AAS 205th Meeting, 9-13 January 2005
Session 59 ISM: Dust and Molecules
Poster, Tuesday, January 11, 2005, 9:20am-6:30pm, Exhibit Hall

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[59.08] Preferential Direction of Supersonic Motion in Molecular Clouds

J. Koda (Caltech/National Astronomical Observatory of Japan), T. Sawada (Nobeyama Radio Observatory)

CO data are analyzed to understand the shape and internal motion of molecular clouds in the Milky Way. For a sample of more than five hundreds molecular clouds, we find on a statistical basis that they are preferentially elongated toward the Galactic plane. The elongations are not supported by internal spins but by internal supersonic motions. It has been known that an external driving mechanism for the supersonic velocity dispersion is necessary to prevent their rapid decay. The mechanism must also account for the preferential direction of molecular clouds. This constraint excludes some suggested mechanisms, such as supernovae and stellar winds, because they do not produce the preferential direction along the Galactic plane.

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Bulletin of the American Astronomical Society, 36 5
© 2004. The American Astronomical Society.