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Molecular Spiral Arms

Published online by Cambridge University Press:  03 August 2017

F. Casoli*
Affiliation:
Radioastronomie, E.N.S. 24 Rue Lhomond F-75231 Paris cedex 05 France, and Observatoire de Meudon

Abstract

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The recent single-dish and interferometric mapping of the disks of nearby spirals in the CO lines are reviewed. In all galaxies with a grand-design structure molecular spiral arms are prominent, with an arm/interarm contrast of 4 or more. CO-poor spirals seem to have more contrasted CO arms. In most galaxies (NGC6946, M31, M83, M81) the CO, HI and Hα ridges are closely associated while in some regions of M51, the CO is upstream and associated with the dust lane and spiral shock. This suggests that there is no unique sequence leading from the gas to the stars in the arms. The differences between these galaxies are probably linked to the strength of the density wave, the location of the resonances and the overall gas content of the galaxy.

Type
III- Observations of Spiral Structure
Copyright
Copyright © Kluwer 1991 

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