By adopting a chemical evolution model for the Milky Way already reproducing
the evolution of several chemical elements, we compare our theoretical results
with accurate and new stellar data of neutron capture elements and we are able
to impose strong constraints on the nucleosynthesis of the studied elements. We
can suggest the stellar sites of production for each element. In particular,
the r-process component of each element (if any) is produced in the mass range
from 10 to 30 Msun, whereas the s-process component arises from stars in the
range from 1 to 3 Msun. Using the same chemical evolution model, extended to
different galactocentric distances, we obtain results on the radial gradients
of the Milky Way. We compare the results of the model not only for the neutron
capture elements but also for alpha-elements and iron peak elements with new
data of Cepheids stars. We give a possible explanation to the considerable
scatter of neutron capture elements observed in low metallicity stars in the
solar vicinity, compared to the small star to star scatter observed for the
alpha-elements. In fact, we have developed a stochastic chemical evolution
model, in which the main assumption is a random formation of new stars, subject
to the condition that the cumulative mass distribution follows a given initial
mass function. With our model we are able to reproduce the different features
of neutron capture elements and alpha-elements. Finally, we test the
prescriptions for neutron capture elements also for the dwarf spheroidal
galaxies of the Local Group. We predict that the chemical evolution of these
elements in dwarf spheroidal galaxies is different from the evolution in the
solar vicinity and indicates that dwarf spheroidal galaxies (we see nowadays)
cannot be the building blocks of our Galaxy.Comment: 182 pages, 74 figures, PhD Thesis. Supervisor: Francesca Matteucci.
High quality figures upon reques
