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Astron. Astrophys. 327, 569-576

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The large scale structure of the galactic center
at low radio frequencies

H. Alvarez, J. Aparici, and J. May

Departamento de Astronomía, Universidad de Chile, Casilla 36-D, Santiago, Chile

Received 26 December 1996 / Accepted 25 June 1997


A region about 10FORMULA around the galactic center (G.C.) has been studied in surveys available between 19.7 and 408 MHz. The maps show a trough near the G.C. sided by two intense emission peaks. Interpreting the observations as produced by an HII region that absorbs the radiation from bright non-thermal sources we propose a model consisting of four sources concentric with the G.C. and embedded in a diffused non-thermal background. Two sources, the broad and the narrow, are non-thermal and we determine their temperature spectrum (indices -2.7 and -2.4, respectively), the third source is an HII region for which we compute the emission measure, and the fourth source is Sgr A complex. The broad source is prominently seen below 408 MHz while the presence of the narrow source is reported here for the first time.

Key words: Galaxy: center - Galaxy: structure - Radio continuum: general

Send offprint requests to: H. Alvarez

© European Southern Observatory (ESO) 1997

Online publication: October 14, 1997
Last change: April 6, 1998