The earliest phases of the chemical evolution of our Galaxy are analysed in the light of the recent VLT results (concerning abundance patterns in the most metal-poor stars of the Galactic halo) and of stellar nucleosynthesis calculations. It is argued that, among the various suggestions made in order to explain the observed abundance patterns, nucleosynthesis in asymmetric supernova explosions appears most promising. The data suggest a correlation between asymmetry and metallicity, which is hard to justify theoretically. The data also confirm the absence of dispersion in abundance ratios, at least up to the Fe peak, in the early Galaxy; this may be related to the (presently poorly known) timescales of homogeneisation of the interstellar medium, but also on small yield variations among massive stars. Finally, the metallicity distribution of halo stars may provide important constraints on the formation of the Milky Way; at present, it is not clear whether observations support the hierarchical formation scenario.

We report on a dedicated effort to identify and study metal-poor stars that are strongly enhanced in r-process elements ($\mbox{[r/Fe]}>+1.0$dex; hereafter r-II stars), the Hamburg/ESO R-process Enhanced Star survey (HERES). In a sample of 253 confirmed metal-poor stars for which “snapshot” spectra ($R\sim 20,000$; $S/N \sim 50/1$ per pixel) were obtained with VLT/UVES, and abundances were determined in an automated fashion using the methods of Barklem et al. (2005), we identified eight new r-II stars. They are now being studied in detail by means of higher resolution and S/N spectroscopy. The new r-II stars have metallicities in the range $-3.2<\mbox{[Fe/H]}<-2.6$. Future searches for r-II stars should therefore focus on stars in this [Fe/H] range. Moderately r-process enhanced stars (i.e., $+0.3\,\mbox{dex}<\mbox{[r/Fe]}<+1.0\,\mbox{dex}$; r-I stars) were found at metallicities as high as $\mbox{[Fe/H]} = -1.5$. The [Fe/H] ranges in which r-I and r-II stars can be found may provide an important constraint for the identification of the site(s) of the r-process(es).

We found that in regions of high mass star formation the CS emission correlates well with the dust continuum emission and is therefore a good tracer of the total mass while the N$_2$H$^+$ distribution is frequently very different. This is opposite to their typical behavior in low-mass cores. The behavior of other high density tracers varies from source to source but most of them are closer to CS. Radial density profiles in massive cores are fitted by power laws with indices about −1.6, as derived from the dust continuum emission. The radial temperature dependence on intermediate scales is close to the theoretically expected one for a centrally heated optically thin cloud. The velocity dispersion either remains constant or decreases from the core center to the edge. Several cores including those without known embedded IR sources show signs of infall motions. They can represent the earliest phases of massive protostars. There are implicit arguments in favor of small-scale clumpiness in the cores.

We present a compiled catalogue of effective temperatures, surface gravities iron and magnesium abundances, along with distances, velocity components, and orbital elements for stars in the solar vicinity. Abundances were found from 1412 determinations in 31 publications for 876 dwarfs and subgiants by means of a three-step iteration averaging procedure, with weights assigned to each source of data as well as to each individual determination. The assumed coverage completeness for data sources containing more than 5 stars, as of late 2003, exceeds 90%. For the vast majority of stars in the catalogue, the spatial-velocity components were derived from modern high-precision astrometric observations, and their galactic-orbit elements were computed using a three-component model of the Galaxy, consisting of a disk, a bulge, and a massive extended halo.

The Magellanic Clouds, consisting of the LMC, the SMC and the Bridge offer an ideal laboratory for studying cluster formation in a lower metal abundance environment at an unrivaled closeness to us among external galaxies. It is known that very young populous clusters like R136 are still being formed in the LMC, where populous clusters include more than 10000 stars tightly gravitationally bound. In this talk, I will present mm and sub-mm CO observations of the Magellanic molecular clouds obtained with NANTEN, SEST, and ASTE at spatial resolutions of 5–50pc. I will then use these CO data to identify the parent cloud cores for populous clusters and discuss the cluster formation by comparing the cloud properties with those of the Milky Way.

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.

From Ge I lines in the near-ultraviolet, germanium abundances are deduced for the Sun, one metal-poor subgiant, and nine turnoff stars spanning a range of metallicities. The abundance of germanium with respect to iron varies widely among the stars, and is always at or below its solar proportion. In four stars, one mildly and the rest extremely metal-poor, Ge is deficient by [ges ]0.5 dex. The nearby elements Zn and Zr show nearly scaled-solar abundances. The Ge deficiency persists when heavy r-process elements such as platinum are extremely enhanced. Among this small sample, Ge deficiency correlates with Al deficiency, of similar size.

A large body of theoretical and computational work shows that jets - modelled as magnetized disk winds - exert an external torque on their underlying disks that can efficiently remove angular momentum and act as major drivers of disk accretion. These predictions have recently been confirmed in direct HST measurements of the jet rotation and angular momentum transport in low mass protostellar systems. We review the theory of disc winds and show that their physics is universal and scales to jets from both low and high mass star forming regions. This explains the observed properties of outflows in massive star forming regions, before the central massive star generates an ultracompact HII region. We also discuss the recent numerical studies on the formation of massive accretion disks and outflows through gravitational collapse, including our own work on 3D Adaptive Mesh simulations (using the FLASH code) of the hydromagnetic collapse of an initial rotating, and cooling Bonner-Ebert sphere. Magnetized collapse gives rise to outflows. Our own simulations show that both a jet-like disk wind on sub AU scales, and a larger scale molecular outflow occur (Banerjee & Pudritz 2005).

We present here the first results (on NGC 2808 and NGC 6752) of a program that studies the anticorrelation between Na and O in a sample of Galactic Globular Clusters, using GIRAFFE spectra obtained with UVES@VLT.

We investigate the main differences between static 1D and 3D time-dependent model stellar atmospheres of red giants at very low metallicities. We focus in particular on the impact of 3D LTE spectral line formation on the derivation of elemental abundances for the extremely metal-poor ([Fe/H] $\approx-$5.3) red giant HE 0107-5240.

We have computed updated models of population II stars on the Spite plateau. We focus here on the light elements abundance predictions when the new tachocline mixing process is accounted for.

Spectroscopic abundances of s- and r-process enriched very metal-poor stars are interpreted as the result of mass transfer in a binary system from an AGB companion assuming an initial composition of the parental cloud pre-enriched in r elements. The spectroscopic determination of [Na/Fe], [Mg/Fe] and [ls/Fe] permits an estimate of the initial AGB stellar mass, while a value [Zr/Nb] ≈ 0 is a nuclear indicator of an extrinsic AGB in a binary system.

We have studied the lithium abundance in 18 extremely metal-poor main-sequence turnoff stars as a function of [Fe/H] and $T_{\rm eff}$, using high-quality VLT/UVES spectra. The sample covers the range $-3.3\le [{\rm Fe}/{\rm H}]\le -2.5$, with half of the stars below [Fe/H] = −3.0. $T_{\rm eff}$ is determined from H$\alpha$ line profiles as well as from B-V, V-K, J-H and J-K colours. The behaviour of A(Li) as a function of metallicity is markedly different when different temperature scales are adopted. However, even when applying standard depletion corrections, it is a robust result that the Li abundance in extremely metal poor dwarfs is far below the prediction of standard big bang nucleosynthesis using a baryonic density consistent with the WMAP data.

PN G 135.9 +55.9 is an extraordinary nebula discovered recently in the Galactic halo (Tovmassian et al. 2001). The first studies estimated its oxygen abundance to be 1/100 of the solar value or even less.

Being extremely metal-poor, PNG 135.9+55.9 offers an unprecedented opportunity to check our understanding of the evolution of intermediate-mass stars at very low metallicity, by complementing the data obtained from metal-poor giants (Spite et al 2005). Indeed, PNG 135.9+55.9 and some of those stars are snapshots of the evolution of very similar stars at different times.

We present our most recent abundance analysis for this object, providing stringent limits on the abundances of C, N, O, and Ne, to be confronted with the predictions for the yields of low metallicity intermediate mass stars.

Star formation at very low metallicity is expected to produce only massive stars. This is a result of the low cooling rate. Hydrodynamical simulations of star formation from zero metallicity gas suggest that the first stars had masses in excess of about 102 M[odot]. These stars can not be observed because of their large redshift and their very short lifetime. However, a similar (but not the same) effect might be observable in regions of star formation close to very luminous radiation sources, where intense radiation may destroy dust and CO molecules in starforming clouds. Such clouds will be warmer than in normal metal rich star forming regions because of the reduced cooling, which is then predominantly due to H2 and atomic C and O. Under those conditions star formation may result in the formation of high mass stars without the normal large numbers of accompanying low mass stars. Observations show that this process may occur close to the centre of the interacting galaxy M51, where the intense radiation of the nuclear starburst and the small dust content destroyed molecular CO in star forming regions. HST observations of this region show the presence of about 30 massive stars, of $25\textlessM\textless 150 M\odot$, without the accompanying clusters of low mass stars.

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 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.

Low mass AGB Stars are the main contributors to the Galactic s-process enrichment. We present new theoretical results obtained by adopting a full network from H to Bi coupled with the physical evolution of the stellar structure. We describe the formation of a 13C pocket as a consequence of H diffusion from the envelope into the He-rich intershell. Such 13C is burnt during the interpulse phase and provides the main neutron source in these stars. We computed two models with the same total mass (that is 2 M[odot]) but two different initial chemical composition, namely (Y=0.269 – Z=0.015) and (Y=0.245 – Z=0.0001), representative of disk and halo stars respectively. We evaluate the differences in the final s-process surface composition and compare the results with the available observational data.

The rare light elements — Li, Be, and B — have a unique and highly coupled history in the Universe. A coordinated analysis of their abundances in very low metallicity stars can help us understand the inner workings of stars and can constrain models of Galactic chemical evolution. We measure the Be abundances of nine stars and the Li isotopic ratio of ten stars. We find three stars with interesting Be abundances and three stars with detectable $^6$Li.

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.