Primordial abundances of light elements are sensitive to the physics of the early Universe and can directly constrain cosmological quantities, such as the baryon-to-photon ratio \(\eta_{10}\), the ...baryon density and the number of neutrino families. Deuterium is especially suited for these studies: its primordial abundance is sensitive and monotonically dependent on \(\eta_{10}\), allowing an independent measurement of the cosmic baryon density that can be compared, for instance, against the Planck satellite data. The primordial deuterium abundance can be measured in high \(H_I\) column density absorption systems towards distant quasars. We report here a new measurement, based on high-resolution ESPRESSO data, of the primordial \(D_I\) abundance of a system at redshift \(z \sim 3.572\), towards PKS1937-101. Using only ESPRESSO data, we find a D/H ratio of \(2.638\pm0.128 \times 10^{-5}\), while including the available UVES data improves the precision, leading to a ratio of \(2.608 \pm 0.102 \times 10^{-5}\). The results of this analysis agree with those of the most precise existing measurements. We find that the relatively low column density of this system (\(\log{N_{\rm H_I}/ {\rm cm}^{-2}}\sim18 \)) introduces modelling uncertainties, which become the main contributor to the error budget.
The ArmazoNes high Dispersion Echelle Spectrograph (ANDES) is the optical and near-infrared high-resolution echelle spectrograph envisioned for the European Extremely Large Telescope (ELT). We ...present a selection of science cases, supported by new calculations and simulations, where ANDES could enable major advances in the fields of stars and stellar populations. We focus on three key areas, including the physics of stellar atmospheres, structure, and evolution; stars of the Milky Way, Local Group, and beyond; and the star-planet connection. The key features of ANDES are its wide wavelength coverage at high spectral resolution and its access to the large collecting area of the ELT. These features position ANDES to address the most compelling and potentially transformative science questions in stellar astrophysics of the decades ahead, including questions which cannot be anticipated today.
Dynamical scalar fields in an effective four-dimensional field theory are naturally expected to couple to the rest of the theory's degrees of freedom, unless some new symmetry is postulated to ...suppress these couplings. In particular, a coupling to the electromagnetic sector will lead to spacetime variations of the fine-structure constant, \(\alpha\). Astrophysical tests of the space-time stability of \(\alpha\) are therefore a powerful probe of new physics. Here we use ESPRESSO and other contemporary measurements of \(\alpha\), together with background cosmology data, local laboratory atomic clock and Weak Equivalence Principle measurements, to place stringent constraints on the simplest examples of the two broad classes of varying \(\alpha\) models: Bekenstein models and quintessence-type dark energy models, both of which are parametric extensions of the canonical \(\Lambda\)CDM model. In both cases, previously reported constraints are improved by more than a factor of ten. This improvement is largely due to the very strong local constraints, but astrophysical measurements can help to break degeneracies between cosmology and fundamental physics parameters.
This paper examines the incidence of unfair trading practices (UTPs) in the dairy food supply chain. Drawing insights from data collected through a field survey among dairy farmers in five selected ...EU regions (France, Germany, Poland and Spain) we seek to understand the presence of UTPs across different stages of contract formulation and execution. The survey data were collected in 2017 and gathered 1248 observations. We identify a total of 29 types of UTPs across all different phases of contract development. Results show that 93% of surveyed farmers have reported at least one UTP, whereas 46% of surveyed farmers have reported at least three UTPs. The highest share of UTPs was found in the contract content followed by contract negotiation and contract execution. Further, our results suggest that there is not a strong relationship between the occurrence of UTPs and contract completeness although it is heterogeneous between studied regions.
The CUBES Science Case Evans, Chris; Cristiani, Stefano; Opitom, Cyrielle ...
arXiv.org,
09/2022
Paper, Journal Article
Odprti dostop
We introduce the scientific motivations for the development of the Cassegrain U-Band Efficient Spectrograph (CUBES) that is now in construction for the Very Large Telescope. The assembled cases span ...a broad range of contemporary topics across Solar System, Galactic and extragalactic astronomy, where observations are limited by the performance of current ground-based spectrographs shortwards of 400nm. A brief background to each case is presented and specific technical requirements on the instrument design that flow-down from each case are identified. These were used as inputs to the CUBES design, that will provide a factor of ten gain in efficiency for astronomical spectroscopy over 300-405nm, at resolving powers of R~24,000 and ~7,000. We include performance estimates that demonstrate the ability of CUBES to observe sources that are up to three magnitudes fainter than currently possible at ground-ultraviolet wavelengths, and we place its predicted performance in the context of existing facillities.
We present the baseline conceptual design of the Cassegrain U-Band Efficient Spectrograph (CUBES) for the Very Large Telescope. CUBES will provide unprecedented sensitivity for spectroscopy on a 8 - ...10 m class telescope in the ground ultraviolet (UV), spanning a bandwidth of > 100 nm that starts at 300 nm, the shortest wavelength accessible from the ground. The design has been optimized for end-to-end efficiency and provides a spectral resolving power of R > 20000, that will unlock a broad range of new topics across solar system, Galactic and extraglactic astronomy. The design also features a second, lower-resolution (R \sim 7000) mode and has the option of a fiberlink to the UVES instrument for simultaneous observations at longer wavelengths. Here we present the optical, mechanical and software design of the various subsystems of the instrument after the Phase A study of the project. We discuss the expected performances for the layout choices and highlight some of the performance trade-offs considered to best meet the instrument top-level requirements. We also introduce the model-based system engineering approach used to organize and manage the project activities and interfaces, in the context that it is increasingly necessary to integrate such tools in the development of complex astronomical projects.
The strong intervening absorption system at redshift 1.15 towards the very bright quasar HE 0515\(-\)4414 is the most studied absorber for measuring possible cosmological variations in the ...fine-structure constant, \(\alpha\). We observed HE 0515\(-\)4414 for 16.1\(\,\)h with the Very Large Telescope and present here the first constraint on relative variations in \(\alpha\) with parts-per-million (ppm) precision from the new ESPRESSO spectrograph: \(\Delta\alpha/\alpha = 1.3 \pm 1.3_{\rm stat} \pm 0.4_{\rm sys}\,{\rm ppm}\). The statistical uncertainty (1\(\sigma\)) is similar to the ensemble precision of previous large samples of absorbers, and derives from the high S/N achieved (\(\approx\)105 per 0.4\(\,\)km\(\,\)s\(^{-1}\) pixel). ESPRESSO's design, and calibration of our observations with its laser frequency comb, effectively removed wavelength calibration errors from our measurement. The high resolving power of our ESPRESSO spectrum (\(R=145000\)) enabled the identification of very narrow components within the absorption profile, allowing a more robust analysis of \(\Delta\alpha/\alpha\). The evidence for the narrow components is corroborated by their correspondence with previously detected molecular hydrogen and neutral carbon. The main remaining systematic errors arise from ambiguities in the absorption profile modelling, effects from redispersing the individual quasar exposures, and convergence of the parameter estimation algorithm. All analyses of the spectrum, including systematic error estimates, were initially blinded to avoid human biases. We make our reduced ESPRESSO spectrum of HE 0515\(-\)4414 publicly available for further analysis. Combining our ESPRESSO result with 28 measurements, from other spectrographs, in which wavelength calibration errors have been mitigated, yields a weighted mean \(\Delta\alpha/\alpha = -0.5 \pm 0.5_{\rm stat} \pm 0.4_{\rm sys}\,\)ppm at redshifts 0.6-2.4.
Observations of metal absorption systems in the spectra of distant quasars allow to constrain a possible variation of the fine-structure constant throughout the history of the Universe. Such a test ...poses utmost demands on the wavelength accuracy and previous studies were limited by systematics in the spectrograph wavelength calibration. A substantial advance in the field is therefore expected from the new ultra-stable high-resolution spectrograph Espresso, recently installed at the VLT. In preparation of the fundamental physics related part of the Espresso GTO program, we present a thorough assessment of the Espresso wavelength accuracy and identify possible systematics at each of the different steps involved in the wavelength calibration process. Most importantly, we compare the default wavelength solution, based on the combination of Thorium-Argon arc lamp spectra and a Fabry-Pérot interferometer, to the fully independent calibration obtained from a laser frequency comb. We find wavelength-dependent discrepancies of up to 24m/s. This substantially exceeds the photon noise and highlights the presence of different sources of systematics, which we characterize in detail as part of this study. Nevertheless, our study demonstrates the outstanding accuracy of Espresso with respect to previously used spectrographs and we show that constraints of a relative change of the fine-structure constant at the \(10^{-6}\) level can be obtained with Espresso without being limited by wavelength calibration systematics.
A&A 666, A57 (2022) The spectrograph ESPRESSO recently obtained a limit on the variation of the
fine-structure constant, $\alpha$, through measurements along the line of sight
of a bright quasar with ...a precision of $1.36$ ppm at $1\sigma$ level. This
imposes new constraints on cosmological models with a varying $\alpha$. We
assume such a model where the electromagnetic sector is coupled to a scalar
field dark energy responsible for the current acceleration of the Universe. We
parametrise the variation of $\alpha$ with two extra parameters, one defining
the cosmological evolution of the quintessence component and the other fixing
the coupling with the electromagnetic field. The objective of this work is to
constrain these parameters with both astrophysical and local probes. We also
carried out a comparative analysis of how each data probe may constrain our
parametrisation. We performed a Bayesian analysis by comparing the predictions
of the model with observations. The astrophysical datasets are composed of
quasar spectra measurements, including the latest ESPRESSO data point, as well
as Planck observations of the cosmic microwave background. We combined these
with local results from atomic clocks and the MICROSCOPE experiment. The
constraints placed on the quintessence parameter are consistent with a null
variation of the field, and are therefore compatible with a $\Lambda$CDM
cosmology. The constraints on the coupling to the electromagnetic sector are
dominated by the E\"otv\"os parameter local bound. More precise measurements
with ESPRESSO will be extremely important to study the cosmological evolution
of $\alpha$ as it probes an interval of redshift not accessible to other types
of observations. However, for this particular model, current available data
favour a null variation of $\alpha$ resulting mostly from the strong MICROSCOPE
limits.
The spectrograph ESPRESSO recently obtained a limit on the variation of the fine-structure constant, \(\alpha\), through measurements along the line of sight of a bright quasar with a precision of ...\(1.36\) ppm at \(1\sigma\) level. This imposes new constraints on cosmological models with a varying \(\alpha\). We assume such a model where the electromagnetic sector is coupled to a scalar field dark energy responsible for the current acceleration of the Universe. We parametrise the variation of \(\alpha\) with two extra parameters, one defining the cosmological evolution of the quintessence component and the other fixing the coupling with the electromagnetic field. The objective of this work is to constrain these parameters with both astrophysical and local probes. We also carried out a comparative analysis of how each data probe may constrain our parametrisation. We performed a Bayesian analysis by comparing the predictions of the model with observations. The astrophysical datasets are composed of quasar spectra measurements, including the latest ESPRESSO data point, as well as Planck observations of the cosmic microwave background. We combined these with local results from atomic clocks and the MICROSCOPE experiment. The constraints placed on the quintessence parameter are consistent with a null variation of the field, and are therefore compatible with a \(\Lambda\)CDM cosmology. The constraints on the coupling to the electromagnetic sector are dominated by the E\"otv\"os parameter local bound. More precise measurements with ESPRESSO will be extremely important to study the cosmological evolution of \(\alpha\) as it probes an interval of redshift not accessible to other types of observations. However, for this particular model, current available data favour a null variation of \(\alpha\) resulting mostly from the strong MICROSCOPE limits.
