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Paper: The Velocity Vectors of Gas in Spiral Galaxies and Influence of the Dynamics on Giant Molecular Associations
Volume: 499, Revolution in Astronomy with ALMA: The Third Year
Page: 159
Authors: Miyamoto, Y.; Nakai, N.; Kuno, N.; Seta, M.; Salak, D.; Kaneko, H.; Nagai, M.; Ishii, S.
Abstract: Giant Molecular Clouds (GMCs) and Giant Molecular Associations (GMAs) are origins of massive stars. Recently, it is suggested that the evolution of GMCs and GMAs in spiral galaxies is greatly influenced by the galactic dynamics, especially kinetic shear motion, due to the arms. We have derived velocity vectors of the molecular gas in spiral galaxies and investigated the influence of shear motion on the evolution of GMAs, where the shear motion in the galactic disk was determined from the velocity vectors. The distributions of GMAs and the shear strength due to the differential rotation show the anti-correlation with each other. In addition to the cutoff in number counts of GMAs in strong shear regions, the existences of GMAs only in the area of the weak shear strength and further on the upstream side of high shear strength suggest that GMAs are fragmented into GMCs by the shear, although surviving in the weak shear.
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