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C.C. Lang (UMASS)
The Galactic center (GC) Arched Filament complex best represents the complicated interplay between the dense molecular clouds, the strong magnetic field, and the massive stellar clusters which characterize galactic nuclei. This complex consists of a series of ionized filaments which lie on the surface of an extensive molecular cloud. They are apparently ionized by the adjacent, massive Arches cluster. This cluster contains > 160 O-stars, some of which are undergoing intense mass-loss. The thermal features are also intersected by a series of linear magnetic filaments which trace a large-scale field in the inner Galaxy and play an important role in determining the physical conditions of the local interstellar medium. Finally, tidal forces at this radius (30 pc) significantly affect the kinematic motions of the gas and thereby influence the morphology of the sources. This work focuses on peculiar kinematics of the ionized and molecular components, and the physical relationships between the stellar, gaseous, and magnetic features that are found in the GC.
VLA H92\alpha line observations of the Arched Filaments show that the physical conditions in the ionized gas are consistent with other GC H II regions. The velocity gradients measured are some of the largest known in the Galaxy, and are consistent with the cloud complex residing on an inner elongated orbit due to the Galaxy's stellar bar, or with a radially infalling cloud. The Arches cluster can account for the ionization and may be located as far as 20 pc from the Arched Filaments, thereby explaining the uniformity of ionization across the source. A high-resolution study of the CS(2-1) line arising from the underlying molecular cloud was made at OVRO and the data were combined with corresponding 30-m data. A comparison reveals that the ionized and molecular gas appear to be physically related based on agreement in velocities, velocity gradients, and morphology. The relative placement of the ionized and molecular gas is complicated. Much of the ionized gas appears to lie on the near side of the molecular cloud, but the reverse occurs in a few regions. Finally, the expanding, ionized winds from eight members of the Arches Cluster have been detected using multi-frequency VLA observations. The estimated mass-loss rates of these stars are among the highest known in the Galaxy.
This work was supported by a predoctoral fellowship at the Very Large Array of the National Radio Astronomy Observatory, which is a facility of the NSF, operated under a cooperative agreement with the Associated Universities, Inc.