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.