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 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.