Life Time of the Galactic Center Arc determined from
43 GHz observations with the 100-m Telescope

Yoshiaki SOFUE(1,2), Wolfgang REICH, Patricia REICH,
and Richard WIELEBINSKI(1)

1.MPIfR, Auf dem Huegel 69, D-53121, Bonn, Germany
2.Inst. Astronomy, Univ. Tokyo, Mitaka, Tokyo 181, Japan

Abstract

High-resolution radio continuum  observations at 43 GHz of the
Radio Arc near the Galactic Center were made using the Effelsberg
100-m telescope. The straight nonthermal filaments are hardly
seen at 43 GHz, while they are clearly seen at 32 GHz and
lower frequencies. The spectral index between 43 and 32 GHz of
the brightest straight filament is as steep as -1, indicating 
sharp turnover of the pectrum at these frequencies. Assuming that 
the magnetic field strength of about 1 mG, we estimate the life 
time of cosmic-ray electrons to be about several thousand years.
We conclude that the sharpest nonthermal radio filaments are very
short-lived structure. On the other hand, the ``sickle" is clearly
visible at 43 GHz and has  a flat spectrum, which confirms its
thermal characteristics. The "pistol" appears to show a peculiar
spectral drop at 32 GHz, suggesting a two-component spectrum.