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

Journal Article · Sat Jul 01 04:00:00 EDT 1989 · Astrophysical Journal; (USA)

DOI:https://doi.org/10.1086/167635· OSTI ID:5397997

Pedlar, A; Anantharamaiah, K R; Ekers, R D; Goss, W M; Van Gorkom, J H ^[1]

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1. Manchester Victoria Univ., Jodrell Bank (England)

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. 48 refs.

• OSTI ID: 5397997
• Journal Information: Astrophysical Journal; (USA), Journal Name: Astrophysical Journal; (USA) Vol. 342; ISSN ASJOA; ISSN 0004-637X
• Country of Publication: United States
• Language: English

Related Subjects

640105* -- Astrophysics & Cosmology-- Galaxies
71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
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FLUIDS
GALAXIES
GALAXY NUCLEI
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RADIOASTRONOMY
RADIOWAVE RADIATION
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