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 supernovae 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.
URI:	http://hdl.handle.net/2289/1387
ISSN:	0004-637X 1538-4357 (online)
Alternative Location:	http://adsabs.harvard.edu/cgi-bin/bib_query?1989ApJ...342..769P
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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