The efficiency of different spectroscopic techniques are examined through four different approaches: detailed analysis of IR spectra from the APOGEE database and examination of persistence, observing extremely metal-poor stars using the Plaskett telescope at the DAO, three analyses of various applications of machine learning in astronomy, and efficient transmission of light through optical fibres. Through the first study, the technical effects of persistence in the APOGEE's IR spectra are examined, and a new technique for removing the persistence is introduced. Most of the globular cluster Pal 1's spectra in the APOGEE database are affected by persistence. Therefore, the Pal 1 spectra are corrected for the persistence and their stellar abundances are determined independently from the APOGEE's pipeline, ASPCAP. Our results for the known members of Pal 1 were in a close agreement with the results from Sakari et al. (2011). Comparison between the results from the corrected and the original spectra suggest that the persistence could have a critical effect on the results. The second study of this thesis focused on observations of extremely metal-poor (EMP) stars from the Pristine survey. Through the DAO-Pristine project, we narrowed down the initial list of the Pristine survey by observing over 50 targets during 25 observing nights. The Ca II triplet absorption lines of the observed targets were examined and used for estimating the metallicity of the objects. Twelve candidate EMP stars with weak Ca II triplet lines are chosen from the observed targets. These candidate EMP stars will be observed with larger telescopes for more accurate determination of their metallicity. This thesis also presents the result of a threefold analysis for using machine learning techniques in astronomy. The supervised machine learning methods are used for determination of the stellar parameters of stars using their raw spectra, and unsupervised machine learning methods are used for classification of supernovae Type Ia from their calibrated spectra. The supervised analysis of the IR and optical spectra suggested that the StarNet neural network (Fabbro et al. 2017) can predict the stellar parameters of the APOGEE database and synthetic spectra, efficiently and accurately. The effect of persistence in the StarNet's results are examined, and we showed that the persistence does not have a critical effect on the overall performance of the StarNet. In addition, multiple unsupervised machine learning techniques such as K-mean and Self Organizing Maps (SOMs) are used for classification of the supernovae Type Ia spectra. The preliminary results suggest that a minimum of three subclasses of supernovae Type Ia can be found from our data, which are consistent with the previous studies. Finally, this thesis presents our final results for an optical system we designed for the MSE project. At UVic, we have used the standard collimated beam method, or "ring test," to measure the Focal Ratio Degradation (FRD) of MSE-like fibres. The FRD of the system is determined from the ratio of the Full Width Half Maximum (FWHM) to the radius of the ring. Early ring test results from a sample of MSE-like fibres show an FRD of 3.7%, which meets the MSE science requirement (i.e. FRD < 5% at f/2). Also, we have automated the ring test for fast, repeatable, and efficient measurements of an individual fibre in multi-fibre bundles. Our future tests will include automated non-static fibres in preparation for the MSE build phases. / Graduate

O presente trabalho propõe uma abordagem abrangente para descrever a evolução da região central da Via Láctea, compreendendo-se aí o bojo, a barra e as interfaces dos mesmos com o limite interno do disco e com a região central do halo. Pretende-se investigar as propriedades químicas e cinemáticas destas estruturas, que são interconectadas, com o objetivo de separá-las e aplicar os resultados daí obtidos a um modelo de formação e evolução do bojo e da região interna do disco que descreva simultaneamente distintos aspectos da evolução da região central da Galáxia. Na primeira parte do trabalho, uma amostra de nebulosas planetárias (NPs) localizadas no disco interno e no bojo da Galáxia é utilizada para encontrar a distância galactocêntrica que melhor separa estas duas populações, do ponto de vista das abundâncias. Foram utilizadas escalas de distâncias estatísticas para o estudo da distribuição das abundâncias na interface bojo-disco. A aplicação do teste Kolmogorov-Smirnov mostrou que, em média, a população interna não segue o gradiente radial de abundâncias do disco na direção do centro galáctico. Baseado neste estudo, propõe-se uma distância galactocêntrica de 1.5 kpc para definir a interface bojo-disco. Na segunda parte do trabalho, foram realizadas observações espectrofotométricas de 21 NPs localizadas na direção do centro da Galáxia com o telescópio SOAR. Estes objetos estão localizados bem próximos ao plano galáctico na direção central da Via Láctea, onde não existem dados de NPs na literatura. Os resultados mostram que as NPs localizadas nesta região apresentam baixas abundâncias de oxigênio comparadas com as NPs do disco interno e de outras regiões do bojo. Os resultados indicam que o bojo apresenta uma complexa composição de populações estelares. Por um lado, a presença de nebulosas com baixas abundâncias mostra que o bojo pode ter se formado a partir de um disco galáctico antigo através de uma evolução secular. Por outro lado, existem alguns objetos do bojo para os quais as abundâncias coincidem com o limite do gradiente radial do disco nesta região. Esta é uma evidência para um bojo composto por duas ou mais populações: uma originada do disco fino, e outra originada do disco espesso. Na última parte do trabalho propõe-se a inclusão de fluxos radiais de gás em um modelo de evolução química para simular os efeitos de uma barra localizada no centro da Galáxia nas distribuições de abundâncias, densidade de gás e taxa de formação estelar (SFR). Os resultados das simulações indicam que os modelos com fluxos de gás apresentam uma SFR mais alta no bojo e que os perfis da SFR e da densidade de gás na região central são melhor reproduzidos após a inclusão dos fluxos radiais no modelo. As simulações indicam ainda que o gradiente de abundâncias do disco é mais plano para o caso da inclusão da barra. Estes resultados indicam que a barra e os fluxos de gás exercem um importante papel na formação de estrelas no centro das galáxias espirais barradas. / This project proposes a comprehensive approach to describe the evolution of the central region of the Galaxy, comprising the bulge, the bar and their interfaces with the inner disk and the central region of the halo. We intend to investigate the chemical and kinematic properties of these structures, which are interconnected, aiming to separate them and apply these results to a model for the formation and evolution of the bulge and inner disk, capable to describe simultaneously distinct aspects of the evolution of the central region of the Galaxy. First, a sample of planetary nebulae (PNe) located in the inner-disk and bulge of the Galaxy is used in order to find the galactocentric distance that better separates these two populations, from the point of view of abundances. Statistical distance scales were used to study the distribution of abundances across the disk-bulge interface. A Kolmogorov-Smirnov test was used to find the distance in which the chemical properties of these regions better separates. The results of the statistical analysis indicate that, on the average, the inner population has lower abundances than the outer. Additionally, for the $\\alpha$-elements abundances, the inner population does not follow the disk radial gradient towards the galactic centre. Based on our results, we suggest a bulge-disk interface at 1.5 kpc, marking the transition between the bulge and inner-disk of the Galaxy, as defined by the intermediate mass population. Second, we present spectrophotometric observations for a sample of 21 PNe located towards the galactic centre of the Galaxy. The abundances are derived based on observations in the optical domain made at the SOAR telescope. Their location is interesting since there are no observations of PNe in this region. The data show lower oxygen abundances compared to those from PNe located in the inner disk and other bulge regions. The results show that the bulge has a complex composition of stellar populations. The presence of PNe with low abundances indicates that the bulge might be formed from an old galactic disk through secular evolution. On the other hand, other objects from our sample have abundances compared to those from inner disk PNe. This is evidence that two or more populations might compose the bulge: one originated from the thin disk, and the other from the thick disk. Last, we propose a chemical evolution model that includes radial gas flows. This is done in order to mimic the effects of the galactic bar on the chemical abundances distributions and the gas density profiles and the star formation rate (SFR). The results of the models with radial flows point to a high SFR in the bulge and, additionally, the SFR and gas density profiles in the inner Galaxy are better reproduced after the inclusion of radial gas flows in the model. After including a specific velocity pattern for the bar, the results show a flattening of the radial abundance gradient. Our results indicate that radial gas flows may play an important role in the star formation near the centre of barred spiral galaxies.

L'étude de la composition chimique et de la cinématique des étoiles de la Voie Lactée est essentielle afin de comprendre comment les grandes structures de notre Galaxie se sont formées. Les étoiles de faible masse gardent en mémoire dans leur atmosphère la composition chimique du milieu interstellaire dans lequel elles sont nées, et leur cinématique est essentielle afin de caractériser les différentes populations stellaires. Dans cette thèse, nous étudions le disque galactique, composante majeure de notre Galaxie. Dans le cadre de la mission spatiale Gaia, nous avons développé une procédure automatique de mesure d'abondances chimiques, GAUGUIN, utilisée dans le cadre du Gaia-ESO Survey GES (abondances chimiques d'éléments alpha et du pic du fer pour 10000 étoiles) et du projet AMBRE (abondances de lithium pour 7300 étoiles). GAUGUIN va être intégré au pipeline d'analyse des spectres RVS de Gaia. Nous avons étudié l'évolution des dispersions des vitesses dans le disque galactique en fonction du [Mg/Fe], utilisé comme proxy de l'âge. A partir de 6800 étoiles de GES, nous avons détecté la présence d'étoiles du disque épais cinématiquement froides mais avec des valeurs élevées du rapport [Mg/Fe], donc possiblement âgées. Dans le contexte d'un milieu turbulent, nous discutons la présence de ces étoiles dans le cadre des différents modèles de formation du disque galactique. Nous avons également montré que l'abondance du lithium dans le disque montre une croissance avec la métallicité sur le domaine -1<[M/H]<+0 dex et décroît pour les métallicités super-solaires. Enfin, le disque mince et le disque épais seraient caractérisés par des évolutions chimiques différentes en abondance de lithium. / Studying both the chemical composition and kinematics of Milky Way stars is essential to understand how big structures of our Galaxy are formed. Indeed, low-mass stars retain in their photosphere the chemical composition of the interstellar medium is which they were born. Additionally, the kinematics are essential to characterize stellar populations. In this thesis, we focus on the galactic disc, a major component of the Milky Way. In the context of the Gaia mission, we have developed an automatic procedure GAUGUIN, devoted to deriving chemical abundances. We first applied our method to the Gaia-ESO Survey (GES) data to derive alpha and iron-peak chemical abundances for 10000 stars. We then derived lithium abundances for 7300 stars from the AMBRE project. GAUGUIN is well adapted to massive spectroscopic surveys, both in terms of computation time and accuracy. GAUGUIN will be soon integrated into the RVS DPAC analysis pipeline of the Gaia mission. We studied the velocity dispersions in the galactic disc as a function of the [Mg/Fe] ratio, used as an age proxy. Thanks to 6800 GES stars, we detected thick disc stars with cool kinematics and high [Mg/Fe] ratio, so presumably old. In the generally turbulent context of the primitive galactic disc, this thesis places these results in the framework of the different disc formation and evolution scenarios. We also showed that the lithium abundance in the galactic disc increases as a function of the metallicity in the domain -1<[M/H]+0 dex and decreases at super-solar metallicities. Finally, the thin and the thick discs could be characterized by different lithium abundance evolutions.

Le bulbe Galactique, est cruciale pour comprendre les processus physiques responsables de la formationde la galaxie. L'étude spectroscopique des étoiles vieilles de faible masse permettre de caractériser endétail la chimie et la cinématique du bulbe. Dans cette thèse, nous avons utilisé des données provenantdu Gaia-ESO survey pour mener une étude détaillée du système du disque ainsi que du bulbeGalactique. La distribution de métallicité du bulbe est bimodale. La population riche en métaux montreune cinématique typique de la barre. Elle présente une caractéristique de double RC et recouvre laséquence du disque mince à haute métallicité dans le plan [Mg/Fe] vs. [Fe/H]. Nous associons cesétoiles avec celles de la barre formée à la suite de l'évolution séculaire du disque mince primordial.D'autre part, la population pauvre en métaux présente une cinématique chaude et ne participe pas à laforme en X du bulbe. Ces étoiles semblent imiter la distribution de celles du disque épais dans le plan[Mg/Fe] vs. [Fe/H]. Quand nous comparons la position en métallicité du genou de cette distribution,qui se trouve à [Fe/H]=-0.37+/-0.09 dex, elle est plus élevée de 0.6 dex par rapport au disque épais. Unmodèle d'évolution chimique permet de bien ajuster cette distribution pour les étoiles du bulbe ensupposant un épisode de formation stellaire rapide (<1 Gyr) et intense. L'origine du bulbe pauvre enmétaux reste encore relativement incomprise, mais divers projets futurs devraient permettre de faire ladistinction entre les processus violents ou ceux liés à une évolution séculaire qui ont pu contribuer à saformation / The Galactic bulge, as a massive and old Galactic component, is key to understand the physicalprocesses responsibles for the formation of the Galaxy. The spectroscopic study of long lived low massstars represents an opportunity to characterize the detailed chemical and kinematical patterns of theeventual mix of stellar populations building up the bulge. In this thesis we made use of data comingfrom the Gaia-ESO survey to conduct a detailed analysis of the disk system as well as bulge stellarpopulations. The bulge metallicity distribution function is bimodal. The metal-rich population exhibitsbar-like kinematics, displays the double RC feature and overlaps the metal-rich end of the thin disksequence in the [Mg/Fe] vs. [Fe/H] plane. We associate these stars with the bar X-shape bulge formedas the product of secular evolution of the early thin disk. On the other hand, the metal-poor populationpresents isotropic hot kinematics and does not participate in the X-shaped bulge. When compared to thethick disk, bulge stars seem to mimic their distribution in the [Mg/Fe] vs. [Fe/H] plane. Whencomparing the metallicity position of the so called ``knee'', that of the bulge is found to be at [Fe/H]=-0.37+/-0.09 dex, being 0.6 dex higher than that of the thick disk. A chemical evolution model suitablyfits the whole bulge sequence by assuming a fast (<1 Gyr) intense burst of star formation taking place atearly epochs. The origin of the metal-poor bulge still remains unconstrained, but further research shouldallow to distinguish between violent processes or secular evolution for its origin