SIMBAD references

The results of the observations of several galactic dense molecular cloud cores in the J=1-0 H¹³CN, H¹³CO⁺, HCN and HCO⁺ lines along with the J=1-0 HCN observations of some high-latitude clouds are presented. In the optically thin approximation the H¹³CN and H¹³CO⁺ column densities (N) are evaluated. HCN and HCO⁺ column densities are derived from N(H¹³CN) and N(H¹³CO⁺) using the [¹²C]/[¹³C] ratios for each cloud calculated from its galactocentric dependence. HCN abundances are found for two objects. The H¹³CO⁺, HCO⁺ and HCN emission region sizes are estimated for some cores. HCO⁺ and H¹³CO⁺ model calculations for S140 show that either the [HCO⁺]/[H¹³CO⁺] abundance ratio is rather low, ∼30, or the object has inhomogeneous structure. The J=1-0 HCN line was detected towards MBM 55B high-latitude cloud. HCN column density in this source is N(HCN)≥10¹¹cm^–2, the HCN abundance is X(HCN)>10^–10.