A [C (II)] 158 MICRON LINE MAP OF THE RHO-OPHIUCHI CLOUD

A detailed map of the [C II] 158 mum line emission from the rho Ophiuchi dark cloud has been obtained using a balloon-borne telescope (BICE). The [C II] emission is extended throughout the cloud (8 pc x 6 pc), indicating that UV radiation in the cloud is not localized but is ubiquitously distributed. The peak of the emission corresponds to the position of the highly reddened B2 V star HD 147889. The ratio I[C II]/I(bol) in the rho Ophiuchi cloud is higher than those found in active star-forming regions with O-type stars, which indicates a higher gas heating efficiency in the rho Ophiuchi cloud. Since the scale length of the [C II] emission in the core region is much larger than that expected in homogeneous clouds, the cloud structure must be highly clumpy to allow UV radiation to penetrate the cloud and form an extended C+ region.