1999ApJS..124..439K

We present millimeter- and centimeter-wave spectroscopic observations of the southern massive star formation region NGC 6334. The cloud has been mapped in several transitions of CO, ¹³CO, CS, and NH₃. The molecular gas shows a complex structure of filaments, in which the massive star formation occurs, and bubbles, some of which contain photodissociated gas. There is an anticorrelation between the presence of dense gas and the 6 cm radio flux: the hottest stars, with the hardest FUV radiation, have dispersed the dense gas from which they formed, whereas the cooler stars have not yet been able to do so. There is a velocity gradient along the star-forming ridge such that the radial velocity peaks in the center of the ridge. Several blueshifted emission features were discovered, one of which was identified with the ``3-kpc'' arm of the Galaxy. Excitation model calculations were used to determine the physical conditions of the molecular gas in NGC 6334. The average kinetic temperature, hydrogen volume, and column densities at the continuum sources are as follows: T_k=56±11 K, log n_H2 (cm^–3)=3.5±0.3, and N_H2 (10²² cm^–2)=7±4, respectively. The properties of the molecular gas are compared to those in other massive star-forming clouds to determine that NGC 6334 is representative of massive star-forming regions in the Galaxy and can therefore be used to test the predictions of the theoretical models of photodissociation regions. The properties of the individual sites of star formation in the cloud are also discussed.