We report on results of VLT/FLAMES observations of the very old cluster Cr 261. We compare the results with those of other clusters older than the Hyades.

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.

Magnetic fields may be observed via the Zeeman effect, linear polarization of dust emission, and linear polarization of spectral-line emission. Useful parameters that can be inferred from observations are the mass-to-flux ratio $M/\Phi$ and the scaling of field strength with density. The former tells us whether magnetic fields exert sufficient pressure to provide support against gravitational contraction; the latter tells whether or not magnetic fields are sufficiently strong to determine the nature (spherical or disk geometry) of the contraction. Examples of massive star formation regions for which detailed observations have been made of magnetic field strengths and morphologies include DR21OH, OMC1, and S106; observational results for these regions and relevant results for the diffuse ISM and masers will be reviewed. Results are that the strength of interstellar magnetic fields remains invariant at $B {\sim} 6\mu$G between 0.1 cm$^{-3} < n(H) < 10^3$ cm$^{-3}$, but increases as $B \propto \rho^{0.4-0.5}$ for $10^3$ cm$^{-3} < n(H_2) < 10^{8}$ cm$^{-3}$. Moreover, $M/\Phi$ is significantly subcritical (strong $B$ with respect to gravity) in diffuse H I clouds that are not self-gravitating, but becomes approximately critical in high-density molecular cloud cores. This suggests that GMCs form primarily by accumulation of matter along magnetic field lines, a process that will increase density but not magnetic field strength. How clumps in GMCs evolve will then depend critically on the $M/\Phi$ ratio in each clump.

Core collapse supernovae are responsible for at least half of the galactic inventory of Fe-group elements and probably for most of the Fe-group abundances seen in metal poor stars. Recent simulations show the emergence of a proton-rich ($Y_e>0.5$) region in the innermost ejected mass zones due to the neutrino interaction with matter. We explore the nucleosynthesis implications of these findings that result in enhanced abundances of 45Sc, 49Ti, and 64Zn, which is consistent with chemical evolution studies and observations of low metallicity stars.

Observed large scatters in abundances of neutron-capture elements in metal-poor stars may suggest incomplete mixing of the interstellar medium at the beginning of the Galaxy. Comparing predictions by an inhomogeneous chemical evolution model and new observational results with Subaru HDS, we attempt to constrain the origins of r-process elements.

We present new carbon-enhanced stars identified from the third public release of the Sloan Digital Sky Survey, SDSS-DR3. We have generated synthetic spectra with varying carbon abundances, and compare them with the SDSS spectra. We have also performed a preliminary analysis of s-process enhancement in several SDSS carbon-enhanced stars. Spectral features that are sensitve to stellar luminosity and temperature have also been explored. These methods will be applied to the large set of public SDSS data, as well as to the forthcoming data from SEGUE, the Sloan Extension for Galactic Understanding and Evolution, in order to study carbon enhancement at different metallicities, the fraction of s-process enhancement that occurs in carbon-enhanced stars, and possibly isotopic carbon abundances and nitrogen abundances.

A new class of carbon-rich stars was revealed by large surveys of very metal-poor objects, the carbon-enhanced metal-poor stars (CEMPs). This carbon enhancement is reminiscent of that found in classical CH stars, which despite being halo stars, are not as metal-poor as CEMPs. Although a mass-transfer scenario similar to that formerly at work in CH stars could account for the abundance pattern of CEMPs, differences arise for some key heavy elements. Moreover, statistical studies find 14%; of metal-poor C-rich stars among very metal-poor stars. Thus, this important population of stars represents a precious testimony for nucleosynthesis and chemical evolution at early stages of the Galaxy. We have started a detailed analysis of a large sample of both CH and metal-poor C-rich stars. Here we present results concerning the chemical composition obtained via high resolution and high signal-to-noise VLT-UVES spectra, with special emphasis on the challenges encountered during the abundance analysis. The discussion also includes preliminary results of our ongoing radial velocity monitoring programme which aims at evaluating the relevance of the binary scenario.

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.

Recent years have seen accumulating evidence for infall and rotation around disk like structures toward young stars of spectral types of early B and possibly late O. Observations indicate that the disks or tori are massive in comparison with the mass of the central stars and geometrically thick. Both properties distinguish them from the disks around low mass stars, in particular T-Tauri type stars.

I review observational techniques used in studying disks around massive young stars and summarize properties of disks derived from observations. I will discuss implications of these findings for the formation of massive stars.

We present the results of analysis of “snapshot” spectra (i.e., R=20,000 and S/N=50 per pixel) of 253 metal-poor halo stars $-3.8<$[Fe/H]$<-1.5$ obtained in the HERES survey. The spectra are analysed using an automated line profile analysis method based on the Spectroscopy Made Easy (SME) codes of Valenti & Piskunov (1996). Elemental abundances of moderate precision (absolute r.m.s. errors of order 0.25 dex) have been obtained for 22 elements, C, Mg, Al, Ca, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Zn, Sr, Y, Zr, Ba, La, Ce, Nd, Sm, and Eu, where detectable. The results are presented and discussed, particularly trends and scatter in the abundance distributions.

We have derived [Fe/H] and [α/Fe] abudnances for Cepheids with Galactocentric distances of 11 to 17 kpc. The stars are as metal-poor as much older open clusters at comparable distances. Like the clusters, and despite their youth, the Cepheids also show enhanced [α/Fe] abundances indicating enhanced contributions from SNe II relative to the Solar neighborhood.

We present results from an Eulerian adaptive mesh refinement simulation demonstrating the formation of a primordial star within an HII region produced by an earlier massive star. Despite the higher temperatures of the ionized gas, this second star formed within 23 million years of its neighbor's death. The enhanced electron fraction within the HII region catalyzes rapid molecular hydrogen formation, leading to enhanced cooling in the preprocessed halo. This “second generation” primordial protostar has a much lower accretion rate than its predecessor, due in part to the higher angular momentum of the halo in which it forms. This situation may allow binaries or multiple systems of low-mass stars to form. The result discussed here is described in more detail in O'Shea et al. (2005).

We present the results of a study of some selected spectral regions, including those around the LiI lines at 6708 Å and 6104 Å in the magnetic chemically peculiar star HD 3980 and in a few other Ap stars with different effective temperatures and different strengths of the magnetic field. High resolution spectroscopic observations were carried out with the Coudé echelle spectrograph at the 74-inch telescope of the Mount Stromlo Observatory ($R=88000$) and with the VLT UV-Visual Echelle Spectrograph UVES at UT2 at ESO ($R=110000$). Using spectral synthesis we determined abundances of Li, Ce, Pr, Nd and some other rare earth elements and showed that the spectral feature at 6708 Å in the spectrum of HD 3980 is due to the Li I doublet with only a minor contribution of the Ce II line at 6708.099 Å.

The rapid neutron capture process (r-process) is understood to be responsible for the synthesis of approximately half of all of the isotopes present in Solar System matter in the mass region from approximately zinc through the actinides. While the general features of this process were identified in the classic papers by B2FH (1957) and Cameron (1957), our current understanding of the r-process remains woefully incomplete. We have yet to cleanly identify which of the studied astrophysical sites contribute significantly to the observed abundance pattern. We have yet to reconcile the apparent duplicity of r-process sites with extant models for the operation of the r-process in diverse astronomical environments. While we may still remain theoretically challenged in our attempts to understand the r-process mechanism and to identify its site, significant clues have come from the observational side. Triggered by the first detections of the element europium (formed predominantly by the r-process) in low metallicity stars (Spite & Spite 1978), observations of heavy element abundances in halo stars have since served to provide tremendously important clues to the nature of the r-process mechanism. Identified constraints include: the utter dominance of the r-process contributions (over those of the s-process in extremely metal deficient stars; an extraordinary robustness of the r-process pattern in the mass range A[gsim]130–140; and the demand for a second r-process site for the production of the A[lsim]130 r-process nuclei. We will review these observational trends and theoretical models in the context of the Galactic (Cosmic) evolution of r-process abundances.

I review recent observational progress on the search for accretion signatures in massive young stellar objects (MYSOs). In this context, the primary tool will be 1–5 μm high resolution ($\lambda/\Delta\lambda \,{=}\,$50,000) spectroscopy. The observational regime is the phase between massive star formation (collapse, accretion, mergers, etc) and the fully revealed OB star photosphere, the phase for which the term “Massive Star Birth” was originally coined. In this phase, we seek both the signature of the earlier accretion process and the photospheric markers of the truly massive star which is on the main sequence. The sample of objects used in this endeavor are massive young stars located in nascent clusters powering Galactic giant H II regions. Emission in the 2.3 μm 2–0 vibrational–rotational bandhead of CO is observed as are the ionized lines of Hydrogen, Helium, and other abundant elements. High spectral resolution is key in giving geometrical clues to the circumstellar emission sources, both through individual line profiles (i.e. shapes) and positions.

Rotating massive stars at $Z=10^{-8}$ and $10^{-5}$ lose a great part of their initial mass through stellar winds. The chemical composition of the rotationally enhanced winds of very low $Z$ stars is very peculiar. The winds show large CNO enhancements by factors of $10^3$ to $10^7$, together with large excesses of $^{13}$C and $^{17}$O and moderate amounts of Na and Al. The excesses of primary N are particularly striking. When these ejecta from the rotationally enhanced winds are diluted with the supernova ejecta from the corresponding CO cores, we find [C/Fe], [N/Fe],[O/Fe] abundance ratios very similar to those observed in the C–rich extremely metal poor stars (CEMP). We show that rotating AGB stars and rotating massive stars have about the same effects on the CNO enhancements. Abundances of s-process elements and the $^{12}$C/$^{13}$C ratio could help us to distinguish between contributions from AGB and massive stars. On the whole, we emphasize the dominant effects of rotation for the chemical yields of extremely metal poor stars.

We present results from our ongoing survey of Galactic Giant HII Regions in the near-infrared. The luminosity function indicates that the IMF is uniform, independent of the galactocentric distance and compatible with Salpeter (1955) slope. Distances measured by the spectroscopic parallax method are systematically smaller than kinematic distances derived from radio techniques. As a consequence, the number of ionizing photons and the star formation rate is much lower than that derived from rotation models. Although the luminosities of the giant HII regions obtained from this method are lower than by other methods, the morphological type of the Milky Way is well in line of previous results, close to Sbc or Sc types.

Using the method of spectral synthesis we derived the abundances of Li in the atmospheres of 100 stars in the range of metallicities −3${<}$[Fe/H]${<}$0.2. The investigated spectra are part of the library collected at the Haute Provence Observatory, they were obtained with the 193 cm telescope equipped with ELODIE spectrometer (R=42000). For the metal-poor dwarfs, in the “Spite plateau” region ([Fe/H]${<}$−1.7, $T_{\rm {eff}}{>}$5700 K) we obtain logA(Li)${=}$2.30${\pm}$0.05, which is in a good agreement with the results of other authors. Our values of Li abundances do not indicate any trends either with $T_{\rm {eff}}$ or with [Fe/H]. The “plateau” is also traced in the metallicity range −0.7${<}$[Fe/H]${<}$−0.3. The behavior of the lithium abundance for stars with [Fe/H]${>}$−1.7, $T_{\rm {eff}}{<}$5700 K shows a depleting mechanism in these stars, the growth of its efficiency with an increase of the metallicity. The “lithium plateau” was also found for thick disk dwarfs with $T_{\rm {eff}}{>}$5800 K.

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.

Chemical abundances and upper limits of three dozen elements have been derived for the binary blue metal-poor, extremely lead-rich star CS29497-030. The findings include a large contribution of s-process material (e.g., [Pb/Fe] >3.5) and a large contribution of r-process material (e.g, [Eu/Fe] ∼2), abundances which place it in the class of objects known as r+s stars. The ratio of [Zr/Nb] ∼0, along with its stellar parameters, indicates that it is not an intrinsic AGB star. Modelling the abundance distribution (which includes the first Bi abundance determination for any metal-poor star) with s-process calculations employing FRANEC models, there is excellent agreement with the observations by adopting a 1.3 M[odot] AGB model with an enhanced 13C-pocket and a pre-enrichment of r-process material. In this scenario, the initial abundances of CS29497-030 and its binary partner arose from a parent cloud with an extreme r-process abundance, in which star formation was triggered by a core-collapse supernova which polluted, snowplowed, and clumped a nearby molecular cloud. Pollution from the former AGB star's dredged-up material subsequently enriched the envelope composition of CS29497-030 (Ivans et al. 2005). Critical tests of this model and scenario include the dependence of abundance ratios on systematics due to non-LTE effects, the choice of stellar parameters and model atmospheres, and the assumed abundance pattern of the protostellar cloud out of which the CS29497-030 binary system formed.