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Paper: Production and Injection of Elements: Summary of the Discussions in Panel B
Volume: 147, Abundance Profiles: Diagnostic Tools for Galaxy History
Page: 224
Authors: Maeder, Andre
Abstract: Several ``hidden parameters'' which drastically influence the chemical yields are identified, such as the core sizes depending very much on mixing and mass-loss, the mass M_BH above which stars form black holes, the mass cut separating the ejected matter in supernovae from that falling into the compact remnant and also the ratio SNIa/SNII, often taken as an adjustable parameter. Specific problems related to the Delta Y/Delta Z ratio, the production of ^3He, ^7Li and ^{10,11}B are examined. A great mystery is the source of primary 14N. It is proposed that transition WN/WC stars are the injectors and that rotational mixing is playing a role. It is emphasized that many useful constraints on massive star injection might be obtained by a simultaneous study of Delta Y/Delta Z, N/O, the element ratio (O-Si)/(Si-Fe) and of r-elements/O, etc. in very metal deficient stars. The case of I Zw 18 raises many questions about the presence of possible new metals either in the cold or in the hot phases of the gas. Why is there a limit of about 140 Z_{\odot} for the minimum Z content? The presence of WR stars in such a low Z galaxy is also a matter of investigation and several questions regarding the dust and particularly its presence around WC stars arise. New supports are given in favor of a universal IMF, independent of $Z$ and being the same in starbursts without lower mass cut. However, cases of deviations from this general rule in the center of very young clusters (thus disregarding dynamical effects) are given, still raising the question of the effect of local conditions in the interstellar medium on the IMF.
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