43-GHz continuum observations of the galactic center

The galactic center region including Sgr A, the radio 'bridge' and 'arc' was mapped in the radio continuum at 43 GHz using the 45-m telescope with a HPBW of 38'. The Sgr A halo is resolved into some spurs and ridges, and the bridge into two complex filaments. The arc is also resolved into two straight filaments. The spectral indices for discrete sources were obtained between 43 and 10 GHz. Most of the sources have flat spectra. The radio arc, which appears to be nonthermal, has also a flat spectrum. This may indicate that high-energy electrons are being supplied or accelerated in the arc in a time scale of a few times 106 yr. (author)