Statistical Properties of Molecular Clouds in the Galactic Center

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Abstract
The data from the Nobeyama Radio Observatory 45 m telescope Galactic Center CO survey have been analyzed to generate a compilation of molecular clouds with intense CO emission in this region. Clouds are identiÐed in an automated manner through the main part of the survey data for all CO emission peaks exceeding 10 K The measured parameters of identiÐed clouds are analyzed and (T R *). cross-correlated to compare with those of clouds in the Galactic disk. For the clouds in the Galactic center (GC), we Ðnd the scaling laws of the type and which are similar to p V P S0.40 M VT P (L CO)0.88, those of clouds in the Galactic disk. All the GC clouds identiÐed have larger velocity widths and virial theorem masses each above the and lines of the disk clouds. We diagnosed gravitational p V-S L CO-M VT stabilities of identiÐed clouds assuming that the disk clouds are nearly at the onset of gravitational instability. All the clouds and cloud complexes in the GC are gravitationally stable, indicating they are in equilibrium with high pressure in the GC environment. Gravitationally less stable clouds follow the main ridge of intense CO emission, part of which deÐne two rigidly rotating molecular arms. The velocity dispersion of a cloud correlates inversely with the degree of gravitational instability. It is concluded that mechanisms such as orbit crowding at the inner Lindblad resonance may promote gravitational instability and subsequent star formation.

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