H I absorption measurements over the Galactic center Radio Arc region

The compact array of the VLA was used to study H I absorption in a 100-pc region in the center of the Galaxy. An absence of gas was observed at 40-50 km/s across the Radio Arc, suggesting that the '40 km/s molecular cloud' possibly associated with Sgr A is placed behind the Arc. At +20 km/s, the observations show absorption by material which could be depolarizing much of the synchrotron emission from the Arc filaments. The kinematic structure revealed by high-resolution molecular and radio recombination line observations is confirmed by the distribution of H I gas at -10 to -60 km/s.