have observed the luminous star formation regions W51 IRS 2, W51 Main, G 34. 3+0. 1, and W49 in the CO J = 7→6 transition at 372 μm, and W51 IRS 2 and W51 Main in the CO 163 μm J = 16→15 transition. All CO 7→6 spectra show emission from the warm quiescent molecular cloud core. A component of high-velocity emission is apparent in the spectra of W51 IRS 2, W51 Main, and possibly W49. The high-velocity emission from W51 IRS 2 comes from hot (≡103K), dense (5×104cm-3) material with a total mass of ≡102Mₛun;. The inferred mass-loss rates in the Galaxy's most luminous star formation regions are at least one order of magnitude larger than in Orion.