This thesis investigates the potential for detection and identification of primordial stars, galaxies, and supernovae at high redshift. Simulations indicate that the first Population III stars should appear in minihalos of mass M = 105-106 Msol at z ≈ 10-30. To assess the detectability of these objects, theoretical models of these stars and their surrounding HII regions are used. We assess the plausibility of detection with the upcoming James Webb Space Telescope (JWST), using the gravitational lensing provided by the galaxy cluster MACSJ0717.5+3745. The conclusion is that the detection of these objects is highly improbable but not impossible. To investigate the prospects of detecting and identifying the first galaxies, the spectral synthesis code Yggdrasil is introduced. According to this code, JWST may be able to detect Population III galaxies with stellar masses as low as 105 Msol at z ≈ 10 in unlensed fields. We find that, over limited redshift intervals, it could be possible to use Hubble Space Telescope (HST) and/or JWST broadband color criteria to single out Population III galaxy candidates. The prospects of detecting gravitationally lensed Population III galaxies with JWST and HST is investigated. A lower limit to detect ≈1 Population III galaxy of ε ≈ 10-2 (HST/CLASH) and ε ≈ 10-3 (JWST using MACS J0717.5+3745 as lens) is derived, where ε is the baryon fraction converted to Population III stars in a host halo. By fitting HST/CLASH data to Yggdrasil and comparison grids, two Population III galaxy candidates are discovered. These two candidates are the first Population III galaxy candidates discovered at z &gt; 6.5. A highly-magnified and doubly lensed extremely high-redshift (z ≈ 7.8) object is also identified. Finally the prospects of detecting core-collapse (CC) supernovae (SN) from the first galaxies at z ≈ 5-12 are investigated. The prediction is that no primordial SN is detectable, but 2-3 CC SN should be discovered by the HST/CLASH. / <p>At the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 5: Submitted. Paper 6: Submitted. Paper 7: Manuscript.</p>

Detailed knowledge of solar-type stars is essential in the understanding of the evolutionary past, presence and future of the Sun as well as the formation of its planetary system. Moreover, solar-type stars are of key significance for the study of the evolution of the Galaxy. The ages of solar-type stars map the full galactic evolution. Their surface layers are well mixed and just little affected by the interior nuclear processes. They may therefore be used as samples of the gas from which the stars were once formed. Models of stellar atmospheres are used to derive fundamental stellar quantities such as chemical composition, effective temperature, surface gravity, age and rotation. It is therefore also important to investigate the progress and shortcomings of the atmospheric models and the reliability of calibrations based upon these. In this thesis we explore the potential of synthetic uvbyHβ colours for deriving atmospheric parameters. The theoretical colours are derived using high-resolution synthetic spectra based on 1D atmosphere models of late-type stars. Furthermore, possible applications of the established synthetic colours on globular stellar clusters are tested. Observations of solar-type stars have demonstrated the existence of stars very similar to the Sun, so-called solar twins. A detailed chemical analysis of these stars, however, shows that most solar-twins are systematically richer, as compared with the Sun, in refractory elements such as Fe, Ni and Al, relative to volatile elements like C, N and O. This chemical abundance pattern has been suggested to be related to the formation of planets or the birth environment of the respective star. In this thesis we present a high-accuracy study on a solar-twin star in the old open cluster M67. We find that the star is very similar to the Sun when comparing their atmospheric parameters, effective temperature, surface gravity and metallicity. Remarkably enough, unlike most solar twins observed in the solar vicinity, the cluster twin shows the same refractory to volatile pattern as the Sun.The reason for this similarity is still unknown but further observations of the cluster will help to clarify the matter. M dwarfs constitute a large fraction of the detectable baryonic matter. In spite of this, detailed knowledge on the numerous neighbouring low-mass stars is still not available. The presence of strong molecular features in the spectra, and incomplete line lists for the corresponding molecules have made metallicity determinations of M dwarfs difficult. Furthermore, the faint M dwarfs require long exposure times for a signal-to-noise ratio sufficient for detailed spectroscopic abundance analysis. In this thesis we present a high resolution spectroscopic study of early-type M dwarfs in the infrared. The lack of prominent molecular bands in parts of the infrared J-band (1100--1400 nm) allows a precise continuum placement. Furthermore, we verify the adequacy of using the model atmospheres for abundance determination by observing a set of binary systems with a solar-type primary and an M dwarf companion. We present a reliable zero-point for the metallicity scale of early-type M dwarfs and verify the reliability of spectroscopic abundance analyses in the infrared.

La mission Gaia de l'Agence Spatiale Européenne (ESA) a pour objectif de cartographier notre galaxie avec une précision astrométrique jamais atteinte auparavant. Il est donc particulièrement important que les données qui seront publiées soient rigoureusement validées afin d'assurer une qualité optimum au Catalogue. Ces validations sont faites par l'une des équipes de l'unité de coordination CU9 du Consortium Gaia DPAC (Data Processing and Analys Consortium) chargé par l'ESA de la production du Catalogue Gaia. Dans le cadre de cette thèse, nous avons mis en place toute l’infrastructure nécessaire à la validation du catalogue Gaia par comparaison avec des catalogues externes. Celle-ci gère toutes les interactions avec l'environnement global des validations et avec la base de données Gaia. Ensuite nous avons développé un ensemble de tests statistiques pour valider les données du premier catalogue Gaia (DR1). Ces tests concernent notamment l’homogénéité des données sur le ciel, la qualité des positions et de la photométrie de l'ensemble des étoiles de DR1 (plus d'un milliard d'étoiles, $V<20$) ainsi que celle des parallaxes et mouvements propres des étoiles de textit{Tycho-Gaia} Astrometric Solution (TGAS), environ deux millions d'étoiles communes aux catalogues Gaia et Tycho-2 ($V<12$). Ces tests statistiques sur la DR1 sont opérationnels et ont déjà été appliqués très récemment sur des données préliminaires. Cela a déjà permis d'améliorer ces données (donc la qualité du catalogue), et d'en caractériser les propriétés statistiques. Cette caractérisation est essentielle à une exploitation scientifique correcte des données. Le premier catalogue Gaia sera publié à la fin de l’été 2016. Parmi les objets observés par Gaia, il y a une population d'étoiles particulièrement intéressantes, les étoiles du Red Clump (RC), très utilisées comme étalons de distance. Nous avons développé et testé deux méthodes pour modéliser les relations couleur-couleur (CC) et température effective - couleur dans toutes les bandes photométriques, de l'ultraviolet au proche-infrarouge. Elles permettront de caractériser le RC dans la bande G de Gaia dès la publication du catalogue: 1. en utilisant des modèles théoriques, et 2. empiriquement, en se basant sur une méthode Monte Carlo Markov Chain (MCMC). Pour cela nous avons très rigoureusement sélectionné des échantillons d'étoiles avec une bonne qualité photométrique, une bonne métallicité, déterminée par spectroscopie, une température effective homogène et une faible extinction interstellaire. À partir de ces calibrations CC et température-couleur, nous avons ensuite développé une méthode par Maximum de Vraisemblance qui permet de déterminer les magnitudes absolues, les températures et les extinctions des étoiles du RC. Les couleurs et extinctions ainsi obtenues ont été testées sur des étoiles avec des températures effectives mesurées spectroscopiquement et une extinction déterminée par la mesure des Bandes Diffuses Interstellaires (DIB). Ces propriétés intrinsèques des étoiles du RC vont permettre de caractériser le Red Clump Gaia et de calibrer, dans la bande Gaia, la magnitude absolue de cet étalon de distance, premier échelon essentiel de la détermination des distances dans l'Univers. / The Gaia mission of the European Space Agency (ESA) aims to map our galaxy with an unprecedented astrometric precision. It is therefore very important that the data that will be published be rigorously validated to ensure an optimal quality in the Catalogue. These validations are done by one of the teams of the coordination unit CU9 of the Gaia DPAC Consortium (Data Processing and Analysis Consortium) commissioned by ESA of the Gaia catalogue production. As part of this thesis, we implemented all the necessary infrastructure to validate the Gaia catalogue by comparison with external catalogues. This last manages all the interactions with the global environment of validations and with the Gaia database. Then we developed a set of statistical tests to validate the data from the first Gaia catalogue (DR1). These tests relate in particular to the homogeneity of data on the sky, the quality of the positions and of photometry of all the stars of DR1 (more than a billion stars, $V <20$) as well as that of the parallaxes and proper motions for textit{Tycho-Gaia} Astrometric Solution (TGAS) stars, around two million stars in common in Gaia and Tycho-2 catalogues ($V <12$).These DR1 statistical tests are operational and were already applied very recently on preliminary data. This has improved the data (thus the quality of the catalog) as well as allowed to characterize the statistical properties. This characterisation is essential for a correct scientific exploitation of the data. The first Gaia catalogue will be released in late summer 2016.Among the objects that Gaia observes, there is a population of stars particularly interesting, the Red Clump (RC) stars, widely used for distance indicators. We developed and tested two methods to model the colour-colour (CC) and effective temperature - colour relations in all photometric bands, from the ultraviolet to the near infrared. They will allow us to characterize the RC in the Gaia G band upon publication of the catalogue: 1. using theoretical models, and 2. empirically, based on a Monte Carlo Markov Chain (MCMC) method. For this we have very carefully selected samples of stars with a good photometric quality, good metallicity determined by spectroscopy, an homogeneous effective temperature and a low interstellar extinction.From these CC and temperature-colour calibrations, we then developed a Maximum Likelihood method that allows to derive absolute magnitudes, temperatures and extinctions of the RC stars. Estimates of colours and extinctions are tested on stars with spectroscopically measured effective temperatures and an extinction determined by the measurement of Diffuse Interstellar Bands (DIB). These intrinsic properties of RC stars will allow to characterize the Gaia RC and calibrate, within the Gaia G band, the absolute magnitude of this standard candle, first essential step of determining distances in the Univers.

We image 104 newly identified low-mass (mostly M-dwarf) pre-main sequence (PMS) members of nearby young moving groups (YMGs) with Magellan Adaptive Optics (MagAO) and identify 27 stellar binaries with instantaneous projected separation as small as 40 mas. Fifteen were previously unknown. The total number of multiple systems in this sample including spectroscopic and visual binaries from the literature is 36, giving a raw stellar multiplicity rate of at least 35(-4)(+5)% for this population. In the separation range of roughly 1-300 au in which infrared AO imaging is most sensitive, the raw multiplicity rate is at least 24(-4)(+5)% for binaries resolved by the MagAO infrared camera (Clio). The M-star subsample of 87 stars yields a raw multiplicity of at least 30(-4)(+5)% over all separations, 21(-4)(+5)% for secondary companions resolved by Clio from 1 to 300 au (23(-4)(+5)% for all known binaries in this separation range). A combined analysis with binaries discovered by the Search for Associations Containing Young stars shows that stellar multiplicity fraction as a function of mass over the range of 0.2 to 1.2M(circle dot) appears to be linearly flat, in contrast to the field, where multiplicity increases with mass. After bias corrections are applied, the multiplicity of low-mass YMG members (0.2-0.6M(circle dot)) is in excess of the field. The overall multiplicity fraction is also consistent with being constant in age and across YMGs, which suggests that multiplicity rates for this mass range are largely set by 10 Myr without appreciable evolution thereafter.

Complexos de rutênio (II) tris(2,2\'-bipiridina) e 5,10, 15,20-tetrakis(1-metilpiridínio-4-il) porfirina de paládio (II) foram empregados como indicadores da concentração de oxigênio dissolvido em solução aquosa, baseando-se no efeito supressor do oxigênio na fluorescência desses íons complexos. Soluções aquosas desses complexos foram empregadas como indicadoras luminescentes, para verificar a eficiência de um sistema de degaseificação aplicado para remoção de oxigênio de amostras de solução. O uso do íon rutênio (II) tris(2,2\'-bipiridina) como indicador foi avaliado no monitoramento do consumo de oxigênio na reação de autoxidação de S(IV) catalisada por Mn(II) e pelo complexo de Ni(II)/tetraglicina. / The complexes of tris(2,2\'-bipyridyl)ruthenium(II) and 5,10,15,20-tetrakis(1-methilpyridyl-4) porphyrin palladium (II), were used as luminescent probes of dissolved oxygen in aqueous solutions, based on the quenching effect of oxygen in fluorescence spectrometry. Aqueous solutions of these complexes served as a luminescent probe to check the performance of one flow degassing device applied to the removal of oxygen from sample solution. The ion tris(2,2\'-bipyridyl)ruthenium(II) was used as one probe to evaluate the oxygen consumption on the autoxidation reactions of S(IV) catalyzed by Mn(II) and Ni(II)/tetraglycine complex.

The goal of this work is to examine the possibility of surface reconstruction from the images produced by the Tobii H5 eye tracker. It starts of by examining classic photometric stereo and its limitations under the illuminator configuration of the eye tracker. It then proceeds to investigate two alternative solutions: photometric stereo under the assumption that the albedo is known and a method that uses the images from the eye tracker as a guide to mold a reference model into the users face. In the second method the pose of the reference model is estimated by minimizing a photometric error under the assumption that the face is Lambertian, using particle swarm optimization. The position of the generic 3D model is then used in an attempt to mold its shape into the face of the user using shape-from-shading.

No description available.

We present new photometric data of 11 hot Jupiter transiting exoplanets (CoRoT-12b, HATP-5b, HAT-P-12b, HAT-P-33b, HAT-P-37b, WASP-2b, WASP-24b, WASP-60b, WASP-80b, WASP-103b and XO-3b) in order to update their planetary parameters and to constrain information about their atmospheres. These observations of CoRoT-12b, HAT-P-37b and WASP-60b are the first follow-up data since their discovery. Additionally, the first near-UV transits of WASP-80b and WASP-103b are presented. We compare the results of our analysis with previous work to search for transit timing variations (TTVs) and a wavelength dependence in the transit depth. TTVs may be evidence of a third body in the system, and variations in planetary radius with wavelength can help constrain the properties of the exoplanet's atmosphere. For WASP-103b and XO-3b, we find a possible variation in the transit depths which may be evidence of scattering in their atmospheres. The B-band transit depth of HAT-P-37b is found to be smaller than its near-IR transit depth and such a variation may indicate TiO/VO absorption. These variations are detected from 2-4.6s, so follow-up observations are needed to confirm these results. Additionally, a flat spectrum across optical wavelengths is found for five of the planets (HAT-P-5b, HAT-P-12b, WASP-2b, WASP-24b and WASP-80b), suggestive that clouds may be present in their atmospheres. We calculate a refined orbital period and ephemeris for all the targets, which will help with future observations. No TTVs are seen in our analysis with the exception of WASP-80b and follow-up observations are needed to confirm this possible detection.

The first transiting planetesimal orbiting a white dwarf was recently detected in K2 data of WD 1145+017 and has been followed up intensively. The multiple, long and variable transits suggest the transiting objects are dust clouds, probably produced by a disintegrating asteroid. In addition, the system contains circumstellar gas, evident by broad absorption lines, mostly in the u' band, and a dust disc, indicated by an infrared excess. Here we present the first detection of a change in colour of WD 1145+017 during transits, using simultaneous multiband fast-photometry ULTRACAM measurements over the u'g'r'i' bands. The observations reveal what appears to be 'bluing' during transits; transits are deeper in the redder bands, with a u' - r' colour difference of up to similar to-0.05 mag. We explore various possible explanations for the bluing, including limb darkening or peculiar dust properties. 'Spectral' photometry obtained by integrating over bandpasses in the spectroscopic data in and out of transit, compared to the photometric data, shows that the observed colour difference is most likely the result of reduced circumstellar absorption in the spectrum during transits. This indicates that the transiting objects and the gas share the same line of sight and that the gas covers the white dwarf only partially, as would be expected if the gas, the transiting debris and the dust emitting the infrared excess are part of the same general disc structure (although possibly at different radii). In addition, we present the results of a week-long monitoring campaign of the system using a global network of telescopes.

This dissertation presents two chemo-dynamical analyses of metal-poor stars found within the Milky Way. 115 metal-poor candidate stars, including 28 confirmed very metal-poor stars, selected from the narrow-band Pristine photometric survey are presented based on CFHT high-resolution ESPaDOnS spectroscopy. An additional 30 confirmed very metal-poor stars selected from Pristine are examined based on Gemini/GRACES spectroscopy. Chemical abundances are determined for a total of 19 elements (Li, Na, Mg, K, Ca, Sc, Ti, Cr, Mn, Fe, Ni, Cu, Zn, Y, Zr, Ba, La, Nd, Eu) across these studies, which are combined with Gaia DR2 parallaxes and proper motions to paint a chemically diverse map of ancient stars in the Galaxy. Abundance patterns similar to those seen in "normal" metal-poor Galactic halo stars are found in a majority of the stars studied here, however new discoveries of a handful of chemically unique and kinematically intriguing metal-poor stars are presented. The chemo-dynamics of these novel stellar relics point towards chemical signatures of unique and potentially unstudied stellar yields, in addition to stars with origins in accreted dwarf galaxies and the ancient progenitors of the proto-Milky Way. The success of these relatively small studies heralds the great contributions to Galactic archaeology expected from the next generation of large multi-object spectroscopic surveys. Contained within are two other projects that introduce data products related to Gemini Observatory instruments. A version of the convolutional neural network StarNet, tuned to medium-resolution R~6000 H-band spectra is presented. This model was trained on synthetic stellar spectra containing a range of data augmentation steps to more accurately reflect the observed spectra expected from medium-resolution instruments, like the Gemini-North Near-Infrared Integral Field Spectrometer (NIFS) or GIRMOS. In an era when spectroscopic surveys are capable of collecting spectra for hundreds of thousands of stars, fast and efficient analysis methods are required to maximize scientific impact, and StarNet delivers on these expectations over a range of spectral resolutions. Finally, a python package called Nifty4Gemini, and its associated Pyraf/Python based pipeline for processing NIFS observations is included. Nifty4Gemini reduces NIFS raw data and produces a flux and wavelength calibrated science cube with the full signal-to-noise, ready for science analysis. / Graduate