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The first results of large-area mapping observations of nearby giant molecular clouds in the CO(J=2-1) emission are presented. The CO(J=2-1)/CO(J=1-0) luminosity ratio is 0.75 and 0.62 for the Orion A and B clouds, respectively. These values are consistent with those observed typically in disks of galaxies (−0.6), and are significantly lower than large values (≳1) often observed in active star-forming regions in galaxies. Active star-forming regions in galaxies cannot be explained by ensemble of Orion-like GMCs; they may contain a different population of molecular clouds with high J-2-1/J=1-0 luminosity ratio.

We have observed Sgr B2 with NMA.Blue- and redshifted features revel the structure of massive core. Massive core was formed by a cloud collision and massive star formation took place by means of collapse of massive core.

We observed W49A with NMA. We found rotational infall motion toward massive core. The rotational velocity and the infall velocity are 2±1 km s−1 /pc and 5±2 km s−1, respectively.

We report a large scale mapping observation of the Galactic center region in the CO (J=2-1) line using the Tokyo-NRO 60cm survey telescope. Distribution of the CO (J=2-1) emission in the I-V plane suggests that molecular clouds forms a huge complex (Nuclear Molecular cloud Complex, NMC). Tracers of star formation activities in the last 106-108 years show that star formation has occured in a ring ~ 100 pc in radius. Relative to this Star Forming Ring, the molecular gas is distributed mainly on the positive longitude side. This may indicate that much of the gas in NMC is in transient orbit to fall into the star forming ring or to the nucleus in the near future.

We have made aperture synthesis observations of CS(2-1) emission using the Nobeyama Millimeter Array (NMA), and obtained ~ 2” × 3” (0.005 × 0.008 pc) resolution image to investigate the velocity structures of Orion-KL. We found not only well-known expanding doughnut but the expanding hemisphere in the Orion-KL hot core.

We discuss the fragmentation of a filamentary molecular cloud on the basis of a magnetohydrodynamical stability analysis and the observations of the Orion A cloud with the Nobeyama 45 m telescope. Our model cloud has axial and helical magnetic fields and rotates around the axis. The dispersion relation for this cloud shows that the presence of a magnetic field and/or rotation shortens the wavelength of the most unstable mode, i.e., the mean distance between the adjacent fragments, measured in units of the filament diameter. We compare the theoretical results with the observed clumpy structure of the filamentary Orion A cloud and find that the sum of magnetic and centrifugal forces in the parent cloud was comparable with the pressure force (thermal and turbulent) and has had significant effects on the fragmentation

A first high-resolution survey of molecular cloud cores in the Orion A giant molecular cloud is reported. We identified 125 molecular cloud cores from an analysis of the spatial and velocity distribution of the CS (1-0) emission. The cores are generally elongated along the filamentary molecular cloud, and the axial ratio is about 0.5. The mass spectrum index of the cores is -1.6 for M≥50 M ○ .. The physical properties of the cores identified in Orion are compared with those of cores in dark clouds reported in the literature. The average radius of the cores in the Orion A cloud, 0.16 pc, is comparable to that of the cores in dark clouds

Japanese activities related to radio astronomy in Antarctica are briefly reviewed.The Japanese base, Showa, is located on the coast and is based on rocks rather than ice. A 10 metre diameter microwave antenna has been built at the Showa station and a series of VLBI experiments have been made between the Showa base and a station in Japan in 1988–1989. The experiments have been geophysically motivated and an accurate measurement of the location of the Showa base was determined relative to Japan, which has a well determined position relative to other continents.

High-resolution ammonia-line images of the M − 0.13 − 0.08 («20 km s −1 ») cloud in the Galactic center region have been obtained with the Nobeyama Millimeter Array. The 20 km s −1 cloud has a finger-like structure extending toward the Galactic center. It almost reaches to the circumnuclear ring (disk) surrounding Sgr A West in projection. A large systematic velocity gradient (5-10 km s −1 arcmin −1 ) along the elongation is found over the whole length of the cloud. We suggest that these characteristics are caused by tidal force in the gravitational field of the Galactic center.

A series of millimeter line observations are made toward L723 region, a low-mass star-formation region with intriguing quadrupolar-looking outflow. In the various spatial scales represented in the dark cloud, the dense core, and the outflow, the nature of L723 region is characterized by the variation of its orientation. This remarkable geometry must contain the history of the cloud collapse and of the impact of the active phenomena produced or triggered by the young objects. The dark cloud of more than 100 M ⊙ extends in the east-west, in 13 CO J = 1-0 observation. The outflow from the FIR source shown in 12 CO maps is analyzed

It is shown here that the published emission line ratios for vibrationally excited molecular hydrogen in the near-IR for the highly luminous galaxy merger system NGC 6240 imply UV excitation followed by IR fluorescence. The line ratios for the central 2 kpc or so of the system are well-reproduced as a mixture of fluorescent and thermal components. Of the total H2 luminosity of 3 {times} 10 to the 9th solar, 70 percent is due to fluorescence. This emission is excited by UV photons probably radiated by many early B stars. The abundance of such stars and the deficit of O stars indicate a sharp upper mass cutoff at about 20 solar masses in the present-day mass spectrum in the central region. A starburst model is presented in which the observations can be reproduced if the central region experienced a cataclysmic starburst which stopped suddenly a few ten billion yr ago and if the initial mass function there had a lower mass cutoff at about 5 solar. 31 refs.

New, high-angular resolution observations of 12 CO, 13 CO, C 18 O J = 1-0 and H 33 α hydrogen recombination line emission from the energetic DR 21 outflow are presented and discussed. The high-velocity CO emission is clearly bipolar with the blueshifted outflow lobe lying to the west and the redshifted lobe to the east of the DR 21 cloud core. These observations suggest that the DR 21 outflow is probably the most massive and energetics young-stellar outflow yet discovered in the Galaxy. In addition to the main outflow, the CO maps reveal a second high-velocity bipolar flow which also originates from within the DR 21 cloud core but extends along a N-S axis, perpendicular to the E-W axis of the main outflow

Aperture synthesis observations of the Orion molecular cloud 1 (OMC-1) have been made in NH{sub 3} (1, 1) and (2, 2) emission at 23.7 GHz, using the Nobeyama Millimeter Array (NMA), and obtained 16 arcsec resolution maps for OMC-1 and 8 arcsec resolution maps for the Orion-KL region. Filamentary structures extending over 0.5 pc from the Orion-KL region to the north and northwest directions were found. These structures are associated with the H2 finger structures and Herbig-Haro objects which are located at the blue-shifted side of the bipolar molecular outflow. The results suggest that these filaments are ambient molecular cloudlets with shocked surfaces caused by the strong stellar wind from the Orion-KL region. The 8 arcsec resolution NH{sub 3} (2, 2) maps show the extended features around the hot core of Orion-KL. These extended features correspond to the rotating disk and shocked shell associated with the bipolar molecular outflow. 37 refs.

High-resolution emission-line images of the central arcminute of S106 in Br-gamma and H2 v = 1-0 S(1) are presented. The high density, together with the low excitation temperature reported earlier for S106, suggests that the origin of the thermal component in the H2 emission measured by Tanaka et al. (1989) is either high-density fluorescence, that is, collisional de-excitation of the UV pumped H2 in photodissociation regions formed on the dense molecular clumps beyond the ionization fronts, or it is radiation from slow shocks driven by the wind from the central source, propagating into the dense clumps. In either case, a novel physical environment is required to understand the observations. 41 refs.

New high-resolution CO (J = 1 approaches 0) observations of the H I-deficient Virgo Cluster Sa galaxy NGC 4419 are presented. Single-dish spectra with 17-arcsec resolution obtained with the Nobeyama Radio Observatory 45 m telescope reveal that the CO emission in the outer disk is significantly asymmetric. Outside of the central kiloparsec, there is 3-4 times more molecular gas on the northwest side of the galaxy than on the southeast side. Aperture synthesis data of the CO emission at 8 x 6 arcsec resolution of NGC 4419 obtained with the Owens Valley Radio Observatory millimeter-wave interferometer shows two significant asymmetries of a smaller magnitude within the central kiloparsec. Emission is detected further from the nucleus to the northwest, consistent with the large-scale asymmetry, but peaks in the southeast are the strongest, as if the gas were compressed. NGC 4419 also has an unusually high global CO/H I flux ratio, indicating that it has 10-15 times more molecular gas than atomic gas. The asymmetry in the CO distribution and the large CO/H I ratio suggest that the interstellar medium (ISM) of NGC 4419 is undergoing a strong interaction with the gas in the intracluster medium (ICM) 32 refs.

Detailed observations of CO, CS, IR continuum, and H2 emission from a large, highly collimated, bipolar outflow in the Monoceros OB1 molecular cloud are presented. The CO observations suggest that molecular gas in the outflow is contained in a shell with higher velocity material situated interior to lower velocity material. The velocities of outflow emission are found to increase with increasing distance from the center of the outflow. Additional detections include shock-excited molecular hydrogen emission from the blueshifted lobe of the outflow and six 2-micron sources in the direction of the outflow. Near-IR and IRAS observations suggest that the driving source for the outflow must have a bolometric luminosity below about 4.5 solar luminosities. It is concluded that the flow is probably not driven by stellar radiation from a central source.

The core region of the W3 molecular cloud has high molecular line luminosities (Dickel et al. 1980; Brackman and Scoville 1980). This region contains luminous infrared sources and ultra compact H II regions. A young star cluster may be forming in this region. Recent interferometric high angular-resolution observation revealed a bipolar outflow toward IRS 5 in the CO emission (Claussen et al. 1984) and a mass condensation in the HCN emission (Wright et al. 1984) in this region.

On a mesure neuf spectres IR le long d'une bande qui croise le front d'ionisation de la barre brillante d'Orion. Le gaz moleculaire est excite a la fois par des chocs et par l'absorption de rayonnement UV. Les observations suggerent que le gaz moleculaire entre le front d'ionisation et le choc est dissocie

Continuum and spectral-line radio observations of the comets IRAS-Araki-Alcock and Sugano-Saigusa-Fujikawa obtained at a number of observatories during May and June, 1983, are compiled in tables and briefly characterized. The species NH3, H2O, CO, and HCN are considered in detail; visible-range observations of CN are compared; and the implications of the results and the experience gained in performing and coordinating the observations for the detection of important species in other comets, especially Halley's Comet, are explored.

The Orion bright bar, a bar shaped optical feature, is seen about 2 arcmin southeast of the Trapezium stars in the Orion nebula. Since the bright bar is probably an ionization front seen edge on, this region has an ideal configuration to investigate a shocked region generated by an expanding H II region.

On presente et on discute un ensemble important de mesures de la polarisation faites avec une grande resolution spatiale dans les 20 sec. arc du centre et avec une faible resolution au-dela, jusqu'a 80 sec. arc de BN. Elles permettent une nouvelle approche des processus physiques et revelent l'existence de grains alignes et d'une emission diffusee de l'hydrogene moleculaire

High resolution images of the Orion Nebula in the millimeter wave emission lines of CS and CO taken with the 45-m telescope at Nobeyama are presented. They cover a field approximately 400″ square with a 15″ – 34″ resolution and reveal a wealth of information on kinematic and density structures. The images of the J=1-0 (49 GHz) and J=2-1 (98 GHz) lines of CS show a long (>1 pc) and narrow (∼0.1 pc) N-S ridge of dense molecular gas. On the ridge, two major clumps are recognized; one is associated with the KL object and the other is 100″ south of it. The images of the J=1-0 (115 GHz) CO line indicate interaction between the molecular cloud and the H II region formed by the Trapezium stars. Bright CO emission is found towards the edges of the denser part of the H II region delineated by radio continuum emission. The CO emission coincides with the emission of vibrationally excited H2 and the 3.3 μm dust emission feature. The CO images reveal filamentary structures (“streamers”) stretching radially from the KL region. On the streamers there are Herbig-Haro objects moving away from the KL region. They may be tracers of weak interaction between the ambient molecular gas and mostly unseen, highly collimated, high-velocity (>200 km/s) jets.

We have made 15″ resolution observations of CO J = 1-0 emission toward L723 and S140 using the Nobeyama 45-m radio telescope. The maps resolved the molecular flow structures clearly. The outflow in the S140 molecular cloud was resolved to be a bipolar structure with its axis being nearly perpendicular to the elongation of the dense core observed in CS emission and to the direction of the infrared polarization. The blueshifted and redshifted components in L723 were resolved into two pairs of bipolar outflows with a point-symmetric structure.

We review new observational and theoretical developments of the understanding of the H2 infrared emission in the last 5 years since the discovery of the fluorescent emission in NGC 2023. An excitation analysis of H2 in a variety of Galactic sources has revealed that in many sources the excitation is expressed as a mixture of thermal and fluorescent components. This finding is in good agreement with theories of photodissociation regions, in which the population of H2 changes its character from pure fluorescence to thermal as the density of the region increases. The ortho/para abundance ratio of the fluorescent H2 is observed to lie within a limited range of 1.1 — 1.8 which is well reproduced by depth-dependent model calculations of the ultraviolet excitation and dissociation of H2 molecules. This may be understood as due to the independent self shielding of each of the ortho- and para-H2, rather than the ortho/para abundance ratio of the predissociated H2, a low formation temperature of H2 on grains, or gas phase interchange reactions. A laser emission of molecular hydrogen discovered in the planetary nebula NGC7027 further demonstrates the nonthermal nature of the H2 emission in photodissociation regions.

Cold HI gas appears as self-absorption dips in the 21-cm line profiles in and around the giant molecular cloud near W3 and W4. The cold HI cloud is ∼150 pc long and extends along the galactic plane. It consists of several fragments, each of which is typically ∼25 pc in diameter and (1 − 4) × 104 M⊙ in mass. The [H2]/[HI] ratio is estimated to be 15 – 50. The mass of the entire HI cloud amounts to ∼105 M⊙, which is comparable to that observed in CO emission.

Observations of the H2 v = 1-0 S(1) line at 35 km/s velocity resolution were obtained at several locations within OMC-1, including the molecular hydrogen reflection nebula. All line profiles are smooth and show no evidence for being composed of discrete components. The data are discussed with respect to a model for the H2 line formation in which the emission originates in discrete clumps moving at different velocities. It is suggested that the extended blue wing may come from fast-moving clumps embedded in a wind.

The search for radio spectral lines from Comet Sugano-Saigusa-Fujikawa (1983e) was conducted using the 45-m telescope of Nobeyama Radio Observatory. The frequency ranges of 44.0–46.0 and 47.5–49.5 GHz were surveyed down to ΔT A ∗ ( rms ) = 20–30 mK , with a beam size of ∼35 arc sec. Upper limits have been established for spectral lines of atomic hydrogen, CS, OCS, SO2, H2CO, CH3OH, HCCCCCN, HCOOCH3, CH3OCH3, and CH3CH2CN. The J = 5−4 line from HCCCN in the vibrational ground state possibly has been detected but not confirmed. The suggested total amount of HCCCN in the coma is consistent with the possible picture that HCCCN is the main parent molecule of CN.

We report NH3 observations of the Sgr A complex region including Sgr A West and the 20 km/s and 50 km/s molecular clouds (M-0. 13-0. 08 and M-0.02-0.07) using the Nobeyama Millimeter Array and the 45m telescope. NH3(1,1) and (2,2) lines were simultaneously observed to estimate the kinetic temperature. Our results suggest strong interaction between the molecular clouds and the continuum sources in the Sgr A complex. The interaction with continuum sources might be an important factor in determining the physical conditions of molecular gas in the galactic center region.

High resolution strip maps of CS (J = 1–0) and H51α line emission across the Orion bright bar are presented. They reveal the existence of a high density molecular layer (molecular sheet) plane parallel to the ionization front. This molecular sheet is redshifted relative to the ambient molecular cloud by about 2 km s − 1. The rapid decrease of the CS emission at about 50 arc sec from the bar suggests that a shock front exists here and the sheet is a post shock layer.

We present high resolution CS and CO maps of Cep A region made with the 45 m telescope at Nobeyama. The CS map shows that a dense cloud surrounding the proto-star cluster extends in the North-South direction and is probably rotating. The bipolar molecular flow apparent in the CO maps is well-collimated along East-West direction within 0.2 pc from the proto-stars. The dense cloud is gravita-tionally unstable and appears to be in a contracting phase to form a cluster of massive stars.