High-resolution imaging of photodissociation regions in NGC 6334

We have used the SPIREX telescope to conduct a wide-field thermal infrared imaging study of the star formation complex NGC 6334 in the southern Galactic plane. We imaged a 30′ region along the main star-forming ridge of NGC 6334 with 0″.6 pixel scale through broadband filters for L (3.5 μm) and M (4.8 μm) and through narrowband filters for the H₂ υ = 1-0 Q-branch (2.42 μm), polycyclic aromatic hydrocarbon (PAH) (3.3 μm), and Brα (4.05 μm) lines. The images reveal the spectacular, complex structure of the photodissociation regions (PDRs) that pervade the region, with enhanced line emission around each of the seven sites of massive star formation along the ridge. Bubbles and loops of PAH emission, typically 1-1.5 pc across, have been carved out of the parent molecular cloud by the intense UV radiation from the massive stars and surround H II regions (seen in Brα) typically 0.2-0.3 pc across. The PAH emission regions coincide with both [C II] 158 μm line emission, indicating that the PAHs are excited in PDR gas, and extensive H₂ emission, which therefore must be fluorescent. However, the textures of the emission regions in PAH and H₂ are different. This is attributable to variations in the physical environment in which the gas is excited. Several compact reddened objects are observed; these are likely to be massive protostars.