18-cm VLA observations of OH towards the Galactic Centre - Absorption and emission in the four ground-state OH lines

The OH distribution in the Sgr A Complex has been observed in the 1612-, 1665-, 1667- and 1720-MHz OH transitions with the Very Large Array (VLA) in BnA configuration. Maps are presented with a channel velocity resolution of about 9 km s -1 and with angular resolutions of 4ʹʹ*3ʹʹ. Some clear results are highlighted here, such as absorption from the Circumnuclear Disk (CND) and the OHStreamer inside the CND near Sgr A*, strong absorption towards most of the eastern and western parts of the Sgr A East shell, lack of absorption towards both Sgr A West and the compact H II-regions to the east of Sgr A East, and double-lobed structure of the High Negative Velocity Gas (HNVG) oriented northeast and southwest of Sgr A*, and finally compact, point-like maser emission in all four transitions, in particular a 1720-MHz maser at -132 km s ^-1 in the CND as counterpart to a 1720-MHz maser at +132 km s ^-1 in the CND.