We report the results of our observations of the S255IR area with the SMA at 1.3 mm in the very extended configuration and at 0.8 mm in the compact configuration as well as with the IRAM-30m at 0.8 mm. The best achieved angular resolution is about 0.4 arcsec. The dust continuum emission and several tens of molecular spectral lines are observed. The majority of the lines is detected only towards the S255IR-SMA1 clump, which represents a rotating structure (probably disk) around the young massive star. The achieved angular resolution is still insufficient for conclusions about Keplerian or non-Keplerian character of the rotation. The temperature of the molecular gas reaches 130-180 K. The size of the clump is about 500 AU. The clump is strongly fragmented as follows from the low beam filling factor. The mass of the hot gas is significantly lower than the mass of the central star. A strong DCN emission near the center of the hot core most probably indicates a presence of a relatively cold ( 80 K) and rather massive clump there. High velocity emission is observed in the CO line as well as in lines of high density tracers HCN, HCO + , CS and other molecules. The outflow morphology obtained from combination of the SMA and IRAM-30m data is significantly different from that derived from the SMA data alone. The CO emission detected with the SMA traces only one boundary of the outflow. The outflow is most probably driven by jet bow shocks created by episodic ejections from the center. We detected a dense high velocity clump associated apparently with one of the bow shocks. The outflow strongly affects the chemical composition of the surrounding medium.

Five regions of massive star formation have been observed in various molecular lines in the frequency range ∼ 85 − 89 GHz. The studied regions possess dense cores, which host young stellar objects. The physical parameters of the cores are estimated, including kinetic temperatures (∼ 20−40 K), sizes of the emitting regions (∼ 0.1−0.6 pc), and virial masses (∼ 40 − 500M ⊙ ). Column densities and abundances of various molecules are calculated in the local thermodynamical equilibrium approximation. The core in 99.982+4.17, associated with the weakest IRAS source, is characterized by reduced molecular abundances. Molecular line widths decrease with increasing distance from the core centers (b). For b > ∼ 0.1 pc, the dependences ∆V (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 indicate systematic motions 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. * Electronic address: pirogov@appl.sci-nnov.ru

We present results of a high resolution study of the filamentary infrared dark cloud G192.76+00.10 in the S254-S258 OB complex in several molecular species tracing different physical conditions. These include three isotopologues of carbon monoxide (CO), ammonia (NH 3 ), carbon monosulfide (CS). The aim of this work is to study the general structure and kinematics of the filamentary cloud, its fragmentation and physical parameters. The gas temperature is derived from the NH 3 (J, K) = (1, 1), (2, 2) and 12 CO(2-1) lines and the 13 CO(1-0), 13 CO(2-1) emission is used to investigate the overall gas distribution and kinematics. Several dense clumps are identified from the CS(2-1) data. Values of the gas temperature lie in the ranges 10 − 35 K, column density N (H 2 ) reaches the value 5.1 10 22 cm −2 . The width of the filament is of order 1 pc. The masses of the dense clumps range from ∼ 30 M to ∼ 160 M . They appear to be gravitationally unstable. The molecular emission shows a gas dynamical coherence along the filament. The velocity pattern may indicate longitudinal collapse.

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