The star formation history of galaxies

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 {dollar}0.09le zle0.54.{dollar} 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.; A deep, broad-band multicolor galaxy survey is assembled and analyzed for information about the star formation evolution of the field galaxy population. A technique is developed to identify the redshifts and spectral types of the survey galaxies using the very low-resolution spectrophotometry provided by the multicolor data. The red galaxy population is examined for signs of active star formation evolution. The blue galaxy population is analyzed using number counts and luminosity functions subdivided by redshift. The two major results are: (1) The U-band selected blue galaxy luminosity function in the redshift range {dollar}0.02le zle0.15{dollar} is very steep and very similar to that of local Magellanic spiral and irregular galaxies. (2) An excess population of starburst galaxies is observed at {dollar}zge0.3{dollar} which is not observed at {dollar}z<0.3.{dollar} These galaxies may contribute significantly to the observed luminosity function evolution at {dollar}zge0.3,{dollar} and then fade and redden at lower redshifts.