Star formation histories of nearby elliptical galaxies

This work presents high signal to noise spectroscopic observations of nearby early-type galaxies. These observations provide strong tests of models for the formation of elliptical galaxies and their star formation histories.; This new data set has nearly doubled the number of galaxies for which high quality spectra are available. Combining these data with the Gonzalez (1993) data set, a volume limited sample of 45 galaxies has been defined. Results are in agreement with previous studies: the existence of the metallicity hyper-plane and the Z-plane of Trager et al. (2000) has been confirmed, and the distribution is clearly due to physical variations in stellar population parameters and not measurement uncertainty. The relation between core profile slope, luminosity, and Mg2 line strength from Carollo et al. (1997) is recreated, with disky, power-law profile galaxies having significantly lower [alpha/Fe] abundance ratios than boxy, core profile galaxies at fixed luminosity. This favors the idea that the angular momentum of a galaxy determines its membership in one of these two elliptical galaxy populations.; A sample of ellipticals believed to be remnants of major merger events was observed. The stellar populations of this sample are consistent with those of the volume-limited sample. The predicted properties of major merger remnants were not observed in any galaxy. Several systems showed signs consistent with a recent minor merger, with a young stellar population overlying an old stellar population that constitutes the majority of the galaxy's stellar mass.; The galaxy NGC 3610, likely to be the remnant of a recent gas-poor major merger, was studied using Keck LRIS spectra beyond one effective radius. Stellar population gradients were measured. No significant radial gradient was seen in age or [alpha/Fe], while a metallicity gradient of -0.30 dex per decade in radius was observed. This metallicity gradient is steeper than most predictions for merger remnants, though it does lie within the range of predicted values. The analysis of these spectra also highlight the difficulties in using Hbeta as the primary age-sensitive index.