2013A&A...556A..92K

We investigate the large-scale structure of the interstellar medium (ISM) around the massive star cluster RCW 38 in the [CII] 158 µm line and polycyclic aromatic hydrocarbon (PAH) emission. We carried out [CII] line mapping of an area of ∼30'x15' for RCW 38 by a Fabry-Perot spectrometer on a 100 cm balloon-borne telescope with an angular resolution of ∼1.5'. We compared the [CII] intensity map with the PAH and dust emission maps obtained by the AKARI satellite. The [CII] emission shows a highly nonuniform distribution around the cluster, exhibiting the structure widely extended to the north and the east from the center. The [CII] intensity rapidly drops toward the southwest direction, where a CO cloud appears to dominate. We decompose the 3-160µm spectral energy distributions of the surrounding ISM structure into PAH as well as warm and cool dust components with the help of 2.5-5µm spectra. We find that the [CII] emission spatially corresponds to the PAH emission better than to the dust emission, confirming the relative importance of PAHs for photo-electric heating of gas in photo-dissociation regions. A naive interpretation based on our observational results indicates that molecular clouds associated with RCW 38 are located both on the side of and behind the cluster.