The Galactic halo is unlikely built up from galaxy populations similar to the dwarf spheroidal galaxies (dSph's) in the Local Group, but it is possible that the halo was formed by accreted dwarf galaxies that had much larger mass and higher star formation rates such as the Saggitarius dSph. Cosmological simulations show that dSph galaxies formed via hierarchical clustering of numerous smaller building blocks. Stars formed at the galaxy centre tend to form from metal-rich infall gas, which builds up the metallicity gradients. Infalling gas has larger rotational velocity and smaller velocity dispersion due to the dissipative processes, resulting the two distinct old stellar populations of different chemical and kinematic properties, which are recently discovered in the Sculptor dSph galaxy.

The chemical composition of 91 stars in the Sculptor dwarf spheroidal galaxy is presented as determined from spectra taken with the FLAMES multiobject spectrograph in the Medusa mode. The analysis methods are outlined. The [α/Fe] ratios are shown for Mg, Ca, and Ti, and compared with those of Galactic stars. Heavy element abundance ratios (Y, Ba, and Eu) are also presented. Since the Sculptor dwarf galaxy has had a significantly different star formation history and chemical evolution than the Galaxy, then comparison of Sculptor's metal-poor (old) stars to similar metallicity stars in the Galaxy can be used to discuss galaxy formation scenarios, as well as test some of our fundamental assumptions in stellar nucleosynthesis.

We have been using VLT – FLAMES facilities to obtain spectra of large samples of stars from the Large Magellanic Cloud in order to infer chemical abundances of some key elements. Target stars have been selected trying to sample as much as possible the hole metallicity range of the population. In the present paper we continue our report on chemical abundances for stars in the Inner Disk of the LMC. In our previous work (Pompéia, Hill & Spite 2004) we have found a peculiar pattern for such stars, with a deficiency of α and Na relative to stars of the Galaxy. For the iron-peak elements we found an offset when compared to stars from the Galaxy which is difficult to explain when taking into account the present nucleosynthetic theories. In the present paper we report abundances derived from line synthesis for Y, Zr, Ba, Cu and Sc. We have found an interesting behavior for the s-process elements: while the heavy-s elements show supersolar values and overlap the galactic samples, the light-s elements are underabundant with many subsolar values. Cu and Sc show deficient patterns compared to MW stars of similar metallicities.

We present the first metallicity distribution (MDF) derived for the bulge of M31. We have used HST WFPC2 V and I images to construct the color-magnitude diagram of a field located at 1.55 kpc from the center of M31. We have translated the RGB star colors into abundances. We describe the M31 bulge MDF properties, compare them to those of the M31 halo. We discuss the analogy with our Galaxy and the implications for the formation of spiral galaxies.

Although carbon is, together with oxygen and nitrogen, one of the most important elements in the study of galactic chemical evolution its production sites are still poorly known and have been much debated (see e.g. Gustafsson et al. 1999; Chiappini et al. 2003). To trace the origin and evolution of carbon we have determined carbon abundances from the forbidden [C I] line at 8727 Å and made comparisons to oxygen abundances from the forbidden [OI] line at 6300 Å in a sample of 51 nearby F and G dwarf stars. These data and the fact that the forbidden [C I] and [O I] lines are very robust abundance indicators (they are essentially insensitive to deviations from LTE and uncertainties in the stellar parameters, see, e.g., Gustafsson et al. 1999; Asplund et al. 2005) enable us to very accurately measure the C/O ratio as well as individual C and O abundances. Our first results indicate that the time-scale for the main source that contribute to the carbon enrichment of the interstellar medium operate on the same time-scale as those that contribute to the iron enrichment (and can possibly be AGB stars…)

Carbon stars found in the Small Magellanic Cloud and the Sagittarius Dwarf Spheroidal galaxy have been chemically analysed. We found that the abundance ratios derived between elements belonging to the first and the second s-process abundance peaks agree remarkably well with the theoretical predictions of low mass metal-poor AGB nucleosynthesis models. Together with their estimated luminosities, their derived abundances and their carbon isotopic ratio we speculate on the evolutionary status of these carbon stars.

The results of a spectrum synthesis analysis of elemental abundances derived from the high-resolution CCD-spectrograms of the SMC red supergiant stars PMMR23 and PMMR39 (stars 23 & 39 in the catalogue Prevot et al. 1983) are presented. The abundances of 35 elements in the atmosphere of PMMR23 have been obtained. Elements with atomic numbers Z<56 are deficient with respect to the solar abundances. The mean underabundance is about –0.7 dex. The abundances of elements heavier than barium are close to the solar value. In the case of PMMR23, the atmosphere is enriched in elements heavier than barium which show abundances close to the solar value. These abundances can be explained as a combination of r- and s-processes. In PMMR39, all the 20 studied elements present abundances deficient with respect to solar values The abundances of 31 elements with Z>30 are determined in the atmosphere of Arcturus.

We follow the evolution of barium and europium in four Local Group Dwarf Spheroidal Galaxies by means of a detailed chemical evolution model. The model adopts up to date nucleosynthesis and takes into account the role played by supernovae of different types (II, Ia). By assuming that barium is produced in low mass AGB stars by s-process but also in massive stars (in the mass range 10–30 M[odot ]) by r-process and that europium is a pure r-process element synthesized in massive stars in the same range of masses (10–30 M[odot ]), we are able to reproduce the observed [Ba/Fe] and [Eu/Fe] as functions of [Fe/H] in all four galaxies studied. We confirm also the important role played by the very low star formation efficiencies (ν = 0.005–0.5 Gyr−1) and by the intense galactic winds (wi = 6–13) in the evolution of these galaxies.

The Fornax dSph is an interesting case as it contains five old globular clusters and its field stars, although predominantly of intermediate (3-8 Gyr old) age, cover a wide range of age and metallicity. Detailed abundance analysis is crucial to our understanding of the earliest star formation epoches, where classic CMD analysis fails to provide a unique answer. It also allows us to measure the chemical evolution of the stellar population following tracers of different enrichment mechanisms through time, e.g. SN type II (alpha elements); AGB stars (s-process elements) etc. With our large sample of abundance measurements we will obtain a detailed picture of the evolution of Fornax and of the role played by small galaxies in the building up of larger ones.

Using a kinematic criterion reveals stars of extragalactic origin from our sample. We show that the ratios of r- and α-elements in all the accreted stars differ sharply from those in the stars that are genetically associated with the Galaxy. Since the majority of accreted stars of our sample exhibit a significant Eu overabundance relative to Mg, we conclude that the maximum masses of the SN II progenitors outside the Galaxy were much lower than those inside it. We provide evidence that the maximum mass of the SN II progenitors increased in the Galaxy with time simultaneously with the increase in mean metallicity.

We present elemental abundance ratios for bright red giants in the old, distant open clusters Berkeley 20, Berkeley 21, NGC 2141, Berkeley 29, and Berkeley 31 as well as for distant field red giants in the direction of the southern Galactic warp. At Galactocentric distances beyond 10 to 12 kpc, the metallicity gradient disappears. The open cluster and field red giants of the outer disk exhibit an almost constant iron abundance [Fe/H] = −0.5. We also measured the abundances for 15 other elements and found very similar compositions in the field and cluster stars. Specifically, they all show enhancements of the α elements O, Mg, Si, Ca, and Ti as well as the r-process element Eu. These abundance patterns reveal a rapid star formation history for the outer Galactic disk. A possible explanation for the measured compositions is that the outer disk formed as a result of star formation triggered by a series of merger or accretion events.

The chemical composition of high-redshift galaxies is an important property that gives clues to their past history and future evolution. Measuring abundances in distant galaxies with current techniques is often a challenge, and the canonical metallicity indicators can often not be applied. I discuss currently available metallicity indicators based on stellar and interstellar absorption and emission lines, and assess their limitations and systematic uncertainties. Recent studies suggest that star-forming galaxies at redshift around 3 have heavy-element abundances already close to solar, in agreement with predictions from cosmological models.

The enrichment of the intergalactic medium (IGM) with heavy elements provides us with a record of past star formation and with an opportunity to study the interactions between galaxies and their environments. We summarize current data analysis methods and observational constraints on abundances in the diffuse, high-redshift (z>2) IGM. This review is targeted at interested outsiders and attempts to answer the following questions: Why should you care? What do we want to measure? How do we do it? What do we know? What are the common misconceptions?

We have recently completed the measurement of the abundances of the elements Zn and Cr in a small, but complete, sample of damped Lyman alpha systems selected irrespectively of their dust content (the CORALS radio sample). We find that at a mean redshift z = 2.4 their metallicity and degree of dust depletion are statistically indistinguishable from those of larger samples of DLAs assembled from optical surveys. Thus we conclude that reasons other than a dust-induced bias must be found to explain the lack of redshift evolution in the metallicity of the galaxies giving rise to DLAs, and their generally low degree of chemical enrichment compared with luminous galaxies observed at the same epoch.

The question of how metals are produced in the Universe and where they are located is fundamental for our understanding of galaxy formation and evolution. This question can be best addressed using absorption lines seen in the spectra of remote quasars. It has been realized that the spatial distribution of metals around galaxies and more generally in the Intergalactic Medium is complex, and it is often very difficult to associate one absorption system with one galaxy. Except for possibly in the special case of DLA systems, it may be more appropriate to discuss the clustering properties of different classes of objects and to measure their correlation functions. I illustrate these issues with three examples: the distribution of metals around galaxies at intermediate redshift, the modelling of the clustering of C IV systems, and the determination of abundances in Damped Lyman-α systems (and in particular the oxygen abundance). Finally, I note that there is a mass-metallicity relation in Damped Lyman-α systems.

By means of chemical evolution models for galaxies of different morphological types (i.e. spirals and irregular/starburst galaxies) we study the nature of Damped Lyman-alpha (DLA) systems. By focusing on individual systems, we can derive important constraints on both their star formation history and their age. Our results indicate that the local conterparts of most DLAs are represented by dwarf galaxies having had low star formation rates, but some systems can also be associated to spirals. Some systems are already old, with ages of ∼1 Gyr, and some others are experiencing the very first star formation episodes.

The Fe/Mg abundance ratio may be one of the fundamental indicators for nucleosynthesis in the Early Universe. Even at the highest redshift, QSO broad-lined regions (BLRs) exhibit prominent 2000-3000Å Fe II(UV) band and Mg II 2800Å resonance doublet emission in the restframe UV. The Mg is formed in Type-II SNe, while Fe has been traditionally thought to be produced in Type Ia SNe. These different origins imply a sharp falloff in Fe abundance at very high-z. However, these predictions are clouded by uncertainties about the nature of the first stars and in the nuclear yields from supernovae models. Our theoretical studies of Fe II in QSO BLRs show that Fe and Mg abundance cannot be directly deduced from the observed Fe II(UV)/Mg II, because it is sensitive to luminosity and microturbulence, as well as abundance. Observationally, support for a luminosity dependence comes from SDSS data for QSOs that show a Fe II(UV)/Mg II correlation with luminosity at z ∼ 1.8–2.0.

We present the values of CN and Mg overabundances with respect to Fe, for a large sample of elliptical galaxies in different environments. Abundances were derived by confronting observed absorption line indices with stellar population model spectra. We obtained significant differences between the [CN/Fe] and [Mg/Fe] abundance ratios as a functions of: i) the environment, and ii) the galaxy mass. This is interpreted as implying varying formation timescales for CN, Mg and Fe, combined with different star formation histories in elliptical galaxies depending on their mass and environment. Our principal conclusions are: 1) CN is sensitive to the characteristic assembly timescales of elliptical galaxies, 2) more massive elliptical galaxies are assembled on shorter timescales than less massive ones, 3) elliptical galaxies in denser environments are assembled on shorter timescales than those in lower density environments, and 4) our results strongly suggest an upper limit for the assembly timescale of ∼1 Gy, in all cases.

Some basic observational properties of Damped Lymna α systems (DLAs) have been examined by Monte Carlo simulation based on the assumption that DLAs are disks form at the center of dark halo at redshift 3. We found that the predicted cosmic star formation rate density contributed by DLAs is consistent with the most recent observations if the star formation timescale in DLAs is assumed to be 1 ∼ 3 Gyr. By comparing the UV luminosity function between DLA host galaxies and that of Lyman Break Galaxies(LBGs), we show that the DLAs host galaxies are much fainter than LBGs, and that only few percent of DLAs can host LBGs. The discrepancy between model prediction and observation in the correlation between metallicity and HI column density for DLAs is reproduced on the basis of Kennicutt star formation formalism at high redshift. It is quite difficult to interpret this concerning the complexities of dust depletion, star formation mode as well as model limitations. Further investigations are needed.

We assume that Damped Lyman-α absorbers are gas rich galaxies on early stages of their evolution, and check this idea on the basis of a spectrophotometric, chemical and dust evolution model. Influence of the dust on the chemical pattern of galaxies is calculated self-consistently according Dwek's (1998) model, where up-to-date dust yields from supernovae, intermediate and low mass stars on their AGB phase are taken into account. We conclude that gas rich galaxies are good candidates on the role of DLA systems.