The Gaia-ESO Survey: N-body modelling of the Gamma Velorum cluster

The Gaia-ESO Survey has recently unveiled the complex kinematic signature of the Gamma Velorum cluster: this cluster is composed of two kinematically distinct populations (hereafter, population A and B), showing two different velocity dispersions and a relative ~2 km s^-1 radial velocity (RV) shift. In this paper, we propose that the two populations of the Gamma Velorum cluster originate from two different sub-clusters, born from the same parent molecular cloud. We investigate this possibility by means of direct-summation N-body simulations. Our scenario is able to reproduce not only the RV shift and the different velocity dispersions, but also the different centroid (~0.5 pc), the different spatial concentration and the different line-of-sight distance (~5 pc) of the two populations. The observed 1-2 Myr age difference between the two populations is also naturally explained by our scenario, in which the two sub-clusters formed in two slightly different star formation episodes. Our simulations suggest that population B is strongly supervirial, while population A is close to virial equilibrium. We discuss the implications of our models for the formation of young star clusters and OB associations in the Milky Way.Comment: 12 pages, 7 figures, 2 tables, Astronomy and Astrophysics, in pres

The Gaia-ESO Survey: Chromospheric Emission, Accretion Properties, and Rotation in γ\gamma Velorum and Chamaeleon I

We use the fundamental parameters delivered by the GES consortium in the first internal data release to select the members of $\gamma$ Vel and Cha I among the UVES and GIRAFFE spectroscopic observations. A total of 140 $\gamma$ Vel members and 74 Cha I members were studied. We calculated stellar luminosities through spectral energy distributions, while stellar masses were derived by comparison with evolutionary tracks. The spectral subtraction of low-activity and slowly rotating templates, which are rotationally broadened to match the $v\sin i$ of the targets, enabled us to measure the equivalent widths (EWs) and the fluxes in the H$\alpha$ and H$\beta$ lines. The H$\alpha$ line was also used for identifying accreting objects and for evaluating the mass accretion rate ($\dot M_{\rm acc}$). The distribution of $v\sin i$ for the members of $\gamma$ Vel displays a peak at about 10 km s$^{-1}$ with a tail toward faster rotators. There is also some indication of a different $v\sin i$ distribution for the members of its two kinematical populations. Only a handful of stars in $\gamma$ Vel display signatures of accretion, while many more accretors were detected in the younger Cha~I. Accreting and active stars occupy two different regions in a $T_{\rm eff}$-flux diagram and we propose a criterion for distinguishing them. We derive $\dot M_{\rm acc}$ in the ranges $10^{-11}$-$10^{-9} M_\odot$yr$^{-1}$ and $10^{-10}$-$10^{-7} M_\odot$yr$^{-1}$ for $\gamma$ Vel and Cha I accretors, respectively. We find less scatter in the $\dot M_{\rm acc}-M_\star$ relation derived through the H$\alpha$ EWs, when compared to the H$\alpha$ $10\%W$ diagnostics, in agreement with other authors

The Gaia-ESO Survey: the most metal-poor stars in the Galactic bulge

We present the first results of the EMBLA survey (Extremely Metal-poor BuLge stars with AAOmega), aimed at finding metal-poor stars in the Milky Way bulge, where the oldest stars should now preferentially reside. EMBLA utilises SkyMapper photometry to pre-select metal-poor candidates, which are subsequently confirmed using AAOmega spectroscopy. We describe the discovery and analysis of four bulge giants with -2.72<=[Fe/H]<=-2.48, the lowest metallicity bulge stars studied with high-resolution spectroscopy to date. Using FLAMES/UVES spectra through the Gaia-ESO Survey we have derived abundances of twelve elements. Given the uncertainties, we find a chemical similarity between these bulge stars and halo stars of the same metallicity, although the abundance scatter may be larger, with some of the stars showing unusual [{\alpha}/Fe] ratios.Comment: 7 pages, 5 figures. Accepted for publication by MNRA

The Gaia-ESO Survey: Detailed Abundances in the Metal-poor Globular Cluster NGC 4372

We present the abundance analysis for a sample of 7 red giant branch stars in the metal-poor globular cluster NGC 4372 based on UVES spectra acquired as part of the Gaia-ESO Survey. This is the first extensive study of this cluster from high resolution spectroscopy. We derive abundances of O, Na, Mg, Al, Si, Ca, Sc, Ti, Fe, Cr, Ni, Y, Ba, and La. We find a metallicity of [Fe/H] = -2.19 $\pm$ 0.03 and find no evidence for a metallicity spread. This metallicity makes NGC 4372 one of the most metal-poor galactic globular clusters. We also find an {\alpha}-enhancement typical of halo globular clusters at this metallicity. Significant spreads are observed in the abundances of light elements. In particular we find a Na-O anti-correlation. Abundances of O are relatively high compared with other globular clusters. This could indicate that NGC 4372 was formed in an environment with high O for its metallicity. A Mg-Al spread is also present which spans a range of more than 0.5 dex in Al abundances. Na is correlated with Al and Mg abundances at a lower significance level. This pattern suggests that the Mg-Al burning cycle is active. This behavior can also be seen in giant stars of other massive, metal-poor clusters. A relation between light and heavy s-process elements has been identified.Comment: 14 pages, 14 figures, accepted for publication in A&

The Gaia-ESO Survey: metallicity of the Chamaeleon I star forming region

Context. Recent metallicity determinations in young open clusters and star-forming regions suggest that the latter may be characterized by a slightly lower metallicity than the Sun and older clusters in the solar vicinity. However, these results are based on small statistics and inhomogeneous analyses. The Gaia-ESO Survey is observing and homogeneously analyzing large samples of stars in several young clusters and star-forming regions, hence allowing us to further investigate this issue. Aims. We present a new metallicity determination of the Chamaeleon I star-forming region, based on the products distributed in the first internal release of the Gaia-ESO Survey. Methods. 48 candidate members of Chamaeleon I have been observed with the high-resolution spectrograph UVES. We use the surface gravity, lithium line equivalent width and position in the Hertzsprung-Russell diagram to confirm the cluster members and we use the iron abundance to derive the mean metallicity of the region. Results. Out of the 48 targets, we confirm 15 high probability members. Considering the metallicity measurements for 9 of them, we find that the iron abundance of Chamaeleon I is slightly subsolar with a mean value [Fe/H]=-0.08+/-0.04 dex. This result is in agreement with the metallicity determination of other nearby star-forming regions and suggests that the chemical pattern of the youngest stars in the solar neighborhood is indeed more metal-poor than the Sun. We argue that this evidence may be related to the chemical distribution of the Gould Belt that contains most of the nearby star-forming regions and young clusters.Comment: 13 pages, 11 figures, 3 tables, Accepted for publication in Astronomy & Astrophysic

The Gaia-ESO Survey: the chemical structure of the Galactic discs from the first internal data release

Most high-resolution spectroscopic studies of the Galactic discs were mostly confined to objects in the solar vicinity. Here we aim at enlarging the volume in which individual chemical abundances are used to characterise both discs, using the first internal data release of the Gaia-ESO survey. We derive and discuss the abundances of eight elements (Mg, Al, Si, Ca, Ti, Fe, Cr, Ni, and Y). The trends of these elemental abundances with iron are very similar to those in the solar neighbourhood. We find a natural division between alpha-rich and alpha-poor stars, best seen in the bimodality of the [Mg/M] distributions in bins of metallicity, which we attribute to thick- and thin-disc sequences, respectively. With the possible exception of Al, the observed dispersion around the trends is well described by the expected errors, leaving little room for astrophysical dispersion. Using previously derived distances from Recio-Blanco et al. (2014b), we further find that the thick-disc is more extended vertically and is more centrally concentrated towards the inner Galaxy than the thin-disc, which indicates a shorter scale-length. We derive the radial and vertical gradients in metallicity, iron, four alpha-element abundances, and Al for the two populations, taking into account the identified correlation between R_GC and |Z|. Radial metallicity gradient is found in the thin disc. The positive radial individual [alpha/M] gradients found are at variance from the gradients observed in the RAVE survey. The thin disc also hosts a negative vertical metallicity gradient, accompanied by positive individual [alpha/M] and [Al/M] gradients. The thick-disc, presents no radial metallicity gradient, a shallower vertical metallicity gradient than the thin-disc, an alpha-elements-to-iron radial gradient in the opposite sense than that of the thin disc, and positive vertical individual [alpha/M] and [Al/M] gradients.Comment: 24 pages, 10 figure

Impact of maternal, antenatal and birth-associated factors on iron stores at birth: data from a prospective maternal–infant birth cohort

Background/Objectives: Low serum ferritin concentrations at birth, which reflect neonatal iron stores, track through to early childhood and have been associated with poorer neurodevelopmental outcomes. We aimed to identify maternal, antenatal and birth-associated factors that influence iron stores at birth in a prospective maternal–infant birth cohort. Subjects/Methods: In a population-based, longitudinal, birth cohort in Ireland, 413 maternal–infant dyads with prospectively collected lifestyle and clinical data from 15 weeks’ gestation had umbilical cord serum ferritin concentrations measured. Regression models were developed to identify independent factors associated with cord ferritin concentrations. Results: Median (IQR) cord ferritin concentrations were 185.7 (131.7, 385.5) μg/l, and 8% (n=33) of infants had low iron stores (ferritin <76 μg/l) at birth. Maternal obesity (BMI 30 kg/m2) at 15 weeks’ gestation (adj. estimate (95% confidence interval (CI)): −66.4 (−106.9, −25.9) μg/l, P<0.0001) and delivery by caesarean section (−38.8 (−70.2, −7.4) μg/l, P=0.016) were inversely associated with cord ferritin concentrations. In addition, maternal smoking at 15 weeks’ gestation (adj. odds ratio (95% CI): 2.9 (1.2, 7), P=0.020) and being born small-for-gestational age (3.4 (1.3, 8.9), P=0.012) were associated with an increased risk of low iron stores (ferritin <76 μg/l) at birth. Conclusions: We have identified a number of potentially modifiable lifestyle factors that influence iron stores at birth, with the important role of overall maternal health and lifestyle during pregnancy highlighted. Public health policies targeting women of child-bearing age to improve nutrition and health outcomes should be prioritised for the health of the next generation

Micrometeoroid Events in LISA Pathfinder

The zodiacal dust complex, a population of dust and small particles that pervades the Solar System, provides important insight into the formation and dynamics of planets, comets, asteroids, and other bodies. Here we present a new set of data obtained using a novel technique: direct measurements of momentum transfer to a spacecraft from individual particle impacts. This technique is made possible by the extreme precision of the instruments flown on the LISA Pathfinder spacecraft, a technology demonstrator for a future space-based gravitational wave observatory that operated near the first Sun-Earth Lagrange point from early 2016 through Summer of 2017. Using a simple model of the impacts and knowledge of the control system, we show that it is possible to detect impacts and measure properties such as the transferred momentum (related to the particle's mass and velocity), direction of travel, and location of impact on the spacecraft. In this paper, we present the results of a systematic search for impacts during 4348 hours of Pathfinder data. We report a total of 54 candidates with momenta ranging from 0.2$\,\mu\textrm{Ns}$ to 230$\,\mu\textrm{Ns}$. We furthermore make a comparison of these candidates with models of micrometeoroid populations in the inner solar system including those resulting from Jupiter-family comets, Oort-cloud comets, Hailey-type comets, and Asteroids. We find that our measured population is consistent with a population dominated by Jupiter-family comets with some evidence for a smaller contribution from Hailey-type comets. This is in agreement with consensus models of the zodiacal dust complex in the momentum range sampled by LISA Pathfinder.Comment: 22 pages, 14 figures, accepted in Ap

Improvements in quality of life in children following epicutaneous immunotherapy (EPIT) for peanut allergy in the PEPITES and PEOPLE studies

Background: Food allergy quality of life (FAQL) is impaired in children with peanut allergy. Food Allergy Quality of Life Questionnaires (FAQLQs) provide disease-specific insight into the burden of peanut allergy and potential FAQL changes after peanut immunotherapy. Objective: To examine FAQL changes in children after treatment with epicutaneous immunotherapy for peanut allergy (250 μg, daily epicutaneous peanut protein; DBV712 250 μg). Methods: FAQL was prospectively measured using the FAQLQ parent proxy form (Food Allergy Quality of Life Questionnaire-Parent Proxy Form [FAQLQ-PF], for children aged ≤12 years) and child form (Food Allergy Quality of Life Questionnaire-Child Form [FAQLQ-CF], child rated if aged ≥8 years) during the 12-month double-blind, randomized, controlled Peanut EPIT Efficacy and Safety Study (PEPITES) trial and the initial 12 months of the open-label PEPITES Open Label Extension Study (PEOPLE) follow-up study. Data were analyzed for between-group differences after treatment unblinding. Results: FAQLQs from placebo participants (FAQLQ-PF: 96; FAQLQ-CF: 47) and treatment group participants (FAQLQ-PF: 209; FAQLQ-CF: 105) were analyzed. Twenty-four–month global FAQL scores (FAQLQ-PF/FAQLQ-CF) were significantly improved in the treatment group versus the placebo group (least squares mean, 0.34, P = .008, and 0.46, P = .023, respectively). At 24 months, there was significant FAQLQ-PF score improvement in participants initially randomized to treatment who met the efficacy primary end point (n = 74; least squares mean, 0.55; P < .001) and in participants with any eliciting dose increase (n = 127; least squares mean, 0.66; P < .001). FAQLQ-PF improvements were observed in social dietary limitations (P = .002), food-related anxiety (P = .029), and emotional impact (P = .048) domains. FAQLQ-CF improvements were observed in risk of accidental exposure (P = .002) and allergen avoidance (P = .04) domains. Nearly all outcomes met a nontreatment context minimal clinically important difference previously cited for FAQLQ. Conclusions: Epicutaneous immunotherapy treatment was observed to be associated with significant global and domain-specific FAQL improvement (FAQLQ-PF/FAQLQ-CF), largely driven by increases in eliciting dose, in children with peanut allergy

Antenatal vitamin D status is not associated with standard neurodevelopmental assessments at age 5 Years in a well-characterized prospective maternal-infant cohort

Background: Although animal studies show evidence for a role of vitamin D during brain development, data from human studies show conflicting signals. Objective: We aimed to explore associations between maternal and neonatal vitamin D status with childhood neurodevelopmental outcomes. Methods: Comprehensive clinical, demographic, and lifestyle data were collected prospectively in 734 maternal-infant dyads from the Cork BASELINE Birth Cohort Study. Serum 25-hydroxyvitamin D [25(OH)D] concentrations were quantified at 15 weeks of gestation and in umbilical cord sera at birth via a CDC-accredited liquid chromatography-tandem mass spectrometry method. Children were assessed at age 5 y through the use of the Kaufman Brief Intelligence Test (2nd Edition, KBIT-2) and the Child Behaviour Checklist (CBCL). Linear regression was used to explore associations between 25(OH)D and neurodevelopmental outcomes. Results: 25(OH)D concentrations were <30 nmol/L in 15% of maternal and 45% of umbilical cord sera and <50 nmol/L in 42% of mothers and 80% of cords. At age 5 y, the mean ± SD KBIT-2 intelligence quotient (IQ) composite score was 104.6 ± 8.6; scores were 107.2 ± 10.0 in verbal and 99.8 ± 8.8 in nonverbal tasks. Developmental delay (scores <85) was seen in <3% of children across all domains. The mean ± SD CBCL total problem score was 21.3 ± 17.5; scores in the abnormal/clinical range for internal, external, and total problem scales were present in 12%, 4%, and 6% of participants, respectively. KBIT-2 and CBCL subscale scores at 5 y were not different between children exposed to low antenatal vitamin D status, either at 30 or 50 nmol/L 25(OH)D thresholds. Neither maternal nor cord 25(OH)D (per 10 nmol/L) were associated with KBIT-2 IQ composite scores [adjusted β (95% CI): maternal –0.01 (−0.03, 0.02); cord 0.01 (−0.03, 0.04] or CBCL total problem scores [maternal 0.01 (−0.04, 0.05); cord 0.01 (−0.07, 0.09)]. Conclusion: In this well-characterized prospective maternal-infant cohort, we found no evidence that antenatal 25(OH)D concentrations are associated with neurodevelopmental outcomes at 5 y. The BASELINE Study was registered at www.clinicaltrials.gov as NCT01498965; the SCOPE Study was registered at http://www.anzctr.org.au as ACTRN1260700055149