The star formation history of galaxies

Abstract

The star formation history of galaxies is the primary influence on galaxy evolution, and hence the evolution of almost all the visible matter in the universe. In this dissertation, I present studies of the star formation history of galaxies which have come from two distinct perspectives: the study of galaxies that have unusual star formation histories, and the search within the general galaxy population for galaxies with unusual star formation histories. A spectrophotometric atlas of 40 merging and strongly interacting galaxies is obtained and analyzed in order to examine their stellar populations and star formation histories. Within the sample, the subsample of 10 ultraluminous IRAS systems is compared with the optically selected subsample. The population of objects in the sample with anomalously strong Balmer absorption lines, a spectral signature indicative of post-starburst evolution, is examined and compared with distant "E+A galaxies" which have similar spectrophotometric properties. Spectrophotometry across the entire optical wavelength range is obtained and analyzed for a sample of 8 E+A galaxies, ranging in redshift from 0.09 ≤ z ≤ 0.54. The method of stellar population modeling, widely used with only minor variations in the astronomical community, is examined and its strengths and limitations are discussed.