Chemical and dynamical analysis of Open Clusters in the context of the Milky Way disc

[eng] This thesis has as a main purpose the determination of the chemical composition of Open Clusters for the study of the chemical gradients in the Galactic disc with: Galactocentric radius, position above the plane, and age. In 3 years and a half we have acquired high-resolution spectra of stars in 18 Open Clusters as a part of the OCCASO survey. We have used three fiber fed high-resolution spectrographs in the Observatorio del Roque de los Muchachos (La Palma, Spain) and the CAHA observatory (Almería, Spain). After a very accurate data reduction we have determined radial velocities, atmospheric parameters (effective temperature, surface gravity) and chemical abundances. Using the derived radial velocities and proper motions from the literature we have done a kinematic study of these clusters in the context of the Galactic disc and the position near the spiral arms. We have obtained radial velocities for OC never studied before with high-resolution spectroscopy: NGC 1907 (vr=2.3+- 0.5 km/s), NGC 6991 (vr=-12.3+-0.6 km/s) and NGC 7245 (vr=-74.0+-1.4km/s). We have computed the possible orbits that the clusters have followed using two models of the Galactic potential: an axysimmetric one, and a model with a bar and spiral arms featuring those of the Milky Way. With this, we have recovered the position of the clusters at birth. We have calculated temperatures, gravities and iron abundances using two different methodologies widely used in the literature. We have made an exhaustive comparison of the behaviour of both methods and the differences obtained among them. We obtained no systematics in effective temperature and surface gravity within the quoted errors, though with a large dispersion in surface gravity. As a sanity check we derived atmospheric parameters from BVI Johnson photometry for the stars from NGC 2420 and NGC 6791. We found systematic differences between spectroscopic and photometric determinations which change with slight variations of the assumed reddening, distance, age and metallicity to compute photometric parameters. Mean uncertainties in the final adopted in temperature and gravity are around 40 K and 0.1 dex. The comparison with literature values gives mean offsets well within uncertainties and dispersions. All these checks provide a study of the precision and accuracy of the obtained results. We have measured abundances of iron-peak elements (Fe, Ni, Cr) and the so-called α-elements (Si, Ca, Ti, Mg, O). From member stars we derive mean Fe cluster abundances with the two methods. We do an extensive star-by-star comparison with literature, showing good agreement. We also derived mean cluster Ni, Cr, Si, Ca and Ti abundances, and its abundance ratios respect to Fe. We see that all the clusters present small dispersions in abundance. The larger ones are 0.03 ([Ni/Fe]), 0.06 ([Cr/Fe]), 0.05 ([Si/Fe]), 0.07 ([Ca/Fe]), 0.05 ([Ti/Fe]) dex, excluding NGC~6791 (for which we have larger errors) We have compared the Galactocentric trend seen with OCCASO clusters with different theoretical models obtaining that the results for the oldest clusters favour a chemo-dynamical model instead of a pure chemical evolution model. Using OCCASO and two complementary samples (40 clusters in total), we have determined new values for the Galactocentric Fe gradient in three age bins, and the age-metallicity relation in four ranges of Galactocentric distance. In particular we have studied NGC 6705 in detail. We have seen that this cluster presents an unexpected α- enhancement for its location in the disc and its young age. We have derived the birth location of this cluster computing the possible orbits that it could have followed in the disc using different models. It seems that its α-enhancement cannot be explained by a very different place of birth of this cluster (i.e. the inner Galaxy), which from our calculations would be at most from a radii of 6.5 kpc.[cat] La present tesi té com a objectiu principal la determinació de la composició química de cúmuls oberts per l'estudi del gradient químic en el disc galàctic, tant amb la distancia al centre galàctic, com amb la posició sobre el disc, com amb l'edat. Durant 3 anys i mig s'han adquirit espectres d'alta resolució d'estrelles en 18 cúmuls oberts dins del projecte OCCASO. Així, després d'una acurada reducció de dades, s'han pogut determinar velocitats radials, paràmetres físics (temperatura efectiva, gravetat superficial) i abundàncies químiques. Amb les velocitats obtingudes i moviments propis de la literatura s'ha realitzat un estudi cinemàtic d'aquests cúmuls en relació amb el disc galàctic segons la seva posició a prop dels braços espirals. En concret s'han computat les possibles òrbites que han tingut els cúmuls a partir de dos models del potencial galàctic. S'han calculat temperatures, gravetats i abundàncies de ferro a partir de dues metodologies àmpliament usades a la literatura. S'ha fet una exhaustiva comparació del comportament dels dos mètodes i de les diferències obtingudes, aportant així un estudi de la precisió dels resultats obtinguts. S'han mesurat abundàncies químiques d'elements del pic del ferro (Fe, Ni, Cr) i d'elements anomenats α (Si, Ca, Ti, Mg, O). S'ha comparat la tendència dels cúmuls OCCASO amb diferents models teòrics i s'ha vist que els resultats dels cúmuls vells afavoreixen el model d'evolució químic-dinàmic front d'un model on només es contempli l'evolució química. Amb aquests resultats d'OCCASO i dues mostres complementaries (en total 40 cúmuls), s'han determinat nous valors pel gradient galactocèntric de Fe en tres rangs d'edat, i la relació edat-metal·licitat en quatre rangs de distancia galactocèntrica. En especial, s'ha estudiat en detall el cúmul NGC 6705. Aquest presenta una sobreabundància d'elements α inesperada per la seva localització en el disc i per ser tant jove. S'ha fet una investigació del lloc de procedència d'aquest cúmul computant les òrbites que podria haver seguit el cúmul en el disc amb diferents models. S'ha descartat que provingui d'un lloc intern de la galàxia que pugui explicar aquesta anomalia en els patrons químics.[spa] La presente tesis tiene como objetivo principal la determinación de la composición química de cúmulos abiertos para el estudio del gradiente químico en el disco galáctico, tanto con la distancia al centro galáctico, como con la posición sobre el disco, como con la edad. Durante 3 años y medio se han adquirido espectros de alta resolución de estrellas en 18 cúmulos abiertos dentro del proyecto OCCASO. Así, después de una acurada reducción de datos, se ha podido determinar velocidades radiales, parámetros físicos (temperatura efectiva, gravedad superficial) y abundancias químicas. Con los resultados de velocidades radiales y los movimientos propios de la literatura se ha realizado un estudio cinemático de dichos cúmulos según su posición en los brazos espirales. En particular se han computado las órbitas a partir de dos modelos del potencial galáctico. Se han calculado temperaturas, gravedades y abundancias de hierro a partir de dos metodologías. Se ha hecho una exhaustiva comparación del comportamiento de los dos métodos y las diferencias que se obtienen, aportando así un estudio de la precisión de los resultados obtenidos. Se han medido abundancias químicas de elementos del pico del hierro (Fe, Ni, Cr) y elementos llamados α (Si, Ca, Ti, Mg, O). Se ha comparado la tendencia de los cúmulos de OCCASO con diferentes modelos teóricos y se ha visto que los resultados de los cúmulos más viejos favorecen el modelo de evolución químico-dinámico frente a un modelo dónde solo se contemple la evolución química. Con estos resultados de OCCASO y dos muestras complementarias (40 cúmulos en total) se han determinado nuevos valores para el gradiente galactocéntrico de Fe en tres rangos de edad, y la relación edad-metalicidad en cuatro rangos de distancia galactocéntrica. En concreto, se ha estudiado con detalle el cúmulo NGC 6705. Éste presenta una sobreabundancia de elementos α inesperada por su localización en el disco y su joven edad. Se ha hecho una investigación del lugar de procedencia de éste cúmulo mediante diferentes modelos. Se ha descartado que provenga de un sitio interno de la Galaxia que pueda explicar esta anomalía en los patrones químicos

Assessment of [Fe/H] determinations for FGK stars in spectroscopic surveys

The number of stars with a measured value of [Fe/H] is considerably increasing thanks to spectroscopic surveys. However different methodologies, inputs and assumptions used in spectral analyses lead to different precisions in [Fe/H] and possibly to systematic differences that need to be evaluated. It is essential to understand the characteristics of each survey to fully exploit their potential, in particular if the surveys are combined. The purpose of this study is to compare [Fe/H] determinations from the largest spectroscopic surveys (APOGEE, GALAH, the Gaia ESO survey, RAVE, LAMOST, SEGUE ) to other catalogues taken as reference. Offsets and dispersions of the residuals are examined as well as their trends with other parameters. We use reference samples providing independent determinations of [Fe/H] which are compared to those from the surveys for common stars. The distribution of the residuals is assessed through simple statistics that measures the offset between two catalogues and the dispersion representative of the precision of both catalogues. When relevant, linear fits are performed. A large sample of FGK-type stars with [Fe/H] based on high-resolution, high signal to noise spectroscopy was built from the PASTEL catalogue to provide a reference sample. We also use FGK members in open and globular clusters to assess the internal consistency of [Fe/H] of each survey. The agreement of median [Fe/H] values for clusters observed by different surveys is discussed. All the surveys overestimate the low metallicities, and some of them also underestimate the high metallicities. They perform well in the most populated intermediate metallicity range, whatever the resolution. In most cases the typical precision that we deduce from the comparisons is in good agreement with the uncertainties quoted in the catalogues. Some exceptions to this general behaviour are discussed.Comment: accepted in A&

Finestres al cel

We present an astronomy educational project intended for 16-year-old high school students that has been successfully deployed for 7 years under the Youth and Science Program of the Catalunya La Pedrera Foundation. The Youth and Science Program aims to encourage talented students to pursue careers in science and technology and a future as researchers. It consists of a two-week crash course covering all major topics in astronomy: stellar evolution, black holes, galaxy formation and evolution, cosmology, simulations, and gravitational waves, among many others. The classes focus on the relevant concepts in each of the aforementioned fields but without a detailed description of the math formalism or the most advanced concepts in modern physics, this to develop the students’ intuition and interest in the wonders of the Universe without overwhelming them. Theoretical sessions are complemented with a set of practical sessions that help students to consolidate the concepts. All theory and practical sessions in this project are being compiled in an outreach book addressed not only to the students of this project but also to the entire amateur astronomy community

The open cluster King 1 in the second quadrant

We analyse the poorly studied open cluster King 1 in the second Galactic quadrant. From wide-field photometry, we have studied the spatial distribution of this cluster. We determined that the centre of King 1 is located at α2000 = 00h22m and δ2000 = +64°23΄. By parameterizing the stellar density with a King profile, we have obtained a central density of ρ0 = 6.5 ± 0.2 star arcmin-2 and a core radius of rcore = 1.9 ± 0.2 arcmin. By comparing the observed colour-magnitude diagram of King 1 with those of similar open clusters and with different sets of isochrones, we have estimated an age of 2.8 ± 0.3 Gyr, a distance modulus of (m - M)o = 10.6 ± 0.1 mag and a reddening of E(B - V) = 0.80 ± 0.05 mag. To complete our analysis, we acquired medium resolution spectra for 189 stars in the area of King 1. From their derived radial velocities, we determined an average velocity = -53.1 ± 3.1 km s-1. From the strength of the infrared Ca II lines in red giants we have determined an average metallicity of = +0.07 ± 0.08 dex. From spectral synthesis, we have also estimated an α-elements abundance of = -0.10 ± 0.08 dex

Gaia FGK Benchmark Stars: fundamental Teff and log g of the third version

Context. Large spectroscopic surveys devoted to the study of the Milky Way, including Gaia, use automated pipelines to massively determine the atmospheric parameters of millions of stars. The Gaia FGK Benchmark Stars are reference stars with Teff and log g derived through fundamental relations, independently of spectroscopy, to be used as anchors for the parameter scale. The first and second versions of the sample have been extensively used for that purpose, and more generally to help constrain stellar models. Aims. We provide the third version of the Gaia FGK Benchmark Stars, an extended set intended to improve the calibration of spectroscopic surveys, and their interconnection. Methods. We have compiled about 200 candidates which have precise measurements of angular diameters and parallaxes. We determined their bolometric fluxes by fitting their spectral energy distribution. Masses were determined using two sets of stellar evolution models. In a companion paper we describe the determination of metallicities and detailed abundances. Results. We provide a new set of 192 Gaia FGK Benchmark Stars with their fundamental Teff and logg, and with uncertainties lower than 2% for most stars. Compared to the previous versions, the homogeneity and accuracy of the fundamental parameters are significantly improved thanks to the high quality of the Gaia data reflecting on distances and bolometric fluxes.Comment: accepted in A&

Gaia FGK Benchmark stars: Opening the black box of stellar element abundance determination

Gaia and its complementary spectroscopic surveys combined will yield the most comprehensive database of kinematic and chemical information of stars in the Milky Way. The Gaia FGK benchmark stars play a central role in this matter as they are calibration pillars for the atmospheric parameters and chemical abundances for various surveys. The spectroscopic analyses of the benchmark stars are done by combining different methods, and the results will be affected by the systematic uncertainties inherent in each method. In this paper, we explore some of these systematic uncertainties. We determined line abundances of Ca, Cr, Mn and Co for four benchmark stars using six different methods. We changed the default input parameters of the different codes in a systematic way and found, in some cases, significant differences between the results. Since there is no consensus on the correct values for many of these default parameters, we urge the community to raise discussions towards standard input parameters that could alleviate the difference in abundances obtained by different methods. In this work, we provide quantitative estimates of uncertainties in elemental abundances due to the effect of differing technical assumptions in spectrum modelling

The OCCASO survey: presentation and radial velocities of 12 Milky Way open clusters

Open clusters (OCs) are crucial for studying the formation and evolution of the Galactic disc. However, the lack of a large number of OCs analysed homogeneously hampers the investigations about chemical patterns and the existence of Galactocentric radial and vertical gradients, or an age-metallicity relation. To overcome this, we have designed the Open Cluster Chemical Abundances from Spanish Observatories (OCCASO) survey. We aim to provide homogeneous radial velocities, physical parameters and individual chemical abundances of six or more red clump stars for a sample of 25 old and intermediate-age OCs visible from the Northern hemisphere. To do so, we use high-resolution spectroscopic facilities (R >= 62 000) available at Spanish observatories. We present the motivation, design and current status of the survey, together with the first data release of radial velocities for 77 stars in 12 OCs, which represents about 50 per cent of the survey. We include clusters never studied with high-resolution spectroscopy before (NGC 1907, NGC 6991, NGC 7762), and clusters in common with other large spectroscopic surveys like the Gaia-ESO Survey (NGC 6705) and Apache Point Observatory Galactic Evolution Experiment (NGC 2682 and NGC 6819). We perform internal comparisons between instruments to evaluate and correct internal systematics of the results, and compare our radial velocities with previous determinations in the literature, when available. Finally, radial velocities for each cluster are used to perform a preliminary kinematic study in relation with the Galactic disc

The young open cluster NGC 7067 using Stromgren photometry

© The Authors 2016. Published by Oxford University Press on behalf of The Royal Astronomical Society. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted reuse, distribution, and reproduction in any medium, provided the original work is properly cited. M. Monguio et al, ' The young open cluster NGC 7067 using Stromgren photometry ', MNRAS Vol 466(3): 3636-3647 (2017), first published online 17 December 2016, the version of record is available online via doi: 10.1093/mnras/stw3302NGC 7067 is a young open cluster located in the direction between the first and the second Galactic quadrants and close to the Perseus spiral arm. This makes it useful for studies of the nature of the Milky Way spiral arms. Stromgren photometry taken with the Wide Field Camera at the Isaac Newton Telescope allowed us to compute individual physical parameters for the bserved stars and hence to derive cluster’s physical parameters. Spectra from the 1.93-m telescope at the Observatoire de Haute-Provence helped to check and improve the results. We obtained photometry for 1233 stars, individual physical parameters for 515 and spectra for 9 of them. The 139 selected cluster members lead to a cluster distance of 4.4±0.4 kpc, with an age below log10(t(yr))=7.3 and a present Mass of 1260±160M⊙. The morphology of the data reveals that the centre of the cluster is at (α,δ)=(21: 24: 13.69,+48: 00: 39.2) J2000, with a radius of 6.′1. Stromgren and spectroscopic data allowed us to improve the previous parameters available for the cluster in the literature.Peer reviewedFinal Published versio

OCCASO - II. Physical parameters and Fe abundances of red clump stars in 18 open clusters

Open clusters have long been used to study the chemodynamical evolution of the Galactic disc. This requires a homogeneously analysed sample covering a wide range of ages and distances. In this paper, we present the Open Clusters Chemical Abundances from Spanish Observatories (OCCASO) second data release. This comprises a sample of high-resolution (R > 65 000) and high signal-to-noise spectra of 115 red clump stars in 18 open clusters. We derive atmospheric parameters (Teff, log g, ξ), and [Fe/H] abundances using two analysis techniques: equivalent widths and spectral synthesis. A detailed comparison and a critical review of the results of the two methods are made. Both methods are carefully tested between them, with the Gaia FGK benchmark stars, and with an extensive sample of literature values. We perform a membership study using radial velocities and the resulting abundances. Finally, we compare our results with a chemodynamical model of the Milky Way thin disc concluding that the oldest open clusters are consistent with the models only when dynamical effects are taken into account

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