| The dissertation consists of two sections. The first one mainly introduce the chemical evolution model and observational constrain, and the second mainly introduce the nucleosynthesis of r-process and the chemical evolution of Ba peak elements.The formation and evolution of the Galaxy has long been a basic and important branch and one of the most active frontiers in the fields of astrophysics. There are several aspects in galactic evolution, such as dynamic evolution, Chemical evolution and thermal evolution, etc. They provide reasonable explanation of the formation and evolution of galaxies in different facets. Among the evolution it is the chemical evolution of the Galaxy showing its exceeding importance. The recognize to the Galaxy chemical evolution builds up the basement of understanding the whole Galaxy evolution.and it can restrict and constrain the evolution and nucleosynthesis of the stellar. The aim of the Galaxy chemical evolution research is to reproduce the element abundance pattern of stars and gas in the Galaxy. Starting from a volume of gas that mass, chemical composition and density are already known, observable parameters of Galaxy evolution are reproduced as a function of the time, applying knowledge of stellar formations, evolution and nucleosynthesis.On the bases of the Galaxy evolution theory, we use the theoretical chemical evolution model of three zones (such as halo, thick disk and thin disk) and multi-phase (diffuse gas, molecular clouds, stars of both low and high mass, the remnants). By comparing with the observational constraints,such as surface densities, age-metallicity relation, G-dwarf metallicity distribution in the solar neighbourhood and the correlation between [ a /Fe] and [Fe/H], supernovae rates,infall rates, the rationality of the model is verified. Based on the theory model, we calculate the abundance of neutron capture elements. The average abundance distributions of heavy elements in metal-poor stars can provide fairlydirect and detailed information on the nucleosynthesis in every stage after the formation of galaxies. Furthermore, it can put more accurate constraints on the chemical evolution of neutron-capture elements. The solution to this problem will have important effect on the solution to a series of problems about nuclear astrophysics and the galactic evolution. This letter aiming at this respect, hints for neutron capture elements are derived:1.Based on the adopted Galactic evolution scenario, together with the three-zone multi-phase model, observational features of the solar vicinity region can be well reproduced. Among those are particularly G-dwarf problem. The G-dwarf problem in halo and thin-disk can be solved.2.We derive the yield of the heavy elements in various supernova. There is a peak (18M< M<33 Mo) in the yield of the heavy elements. Thus, massive stars (i.e.18M< M<33 M) is the primary sites of the nucleosynthesis of the r-process and can explain the galaxy chemical evolution.3.We present formula to calculat the r-process galactic chemical evolution of Ba peak elements. This formula contains metallicity abundance and points out the relation of the Ba peak elements and discusses the effect of various mass supersnova.Besides, our formula can be confirmed by a lot of observations.4.our results suggest that the r-process could be associated with a secondary sites in massive Type II supernovae stars (i.e.18M< M<33 M) requiring preexisting "seed "material, which occurs in supernovae of massive stars,but with a neutron source (13C(a,n)16O or 22Ne(a,n)25Mg). We also find that the [Eu/Fe] ratio in such secondary r-process scenarios (e.g., 22Ne(a,n)25Mg) is always less than the solar system value. Thus, this kind of secondary r-process site seems ruled out by the observations.Recently, the abundance evolution of n-capture elements in metal-poor starsplays more and more important and active role in chemical evolution of the Galaxy. The study to the field nowadays is mainly that simulating the observed data. But theory model develops slow... |
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