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Paper: Wide Field Radio Imaging of the Galactic Center
Volume: 186, The Central Parsecs of the Galaxy
Page: 403
Authors: Kassim, N. E.; Larosa, T. N.; Lazio, T. J. W.; Hyman, S. D.
Abstract: We present a large and sensitive sub-arcminute resolution meter wavelength image of the Galactic Center. Archival 330 MHz (λ0.9 m) VLA observations were reprocessed utilizing wide-field imaging [index wide-field imaging] algorithms developed at the National Radio Astronomy Laboratory and the Naval Research Laboratory. The resulting image is a significant improvement over previous ones, both providing higher fidelity images of known sources and revealing many new sources. We have also used ``targeted faceting'' to generate images at the full resolution of the data for the first time for regions well away from Sgr A [index Source ! Sgr A]. At 330 MHz the VLA is sensitive to both thermal and non-thermal sources, and this image provides an excellent overview of the large-scale structure (2° times 2°) in the Galactic Center. Several new sources have been found, and a catalogue of over 100 sources is being prepared. Subsequent observations of one of these new features has led to the discovery of a new non-thermal filament with a unique orientation along the plane; observations of other new features are in progress. Improved imaging and sensitivity has allowed for better spectral index determinations. In particular, the spectral index (between 330 and 1400 MHz) as a function of length along several non-thermal filaments has been measured. The spectral index was found to be constant, indicating that these may be young features. A second epoch 330 MHz Galactic Center imaging campaign, an efficient monitor for source variability and transients [index transients], is in progress as is a first epoch campaign with the new 74 MHz VLA observing system.
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