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[61.05] Observation of the [CI] ³P₁-³P₀ line toward the IC1396 region

K. Tanaka (Dept. of Physics, Univ of Tokyo), T. Oka, S. Yamamoto (Dpet. of Physucs, Univ of Tokyo)

We present the result of a [CI]{{³P₁}--{³P₀}} observation toward the IC1396 region carried out with the Mount Fuji submillimeter-wave telescope in 2002.

The IC1396 region is an HII region containing a lot of bright-rimmed globules, which are considered as ideal samples of edge-on PDRs. The PDR models predict that {\rm C⁰} mainly distributes on the surface of the cloud, and [CI] emission should have a rim-brightening structure in the bright-rimmed globules. We conducted a mapping observation of [CI]{{³P₁}--{³P₀}} emission toward the IC1396 region in order to examine wheather the [CI] emission is rim-brightening. We also observed the {\rm C{¹⁸O}}\ J=1-0, SO J_{\rm N}=3₂-2₁ and {\rm N₂H⁺}\ J=1-0 emissions with the NRO 45 m telescope.

We mapped 0.5 \rm deg² area containing 13 globules, and found that [CI] does not have a rim-brightening structure in any globule. The maximuma of N(\rm C⁰) appear at the positions where the N(\rm C⁰) is also peaked, or behind the CO peak with respect to the UV source. In order to explain the observed distribution, an additional component of {\rm C⁰} which does not originate from a PDR should be considered.

We found that the globules with IRAS point sources or \rm N₂H⁺ cores (group I) systematically have lower {\rm C⁰}/CO ratio than the globules without those objects (group II). There is a tendency that the globules of the group I are nearly gravitationally bound, while the globules of the group II seem to be pressure bound. We also estimated N({\rm SO})/N({\rm CO}) ratio and found that the group I have a higher N({\rm SO})/N({{\rm CO}}) ratio than the group II. These results indicate that the globules of the group I would be in advanced phase of dynamical and chemical evolution, supporting the {\rm C⁰}/CO ratio reflects the evolutionary stage of the cloud.

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Bulletin of the American Astronomical Society, 36 #2
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