Survey of the Star-Formation Regions Associated with Infrared Sources Observed in the J = 1−0 Line of the CO Molecule and Its Isotopes. Results of Observations Performed in the C¹⁸O(J = 1−0) Line

Abstract

We present results of observations of 23 compact cores of molecular clouds associated with IRAS “ cold” infrared sources. The observations were performed in the J = 1−0 line of the C¹⁸O molecule on a 13.7-meter radio telescope of the Purple Mountain Observatory, China. The C¹⁸O (J = 1−0) line was detected in the emission of 21 objects. Column densities of the C¹⁸O and H₂ molecules towards the maximum of integral intensity of the C¹⁸O emission were estimated in the approximation of local thermodynamic equilibrium and amounted to (2.5–10.4) · 10¹⁵cm⁻² and (1.5–6.1) · 10²² cm⁻², respectively. The kinetic temperatures determined for these maxima from the CO lines vary from 14 to 45 K. For six objects, whose mapping has been almost completed, the dimensions of the C¹⁸O emission regions are estimated to range from 0.5 to 1.2 pc. The masses of these objects lie in the range of (390–1750) M_⊙ and are close to the estimates following from the virial theorem. The range of average densities of the objects is (0.3–1.4) · 10⁴ cm⁻³.