Large-scale mapping of the massive star-forming region RCW38 in the (CII) and PAH emission

Aims. We investigate the large-scale structure of the interstell ar medium (ISM) around the massive star cluster RCW 38 in the [CII] 158 µm line and polycyclic aromatic hydrocarbon (PAH) emission. Methods. We carried out [CII] line mapping of an area of∼ 30 ′ × 15 ′ 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. Results. The [CII] emission shows a highly nonuniform distribution around the cluster, exhibiting the structure widely extende d to the north and the east from the center. The [CII] intensity ra pidly drops toward the southwest direction, where a CO cloud appears to dominate. We decompose the 3‐160µm spectral energy distributions of the surrounding ISM stru cture into PAH as well as warm and cool dust components with the help of 2.5‐5 µm spectra. Conclusions. We find that the [CII] emission spatially corresponds to the P AH 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 interpretati on based on our observational results indicates that molecular clouds ass ociated with RCW 38 are located both on the side of and behind the cluster.