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HI Absorption Against the 40 km s−1 Cloud and the Circum-nuclear Disk in Sgr A

Published online by Cambridge University Press:  23 September 2016

Joan Lasenby ,
F. Yusef-Zadeh  and
Anthony N. Lasenby
Joan Lasenby
Affiliation:
Mullard Radio Astronomy Observatory, Cambridge, UK
F. Yusef-Zadeh
Affiliation:
NASA/Goddard Space Flight Center and Northwestern University

Abstract

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HI absorption studies of the Sgr A complex based upon recent VLA2 observations, show that the 40 km s−1 molecular cloud lies behind the Sgr A West region, and that the cloud may be physically associated with the Sgr A East non-thermal shell. The absorbing gas over the range +30 to +60km s−1 lies mainly between the eastern edge of the Sgr A East shell and the western boundary of a cluster of HII regions. There is a pronounced velocity gradient over this region, and at 40 km s−1 similar morphology is apparent between the distribution of atomic hydrogen and the edge of the Sgr A East shell. The physical association of the 40 km s−1 cloud and the Sgr A East shell, and the placing of the 40 km s−1 cloud behind Sgr A West, are consistent with recent evidence which has demonstrated that Sgr A West lies infront of Sgr A East. The HI optical depth maps of the circum-nuclear disk plus a new HI feature associated with the northern extension of Sgr A West will be presented.

Type
The Environment of the SGR A Complex
Information
Symposium - International Astronomical Union , Volume 136: The Galactic Center , 1989 , pp. 365 - 370
Copyright
Copyright © Kluwer 1989 

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