Physics – Optics
Scientific paper
Jan 1992
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1992phdt........30z&link_type=abstract
Thesis (PH.D.)--UNIVERSITY OF CALIFORNIA, BERKELEY, 1992.Source: Dissertation Abstracts International, Volume: 54-06, Section: B
Physics
Optics
7
Galactic Evolution, Spiral Galaxies
Scientific paper
The work included in this dissertation spans the area of radio astronomical instrumentation, radio observations and the theoretical studies of galactic evolution. The instrumentation on the Berkeley-Illinois-Maryland interferometer focuses on the upgrading of the optical train to improve the aperture efficiencies of the radio telescopes. A newly designed corrugated feed-horn achieved wide-band low-return-loss impedance matching and wide-band single mode operation. Together with the use of tertiary focus optics, the new feed/optical train has a theoretical aperture efficiency of 84%. It provided a relative improvement in aperture efficiency of more than 50% at the higher frequencies. The observational study in this work concerns galaxy interaction and the resultant evolution effects. The interstellar medium of an external galaxy NGC 3627 was mapped in CO 1-0, HI and CO 2-1 with high resolutions. The radio images and the kinematic information provide added details to the history of the past close-encounter of NGC 3627 with NGC 3628. It also confirms the idea that interaction triggers a sequence of physical processes in a galaxy which enhance the chance of its becoming a star-burst and nuclear active galaxy. The theme of the theoretical study is the dynamical evolution of spiral galaxies. The general direction of this evolution is towards an ever increasing central concentration. In this work, it is demonstrated that the emergence of global spiral structures greatly accelerated the speed of the radial mass accretion process in disk galaxies. The underlying physical mechanisms are also responsible for the formation of the Giant-Molecular-Cloud complexes in spiral arms, the secular heating effect which gives rise to the age -velocity dispersion relation for disk stars, and the formation of bulges in galaxies. The thermodynamic basis of this dynamical evolution proposal is sought by applying the non-equilibrium thermodynamical theory of I. Prigogine to the cosmic initial and boundary conditions. This work has provided for the first time a coherent dynamical evolution picture for spiral galaxies.
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