Multifrequency studies of massive cores with complex spatial and kinematic structures

Resumo

Five regions of massive-star formation have been observed in various molecular lines in the frequency range∼85−89 GHz. The studied regions comprise dense cores, which host young stellar objects. The physical parameters of the cores are estimated, including the kinetic temperatures (∼20−40 K), the sizes of the emitting regions (∼0.1−0.6 pc), and the virial masses (∼40−500 M_⊙). The column densities and abundances of various molecules are calculated assuming Local Thermodynamical Equilibrium(LTE). The core in 99.982+4.17, which is associated with the weakest IRAS source, is characterized by reduced molecular abundances. The molecular line widths decrease with increasing distance from the core centers (b). For b ≳ 0.1 pc, the dependences ΔV (b) are close to power laws (∝b^−p), where p varies from ~0.2 to ~0.5, depending on the object. In four cores, the asymmetries of the optically thick HCN(1–0) and HCO⁺(1–0) lines indicates systematicmotions along the line of sight: collapse in two cores and expansion in two others. Approximate estimates of the accretion rates in the collapsing cores indicate that the forming stars have masses exceeding the solar mass.