The data from the Nobeyama Radio Observatory 45 m telescope Galactic Center CO survey have been analyzed to generate a compilation of molecular clouds with intense CO emission in this region. Clouds are identiÐed in an automated manner through the main part of the survey data for all CO emission peaks exceeding 10 K The measured parameters of identiÐed clouds are analyzed and (T R *). cross-correlated to compare with those of clouds in the Galactic disk. For the clouds in the Galactic center (GC), we Ðnd the scaling laws of the type and which are similar to88, those of clouds in the Galactic disk. All the GC clouds identiÐed have larger velocity widths and virial theorem masses each above the and lines of the disk clouds. We diagnosed gravitational p V -S L CO -M VT stabilities of identiÐed clouds assuming that the disk clouds are nearly at the onset of gravitational instability. All the clouds and cloud complexes in the GC are gravitationally stable, indicating they are in equilibrium with high pressure in the GC environment. Gravitationally less stable clouds follow the main ridge of intense CO emission, part of which deÐne two rigidly rotating molecular arms. The velocity dispersion of a cloud correlates inversely with the degree of gravitational instability. It is concluded that mechanisms such as orbit crowding at the inner Lindblad resonance may promote gravitational instability and subsequent star formation.
We present high-resolution CO images of the Galactic center region taken with the 2 ] 2 focal-plane array receiver mounted on the 45 m telescope of Nobeyama Radio Observatory. We have collected about 44,000 12C16O (J \ 1È0) spectra and over 13,000 13C16O (J \ 1È0) spectra with a 34A (1.4 pc) grid spacing. The 12CO mapping area is roughly and which covers.6, almost the full extent of the molecular gas concentration in the Galactic center. These CO images demonstrate extremely complex distribution and kinematics of molecular gas in the Galactic center. While its large-scale behavior can be attributed to the well-known coherent features, bright CO emission arises from a number of compact (d ¹ 10 pc) clouds with large velocity widths (*V º 30 km s~1 ). The small-scale structure of molecular gas is characterized by Ðlaments, arcs, and shells. The boisterous molecular gas kinematics there may be a result of violent release of kinetic energy by a number of supernova explosions and/or Wolf-Rayet stellar winds.
We determine the magnetic field strength in the OMC 1 region of the Orion A filament via a new implementation of the Chandrasekhar-Fermi method using observations performed as part of the James Clerk Maxwell Telescope (JCMT) B-Fields In Star-Forming Region Observations (BISTRO) survey with the POL-2 instrument. We combine BISTRO data with archival SCUBA-2 and HARP observations to find a plane-of-sky magnetic field strength in OMC 1 of B pos = 6.6 ± 4.7 mG, where δB pos = 4.7 mG represents a predominantly systematic uncertainty. We develop a new method for measuring angular dispersion, analogous to unsharp masking. We find a magnetic energy density of ∼ 1.7 × 10 −7 J m −3 in OMC 1, comparable both to the gravitational potential energy density of OMC 1 (∼ 10 −7 J m −3 ), and to the energy density in the Orion BN/KL outflow (∼ 10 −7 J m −3 ). We find that neither the Alfvén velocity in OMC 1 nor the velocity of the super-Alfvénic outflow ejecta is sufficiently large for the BN/KL outflow to have caused large-scale distortion of the local magnetic field in the ∼500-year lifetime of the outflow. Hence, we propose that the hour-glass field morphology in OMC 1 is caused by the distortion of a primordial cylindrically-symmetric magnetic field by the gravitational fragmentation of the filament and/or the gravitational interaction of the BN/KL and S clumps. We find that OMC 1 is currently in or near magnetically-supported equilibrium, and that the current large-scale morphology of the BN/KL outflow is regulated by the geometry of the magnetic field in OMC 1, and not vice versa.
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