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Title: Radio studies of the Galactic Center. I. The Sagittarius A complex
Authors: Pedlar, A.
Anantharamaiah, K.R.
Ekers, R.D.
Goss, W.M.
Van Gorkom, J.H.
Schwarz, U.J.
Zhao, J.H.
Keywords: centimeter waves
galactic nuclei
galactic structure
milky way galaxy
radio astronomy
active galactic nuclei
sagittarius constellation
star formation
very large array (VLA)
Issue Date: 15-Jul-1989
Publisher: The University of Chicago Press for the American Astronomical Society
Citation: Astrophysical Journal, 1989, Vol.342, p 769-784
Abstract: VLA observations of the Sgr A complex at 90 cm, 20 cm, and 6 cm are combined to obtain spectral index and optical depth distributions across the source and are used to constrain the three-dimensional structure at the Galactic center. At 90 cm the 'spiral' structure of the thermal source Sgr A West is clearly seen in absorption against the nonthermal emission of Sgr A East, showing conclusively that the former is in front of the latter. The entire shell of Sgr A East shows a low-frequency turnover corresponding to an optical depth of 1-2. This turnover corresponds to free-free absorption with an emission measure of about 100,000 pc/cm exp 6 if the electron temperature is about 5000 K. The approximately 7 arcmin halo surrounding Sgr A East and West also shows a low-frequency turnover. It is suggested that the halo contains a mixture of thermal and nonthermal gas and that the thermal component is responsible for the absorption extending across Sgr A East.
ISSN: 0004-637X
1538-4357 (online)
Alternative Location:
Copyright: (1989) by the American Astronomical Society. Scanned images provided by the NASA ADS Data System.
Appears in Collections:Research Papers (A&A)

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