Physical Properties and Kinematics of Dense Cores Associated with Regions of Massive Star Formation from the Southern Sky

The results of spectral observations in the \( \sim {\kern 1pt} 84{-} 92\) GHz frequency range of six objects in the southern sky containing dense cores and associated with regions of formation of massive stars and star clusters are presented. The observations were carried out with the MOPRA-22m radio telescope. Within the framework of the local thermodynamic equilibrium (LTE) approximation, the column densities and abundances of the H¹³CN, H¹³CO⁺, HN¹³C, HC₃N, c-C₃H₂, SiO, CH₃C₂H and CH₃CN molecules were calculated. Estimates of kinetic temperatures (\( \sim 30{-} 50\) K), sizes of emission regions (\( \sim 0.2{-} 3.1\) pc) and virial masses (\( \sim 70{-} 4600{\kern 1pt} {{M}_{ \odot }}\)) were obtained. The linewidths in the three cores decrease with increasing distance from the center. In four cores, asymmetry in the profiles of the optically thick lines HCO⁺(1–0) and HCN(1–0) is observed, indicating the presence of systematic motions along the line of sight. In two cases, the asymmetry can be caused by contraction of gas. The model spectral maps of HCO⁺(1–0) and H¹³CO⁺(1–0), obtained within the framework of the non-LTE spherically symmetric model, were fitted into the observed ones. The radial profiles of density (\( \propto {\kern 1pt} {{r}^{{ - 1.6}}}\)), turbulent velocity (\( \propto {\kern 1pt} {{r}^{{ - 0.2}}}\)), and contraction velocity (\( \propto {\kern 1pt} {{r}^{{0.5}}}\)) in the G268.42–0.85 core have been calculated. The contraction velocity profile differs from that expected both in the case of free fall of gas onto a protostar (\({{r}^{{ - 0.5}}}\)), and in the case of global core collapse (contraction velocity does not depend on distance). A discussion of the obtained results is provided.