Large-Scale Mapping Observations of the C [CSC][CLC]i[/CLC][/CSC] [TSUP]3[/TSUP][ITAL]P[/ITAL][TINF]1[/TINF]–[TSUP]3[/TSUP][ITAL]P[/ITAL][TINF]0[/TINF] Line toward Heiles Cloud 2 in the Taurus Dark Cloud

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Abstract
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 deg2 covering a whole region of HCL2 has been mapped with the 3P1-3P0 fine-structure line (492 GHz) of C I. The global extent of the C I emission is similar to that of 13CO, extending from southeast to northwest. However, the C I intensity is found to be rather weak in dense cores traced by the J = 1-0 line of C18O. On the other hand, strong C I emission is observed in a south part of HCL2 in which the C18O 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.