ABSTRACT
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 $2.638\pm 10^{-5}$, while including the available UVES data improves the precision, leading to a ratio of $2.608 \pm 10^{-5}$. 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 ($\log {N_{\rm H_I}/ {\rm cm}^{-2}}\sim 18$) introduces modelling uncertainties, which become the main contributor to the error budget.
ABSTRACT
The gravitationally lensed quasar J014516.6-094517 at z = 2.719 has been observed with the ESPRESSO instrument at the ESO VLT to obtain high-fidelity spectra of the two images A and B with a ...resolving power R = 70 000. At the redshifts under investigation (2.1 ≲ z ≲ 2.7), the Lyman forests along the two sightlines are separated by sub-kiloparsec physical distances and exhibit a strong correlation. We find that the two forests are indistinguishable at the present level of signal-to-noise ratio and do not show any global velocity shift, with the cross-correlation peaking at Δv = 12 ± 48 $\rm m~s^{-1}$. The distribution of the difference in velocity of individual Ly α features is compatible with a null average and a mean absolute deviation of 930 $\rm m~s^{-1}$. Significant differences in NH i column density are not detected, putting a limit to the RMS fluctuation in the baryon density on ≲1 proper kpc scales of Δρ/ρ ≲ 3 per cent. On the other hand, metal lines show significant differences both in velocity structure and in column density. A toy model shows that the difference in velocity of the metal features between the two sightlines is compatible with the motions of the baryonic component associated with dark matter haloes of typical mass M ≃ 2 × 1010 M⊙, also compatible with the observed incidence of the metal systems. The present observations confirm the feasibility of the Sandage test of the cosmic redshift drift with high-fidelity spectroscopy of the Lyman forest of distant, bright quasars, but also provide an element of caution about the intrinsic noise associated with the usage of metal features for the same purpose.
An intriguing reference to the existence of a self-portrait by Galileo Galilei is contained in the biography of the scientist by Thomas Salusbury dated ca. 1665, of which only one incomplete and ...inaccessible copy exists. Galileo grew up in a Renaissance atmosphere, acquiring an artistic touch. He was a musician, a writer and also a painter, as reported by Viviani and documented by his watercolours of the Moon and drawings of solar spots. Recently a new portrait with a remarkable similarity to the portraits of Galileo Galilei by Santi di Tito (1601), Domenico Tintoretto (ca. 1604), and Furini (ca. 1612) has been found and examined using sophisticated face recognition techniques. If the identity could be confirmed, other elements, such as the young age of Galileo or the seam in the canvas revealed by infrared and X-ray analysis, may suggest a possible link with the self-portrait mentioned by Salusbury.
Context. INTEGRAL observed Nova Sgr 2015 No. 2 (V5668 Sgr) around the time of its optical emission maximum on 21 March 2015. Studies at UV wavelengths showed spectral lines of freshly produced 7Be. ...This could also be measurable in gamma rays at 478 keV from the decay to 7Li. Novae are also expected to synthesise 22Na which decays to 22Ne, emitting a 1275 keV photon. About one week before the optical maximum, a strong gamma-ray flash on timescales of hours is expected from short-lived radioactive nuclei such as 13N and 18F. These nuclei are β+-unstable, and should yield emission of up to 511 keV, but this emission has never been observed from any nova. Aims. The SPectrometer on INTEGRAL (SPI) pointed towards V5668 Sgr by chance. We use these observations to search for possible gamma-ray emission of decaying 7Be, and to directly measure the synthesised mass during explosive burning. We also aim to constrain possible burst-like emission days to weeks before the optical maximum using the SPI anticoincidence shield (ACS), i.e. at times when SPI was not pointing to the source. Methods. We extracted spectral and temporal information to determine the fluxes of gamma-ray lines at 478 keV, 511 keV, and 1275 keV. Using distance and radioactive decay, a measured flux converts into the 7Be amount produced in the nova. The SPI-ACS rates are analysed for burst-like emission using a nova model light curve. For the obtained nova flash candidate events, we discuss possible origins using directional, spectral, and temporal information. Results. No significant excess for the 478 keV, the 511 keV, or the 1275 keV lines is found. Our upper limits (3σ) on the synthesised 7Be and 22Na mass depend on the uncertainties of the distance to V5668 Sgr: the 7Be mass is constrained to less than 4.8 × 10−9 (dkpc−1)2 M⊙ $4.8 \times 10^{-9}\,(\textrm{d}{\mathrm{kpc}}^{-1})^2\,{M_{\odot}}$4.8×10−9 (dkpc−1)2 M⊙, and the 22Na mass to less than 2.4 × 10−8 (dkpc−1)2 M⊙ $2.4 \times 10^{-8}\,(\textrm{d}{\mathrm{kpc}}^{-1})^2\,{M_{\odot}}$2.4×10−8 (dkpc−1)2 M⊙. For the 7Be mass estimate from UV studies, the distance to V5668 Sgr must be greater than 1.2 kpc (3σ). During the three weeks before the optical maximum, we find 23 burst-like events in the ACS rate, of which 6 could possibly be associated with V5668.
Raman scattering enables unforeseen uses for the laser guide-star system of the Very Large Telescope. Here, we present the observation of one up-link sodium laser beam acquired with the ESPRESSO ...spectrograph at a resolution λ/Δλ∼140 000. In 900 s on source, we detect the pure rotational Raman lines of ^{16}O_{2}, ^{14}N_{2}, and ^{14}N^{15}N (tentatively) up to rotational quantum numbers J of 27, 24, and 9, respectively. We detect the ^{16}O_{2} fine-structure lines induced by the interaction of the electronic spin S and end-over-end rotational angular momentum N in the electronic ground state of this molecule up to N=9. The same spectrum also reveals the ν_{1←0} rotational-vibrational Q-branch for ^{16}O_{2} and ^{14}N_{2}. These observations demonstrate the potential of using laser guide-star systems as accurate calibration sources for characterizing new astronomical spectrographs.
Context.
The spectrograph ESPRESSO recently obtained a limit on the variation of the fine-structure constant,
α
, through measurements along the line of sight of a bright quasar with a precision of ...1.36 ppm at 1
σ
level. This imposes new constraints on cosmological models with a varying
α
. 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
α
with two extra parameters, one defining the cosmological evolution of the quintessence component and the other fixing the coupling with the electromagnetic field.
Aims.
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.
Methods.
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.
Results.
The constraints placed on the quintessence parameter are consistent with a null variation of the field, and are therefore compatible with a ΛCDM cosmology. The constraints on the coupling to the electromagnetic sector are dominated by the Eötvös parameter local bound.
Conclusions.
More precise measurements with ESPRESSO will be extremely important to study the cosmological evolution of
α
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
α
resulting mostly from the strong MICROSCOPE limits.
In this work, we study argon abundances in the interstellar medium of high-redshift galaxies (2.0 less than or equal to z... less than or equal to 4.2) detected as damped Ly alpha absorbers (DLA) in ...the spectra of background quasars. We use high-resolution quasar spectra obtained from the European Southern Observatory Ultraviolet-Visual Echelle Spectrograph Advanced Data Products data base. We present three new measurements and five upper limits of Ar I. We further compiled DLAs/sub-DLA data from the literature with measurements available of argon and alpha -capture elements (S or Si), making up a total of 37 systems, i.e. the largest DLA argon sample investigated so far. We confirm that argon is generally deficient in DLAs, with a mean value Ar/ alpha ... -0.4 plus or minus 0.06 dex (standard error of the mean). The Ar/ alpha ratios show a weak, positive trend with increasing H I column density and increasing absorption redshift, and a weak, negative trend with dust-free metallicity, S/H. Detailed analysis of the abundance ratios indicates that Ar I ionization, rather than dust depletion or nucleosynthetic evolution, is responsible for the argon deficiency. Altogether, the observational evidence is consistent with a scenario of argon ionization dominated by quasar metagalactic radiation modulated by local H I self-shielding inside the DLA host galaxies. Our measurements and limits of argon abundances suggest that the cosmic reionization of He II is completed above z ... 3, but more measurements at z... > 3.5 are required to probe the final stages of this process of cosmic reionization. (ProQuest: ... denotes formulae/symbols omitted.)
Li abundances for 9 Turn-off (TO) stars of the intermediate metallicity cluster (Fe/H = –1.4) NGC 6752 are presented. The cluster is known to show abundance anomalies and anticorrelations observed in ...both evolved and main sequence stars. We find that Li abundance anticorrelates with Na (and N) and correlates with O in these Turn-Off stars. For the first time we observe Pop II hot dwarfs systematically departing from the Spite plateau. The observed anticorrelations are in qualitative agreement with what is expected if the original gas were contaminated by Intermediate Mass AGB – processed material. However, a quantitative comparison shows that none of the existing models can reproduce all the observations at once. The very large amount of processed gas present in the cluster does not imply a “pollution”, but rather that the whole protocluster cloud was enriched by a previous generation of stars. We finally note that the different abundance patterns in NGC 6397 and NGC 6752 imply different composition of the pre-enrichment ejecta for the two clusters.
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