Radio studies of the Galactic center. I - the Sagittarius A complex

Pedlar, A. ; Anantharamaiah, K. R. ; Ekers, R. D. ; Goss, W. M. ; van Gorkom, J. H. ; Schwarz, U. J. ; Zhao, Jun-Hui (1989) Radio studies of the Galactic center. I - the Sagittarius A complex The Astrophysical Journal, 342 . pp. 769-784. ISSN 0004-637X

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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/cm6 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.

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ID Code:27995
Deposited On:15 Dec 2010 12:37
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