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Astron. Astrophys. 327, 569-576 (1997)

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5. Conclusions

We have studied the large scale structure around the galactic center in low frequency ([FORMULA] MHz) surveys. To account for the observations we propose a model consisting of four spherical sources concentric with the galactic center and embedded in a diffused non-thermal background. The components of the model are:

  1. A non-thermal source several degrees wide, with a temperature spectral index -2.7, and prominently seen in surveys below 408 MHz. At 45 MHz it radiates about 9.4 1019 W Hz-1, 1% of the whole Galaxy, and we define it as the radio bulge. In low resolution maps below 85 MHz, the center of this source appears displaced towards positive longitudes. It is suggestive that a similar situation has been found for the centroid of the molecular gas near the G.C.
  2. A non-thermal source, evidence for which is found at 408 MHz, about one degree wide and with a temperature spectral index -2.4.
  3. An HII region with an angular extent of 1.5[FORMULA] x 1.0[FORMULA] and an emission measure of 3.6 104 pc cm-6.
  4. The Sgr A complex.
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© European Southern Observatory (ESO) 1997

Online publication: April 6, 1998