ABUNDANCE RATIO TRENDS AND NUCLEOSYNTHESIS IN ELLIPTIC GALAXIES AND SPHEROIDS

Model and observed spectral feature indices indicate that, in galaxies of all types with velocity dispersions larger than about 225 km s(-1) , [Mg/Fe] progressively drifts greater than zero, until it reaches abo ut 0.3 in the largest ellipticals. For elliptical galaxies that have a bsorption-line data for more elements, the abundances of Na and N elev ate in a similar fashion, relative to both Ca and Fe ([Ca/Fe] approxim ate to 0; [Na, N/Fe] progressively > 0). Titanium may also share this apparently generic light-element behavior. The abundance pattern in el liptical galaxies matches neither the disk, the halo, nor the bulge of our own Galaxy, although the bulge appears to come the closest. N is depleted in the Galactic bulge but elevated in M31, M31's metal-rich g lobular clusters, and large elliptical galaxies. If all measured eleme nts are considered, the abundance patterns in our own Galaxy and in ex ternal galaxies requires the presence of at least three sources of che mical enrichment whose relative contributions can vary from environmen t to environment. These three sources of enrichment may correspond to Type Ia supernovae (SNe), Type II SNe, and N-rich mass loss from inter mediate-mass stars, but the behavior of O, Ca. Si, Sc, V, and Ti in th e Galactic bulge, disk, and halo seems to require at least one additio nal supernova flavor. Abundance ratio effects represent a barrier to t he estimation of mean ages from integrated light, a barrier that is gr eater than that of isochrone error. Isochrone grids allowing for the v ariation of individual elements are needed, but relative changes in is ochrone temperatures computed as a function of abundance pattern need to be accurate to roughly 7 K if 5% age estimates are desired.