The Observability of Abundance Ratio Effects in Dynamically Hot Stellar Systems

Abstract

Using synthetic spectra, we construct a simple model of an elliptical galaxy with a velocity dispersion σ = 200 km s-1. Absorption feature indices are defined that are sensitive to the abundances of C, N, O, Na, Mg, Al, Si, S, K, Ca, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Sr, Ba, and Eu as a first step in determining the abundances of these elements in stellar populations such as elliptical galaxies for which integrated spectra are available. Using these indices and assuming a photon statistical error such that S/N = 100 around 5000 A, the feasibility of measuring individual elements in real galaxies is assessed. Of the elements studied, only S, K, Cu, Zn, and Eu appear to be difficult to determine. The rest appear to be measurable with high-quality data and models. The effects of abundance changes on Lick IDS indices, Rose indices, and BRVI colors are also tabulated.