Abundance Ratio Trends and Nucleosynthesis in Elliptical 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 about 0.3 in the largest ellipticals. For elliptical galaxies that have absorption‐line data for more elements, the abundances of Na and N elevate in a similar fashion, relative to both Ca and Fe ([Ca/Fe] ≈ 0; [Na, N/Fe] progressively > 0). Titanium may also share this apparently generic light‐element behavior.