Other
Scientific paper
Sep 1993
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1993phdt.........1u&link_type=abstract
Ph.D. Thesis California Univ., Los Angeles.
Other
4
Galactic Nuclei, Gas Flow, Infrared Radiation, Molecular Gases, Neutral Gases, Hypotheses, Microwave Spectra, Millimeter Waves, O Stars, Star Clusters
Scientific paper
The Galactic center region exhibits anomalous gas motions that may either indicate the radial ejection of gas due to a energetic central outburst or, alternatively, orbital motion in a non axisymmetric central potential, such as that of a bar. The purpose of this dissertation has been to explore these alternatives by examining new evidence of energetic activity in the Galactic center region. Particular emphasis has been placed on the unusual infrared hotspot AFGL 5376 and the radio continuum shell G359.1-0.5. What these objects have in common, and what has drawn attention to them, is their association with prominent molecular gas features extending well out of the Galactic plane. The nonthermal shell G359.1-0.5 is completely ringed by one such massive protrusion. AFGL 5376 is associated with another -- a well-defined, 90-pc spur of gas. This dissertation also reports on a new set of far-infrared continuum structures (the IR Spurs) which, like the molecular features, extend away from the Galactic plane. The data which have been acquired and analyzed for this investigation include (1) millimeter-wave molecular line ((12)CO J = 2-1 and 1-0) observations of AFGL 5376 and G359.1-0.5, (2) lambda 21 cm neutral hydrogen line and continuum observations toward G359.1-0.5, and (3) 12, 25, 60 and 100 microns IRAS images of the 'IR Spurs'. In addition, a kinematic code was developed to model the expansion of, and the effects of Galactic shear on the localized molecular ring associated with and surrounding G359.1-0.5. The energy output from a star cluster composed of nearly 200 O-type stars is apparently needed to account for the expansion of the ring. AFGL 5376 provides strong evidence of a recent major release of energy from the Galactic center; it is the locus of a large-scale vertical shock which bisects the entire length of its associated molecular spur. It is most readily understood in terms of explosion-induced expansion motions from the nucleus. A central energy release is the favored hypothesis for the observed anomalous gas motions, although the response of the gas to a bar remains a viable alternative.
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