An Investigation of Physical Factors that Determine Galaxy Structure Based upon a New Method of Quantitative Analysis.

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The aim of the project is to understand what physical factors are responsible for the wide variety of galaxy structure on the basis of quantitative analyses of a large number of galaxy images. Results of this 5-year project are summarized as follows.1. Investigation of Galaxy Structure. We have found that (1) the number of physical factors that determine the global structure of galaxies is two, (2) the leading factor which is responsible for the wide variety of galaxian shape is the structure of the spheroidal component rather than that of the disk component, and (3) there is a well-bahaved correlation between the total luminosity of galaxies and the average phase-space density. The last correlation will ne a powerful tool to understand the mechanism of galaxy formation in the presence of dark matter. (4) Several problems related to the quantitative analyses have been studied in some detail. They include internal absorption, ultraviolet rediation, and peculiarity of galaxies, and image processing technique.2. Database of Galaxies A database has been constructed which includes two-dimensional luminosity distribution of about 800 galaxies. The detabase will be distributed on the world-wide basis to those who are interested in it.3. Astronomical Image Data Processing System. An efficient astronomical image data processing system has been developed on a dedicated superminicomputer with a variety of image I/O peripherals. A photographic plate scanning machine was introduced and has been successfully operated as an integral part of the system.