(HCO-C-13 AND CH3OH LINE OBSERVATIONS OF PRESTELLAR DENSE CORES IN THE TMC-1C REGION())

We have mapped the entire TMC-1C region in the (HCO+)-C-13 (J = 1-0) a nd CH3OH (J(K) = 2(0)-1(0)A(+)) lines at a grid spacing of 50'' with t he 45 m telescope at Nobeyama Radio Observatory. We have also conducte d high spatial resolution mapping observations of the TMC-1C region at a grid spacing of 34 '' in both lines toward a 6' x 6' portion in the south and a 4' x 4' portion in the north. We found that the structure of TMC-1C is filamentary in both molecular lines. The size and positi on angle of the filament are 0.75 pc x 0.17 pc and 135 degrees, respec tively. The filament consists of dense (similar to 10(5) cm(-3)) cores which are traced by either (HCO+)-C-13 or CH3OH lines. We found that the distribution of cores seen in (HCO+)-C-13 is quite different from the distribution of cores seen in CH3OH. The large velocity gradient a nalyses indicate that this difference is a result of the relative abun dance variation between (HCO+)-C-13 and CH3OH in the cores by about 1 order of magnitude. We have also carried out multitransitional observa tions of C3H2 (J(K',K '') = 2(1,2)-1(0,1) and 3(1,2)-3(0,3)) at two po sitions in the same cloud in order to estimate the molecular hydrogen densities for H13CO+ and CH3OH cores and found that the densities are around 10(5) cm(-3) for both cores. These starless cores (no IRAS sour ce), considered to be prestellar cores, seem to be at chemically diffe rent evolutionary stages; the (HCO+)-C-13 cores are more evolved and c loser to protostar formation than CH3OH cores. On the other hand, we f ound no difference in physical properties, i.e., the size, line width, and mass, between (HCO+)-C-13 and CH3OH cores; the averages are about 0.07 pc, 0.3 km s(-1), and 2 M-., respectively.