Large-Scale Mapping Observations of the C I 3P1-3P0 Line toward Heiles Cloud 2 in the Taurus Dark Cloud

A distribution of the neutral carbon atom (C i) in Heiles cloud 2 (HCL2) has been investigated with the Mount Fuji submillimeter-wave telescope. A region of 1.2 deg 2 covering a whole region of HCL2 has been mapped with the 3 P1‐ 3 P0 fine-structure line (492 GHz) of C i. The global extent of the C i emission is similar to that of 13 CO, extending from southeast to northwest. However, the C i intensity is found to be rather weak in dense cores traced by the line of C 18 O. On the other hand, strong C i emission is observed in a south part of J= 1‐0 HCL2 in which the C 18 O intensity is fairly weak. The C i/CO abundance ratio is greater than 0.8 for the C i peak, whereas it is 0.1 for the dense cores such as the cyanopolyyne peak. The C i‐rich cloud found in the south part may be in the early evolutionary stage of dense core formation where C i has not yet been converted completely into CO. This result implies that formation of dense cores is taking place from north to south in HCL2. Subject headings: ISM: atoms — ISM: clouds — ISM: evolution — ISM: individual (Heiles’s cloud 2)

[1]  C. Heiles.  Normal OH Emission and Interstellar Dust Clouds , 1968 .

[2]  J. Elias.  A study of the Taurus dark cloud complex , 1978 .

[3]  L. T. Little,et al.  The relative distribution of ammonia and cyanobutadiyne emission in Heiles 2 dust cloud , 1979 .

[4]  W. Langer,et al.  Determination of density structure in dark clouds from CS observations , 1982 .

[5]  E. Herbst,et al.  Synthesis of complex molecules in dense interstellar clouds via gas-phase chemistry: a pseudo time-dependent calculation , 1984 .

[6]  F. Schloerb,et al.  Large-scale structure of molecular gas in Heiles Cloud 2: a remarkable rotating ring. , 1984, The Astrophysical journal.

[7]  Gordon J. Stacey,et al.  Submillimeter and far-infrared line observations of M17 SW - A clumpy molecular cloud penetrated by ultraviolet radiation , 1988 .

[8]  J. Stutzki,et al.  High spatial resolution observations of neutral atomic carbon in the molecular clouds M17 and W51 , 1988 .

[9]  P. Myers,et al.  A survey for dense cores in dark clouds , 1989 .

[10]  A. Tielens,et al.  Line emission from clumpy photodissociation regions , 1990 .

[11]  S. Saito,et al.  Laboratory observation of the 3P1-3P0 transition of the neutral carbon atom by submillimeter-wave absorption spectroscopy , 1991 .

[12]  Masatoshi Ohishi,et al.  A survey of CCS, HC3N, HC5N, and NH3 toward dark cloud cores and their production chemistry , 1992 .

[13]  K. Kawaguchi,et al.  Mapping observations of sulfur-containing carbon-chain molecules in Taurus Molecular Cloud 1 (TMC-1) , 1992 .

[14]  W. Irvine,et al.  Molecular Abundance Variations Among and Within Cold, Dark Molecular Clouds , 1992 .

[15]  Y. Fukui,et al.  Overall Distribution of Dense Molecular Gas and Star Formation in the Taurus Cloud Complex , 1995 .

[16]  Y. Sekimoto,et al.  Measurements of 220 GHz atmospheric opacity on Mt. Fuji with a radiometer/radome system , 1996 .

[17]  A. Kawamura,et al.  A C 18O Survey of Dense Cloud Cores in Taurus: Core Properties , 1996 .

[18]  M. Tamura,et al.  A Near-Infrared Survey of the Taurus Molecular Cloud: Near-Infrared Luminosity Function , 1996 .

[19]  Atomic Carbon in Southern Hemisphere High-Latitude Clouds , 1997 .

[20]  E. Bergin,et al.  A Study of the Physics and Chemistry of TMC-1 , 1997, The Astrophysical journal.

[21]  Sheng-Cai Shi,et al.  Development of a 500-GHz band SIS mixer , 1997, IEEE Transactions on Applied Superconductivity.

[22]  A. Kawamura,et al.  A C18O Survey of Dense Cloud Cores in Taurus: Star Formation , 1998 .

[23]  D. Jaffe,et al.  Large-Scale C I Emission from Molecular Clouds with Associated Ultraviolet Sources , 1999 .

[24]  M. Tamura,et al.  A Near-Infrared Search for Companions around Very Low Luminosity Young Stellar Objects in Taurus , 1999 .