Spatial and temporal variations in the electron-to-proton mass ratio, μ, and in the fine-structure constant, α, are not present in the Standard Model of particle physics but they arise quite naturally in grant unification theories, multidimensional theories and in general when a coupling of light scalar fields to baryonic matter is considered. The light scalar fields are usually attributed to a negative pressure substance permeating the entire visible Universe and known as dark energy. This substance is thought to be responsible for a cosmic acceleration at low redshifts, z < 1. A strong dependence of μ and α on the ambient matter density is predicted by chameleon-like scalar field models. Calculations of atomic and molecular spectra show that different transitions have different sensitivities to changes in fundamental constants. Thus, measuring the relative line positions, Δ V, between such transitions one can probe the hypothetical variability of physical constants. In particular, interstellar molecular clouds can be used to test the matter density dependence of μ, since gas density in these clouds is ~15 orders of magnitude lower than that in terrestrial environment. We use the best quality radio spectra of the inversion transition of NH3 (J,K)=(1,1) and rotational transitions of other molecules to estimate the radial velocity offsets, Δ V ≡ Vrot - Vinv. The obtained value of Δ V shows a statistically significant positive shift of 23±4stat±3sys m s−1 (1σ). Being interpreted in terms of the electron-to-proton mass ratio variation, this gives Δμ/μ = (22±4stat±3sys)×10−9. A strong constraint on variation of the quantity F = α2/μ in the Milky Way is found from comparison of the fine-structure transition J=1-0 in atomic carbon C i with the low-J rotational lines in carbon monoxide 13CO arising in the interstellar molecular clouds: |Δ F/F| < 3×10−7. This yields |Δ α/α| < 1.5×10−7 at z = 0. Since extragalactic absorbers have gas densities similar to those in the ISM, the values of |Δ α/α| and |Δ μ/μ| at high-z are expected to be at the same level as estimated in the Milky Way providing no temporal dependence of α and μ is present. We re-analyzed and reviewed the available optical spectra of quasars to probe Δα/α from intervening absorbers. The Fe i system at z = 0.45 towards HE 0000–2340 provides one of the best opportunities for precise measurements of Δα/α at low redshift. The current estimate is Δα/α = (7±7)×10−6. With the updated sensitivity coefficients for the Fe ii lines we re-analyzed the z = 1.84 system from the high-resolution UVES/VLT spectrum of Q 1101–264 (FWHM = 3.8 km s−1) and found Δα/α = (4.0±2.8)×10−6. The most accurate upper limit on cosmological variability of α is obtained from the Fe ii system at z = 1.15 towards the bright quasar HE 0515–4414 (V=14.9): Δα/α = (-0.12±1.79)×10−6, or |Δα/α| < 2×10−6. The limit of 2×10−6 corresponds to the utmost accuracy which can be reached with available to date optical facilities.

Cosmology contributes a good deal to the investigation of variation of fundamental physical constants. High resolution data is available and allows for detailed analysis over cosmological distances and a multitude of methods were developed. The raised demand for precision requires a deep understanding of the limiting errors involved. The achievable accuracy is under debate and current observing proposals max out the capabilities of today's technology. The question for self-consistency in data analysis and effective techniques to handle unknown systematic errors is of increasing importance. This work is motivated by numerous findings of different groups that partially are in disagreement witch each other. A large part of these discrepancies reflects the different methods of handling systematic errors. Evidently systematics are not yet under control or fully understood. We try to emphasize the importance to take these errors, namely calibration issues, into account and put forward some measures adapted to the problem. Alternative approaches for some of the steps involved are introduced.

We recently presented (Sbordone et al., 2009a) the largest sample to date of lithium abundances in extremely metal-poor (EMP) Halo dwarf and Turn-Off (TO) stars. One of the most crucial aspects in estimating Li abundances is the Teff determination, since the Li I 670.8 nm doublet is highly temperature sensitive. In this short contribution we concentrate on the Teff determination based on Hα wings fitting, and on its sensitivity to the chosen stellar gravity.

The abundance derivation of heavy r-elements may provide a better understanding of the r-process, and the determination of several reference r-elements should allow a better determination of the star's age. The spatial ultraviolet (UV) region presents a large number of lines of heavy elements, and in some cases such as Bi, Pt, Au, detectable lines are only available in the UV. The extreme “r-process star” CS 31082-001 ([Fe/H] = −2.9) was observed in the spatial UV in order to determine abundances of the heavy elements, using STIS on board HST.

We present the largest sample available to date of lithium abundances in extremely metal poor (EMP) Halo dwarfs. Four Teff estimators are used, including IRFM and Hα wings fitting against 3D hydrodynamical synthetic profiles. Lithium abundances are computed by means of 1D and 3D-hydrodynamical NLTE computations. Below [Fe/H]~−3, a strong positive correlation of A(Li) with [Fe/H] appears, not influenced by the choice of the Teff estimator. A linear fit finds a slope of about 0.30 dex in A(Li) per dex in [Fe/H], significant to 2–3 σ, and consistent within 1 σ among all the Teff estimators. The scatter in A(Li) increases significantly below [Fe/H]~−3. Above, the plateau lies at 〈A(Li)3D, NLTE〉 = 2.199 ± 0.086. If the primordial A(Li) is the one derived from standard Big Bang Nucleosynthesis (BBN), it appears difficult to envision a single depletion phenomenon producing a thin, metallicity independent plateau above [Fe/H] = −2.8, and a highly scattered, metallicity dependent distribution below.

From NLTE computations of the magnesium abundance in a sample of extremely metal-poor giants we derive [Mg/Fe]=+0.7, leading to [Al/Mg]=−0.80 and [Na/Mg]=−0.85 in the early Galaxy. The ratio [O/Mg] should be near to the solar value. Measurements of nitrogen abundances derived from the analysis of the NH band in eight more stars confirm the large scatter of the ratios [N/Fe] and [N/O] in the early Galaxy.

Verification of theoretical predictions of an oscillating behavior of the fine-structure constant, $\alpha$, with cosmic time requires high precision measurements at individual redshifts, while in earlier studies the mean $\Delta\alpha/\alpha$ values averaged over wide redshift intervals were usually reported. This requirement can be met via the Single Ion Differential $\alpha$ Measurement (SIDAM) procedure. We apply SIDAM to the FeII lines associated with the damped Ly$\alpha$ system observed at $z = 1.15$ in the spectrum of HE0515–4414. The weighted mean calculated on the base of carefully selected 34 FeII pairs is $\langle \Delta\alpha/\alpha \rangle = (-0.07\,{\pm}\,0.84)\times10^{-6}$. The precision of this estimate represents a large improvement over previous measurements of $\Delta\alpha/\alpha$.

The combination of the collecting power of an ELT with an ultra-stable high resolution spectrograph opens up the possibility to measure for the first time directly the dynamical effect of the acceleration of the Universe. CODEX will also provide unique opportunities for advance in many other branches of astrophysics. The CODEX design is based on an array of several identical spectrographs. It is highly modular and can be easily adapted to a large range of sky apertures and telescope diameters. CODEX is designed to work as a seeing limited instrument. The requirements for the telescope are moderate and clearly identified.

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.

Five giants and 11 subgiants of the metal-poor globular cluster NGC 6397 are analysed. In this Poster we present the lithium abundances derived. The present Li abundances and those of turnoff stars by Pasquini & Molaro (1996) are complementary in terms of stellar evolution stage, and show the Li abundances decreasing off the main sequence along the red giant branch.

The photometric study of the Sagittarius dwarf galaxy by Marconi et al. (1998) has suggested the presence of a spread in metallicity (-0.7 ≤ [Fe/H] ≤ −1.6), which may result from different bursts of star formation. We present the results from a Multi Object Slit spectroscopy program carried out at the NTT with the aim to determine spectroscopic abundances of Sagittarius giants selected from the CCD photometry. From our intermediate resolution (R~1500) spectra, radial velocities are determined to confirm the membership and metallicities are derived by using spectral synthesis codes for stars down to V ~ 18, i.e. below the RGB clump. Out of 57 observed stars, 23 have a radial velocity consistent with Sagittarius membership; here we present results for 8 of these. No star with [Fe/H]< −1.0 is found, three stars are found to be metal-rich.

The lithium observed in the atmospheres of unevolved halo stars is believed to be an essentially unproccessed element which reflects the primordial yields. The primordial nature of Li is inferred from the presence of a constant Li abundance for all the halo dwarfs where convection is not effective (Teff ≥ 5600 K). Such an uniformity is taken as evidence for the absence of any stellar depletion during the formation and the long life of the halo stars and also as evidence for the absence of any production mechanism acting either before or at the same time of the formation of the halo population. The existence of a real plateau has been recently questioned by Thorburn (1994), Norris et al (1994) and Deliyannis et al (1993). These results open the possibility of substantial depletion by rotational mixing where a certain degree of dispersion is foreseen for different initial angular momenta of the stars and/or to a significant Galactic Li enrichment within the first few Gyrs.

Lithium abundances in a sample (39) of halo dwarfs have been redetermined by using the new Teff derived by Fuhrmann et al (1994) from modelling of the Balmer lines. These Teff are reddening independent, homogeneous and of higher quality than those based on broad band photometry. The sample represent a significant fraction of the presently available Li determinations, and form an unique sample with a good and homogeneous Teff Fuhrmann et al are also able to provide errors in the Teff for individual stars and in most cases they are as good as ± 50 K, which is a factor 2 smaller than the grossly estimated errors for photometric-based Teff. The Li equivalent widths have been taken from the literature and the theoretically derived random errors from Deliyannis et al (1993) or computed following their prescriptions. Abundances have been derived by generating new atmospheric models by using the ATLAS-9 code by Kurucz (1993) with enhanced α-elements and without the overshooting option. If we use the Kurucz 1993 grid which includes overshooting the Li abundance is increased by ≈ 0.08 dex.

We present CaII and NaI spectra for a sample of stars in a 30'×30' field connecting 30 Dor with SN 1987A. Observations were taken with the CES spectrograph linked via fibres with the 3.6m ESO telescope at a resolution of ˜ 6 km s−1. The LMC gas shows a complex structure with both single and multiple components spanning 250 to 300 km s−1. Results can be interpreted using the multi-layer structure suggested by 21 cm observations. Comparing our optical absorptions with 21 cm emissions yields evidence that layers with increasing radial velocity are located one behind the other. The intermediate velocity components are numerous in CaII, but rare in NaI. Towards Sk-69 211, for which we have the highest S/N CaII spectrum, we have detected a number of components comparable to that found in SN 1987A. The 64 km s−1 cloud is detected in a well-confined region of the field, showing remarkable constancy in the radial velocity, which we interpret as evidence that this cloud is located close to the Galaxy.

High-resolution (λ/δλ ⋍ 6 x 104) spectra of R136 (the central object of 30 Dor) and of 2 LMC supergiants obtained at ESO with the 1.4-m telescope have been analysed in order to study the high-velocity absorption components at VLSR ⋍ +60 km s-1 and ⋍ +130 km s-1 first seen in satellite ultraviolet spectra in the general direction of the LMC. Our data have been integrated with previous literature results of SN1987a and of other 4 LMC supergiants obtained from spectra of similar spectral resolution.

At least 6 (possibly 9) interstellar components are found in the range +40 km s-1 ≤ VISR ≤ + 150 km s-1, suggesting that the IUE features at ⋍ +60 km s-1 and ⋍ +130 km s-1 are in fact splitted in several components when observed at higher resolution. Two components originally discovered toward SN1987a (VLSR ⋍ +42 km s-1 and +107 km s-1), are detected for the first time in the Call interstellar spectrum of R136. A component at VLSR ⋍ +49 km s-1 shows significant variations both in Call and in Nal along the different lines of sight. A relatively broad component at VLSR ⋍ +58 km s-1 is present in Call toward R136, but is generally undetected in Nal in the other lines of sight. Also the components in the range +100 km s-1 ≤ VLSR ≤ +150 km s-1 are detected in Call, but not in Nal. Two weak absorptions, detected at +125 km s-1 and +141 km s-1 toward R136, may be associated with the ⋍ +130 km s-1 component characteristic of the ultraviolet spectra.

The almost perfect velocity coincidence of the +107 km s-1, +42 km s-1, +49 km s-1 and +57 km s-1 components along different lines of sight suggests a common origin of the absorbing gas and a location close to our Galaxy. In spite of the low detection limit in our spectra (Wλ ⋍ 5 mÅ), the lack of detection of Nal is compatible with the presence of foreground gas clouds with hydrogen column density N(HI) ≤ 2 x 1019 cm-2, or even greater. The fact that we can detect more easily Call absorptions than the corresponding Nal absorptions indicates a very low value of Call depletion.

We present high resolution (FWHM≈7 km/sec) and high signal-to-noise observations of the bright Seyfert galaxy NGC3783 obtained with the CES spectrograph linked by fibres to the 3.6m telescope at La Silla, Chile.

IUE spectra of Mg II h and k in late type dwarfs and giants have been used to detect and measure absorption components due to the LISM. This technique gives a method of probing the awkward range from d = 3 pc to d = 80 pc from the sun . In spite of interpretational uncertainties we can plot the HI component of the LISM well enough to confirm it as a cloud some 20-30 pc in extent, peaking sharply in density towards , moving towards the sun from , at 28 Km/sec. The “hole” towards is confirmed, suggesting a solar position close to the cloud's edge in this direction.

Detection of narrow ( δλ< 0.5 A ) absorption features in C IV at λ λ 1548 and 1550 have been made in the spectra of 4 late B dwarfs within 200 pc of the sun; the Si IV doublet at λ λ 1393 and 1403 shows up in two of them. We argue that it is difficult to account for the strengths, widths, shapes , and C IV/Si IV ratios in terms consistent with a circumstellar origin except possibly for an asymmetric C IV component in one star (HD 135037). The most probable source is “semi-torrid” gas (cf. Bruhweiler et al. 1980) in the 50,000 K range forming the interfaces between cooler H I clouds and the ambient medium at coronal temperatures. Our technique, using late B rapid rotators, is useful for LISM probing of this kind.

The spectrum of 17 Lep is dominated by numerous and strong shell lines of once-ionized metals. The shell shows a composite radial velocity structure which indicates the presence of multiple components with a velocity range between −50 and −250 km s−1. Unlike in the visible, where these multiple components are present only during outburst, in the ultraviolet such components seem to be a permanent feature.