18-cm VLA Observations of OH Towards the Galactic Centre.
Absorption and Emission in the Four Ground-State OH Lines.


<i>R. Karlsson</i>,L.O. Sjouwerman, <i>Aa Sandqvist</i>,  J.B. Whiteoak


A&A


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 and with angular
  resolutions of 4" x 3". Some clear results are
  highlighted here, such as absorption from the Circumnuclear Disk
  (CND) and the OH-Streamer 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 HII-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 in the CND as counterpart to a
  1720-MHz maser at +132 km/s in the CND.