Physics
Scientific paper
Mar 1982
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1982phdt........37c&link_type=abstract
Thesis (PH.D.)--YALE UNIVERSITY, 1982.Source: Dissertation Abstracts International, Volume: 43-04, Section: B, page: 1142.
Physics
15
Scientific paper
Observational studies of the recent star formation histories in SO and elliptical galaxies are described in this thesis. A photometric system using a broad-band color combined with a line strength index is used to distinguish age differences from metallicity differences between the bulges and disks of SO galaxies. A color difference of (DELTA)(U-V)(TURN)0.10 is found for the sample of galaxies observed here. Several SOs have absorption line strengths that indicate the disks are as metal rich as the most luminous ellipticals. It is concluded that the disks of SOs are younger than the bulges, but the distinction between a younger turnoff and residual star formation cannot be made. The case for star formation in ellipticals is reviewed as a prelude to several new observational studies which indicate that the phenomenon does exist. The rate of Type I supernova in early type galaxies is higher for galaxies that are in regions where gas stripping processes are unlikely to be present than is the rate in dense clusters. The color magnitude relation for ellipticals is shown to give information not only on the dependence of metallicity on luminosity, but also on the relative amounts of young stars in ellipticals. The residuals in color at a given luminosity are due mostly to variations in the proportion of young stars in the galaxies. Ellipticals that do not reside in dense clusters are in the mean bluer by 0.10 in U-V than those in dense clusters. New photometry of low surface brightness dwarf ellipticals extends the color magnitude relation for ellipticals to M = -15, and indicates that while few of these galaxies have the proportion of young stars in galaxies such as NGC 205, modest youthful populations are probably present in many of these low surface brightness dwarfs. An emission line survey of ellipticals has resulted in the detection of 40% of the galaxies in {0 II}. This probably means that galactic winds are not efficient in removing the interstellar gas in ellipticals, although the total amount of gas is still much lower than would be expected. The kinematics of the gas in those cases where rotation velocity information can be obtained indicates that the gas has an extragalactic origin. An appendix on the surface brightness profiles of the dwarf ellipticals is also presented.
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