Cette thèse porte sur le rôle des amas de galaxies dans la cosmologie et l'évolution des galaxies. J'utilise des observations photométriques et spectroscopiques multi-longueur d'onde (optiques, mm, proche/moyen-IR) que j'analyse avec des méthodes statistiques. Pour un échantillon d'amas détectés par le satellite Planck et ré-observés avec le télescope optique Gemini, j'étudie la dynamique des galaxies dans les amas afin de déterminer leur masse et de comprendre les erreurs systématiques sur ces estimations, d'une importance cruciale dans la cosmologie à l'heure actuelle. Dans le cadre de la collaboration CARLA (Clusters Around Radio Loud AGN), j’étudie les populations stellaires des galaxies dans les amas et les proto-amas dans leurs premières phases d'assemblage (z>1.4), afin d'étudier la suppression de la formation des étoiles et le rôle de l'environnement sur l'évolution des galaxies. / This thesis focuses on the role of galaxy clusters in cosmology and galaxy evolution. I use multi-wavelenght photometric and spectroscopic observations (optical, mm, near/mid- IR) which I analyse with statistical methods. For a sample of clusters detected by the Planck satellite and re-observed with the Gemini optical telescope, I have studied the dynamics of member galaxies to probe their mass and understand possible systematics affecting such estimates, of crucial importance in cluster cosmology at present. Within the CARLA (Clusters Around Radio Loud AGN) collaboration, I examine morphology and stellar populations of galaxies in clusters and proto-clusters in their first assembly phases (z>1.4), with the aim of shedding light on the quenching of star formation and the role of the environment on galaxy evolution.

In this thesis we use both observations and modelling to explore the gas content of galaxies. We use the L-Galaxies semi-analytic model to simultaneously match the Hɪ and stellar mass properties of model galaxies to observations using Markov Chain Monte Carlo methods. We add the observed Hɪ mass function as an extra model constraint and successfully match the Hɪ and stellar mass functions. However, the fit to the star formation properties has been weakened compared to without the Hɪ constraint. We suggest that this problem may be partially resolved by forming stars out of only H2 gas instead of the total cold gas. The environment in which a galaxy resides can affect its evolution. We use the counts in a fixed size cylinder method to estimate 3 environment measures for the GAMA survey. We use density and edge corrections to allow us to calculate estimates for every galaxy out to z = 0.4 in our flux limited sample. We then use these estimates to examine the effect of environment on the luminosity and stellar mass functions. Using Hɪ observations of the groups and galaxies in the ALFALFA and GAMA surveys we calculate Hɪ masses using the stacking technique. The use of the stacking technique has allowed us to exploit survey data that would not otherwise be possible. We stack galaxies in halo mass bins and calculate the Hɪ to halo mass fraction as a function of halo mass. We see a steady decline in the Hɪ fraction as we move to higher mass halos. These are the highest density environments where there is less cold gas. Combining this fraction with the halo mass function we are able to calculate a lower limit value for ΩHɪ of 1.8 ± 0.39 x 10-4h-¹.

Evolution of galaxies is one of the most important topics in astronomy to understand how the universe has been evolving. In particular, galaxy groups are important because they are the observable equivalent of dark matter (DM) haloes, and thus offer a direct insight into the physics that has occurred in the DM haloes in the Universe up to the present day. Isolated galaxies are crucial for studying intrinsic and secular processes able to affect the structure, morphology, and dynamics of galaxies for obtaining clear relationships and correlations to be confronted with the model predictions. The main goal of this work is to characterize the GAMA G3Cv1 galaxy groups catalogue and the UNAM-KIAS catalogue of isolated galaxies by one of the most important statistical studies, the galaxy Luminosity Function (LF), that helps to constrain the models of formation and evolution of galaxies. LFs have been estimated for galaxies in groups and isolated galaxies. The LF for groups has been characterized by the physical properties of the groups (mass and velocity dispersion), the photometry (colour), the morphological type and eleven wavelengths from the far infra-red to the ultra violet. The LF estimated for the isolated galaxies is characterized by morphology and the colour in the five SDSS bands. The results obtained constrain more effectively the formation and evolution models of the universe than previous samples. The differences between both catalogues are presented in the conclusions. Additionally, the galaxy morphology is one of the no well understood problems in the galaxy evolution process to support the hierarchical model of formation of large objects. In this work, a classification based on the colour and concentration of light was considered. However, due to the low resolution of the images, the confidence of this classification was only ~60%.

Several hundred million years after the Big Bang, the Epoch of Reionisation(EoR) started as the photons from the first objects ionised neutral baryons in the Universe. The observations such as the Gunn-Peterson troughs in quasar absorption spectra and the linear polarisation of the cosmic microwave background (CMB) impose strong constraints on reionisation models of the EoR. Recent data provide the rest-frame ultraviolet luminosity of galaxies up to redshift 10. However, the observation of star formations in low mass galaxies is still not practicable. Their star formations are expected to be suppressed by the increase of ionised baryons and greatly affect the reionisation models. We develop a flexible pipeline which utilises the Munich Semi-Analytic Model of galaxy formation, L-Galaxies, and a semi-numerical modelling of cosmic reionisation. This combination allows us to create a self-consistent reionisation simulation in computational models of galaxy formation. We use this pipeline on a high resolution cosmological Nbody simulation to produce the redshift evolution of the star forming galaxies during the EoR. Comparisons of the properties of mock galaxies and the growth of ionised hydrogen bubbles suggest that the reionisation history heavily depends on the suppression models used in the modeling of dwarf galaxy formation. During this research, some numerical flaws of merger tree generation algorithms were identified. We investigated the origins of these problems and present suggestions for solving them.

No description available.

Using a state of the art galaxy formation software package, GCD+, we model the formation and evolution of galaxies which resemble our own Galaxy, the Milky Way. The simulations include gravity, gas dynamics, radiative gas cooling, star formation and stellar evolution, tracing the production of several elements and the subsequent pollution of the interstellar medium. The simulations are compared with observations in order to unravel the details of the Milky Way's formation. Several unresolved issues regarding the Galaxy's evolution are specifically addressed. In our first study, limits are placed on the mass contribution of white dwarfs to the dark matter halo which envelopes the Milky Way. We obtain this result by comparing the abundances of carbon and nitrogen produced by a white dwarf-progenitor-dominated halo with the abundances observed in the present day halo. Our results are inconsistent with a white dwarf component in the halo 5% (by mass), however mass fractions of ~1-2% cannot be ruled out. In combination with other studies, this result suggests that the dark matter in the Milky Way is probably non-baryonic. The second component of this thesis probes the dynamical signatures of the formation of the stellar halo. By tracing the halo stars in our simulation, we identify a group of high-eccentricity stars that can be traced to now-disrupted satellites that were accreted by the host galaxy. By comparing the phase space distribution of these stars in our simulations to observed high-eccentricity stars in the solar neighbourhood, we find devidence that such a group of stars - a 'stellar stream' - exists locally in our own Galaxy. Our next set of simulations demonstrate the importance of strong energy feedback from supernova explosions to the regulation of star formation. Strong feedback ensures that the building blocks of galaxy formation remain gas-rich at early epochs. We demonstrate that this process is necessary to reproduce the observed low mass and low metallicity of the stellar halo of the Milky Way. Our simulated galaxy is shown to have a thick disk component similar to that observed in the Milky Way through an abrupt discontinuity in the velocity dispersion-versus-age relation for solar neighbourhood stars. This final study suggests that the thick disk forms in a chaotic merging period during the Galaxy's formation. Our thick disk formation scenario is shown to be consistent with observed properties of the thick disk of the Milky Way.

This thesis explores the chemical signatures of galaxy formation and evolution using a software package designed specifically for this investigation. We describe the development of this multi-zone chemical evolution code, which simulates the spacetime evolution of stars, gas and a vast array of chemical elements within galactic systems. We use this tool to analyse observations of a wide range of astrophysical systems. The chemical evolution code is first calibrated using empirical constraints from the Milky Way. These simulations help shed light on the nature of the gas accretion processes that fueled the formation of our Galaxy. We demonstrate the importance of low- and intermediate-mass stars in explaining the elemental and isotopic abundance patterns measured in Galactic stars. An intriguing question in astrophysics is whether pollution from intermediate-mass stellar winds is responsible for anomalous abundances in globular cluster stars. We test this scenario by modelling the formation and chemical evolution of a globular cluster. Recently, the most detailed abundance pattern ever measured beyond the local universe was obtained for a high-redshift quasar absorption cloud, providing an exciting opportunity to explore early conditions of galaxy formation. We compare the chemical abundances in this distant object with predictions from a series of models, in order to gain insight into the protogalaxy's age and star formation history. We continue investigating the high-redshift universe, turning our attention to the issue of space-time variations in the fine-structure constant, as suggested by quasar absorption-line constraints. An excess abundance of heavy Mg isotopes in the absorbing clouds could partly account for the data, without needing to invoke variations in fundamental constants of nature. An enhanced early population of intermediate-mass stars could lead to such extreme Mg isotopic ratios, but we show that additional chemical consequences of this scenario conflict with observations.

Thesis (Ph. D.)--University of Chicago, Dept. of Astronomy & Astrophysics. / Includes bibliographical references. Also available on the Internet.

Ce travail consiste en létude de deux échantillons de quasars lumineux et proches. Tout dabord, nous effectuons une étude simultanée de données provenant du Hubble Space Telescope et du Very Large Telescope dans le but détudier dans le détail les caractéristiques des galaxies hôtes de 6 quasars. Un traitement adéquat des données spectrales du VLT et des images du HST, basé sur la méthode de déconvolution MCS, permet de décrire avec une grande précision la structure de la galaxie hôte ainsi que diverses propriétés du système. Ainsi, nous pouvons caractériser linfluence du quasar sur son environnement. Nos analyses prouvent en effet la présence de gaz ionisé par le quasar dans des régions éloignées du centre et apparemment dépourvues détoiles, mais aussi lexistence de zones galactiques réfléchissant le rayonnement du quasar via des électrons libres ou de la poussière. La dynamique du gaz entourant le quasar est analysée via la courbe de rotation du système. Nos méthodes permettent également de résoudre les régions centrales (< 1 kpc) des galaxies hôtes et den analyser le contenu. Suite à ce projet, une étude dun plus grand échantillon de 104 quasars de bas redshift a été menée. Les résultats obtenus pour un sous échantillon de 69 quasars (observé avec le NTT/SUSI2 et complété par des données darchives), formant lessentiel de la seconde partie du travail, peuvent se résumer comme suit : La magnitude absolue du quasar ne se corrèle pas fortement avec celle de la galaxie hôte sur lensemble de léchantillon. Cependant, la corrélation est plus robuste si lon ne considère que les galaxies elliptiques. La proportion de galaxies arborant des traces dinteractions gravitationnelles (' 60%) est assez élevée, mais cela ne permet pas de déterminer univoquement si elles influencent lactivation du quasar. Les hôtes possèdent en moyenne une plus grande quantité de gaz ionisé par rapport aux galaxies inactives. Cette tendance est encore plus forte pour les elliptiques, qui pourtant ne contiennent quune faible quantité de gaz lorsquelle sont inactives. Les galaxies hôtes les plus asymétriques, associées à des collisions galactiques majeures, contiennent également plus de gaz ionisé que les moins asymétriques. Quelques elliptiques de léchantillon possèdent un noyau actif décentré par rapport au centre de leur galaxie. Ce décentrage suggère une collision galactique importante, voire même une éjection du trou noir avec son disque daccrétion à partir de la fusion dun système binaire de trous noirs. Quelques cas particuliers, méritant dêtre observés à plus haute résolution spatiale et en spectro-3D, sont décrits pour la première fois. La thèse se compose des deux articles liés aux études résumées ci-dessus. Le premier, publié dans lAstrophysical Journal en juin 2008 (Letawe et al. [72]), traite des images HST et des spectres VLT, et le second, soumis au Monthly Notices of the Royal Astronomical Society en septembre 2009, contient lanalyse de léchantillon SUSI2. Ces articles sont complétés par des contextualisations et analyses supplémentaires non publiées. This work consists in the study of two samples of nearby luminous quasars. First of all,we compare quasar images obtained from the Hubble Space Telescope and slit spectra from the VLT/FORS1 in order to study the properties of six quasar host galaxies. An appropriate data processing, based on the MCS deconvolution method, allows to separate the central source from the host and to describe their content in detail. We are able to characterize the quasars influence on its surrounding. Indeed, our analysis proves the presence of gas ionized by the quasar in remote regions apparently devoid of stars, but also the presence of quasar emission lines reflected by free electrons or dust. The dynamics of the gas surrounding the quasar is revealed via rotation curves and information about the central regions (< 1 kpc) is accessible thanks to our powerful quasar-host separation methods. As a second part, a study of a larger sample of 104 nearby quasars is made. Results for a subsample of 69 quasars (observed with NTT/SUSI2 and completed with archive data) form the second part of this work. They can be summarized as follows : The quasars absolute magnitude does not correlate strongly with the host magnitude. However, this correlation becomes more robust if we consider only elliptical hosts. The proportion of galaxies showing signs of gravitational interactions is quite large (' 60%), but this does not allow to assess unequivocally their influence in the triggering of the quasar activity. There is a tendency for quasar hosts to contain more ionized gas than in inactive galaxies. This trend is even stronger for ellipticals, which, when inactive, do not usually contain much gas. The most asymmetric hosts, linked to strong merging processes, also tend to have more ionized gas than less asymmetric ones. A few ellipticals have their active nucleus shifted compared to the galactic center. Such ff-nuclear activity is suggestive of important galactic collisions, and may be due to a gravitational black hole recoil in the fusion of binary black holes system. A few peculiar cases, deserving higher resolution imaging or 3D-spectroscopy, are described here for the first time. The thesis is composed of two articles linked to the two studies summarized above. The first one, published in the Astrophysical Journal in June 2008 (Letawe et al. [72]), deals with HST and VLT data. The second one, submitted to the Monthly Notices of the Royal Astronomical Society in September 2009, contains the analysis of the SUSI2 sample. These articles are completed by introductions and unplublished supplementary analyses and results.

No description available.