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In this review, I will discuss the comparison between model results and observational data for the Milky Way, the predictive power of such models as well as their limits. Such a comparison, known as Galactic archaeology, allows us to impose constraints on stellar nucleosynthesis and timescales of formation of the various Galactic components (halo, bulge, thick disk and thin disk).

Terzan 5 is a heavily obscured stellar system located in the inner Galaxy. It has been postulated to be a stellar relic, a bulge fossil fragment witnessing the complex history of the assembly of the Milky Way bulge. In this paper, we follow the chemical enrichment of a set of putative progenitors of Terzan 5 to assess whether the chemical properties of this cluster fit within a formation scenario in which it is the remnant of a primordial building block of the bulge. We can explain the metallicity distribution function and the runs of different element-to-iron abundance ratios as functions of [Fe/H] derived from optical-infrared spectroscopy of giant stars in Terzan 5 by assuming that the cluster experienced two major star formation bursts separated by a long quiescent phase. We further predict that the most metal-rich stars in Terzan 5 are moderately He-enhanced, and we predict a large spread of He abundances in the cluster, Y ≃ 0.26–0.335. We conclude that current observations fit within a formation scenario in which Terzan 5 originated from a pristine or slightly metal-enriched gas clump about one order of magnitude more massive than its present-day mass. Losses of gas and stars played a major role in shaping Terzan 5 the way we see it now. The iron content of the youngest stellar population is better explained if the white dwarfs that give rise to type Ia supernovae (the main Fe factories) sink toward the cluster center, rather than being stripped by the strong tidal forces exerted by the Milky Way in the outer regions.

In this review, we discuss the impact of s-process nucleosynthesis in asymptotic giant branch stars on the enrichment of heavy elements. We review the main steps made on this subject in the last 40 years and discuss the importance of modelling the evolution of the abundances of such elements in our Milky Way. From the comparison between model results and observations, we can impose strong constraints on stellar nucleosynthesis, as well as on the evolution of the Milky Way.

This is the first of a series of papers that will introduce a user-friendly, detailed, and modular Galactic Chemical Evolution Model, GalCEM, that tracks isotope masses as a function of time in a given galaxy. The list of tracked isotopes automatically adapts to the complete set provided by the input yields. The present iteration of GalCEM tracks 86 elements broken down into 451 isotopes. The prescription includes massive stars, low-to-intermediate-mass stars, and Type Ia supernovae as enrichment channels. We have developed a preprocessing tool that extracts multidimensional interpolation curves from the input yield tables. These interpolation curves improve the computation speeds of the full convolution integrals, which are computed for each isotope and for each enrichment channel. We map the integrand quantities onto consistent array grids in order to perform the numerical integration at each time step. The differential equation is solved with a fourth-order Runge–Kutta method. We constrain our analysis to the evolution of all light and intermediate elements from carbon to zinc, and lithium. Our results are consistent up to the extremely metal-poor regime with Galactic abundances. We provide tools to track the mass rate change of individual isotopes on a typical spiral galaxy with a final baryonic mass of 5 × 1010 M ⊙. Future iterations of the work will extend to the full periodic table by including the enrichment from neutron-capture channels as well as spatially dependent treatments of galaxy properties. GalCEM is publicly available at https://github.com/egjergo/GalCEM.

In this lecture I will introduce the concept of galactic chemical evolution, namely the study of how and where the chemical elements formed and how they were distributed in the stars and gas in galaxies. The main ingredients to build models of galactic chemical evolution will be described. They include: initial conditions, star formation history, stellar nucleosynthesis and gas flows in and out of galaxies. Then some simple analytical models and their solutions will be discussed together with the main criticisms associated to them. The yield per stellar generation will be defined and the hypothesis of instantaneous recycling approximation will be critically discussed. Detailed numerical models of chemical evolution of galaxies of different morphological type, able to follow the time evolution of the abundances of single elements, will be discussed and their predictions will be compared to observational data. The comparisons will include stellar abundances as well as interstellar medium ones, measured in galaxies. I will show how, from these comparisons, one can derive important constraints on stellar nucleosynthesis and galaxy formation mechanisms. Most of the concepts described in this lecture can be found in the monograph by Matteucci (2012).

We are briefly introducing the most important ingredients to study galactic evolution. In particular the roles of star formation, nucleosynthesis and gas flows. Then we are discussing the two different approaches to galactic evolution: the stellar population approach (chemical evolution models) and the hierarchical clustering scenario for galaxy formation. It is shown that there are still some controversial points in the two approaches, as is evident in the brief summary of the discussion.

In this paper we discuss the impact of the s-process nucleosynthesis in Asymptotic Giant Branch stars on the enrichment of heavy elements. We review the main steps made on this subject in the last 40 years and discuss the importance of modelling the evolution of the abundances of such elements in our Milky Way. From the comparison between model results and observations, we can impose strong constraints on stellar nucleosynthesis as well as on the evolution of the Milky Way.

The time-delay model is the way we interpret the diagram [X/Fe] vs. [Fe/H], where X is the abundance of a generic element from carbon to uranium. This interpretation is based on the lifetimes of stars of different masses producing different elements. The abundance of Fe ([Fe/H]) traces the \"stellar metallicity\" and is due to supernovae Type Ia, which are believed to be the major producers of Fe, and in part to supernovae core-collapse. In particular, if X is an alpha-element, produced on short timescales from massive stars, the ratio [alpha/Fe] will show an overabundance of the alpha-elements relative to Fe at low metallicity. In fact, the bulk of Fe is produced with a time delay relative to alpha-elements, since Type Ia supernovae are white dwarfs in binary systems and they can have lifetimes as long as the age of the Universe. In this paper, I will show how powerful is the time-delay model in order to interpret the abundance patterns observed in stars and interstellar gas, since it allows us to put constraints on stellar nucleosynthesis as well as on the star formation histories of galaxies. I will present some applications of the time-delay model, in particular to the chemical evolution of the Milky Way and galaxies of different morphological type as well as to the identification of high redshift objects by means of their abundances.

We discuss some important topics concerning the chemical evolution of the Milky Way. In particular, we compare the predictions of theoretical chemical models for our Galaxy with the latest observational data in order to derive constraint on the formation and evolution of the various Galactic components.

In this review I will discuss the comparison between model results and observational data for the Milky Way, the predictive power of such models as well as their limits. Such a comparison, known as Galactic archaeology, allows us to impose constraints on stellar nucleosynthesis and timescales of formation of the various Galactic components (halo, bulge, thick disk and thin disk).