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Session 42 - Molecular Clouds: Models and Observations.
Display session, Tuesday, June 11
Great Hall,
We present a kinematic analysis of the atomic and molecular gas in the Ursa Major molecular clouds. The analysis is based on a new CO survey of complex made with linear resolution of 0.05 pc and existing HI surveys. The structure of complex is dominated by several long (> 5 pc) filaments, some of which are both extremely straight and extremely narrow (< 0.2 pc across). These filaments are enclosed in a sheath of neutral atomic hydrogen. We find an offset of up to 4 km s^-1 between the centroid velocities of the CO and HI, a large-scale velocity gradient in the gas of \sim 0.3 km s^-1 pcu^-1, and a similarly large-scale gradient in the HI line width. The molecular mass of the region mapped is about 220 solar masses.
The clouds lie in projection on an expanding shell of material known as the North Celestial Pole Loop. The velocity offset, the velocity gradient, and the line width gradient can all be explained by a model in which the clouds lie on the surface of the expanding bubble.
