AAS 196th Meeting, June 2000
Session 25. The Milky Way Galaxy
Display, Tuesday, June 6, 2000, 10:00am-6:30pm, Empire Hall South

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[25.04] The BU-FCRAO Milky Way Galactic Ring Survey: Structure and Equilibrium of four Molecular Clouds

R. Simon, J.M. Jackson, T.M. Bania, D.P. Clemens (Institute for Astrophysical Research, Boston University), M.H. Heyer (Five College Radio Astronomy Observatory, University of Massachusetts, Amherst)

We present results on cloud structure of four molecular clouds selected from the BU-FCRAO Milky Way Galactic Ring Survey (GRS), a high resolution study of 13CO in the first Galactic quadrant using the FCRAO 14m telescope. The clouds span a large range of star formation activity, from W49, the most luminous star forming region in the Milky Way, to G045.46+0.05, which has no obvious star formation activity. We use a three-dimensional, gaussian-clump decomposition to identify clumps and deduce their sizes, masses, and line widths.

Every cloud has the same clump mass spectrum independent of star formation activity. Relations of clump size with mass and density differ from the conventional Larson relations and the line width shows only a weak dependence with clump size. While the clouds as a whole are in gravitational virial equilibrium, most clumps are not. Star forming clouds have a much higher fraction of gravitationally bound clumps than non star forming clouds. The unbound clumps are probably confined by the weight of the self-gravitating complex and the pressures needed to bind these clumps are largest for the star forming clouds.

The Galactic Ring Survey acknowledges support by the NSF via grant AST--9800334.

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