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Hat Creek HCO+ and HCN Observations of Sgr A

Published online by Cambridge University Press:  23 September 2016

M.C.H. Wright ,
J. M. Marr  and
D. C. Backer
M.C.H. Wright
Affiliation:
Radio Astronomy Laboratory, U.C. Berkeley, CA 94720
J. M. Marr
Affiliation:
Radio Astronomy Laboratory, U.C. Berkeley, CA 94720
D. C. Backer
Affiliation:
Radio Astronomy Laboratory, U.C. Berkeley, CA 94720

Abstract

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We report aperture synthesis observations of the HCO+ and HCN J=1–0 molecular lines towards the Galactic center. These data complement existing HCN data and trace a dense molecular ring surrounding the ionized central 2 pc of the Galaxy. The new data are consistent with the model of a clumpy, almost complete ring which is inclined to the line of sight at 50 to 75 degrees. The same structure is seen in HCO+ and in HCN with the exception of an HCN feature at 60 to 100 km/s in the western part of the ring, which is not detected in HCO+ emission. The HCN and HCO+ are collisionally excited in clumps with densities around 10 cm and volume filling factor 1/3 to 1/30. H13 CN emission from the ring was detected at about 1/7 of the intensity of the HCN; the latter is optically thick and is mapping a combination of surface density and excitation temperature. The HCO+ emission shows deep absorption features associated with galactic structure along the line of sight. Absorption features corresponding to the 3 kpc arm, the inner disk and an expanding ring at −195 km/s can be seen in absorption against the Sgr A radio continuum.

Type
Sagittarius A West and the Circumnuclear Disk
Information
Symposium - International Astronomical Union , Volume 136: The Galactic Center , 1989 , pp. 407 - 410
Copyright
Copyright © Kluwer 1989 

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