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  • Print publication year: 2008
  • Online publication date: December 2009

28 - The metallicity distribution of the stars in elliptical galaxies

Summary

Elliptical galaxies probably host the most metal-rich stellar populations in the Universe. The processes leading to both the formation and the evolution of such stars are discussed in terms of a new multi-zone photochemical-evolution model, taking into account detailed nucleosynthetic yields, feedback from supernovae, Population-III stars and an initial infall episode. Moreover, the radial variations in the metallicity distributions of these stars are investigated using G-dwarf-like diagrams.

By comparing model predictions with observations, we derive a picture of galaxy formation in which the higher the mass of the galaxy, the shorter are the infall and the star-formation timescales. Therefore, the stellar component of the most massive and luminous galaxies might attain a metallicity Z ≥ Z in only 0.5 Gyr.

Each galaxy is created outside-in, i.e. the outermost regions accrete gas, form stars and develop a galactic wind very quickly, in contrast to the central core in which star formation can last up to ∼ 1.3 Gyr. This finding will be discussed in the light of recent observations of the galaxy NGC 4697 which clearly exhibits a strong radial gradient in the mean stellar [〈Mg/Fe〉] ratio.