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

R. Karlsson(1), L. O. Sjouwerman(2), Aa. Sandqvist(1), J. B. Whiteoak(3)

(1) Stockholm Observatory, SCFAB-AlbaNova, SE-106 91 Stockholm, Sweden (rolandk, aage@astro.su.se)
(2) NRAO Array Operations Center, P.O.Box 0, Socorro NM 87801, USA (lsjouwer@aoc.nrao.edu)
(3) CSIRO, Australian Telescope National Facility, Box 76, Epping NSW 2121, Australia (jwhiteoa@atnf.csiro.au)

Paper: A&A 403, 1011 (2003)


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 4''x3''. 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 -132km s-1 in the CND as counterpart to a 1720-MHz maser at +132km s-1 in the CND.

Preprints available from the authors at aage@astro.su.se , or the raw TeX (no figures) if you click here.

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