(HCN)-C-13, (HCO-C-13, HCN AND HCO+ OBSERVATIONS OF DENSE GAS IN GALACTIC MOLECULAR CLOUDS())

The results of the observations of several galactic dense molecular cl oud cores in the J = 1 - 0 (HCN)-C-13, (HCO+)-C-13, HCN and HCO+ lines along with the J = 1 - 0 HCN observations of some high-latitude cloud s are presented. In the optically thin approximation the (HCN)-C-13 an d (HCO+)-C-13 column densities (N) are evaluated. HCN and HCO+ column densities are derived from N((HCN)-C-13) and N((HCO+)-C-13) using the [C-12]/[C-13] ratios for each cloud calculated from its galactocentric dependence. HCN abundances are found for two objects. The (HCO+)-C-13 , HCO+ and HCN emission region sizes are estimated for some cores. HCO + and (HCO+)-C-13 model calculations for S140 show that either the [HC O+]/[(HCO+)-C-13] abundance ratio is rather low, similar to 30, or the object has inhomogeneous structure. The J = 1 - 0 HCN line was detect ed towards MBM 55B high-latitude cloud. HCN column density in this sou rce is N(HCN)greater than or equal to 9 10(11) cm(-2), the HCN abundan ce is X(HCN) > 10(-10).