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The Galactic Centre

Published online by Cambridge University Press:  14 August 2015

J. H. Oort
J. H. Oort*
Affiliation:
Sterrewacht, Leiden, The Netherlands

Abstract

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The phenomena displayed by the interstellar medium in the galactic centre are considered. The asymmetries shown by the features between 1 and 3 kpc from the centre together with the presence of material lying out of the galactic plane favour the expulsion hypothesis for their origin. The nuclear disk shows a perturbation which might have resulted from such expulsion. The dense molecular clouds in the disk may well be considered as the most direct evidence that matter is expelled from the nucleus and that this occurs at a high rate. The +50 km s-1 feature in the direction of Sgr A may be the most recently expelled body of molecular gas. New observations of the central radio source, Sgr A, have revealed details on a very small scale, and the infrared core also shows a complicated structure. Probably a number of individual concentrations of gas and dust are present. While the position of the actual nucleus seems now to have been defined to within a few arcseconds, no indication has yet been found concerning its nature nor concerning the mechanism that enables it to expel the vast expanding masses of gas observed in the central region.

Type
Part 5: The Galactic Center
Information
Symposium - International Astronomical Union , Volume 60: Galactic Radio Astronomy , 1974 , pp. 539 - 547
Copyright
Copyright © Reidel 1974 

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