Ingredients of GCE models

The net result of all these processes is to produce a standard or local Galactic abundance distribution in our vicinity with typical mass fractions X — 0.7 for hydrogen, Y — 0.28 for helium and Z 0.01 to 0.02 for heavier elements consisting chiefly of O, C, N, Ne, Mg, Si and Fe (see Fig. 1.4). 

To put together a model for the chemical evolution of galaxies, one needs the 

Other representative data for stars with different initial masses are given in Table 7.1. Numbers in brackets refer to Z = 0.001, Y = 0.24, others to Z = 0.02, Y = 0.28, i.e. near solar. The luminosities of the most massive stars are quite insensitive to Z. 

The contributions of different stars to nucleosynthesis depend on their initial mass and chemical composition, their mass loss history in the course of evolution and effects of close binaries (especially SN la). When mass loss is small, as is believed to be the case for low metallicities, the distribution of primary elements (those synthesized directly from hydrogen and helium) in ejecta from massive stars is mainly the result of hydrostatic evolution with some modifications to deeper layers resulting from explosive nucleosynthesis in the final SN outburst, classically 

Some sample results of calculations of stellar yields, i.e. the mass of a nuclear species freshly synthesized and ejected from a star of given initial mass and chemical composition, are given in Tables 7.2, 7.3 and 7.4. The last column of Table 7.2 gives an IMF-integrated yield which can be compared with the Solar-System abundances. 

---