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Satoshi Yamamoto and Nobuyuki Kuboi Department of Physics

Submillimeter-wave CI Line Survey in Molecular Clouds. Satoshi Yamamoto and Nobuyuki Kuboi Department of Physics The University of Tokyo. Why Atomic Carbon?. The fourth abundant element after H, He, and O Two fine structure lines at submm band

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Satoshi Yamamoto and Nobuyuki Kuboi Department of Physics

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  1. Submillimeter-wave CI Line Survey in Molecular Clouds Satoshi Yamamoto and Nobuyuki Kuboi Department of Physics The University of Tokyo

  2. Why Atomic Carbon? • The fourth abundant element after H, He, and O • Two fine structure lines at submm band 3P1-3P0 492 GHz, 3P2-3P1 809 GHz • Low ionization potential HII region PDR MC C+ C CO Tracer of an interface between PDR and MC →Formation and Evolution of Molecular Clouds

  3. [CI] Observations with Mt. Fuji Submillimeter-wave Telescope • [CI] 3P1-3P0 (492 GHz) Large-scale Mapping (> 50 deg2) GMC: Orion A, Orion B, M17, W51, DR15, DR21, W3, W44 etc. Dark Cloud: Taurus, NGC1333, rho Oph, L134 , Bright Rimmed Clouds, etc. Translucent Cloud: G216-2.5, MBM12, Draco • [CI] 3P2-3P1 (809 GHz) Mapping toward representative sources Orion A, Orion B, DR21, NGC1333 etc.

  4. Taurus Dark Cloud • Distance ～140 pc • Active formation site of low-mass stars (Extensive studies with molecular lines) • No OB stars associated • No SNR associated 　　　　　　　　　　　↓ Spontaneous formation and evolution of molecular clouds

  5. Dense Cores CI rich cloud CI/13CO(1-0) Integrated Intensity Ratio CI Integrated Intensity Translucent Cloud

  6. TMC-1 Hirahara et al. 1992 Late Early

  7. CI Rich Cloud in HCL2 • High C/CO ratio > 0.8 Av > 6 H2 density ～ 5 x 103 cm-3 No enhancement in IRAS color Early stage of chemical evolution? • Interface between translucent part and dense part • Consistent with chemical evolution scheme in the TMC-1 ridge →Formation site of molecular cloud cores

  8. CI Peak Av=6, C/CO=0.6 CI/C18O(1-0) Integrated Intensity Ratio CI/13CO(1-0) Integrated Intensity Ratio CI Integrated Intensity

  9. CI Peak of L1495 Early Stage of Chemical Evolution?

  10. CI/13CO(1-0) Integrated Intensity Ratio No translucent part Is associated. CI/C18O(1-0) Integrated Intensity Ratio Relatively low C/CO ratio (0.2)

  11. B18 is more evolved than HCL2 and L1495 ? A lack of translucent part in B18

  12. Summary • CI/13CO(1-0) intensity ratio is a good indicator of a translucent part of a molecular cloud. • HCL2 and L1495 regions contain an interface between a translucent part and a dense part. >>> Formation site of molecular cloud cores? • B18 does not contain a clear interface. >>> More evolved than HCL2 and L1495 • CI line >>>Unique probe of cloud core formation and evolution

  13. Diffuse part is not Associated.

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