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Hydroxyl, water, ammonia, carbon monoxide and neutral carbon towards the Sgr A complex

Published online by Cambridge University Press:  22 May 2014

R. Karlsson
Affiliation:
Stockholm Observatory, Department of Astronomy, Stockholm University, AlbaNova University Center, SE-106 91 Stockholm, Sweden
Aa. Sandqvist
Affiliation:
Stockholm Observatory, Department of Astronomy, Stockholm University, AlbaNova University Center, SE-106 91 Stockholm, Sweden
Å. Hjalmarson
Affiliation:
Onsala Space Observatory, Chalmers University of Technology, SE-439 92 Onsala, Sweden
A. Winnberg
Affiliation:
Onsala Space Observatory, Chalmers University of Technology, SE-439 92 Onsala, Sweden
K. Fathi
Affiliation:
Stockholm Observatory, Department of Astronomy, Stockholm University, AlbaNova University Center, SE-106 91 Stockholm, Sweden
U. Frisk
Affiliation:
Omnisys Instruments AB, Solna Strandväg 78, SE-171 54 Solna, Sweden
M. Olberg
Affiliation:
Onsala Space Observatory, Chalmers University of Technology, SE-439 92 Onsala, Sweden
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Abstract

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We observed Hydroxyl, water, ammonia, carbon monoxide and neutral carbon towards the +50 km s−1 cloud (M−0.02−0.07), the circumnuclear disk (CND) and the +20 km s−1 (M−0.13−0.08) cloud in the Sgr A complex with the VLA, Odin and SEST. Strong OH absorption, H2O emission and absorption lines were seen at all three positions. Strong C18O emissions were seen towards the +50 and +20 km s−1 clouds. The CND is rich in H2O and OH, and these abundances are considerably higher than in the surrounding clouds, indicating that shocks, star formation and clump collisions prevail in those objects. A comparison with the literature reveals that it is likely that PDR chemistry including grain surface reactions, and perhaps also the influences of shocks has led to the observed abundances of the observed molecular species studied here. In the redward high-velocity line wings of both the +50 and +20 km s−1 clouds and the CND, the very high H2O abundances are suggested to be caused by the combined action of shock desorption from icy grain mantles and high-temperature, gas-phase shock chemistry. Only three of the molecules are briefly discussed here. For OH and H2O three of the nine observed positions are shown, while a map of the C18O emission is provided. An extensive paper was recently published with Open Access (Karlsson et al. 2013, A&A 554, A141).

Type
Contributed Papers
Copyright
Copyright © International Astronomical Union 2014 

References

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Hydroxyl, water, ammonia, carbon monoxide and neutral carbon towards the Sgr A complex
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