The role of radial migration in open cluster and field star populations with Gaia dr3

The survival time of a star cluster depends on its total mass, density, and thus size, as well as on the environment in which it was born and in which lies. Its dynamical evolution is influenced by various factors such as gravitational effects of the Galactic bar, spiral structures, and molecular clouds. Overall, the factors that determine the longevity of a cluster are complex and not fully understood. This study aims to investigate if open clusters and field stars respond differently to the perturbations that cause radial migration. In particular, we aim at understanding the nature of the oldest surviving clusters. We compared the time evolution of the kinematic properties of two Gaia DR3 samples: the first sample is composed of $\sim$40 open clusters and the second one of $\sim$66,000 MSTO field stars. Both selected samples are composed of stars selected with the same quality criterion, belonging to the thin disc, in a similar metallicity range, located in the same Galactocentric region [7.5-9 kpc] and with ages >1 Gyr. We performed a statistical analysis comparing the properties of the samples of field stars and of open clusters. A qualitative comparison of kinematic and orbital properties reveals that clusters younger than 2-3 Gyr are more resistant to perturbations than field stars and they move along quasi-circular orbits. Conversely, clusters older than approximately 3 Gyr have more eccentric and inclined orbits than isolated stars in the same age range. Such orbits lead them to reach higher elevations on the Galactic plane, maximising their probability to survive several Gyr longer. A formal statistical analysis reveals that there are differences among the time evolution of most of the kinematic and orbital properties of field stars and open clusters. Our results suggest that oldest survived clusters are usually more massive and move on orbits with higher eccentricity.Comment: 13 pages, 20 figures, 2 tables. Article accepted for publication in A&

Determination of stellar parameters for Ariel targets: a comparison analysis between different spectroscopic methods

Ariel has been selected as the next ESA M4 science mission and it is expected to be launched in 2028. During its 4-year mission, Ariel will observe the atmospheres of a large and diversified population of transiting exoplanets. A key factor for the achievement of the scientific goal of Ariel is the selection strategy for the definition of the input target list. A meaningful choice of the targets requires an accurate knowledge of the planet hosting star properties and this is necessary to be obtained well before the launch. In this work, we present the results of a bench-marking analysis between three different spectroscopic techniques used to determine stellar parameters for a selected number of targets belonging to the Ariel reference sample. We aim to consolidate a method that will be used to homogeneously determine the stellar parameters of the complete Ariel reference sample. Homogeneous, accurate and precise derivation of stellar parameters is crucial for characterising exoplanet-host stars and in turn is a key factor for the accuracy of the planet properties

Ariel stellar characterisation. I. Homogeneous stellar parameters of 187 FGK planet host stars: Description and validation of the method

Context. In 2020 the European Space Agency selected Ariel as the next mission to join the space fleet of observatories to study planets outside our Solar System. Ariel will be devoted to the characterisation of 1000 planetary atmospheres in order to understand what exoplanets are made of, how they form, and how they evolve. To achieve the last two goals all planets need to be studied within the context of their own host stars, which in turn must be analysed with the same technique, in a uniform way. Aims: We present the spectro-photometric method we developed to infer the atmospheric parameters of the known host stars in the Tier 1 of the Ariel Reference Sample. Methods: Our method is based on an iterative approach that combines spectral analysis, the determination of the surface gravity from Gaia data, and the determination of stellar masses from isochrone fitting. We validated our approach with the analysis of a control sample, composed of members of three open clusters with well-known ages and metallicities. Results: We measured effective temperature Teff, surface gravity log g, and the metallicity [Fe/H] of 187 F-G-K stars within the Ariel Reference Sample. We presented the general properties of the sample, including their kinematics, which allows us to classify them into thin- and thick-disc populations. Conclusions: A homogeneous determination of the parameters of the host stars is fundamental in the study of the stars themselves and their planetary systems. Our analysis systematically improves agreement with theoretical models and decreases uncertainties in the mass estimate (from 0.21 ± 0.30 to 0.10 ± 0.02 M⊙), providing useful data for the Ariel consortium and the astronomical community at large. Tables A.1 and A.2 are only available at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (ftp://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/cat/J/A+A/663/A161</A

The homogeneous characterisation of Ariel host stars

The Ariel mission will characterise the chemical and thermal properties of the atmospheres of about a thousand exoplanets transiting their host star(s). The observation of such a large sample of planets will allow to deepen our understanding of planetary and atmospheric formation at the early stages, providing a truly representative picture of the chemical nature of exoplanets, and relating this directly to the type and chemical environment of the host star. Hence, the accurate and precise determination of the host star fundamental properties is essential to Ariel for drawing a comprehensive picture of the underlying essence of these planetary systems. We present here a structured approach for the characterisation of Ariel stars that accounts for the concepts of homogeneity and coherence among a large set of stellar parameters. We present here the studies and benchmark analyses we have been performing to determine robust stellar fundamental parameters, elemental abundances, activity indices, and stellar ages. In particular, we present results for the homogeneous estimation of the activity indices S and log (RHK') , and preliminary results for elemental abundances of Na, Al, Mg, Si, C, N. In addition, we analyse the variation of a planetary spectrum, obtained with Ariel, as a function of the uncertainty on the stellar effective temperature. Finally, we present our observational campaign for precisely and homogeneously characterising all Ariel stars in order to perform a meaningful choice of final targets before the mission launch

VizieR Online Data Catalog: Complete line list and solar values (Baratella+, 2020)

Line list used in this study (table2.dat), complete of the atomic data, references of the log(gf) values adopted and with equivalent width and abundances measured in the Sun. (1 data file)

The wide-field, multiplexed, spectroscopic facility WEAVE : survey design, overview, and simulated implementation

Funding for the WEAVE facility has been provided by UKRI STFC, the University of Oxford, NOVA, NWO, Instituto de Astrofísica de Canarias (IAC), the Isaac Newton Group partners (STFC, NWO, and Spain, led by the IAC), INAF, CNRS-INSU, the Observatoire de Paris, Région Île-de-France, CONCYT through INAOE, Konkoly Observatory (CSFK), Max-Planck-Institut für Astronomie (MPIA Heidelberg), Lund University, the Leibniz Institute for Astrophysics Potsdam (AIP), the Swedish Research Council, the European Commission, and the University of Pennsylvania.WEAVE, the new wide-field, massively multiplexed spectroscopic survey facility for the William Herschel Telescope, will see first light in late 2022. WEAVE comprises a new 2-degree field-of-view prime-focus corrector system, a nearly 1000-multiplex fibre positioner, 20 individually deployable 'mini' integral field units (IFUs), and a single large IFU. These fibre systems feed a dual-beam spectrograph covering the wavelength range 366-959 nm at R ∼ 5000, or two shorter ranges at R ∼ 20,000. After summarising the design and implementation of WEAVE and its data systems, we present the organisation, science drivers and design of a five- to seven-year programme of eight individual surveys to: (i) study our Galaxy's origins by completing Gaia's phase-space information, providing metallicities to its limiting magnitude for ∼ 3 million stars and detailed abundances for ∼ 1.5 million brighter field and open-cluster stars; (ii) survey ∼ 0.4 million Galactic-plane OBA stars, young stellar objects and nearby gas to understand the evolution of young stars and their environments; (iii) perform an extensive spectral survey of white dwarfs; (iv) survey  ∼ 400 neutral-hydrogen-selected galaxies with the IFUs; (v) study properties and kinematics of stellar populations and ionised gas in z 1 million spectra of LOFAR-selected radio sources; (viii) trace structures using intergalactic/circumgalactic gas at z > 2. Finally, we describe the WEAVE Operational Rehearsals using the WEAVE Simulator.PostprintPeer reviewe

The wide-field, multiplexed, spectroscopic facility WEAVE: Survey design, overview, and simulated implementation

WEAVE, the new wide-field, massively multiplexed spectroscopic survey facility for the William Herschel Telescope, will see first light in late 2022. WEAVE comprises a new 2-degree field-of-view prime-focus corrector system, a nearly 1000-multiplex fibre positioner, 20 individually deployable 'mini' integral field units (IFUs), and a single large IFU. These fibre systems feed a dual-beam spectrograph covering the wavelength range 366$-$959\,nm at $R\sim5000$, or two shorter ranges at $R\sim20\,000$. After summarising the design and implementation of WEAVE and its data systems, we present the organisation, science drivers and design of a five- to seven-year programme of eight individual surveys to: (i) study our Galaxy's origins by completing Gaia's phase-space information, providing metallicities to its limiting magnitude for $\sim$3 million stars and detailed abundances for $\sim1.5$ million brighter field and open-cluster stars; (ii) survey $\sim0.4$ million Galactic-plane OBA stars, young stellar objects and nearby gas to understand the evolution of young stars and their environments; (iii) perform an extensive spectral survey of white dwarfs; (iv) survey $\sim400$ neutral-hydrogen-selected galaxies with the IFUs; (v) study properties and kinematics of stellar populations and ionised gas in $z<0.5$ cluster galaxies; (vi) survey stellar populations and kinematics in $\sim25\,000$ field galaxies at $0.3\lesssim z \lesssim 0.7$; (vii) study the cosmic evolution of accretion and star formation using $>1$ million spectra of LOFAR-selected radio sources; (viii) trace structures using intergalactic/circumgalactic gas at $z>2$. Finally, we describe the WEAVE Operational Rehearsals using the WEAVE Simulator.Comment: 41 pages, 27 figures, accepted for publication by MNRA

Enabling planetary science across light-years. Ariel Definition Study Report

Ariel, the Atmospheric Remote-sensing Infrared Exoplanet Large-survey, was adopted as the fourth medium-class mission in ESA's Cosmic Vision programme to be launched in 2029. During its 4-year mission, Ariel will study what exoplanets are made of, how they formed and how they evolve, by surveying a diverse sample of about 1000 extrasolar planets, simultaneously in visible and infrared wavelengths. It is the first mission dedicated to measuring the chemical composition and thermal structures of hundreds of transiting exoplanets, enabling planetary science far beyond the boundaries of the Solar System. The payload consists of an off-axis Cassegrain telescope (primary mirror 1100 mm x 730 mm ellipse) and two separate instruments (FGS and AIRS) covering simultaneously 0.5-7.8 micron spectral range. The satellite is best placed into an L2 orbit to maximise the thermal stability and the field of regard. The payload module is passively cooled via a series of V-Groove radiators; the detectors for the AIRS are the only items that require active cooling via an active Ne JT cooler. The Ariel payload is developed by a consortium of more than 50 institutes from 16 ESA countries, which include the UK, France, Italy, Belgium, Poland, Spain, Austria, Denmark, Ireland, Portugal, Czech Republic, Hungary, the Netherlands, Sweden, Norway, Estonia, and a NASA contribution

The wide-field, multiplexed, spectroscopic facility WEAVE: Survey design, overview, and simulated implementation

WEAVE, the new wide-field, massively multiplexed spectroscopic survey facility for the William Herschel Telescope, will see first light in late 2022. WEAVE comprises a new 2-degree field-of-view prime-focus corrector system, a nearly 1000-multiplex fibre positioner, 20 individually deployable 'mini' integral field units (IFUs), and a single large IFU. These fibre systems feed a dual-beam spectrograph covering the wavelength range 366−959\,nm at R∼5000, or two shorter ranges at R∼20000. After summarising the design and implementation of WEAVE and its data systems, we present the organisation, science drivers and design of a five- to seven-year programme of eight individual surveys to: (i) study our Galaxy's origins by completing Gaia's phase-space information, providing metallicities to its limiting magnitude for ∼3 million stars and detailed abundances for ∼1.5 million brighter field and open-cluster stars; (ii) survey ∼0.4 million Galactic-plane OBA stars, young stellar objects and nearby gas to understand the evolution of young stars and their environments; (iii) perform an extensive spectral survey of white dwarfs; (iv) survey ∼400 neutral-hydrogen-selected galaxies with the IFUs; (v) study properties and kinematics of stellar populations and ionised gas in z1 million spectra of LOFAR-selected radio sources; (viii) trace structures using intergalactic/circumgalactic gas at z>2. Finally, we describe the WEAVE Operational Rehearsals using the WEAVE Simulator

Chemical evolution of the Large Magellanic Cloud

Malgré des années de travaux théoriques et observationnels intensifs, nous sommes toujours loin d’une complète compréhension de l’univers proche, la Voie Lactée (MW) et ses galaxies voisines. Parmi les satellites de la MW, le Petit et le Grand Nuage de Magellan (LMC) sont particulièrement intéressants puisqu’ils forment le plus proche exemple de galaxies en interaction gravitationnelle et hydrodynamique, et partant, constituent un laboratoire unique pour étudier les effets des marées et l’échange de matière sur l’évolution chimique et l’histoire de la formation stellaire d’une galaxie. Le LMC est une galaxie de petite masse barrée à disque, prototype des galaxies riches en gaz que l’on pense jouer un rôle important dans la construction des grandes galaxies dans le cadre du ΛCDM. De plus, avec sa métallicité actuelle d’environ le tiers de la métallicité solaire, le chemin d’enrichissement chimique suivi par le LMC donne un grand poids aux yields des générations stellaires pauvres en métaux, ce qui fait du LMC un environnement idéal pour étudier la nucléosynthèse aux basses métallicités. Ce travail de doctorat vise à: 1) caractériser chimiquement la population de la barre du LMC, 2) comparer les tendances des éléments de la MW et du LMC et interpréter les différences ou ressemblance en termes d’évolution chimique et/ou de processus nucléosynthétiques (contraintes sur les sites et les processus nucléosynthétiques), 3) comparer l’évolution chimique de la barre et du disque interne du LMC et interpréter les différence ou ressemblance dans le contexte de la formation de la barre. Nos résultats montrent que l’histoire chimique du LMC a connu un forte contribution des supernovae de type I ainsi qu’un fort enrichissement en éléments s par les vents d’étoiles AGB pauvres en métaux. Par rapport à la MW, les étoiles massives ont eu une contribution plus petite à l’enrichissement chimique du LMC. Les différences observées entre la barre et le disque parlent en faveur d’un épisode de formation stellaire accrue il y a quelques Gyr, ayant lieu dans les zones centrales du LMC et conduisant à la formation de la barre. Ceci est en accord avec les histoires de la formation stellaire récemment dérivées.Despite decades of intensive observational and theoretical work, we are still far from a complete and clear understanding of the nearby universe, the Milky Way (MW) and its neighbours. Among the satellites of the MW, the Small and Large Magellanic Cloud (LMC) are of particular interest since they form the closest example of galaxies in gravitational and hydrodynamical interaction, and therefore constitute a unique laboratory to study the effect of tides and matter exchange on the chemical evolution and star formation history of a galaxy. The LMC is a low-mass barred disc galaxy, prototypical of gas-rich galaxies that are thought to play an important role in the build-up of large galaxies in the ΛCDM framework. Furthermore, with its present day metallicity of only third of solar, the chemical enrichment path followed by the LMC gives a heavy weight to the yields of metal-poor stellar generations, which makes the LMC an ideal environment to study nucleosynthesis at low metallicities. This thesis work aims at: 1) chemically characterizing the LMC bar population, 2) comparing the elemental trends of the MW and the LMC and interpreting the differences or similarities in terms of chemical evolution and/or nucleosynthesis processes (constraints on the nucleosynthetic sites and processes), 3) comparing the chemical evolution of the LMC bar and inner disc and interpreting the differences or similarities between the LMC bar and inner disc in the context of the bar formation. Our results show that the chemical history of the LMC experienced a strong contribution from type Ia supernovae as well as a strong s-process enrichment from metal-poor AGB winds. Massive stars made a smaller contribution to the chemical enrichment compared to the MW. The observed differences between the bar and the disc speak in favour of an episode of enhanced star formation a few Gyr ago, occurring in the central parts of the LMC and leading to the formation of the bar. This is in agreement with recently derived star formation histories