  We investigate the large-scale structure of the interstellar medium (ISM)
around the massive star cluster RCW38 in the [CII] 158 um 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 3-160 um
spectral energy distributions of the surrounding ISM structure into PAH as well
as warm and cool dust components with the help of 2.5-5 um 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 RCW38 are located both on the side of and behind the
cluster.
