AAS 201st Meeting, January, 2003
Session 50. The Milky Way: From Center to Halo
Poster, Tuesday, January 7, 2003, 9:20am-6:30pm, Exhibit Hall AB

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[50.01] A high resolution VLA HI Absorption Mosaic of the Central 200pc of the Galaxy

C.J. Cyganowski (Harvard, NRAO), C.C. Lang (U. of Iowa), W.M. Goss (NRAO Socorro, NM), J.H. Zhao, S. Kim (CfA)

HI absorption towards the central 200pc of the Galaxy was observed with the Very Large Array (VLA) in the DnC and CnB configurations in a five pointing mosaic. The combined data has ~15" angular resolution, ~2.5 km s-1 velocity resolution, velocity coverage from ~150 km s-1 to ~150 km s-1, and is sensitive to extended structure up to ~15' in size. The continuum image created from the line-free channels in this dataset is one of the sharpest 20cm images of the entire central 200pc to date. The overall goals of this study are to clarify the nature of the physical associations among the unique radio continuum sources of the Galactic Center (GC) and the atomic and molecular components, to determine the relative distances of these components along the line of sight, and to estimate the column densities.

Integrated, continuum-weighted HI spectra were made towards 41 continuum sources, consisting of both known sources and newly-identified compact sources. A subset of this HI spectral catalog will be presented. In addition, images of the HI opacity distribution towards the GC Arched Filament Complex will be presented, along with preliminary comparisons to molecular data. The distribution of atomic gas along the line of sight towards this region is complex. Higher HI opacities towards the Western Arched Filaments in the range of v~-15 to -65 km s-1 support the suggestion by Lang, Goss & Morris (2001) that the ionized regions of the Eastern Arched Filaments (E1 and E2) are more intermingled with the molecular material of the -30 km s-1 cloud than those of the Western Arched Filaments. In addition, we detected HI at ~40-50 km s-1 and ~60-70 km s-1 towards the Western Arched Filaments and E2, not detected by Lasenby et al (1989).

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Bulletin of the American Astronomical Society, 34, #4
© 2002. The American Astronomical Soceity.