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Date and Time of the Query: 2019-06-19 T22:24:52 PDT
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For refcode 2001PASJ...53..757N:
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Copyright by Astronomical Society of Japan. 2001PASJ...53..757N CO Survey of Nearby Spiral Galaxies with the Nobeyama 45-m Telescope: II. Distribution and Dynamics of Molecular Gas Kohta NISHIYAMA, Naomasa NAKAI, and Nario KUNO Nobeyama Radio Observatory, Minamimaki-mura, Minamisaku-gun, Nagano 384-1305 kota@bsgc.isforum.or.jp, nakai@nro.nao.ac.jp, kuno@nro.nao.ac.jp (Received 1998 June 2; accepted 2001 September 4) Abstract We have studied the distribution and dynamics of molecular gas in galaxies by observing CO emission mainly along the major and minor axes of 28 nearby spiral galaxies with the 45-m telescope of the Nobeyama Radio Observatory. The observations showed that the surface density of molecular gas indicates an exponential distribution in the region of the flat (differential) rotation curve for all spiral galaxies. This could be because the radial distribution is determined by gas inflow due to the viscosity of molecular clouds. The surface density of molecular gas in barred galaxies also shows a characteristic distribution in the region of the bar, suggesting gas inflow along the bar by the bar potential and perpendicular to the bar by viscosity. Such a transfer of molecular gas increases the gas density in the central region, probably causing the evolution of the rotation curve, which is determined by the mass distribution, on the time scale of the galaxy age. We compared the radial distribution of the surface density of H I with that of H_2_, and found same scale length of the exponential distribution in the Virgo galaxies and a much larger scale length in field galaxies for H I . This could be due to a difference in the viscosity coefficient of the H I gas. Key Words: galaxies: evolution - galaxies: general - galaxies: kinematics and dynamics - galaxies: spiral - ISM: molecules - radio lines: galaxies
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