Aperture synthesis observations of the molecular ring in the galactic center

Details Aperture synthesis observations of the molecular ring in the galactic center Aperture synthesis observations of the molecular ring in the galactic center

Oct 1986

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1986inpr.conf...75g&link_type=abstract

In NASA. Ames Research Center Summer School on Interstellar Processes: Abstracts of Contributed Papers p 75-76 (SEE N87-15043 0

Physics

Galactic Nuclei, Imaging Techniques, Molecular Clouds, Synthetic Apertures, Clumps, Cn Emission, Hydrocyanic Acid, Spatial Resolution, Spectral Resolution

Scientific paper

Reported are 88 GHz aperture synthesis observations of HCN J=1 yields 0 emission and absorption in the central 5 pc of the Galaxy. The data, taken by the Hat Creek mm-interferometer at 5" to 10" spatial and 4 km/s spectral resolution, show a complete, clumpy ring of molecular gas surrounding the ionized central 2 pc of the Galaxy. The ring is the inner edge of a larger disk extending to about 5 pc. Comparison with sub-mm line data suggests that the HCN 1-0 line is slightly optically thick and originates in subthermally populated gas. The clumpy line emission distribution reflects a combination of hydrogen volume and column density variations. The new data clearly show a close physical relation between the molecular and the ionized gas in the central cavity. The western arc appears to be the ionized inner surface of the molecular ring, and the northern arm and bar may be streamers of ionized gas falling from the ring toward the center. The dominant large scale velocity pattern of the majority of the molecular gas in the inner 5 pc is rotation. No overall radial motion of the ring greater than about 20 km/s is apparent. The rotation is perturbed in several ways; (1) there is a very large local velocity dispersion, (2) the ring shows changes in position angle and inclination (warps), (3) there is a bright, redshifted cloud which appears to be located in the western part of the ring but does not participate in the rotation. These characteristics and the high degree of clumpiness indicate a non-equilibrium configuration of short (less than or approx. 10 to the 4th power to 10 to the 5th power y) dynamical lifetime. The warping and tilting of the structure and the short dynamical lifetime make an accurate determination of equilibrium rotation velocity uncertain.

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