A hierarquia de equações de Boltzmann que descreve a temperatura e polarização da radiação cósmica de fundo ´e tratada no espaço das posições. Mostramos neste formalismo que temperatura e polarização podem ser descritas como medias dos termos de fonte ponderados por probabilidades associadas a um problema de voos aleatórios. Decorre da estrutura geral da hierarquia que se pode fazer uma expansão da temperatura e polarização em termos do numero de espalhamentos ocorridos durante a recombinação. Incorporamos o efeito de lentes gravitacionais sobre a radiação cósmica de fundo tirando proveito da estrutura das equações no espaço das posições. Mostraremos que o efeito ´e incorporado através de correções aos coeficientes da decomposição angular dos campos de temperatura e polarização. Para descrever o efeito de lentes gravitacionais fazemos uma revisão sobre resultados formais da teoria e apresentamos uma derivação de equações centrais em espaços-tempo arbitrários. / The Boltzmann hierarchy describing the temperature and polarization of the cosmic microwave background is presented in a position space formalism. We show that temperature and polarization can be described in terms of averages over source terms weighted by probabilities densities that appear in problems of random flights. The temperature and polarization signals can be expanded in terms of the number of scatterings photons suffered during the recombination. The gravitational lensing effects are incorporated over the free-propagation phase of the CMB photons. This effect can be included in the position space formalism as a correction to the expansion coefficients of the temperature and polarization fields. The bases of the theory of gravitational lensing are also presented and a rederivation of the central equations of the theory in arbitrary spacetimes is here developed.

Orientador: Prof. Dr. Roldão da Rocha Jr. / Tese (doutorado) - Universidade Federal do ABC, Programa de Pós-Graduação em Física, 2017. / Neste trabalho foram investigadas algumas conseguências da física de buracos negros em teorias cujo domínio está além do domínio da relatividade geral, em especial em teorias efetivos com dimensões extras. A investigação foi em substancialmente conduzida baseando-se em três efeitos gravitacionais, a saber, a radiação Hawking, o regime de deflexão forte de lentes gravitacionais e a formação de buracos negros quânticos. Uma solução de modelo cosmológico imerso em uma brana espessa foi também investigada. Modelos e teorias efetivas fornecem meios para testar os limites de validade de teorias conhecidas e indicam o que deveríamos esperar além desses limites. Baseado nessa ideia foram usados alguns modelos efetivos para estudar efeitos não previstos pela relatividade geral, associados a cada um dos fenômenos mencionados. / This work is devoted to investigate some consequences of black holes physics beyond the domain of general relativity, mainly in effective extra dimensional models. The investigation is carried along three gravitational effects, namely the Hawking radiation, the strong deflection of gravitational lensing and the formation of quantum black holes. A cosmological thick brane solution is also investigated. Effective theories and models provide a prominent approach for testing the limits of known theories and show what would be expected beyond that. Based on such idea we have used effective models for finding deviations of general relativity associated to each of the mentioned phenomena.

Les amas de galaxies sont des structures massives composées à plus de 80% de matière noire. Leur coeur peut atteindre une densité de masse critique qui en déformant l'espace-temps fait converger les rayons lumineux vers l'observateur. Grâce à des relevés photométriques profonds de l'amas Abell 2744, de nombreux systèmes multiples ont été découverts. Identifier ces systèmes reste un défi, j'ai donc développé une méthode robuste basée sur les propriétés photométriques conservées par l'effet de lentille gravitationnelle qui permet de les détecter automatiquement. Le meilleur moyen de prouver que des images proviennent de la même galaxie reste la mesure de leur distance(redshifts) grâce à leur spectre. En analysant les données collectées par le spectrographe à intégrale de champ MUSE j'ai mesuré un grand nombre de sources (514) dont 83 d'entre elles sont des images multiples. Bénéficiant de cette large couverture spectrale, j'ai créé un modèle paramétrique de masse parmi les plus contraints à ce jour. La sensibilité atteinte par le modèle permet de sonder l'influence de structures périphériques (jusqu'à une distance de 700kpc), révélant ainsi des erreurs systématiques sur la mesure de la masse due à la paramétrisation du modèle (6%). Comparé aux précédentes études, on voit une diminution de 10% de la masse dans un rayon 100 kpc montrant ainsi en partie le gain offert par la spectroscopie. Ce gain, bien que négligeable sur la mesure de l'amplification, s'est avéré pouvoir contraindre la balance en masse entre les différentes composantes de notre modèle, dépassant par endroits 2 fois l'incertitude statistique / Clusters of galaxies are large and massive structures containing more than 80% of dark matter. In the cluster core, the mass density can reach a critical threshold making the curvature of space-time large enough to bend light path and then allow multiple convergence of images from the same sources to appear on the observer field of view. Thanks to deep photometric coverage of Abell 2744, a lot of multiply-imaged systems were discovered. Nevertheless, finding them remain a challenge and based on the preserved photometric properties by lensing, I developed a robust method to automatically find them. However, measuring the redshifts for each multiple images remains the best way to surely associate them. The deep coverage of the integral field spectrograph MUSE allowed me to identify a large number of sources ( 514 ) among them 83 were multiple images. Thanks to this large spectroscopic coverage, I built one of the most constrained parametric mass model for lensing cluster to date. The sensitivity raised by this model allow me to probe the influence of outskirts substructures ( at 700 kpc distance ), revealing systematic sources of uncertainties related to the mass model parametrisation ( 6% ). Compared to previous studies, I notice a 10% lower mass in the center ( within 100kpc ) showing one of the benefit of large spectroscopic constraints. This benefit, is smaller on the amplification estimation but shows a significant discrepancy between different mass counterparts in the models, up to 2 times the statistical uncertainties

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<p>Galaxies live in extended, non-luminous haloes of dark matter. How dark matter haloes are affected by environment has been examined using cosmological simulations, and resulting predictions tested for isolated and cluster galaxies. However, predictions have have yet to be tested in the intermediate density environment of galaxy groups. We present a weak galaxy-galaxy lensing analysis of galaxies in groups, with the aim of examining how the group environment affects the dark matter haloes of member galaxies. In particular, we address three questions: 1) whether the dark matter haloes of galaxies in groups are truncated relative to galaxies in the field, 2) how dark matter is distributed within the group environment and 3) whether the halo-to-stellar mass ratio is different between field and group galaxies. We use a basic stacking method and a maximum likelihood technique to parameterize the dark matter haloes of group and field galaxies. Our samples of intermediate redshift group and field galaxies were identified by the Group Environment and Evolution Collaboration in the CNOC2 Redshift Survey. For these data, we measure the average radial extent of a group galaxy dark matter halo to be $s_* = 54^{+114}_{-39}$ kpc, which hints at the possible truncation of galaxy haloes in the group environment. We develop a method of examining the distribution of dark matter within the galaxy group itself, but obtain inconclusive results. Our preliminary analysis of star formation efficiency (halo-to-stellar mass ratio) indicates group galaxies may be less efficient at forming stars compared to galaxies in the field. Larger data samples are required in order to conduct a more rigorous analysis.</p> / Master of Science (MSc)

The last twenty-five years have seen our understanding of the formation and abundance of planets revolutionised, thanks to the first detections of debris discs, and, a decade later, of the first extrasolar planets. Hardly a week now goes by without a planet discovery, and the range of methods used to search for planets has expanded to include techniques that are efficient at detecting different types of planets. By combining the discoveries of the various methods, we therefore have the opportunity to build a picture of planet populations across the Galaxy. In this thesis, I am presenting work done as a basis towards such an effort: first I present work carried out to improve modelling methods for gravitational microlensing events. Since the first microlensing observing campaigns, the amount of data of anomalous events has been increasing ever faster, meaning that the time required to model all observed anomalous events is putting a strain on available human and computational resources. I present work to develop a method to fit anomalous microlensing events automatically and show that it is possible to conduct a thorough and unbiased search of the parameter space, illustrating this by analysing an event from the 2007 observing season. I then discuss the possible models found with this method for this event, and their implication (Kains et al. 2009), and find that this algorithm locates good-fit models in regions of parameters that would have been very unlikely to be found using standard modelling methods. Results indicate that it is necessary to use a full Bayesian approach, in order to include prior information on the parameters. I discuss the analytical priors calculated by Cassan et al. (2009) and suggest a possible form of an automatic fitting algorithm by incorporating these priors in the algorithm used by Kains et al. (2009). Another topic with which this thesis is concerned is the evolution of debris discs around solar-type stars. Late-type stars are expected to be the most numerous host stars of planets detected with the microlensing technique. Understanding how their debris discs evolve equates to understanding the earliest stages of planet formation around these stars, allowing us to truly put our Solar System in perspective. Using the analytical model of Wyatt et al. (2007a), I modelled the evolution of infrared excess flux at 24 and 70 microns using published data of debris discs around solar-type (spectral types F, G and K) stars from the Spitzer Space Telescope. By comparing the results of this study to an analogous study carried out by for A stars by Wyatt et al. (2007b), I find that although best-fit parameters are significantly different for solar-type stars, this may be due to the varying number of inefficient emitters around stars of different spectral types. I suggest that although effective properties are different by an order of magnitude or more, intrinsic properties, while still different, are so by a much smaller factor. These differences may be due to the longer timescales over which solar-type stars evolve, which allow for the formation of larger and stronger planetesimals.

Briser la frontière observationnelle de l’Univers lointain suscite de nombreux axes de recherches dans la cosmologie moderne. Exigeantes par la sensibilité demandée, ces observations constituent aussi bien un défi technologique pour les prochaines générations d’instruments qu’une étape nécessaire à la compréhension des différentes étapes d’évolution de l’Univers. Une des étapes importantes est la réionisation du milieu intergalactique, époque charnière marquant la fin des “Âges Sombres”. Déterminer quand et comment ce processus s’est déroulé et quelles ont été les sources l’ayant déclenché et entretenu sont les principales questions motivant ces recherches. Les travaux présentés dans cette thèse participent à l’effort de la communauté scientifique internationale dans la caractérisation de l’histoire de l’époque de la réionisation en recherchant des galaxies à grand décalage spectral vers le rouge (redshift). Après un panorama complet des contraintes observationnelles actuelles sur l’époque de la réionisation, sont ensuite présentés les deux projets ayant fournis les données constituant la matière première de cette analyse. En utilisant une même technique d’imagerie en bande étroite dans le domaine de longueurs d’onde proche-infrarouge, des observations avec l’instrument WIRCAM (CFHT) et d’autres avec l’instrument HAWK-I (VLT) ont permis d’établir des contraintes robustes sur la fonction deluminosité des Emetteurs Lyman-α au redshift z = 7.7. A l’occasion de la présentation du second projet, la problématique de la stratégie observationnelle est abordée, notamment via l’utilisation des amas de galaxies comme lentilles gravitationnelles amplifiant le flux des sources d’arrière-plan. L’absence de confirmation spectroscopique des Emetteurs Lyman-– sélectionnés durant l’analyse des données WIRCAM et l’absence de candidats dans le sondage HAWK-I suggèrent une évolution de la fonction de luminosité des Emetteurs Lyman-– entre les redshifts z = 6.5, telle quedéterminée dans d’autres études, et z = 7.7. La tendance de cette évolution, en luminosité ou en densité de galaxies, ne peut pas encore être déterminée compte tenu de la variabilité des résultats obtenus à plus bas redshift. Si cette évolutions’effectuait en luminosité, ce pourrait être le signe d’une augmentation de l’opacité du milieu intergalactique au rayonnement Lyman-α causée par une plus importante fraction d’hydrogène neutre, ce qui est une signature attendue de la réionisation. / Breaking through the observational frontier of the distant universe motivates numerous scientific cases in modern cosmology. Demanding by the required sensitivity, high-redshift observations provide both a technological challenge for next generation instruments and a necessary step toward the understanding of cosmic evolution. One critical epoch is the reionization of the intergalactic medium bringing to light the end of the so-called “Dark Ages”. Determine when and how this process took place and what were the sources that started and maintained the reionization are the mainquestions motivating this research. The work presented in this thesis contributes to the effort of the internationalscientific community in characterizing the reionization epoch history by searching for galaxies at high redshift. First, I describe the current observational constraints in a comprehensive chapter. Then the two datasets used in that work are presented. From narrow-band observations in the near-infrared with WIRCAM at the CFHT and HAWK-I at the VLT, I put strong constraints on the luminosity function of Lyman-α Emitters at z = 7.7. The best strategy for this type of survey is discussed, in particular with the use of massive galaxy clusters acting as gravitational lenses that amplify the flux from background sources. The lack of spectroscopic confirmation of candidates found with WIRCAM and the lack of candidates found with HAWK-I suggest an evolution of the luminosity function from z = 6.5. This evolution could be either in luminosity or in number density but somewhat discrepant results at lower redshift prevent any definitive answer to this question. If the evolution was mostly in luminosity, it could be interpreted as an increase in the opacity of the intergalactic medium caused by an increased fraction of neutral hydrogen, which is an expected signature of reionization.

Esta tese tem como objetivo o estudo de aspectos dinâmicos e estatísticos da matéria escura em distribuições esféricas de massa. O fato de suas partículas constituintes interagirem gravitacionalmente mas não eletromagneticamente, e portanto sua evolução ser regida por interações de longo alcance, traz algumas complicações teóricas na descrição de suas propriedades nos termos da mecânica estatística, dificuldades compartilhadas com sistemas auto-gravitantes em geral. Para melhor compreender essas propriedades, estudamos as distribuições de matéria escura em três abordagens diferentes. Na primeira, utilizamos dados observacionais, utilizando lentes gravitacionais, em aglomerados de galáxias para comparar a performance de alguns modelos propostos para o perfil de densidade da matéria escura. Dividimos estes modelos em fenomenológicos ou teóricos. Dos primeiros, todos são capazes de descrever os dados observacionais com performance comparável. Entre os modelos teóricos estudados, o modelo chamado DARKexp descreve os dados tão bem quanto os primeiros. Numa segunda abordagem, utilizamos dados de simulações numéricas para testar uma função proposta para a distribuição de velocidades das partículas. Esta função inclui a anisotropia no campo de velocidades na chamada distribuição q-gaussiana. Comparamos a performance desta função com a da função gaussiana e concluímos que a primeira representa uma melhor descrição dos dados, mesmo levando em conta a introdução de um parâmetro extra, apesar de ainda apresentar algumas discrepâncias, especialmente nas regiões internas dos halos. Por fim, discutimos a possível relevância do conceito de indistinguibilidade na determinação dos estados de equilíbrio de sistemas auto-gravitantes em geral, propondo uma associação deste conceito com o nível de mistura do sistema. Implementamos esta associação numa análise combinatória e estudamos as conseqüências para a determinação da função distribuição e do perfil de densidades. Esta associação também levanta algumas dúvidas sobre a validade da equação de Vlasov durante o processo de relaxação violenta. / This thesis aims to study the dynamic and statistical aspects of dark matter in spherical distributions. The fact that their constituent particles interact gravitationally but not electromagnetically, and therefore its evolution is governed by long-range interactions, brings some theoretical complications in their description in terms of the statistical mechanics, difficulties shared with self-gravitating systems in general. To better understand these properties, we studied the distributions of dark matter in three different approaches. First, we used observational data, using gravitational lensing in galaxy clusters to compare the performance of some proposed models for the dark matter density profile. We divide these models in phenomenological or theoretical. All of the formers are able to describe the observational data with comparable performance. Among the theoretical models studied, the model called DARKexp describes the data as well as the formers. In a second approach, we use numerical simulation data to test a proposed function for the velocity distribution. This function includes the velocity anisotropy into the so called q-Gaussian distribution. We compared the performance of this function with the Gaussian function and concluded that the first is a better description of the data, even taking into account the introduction of an extra parameter, although still presenting some discrepancies, especially in the inner regions of the halo. Finally, we discuss the relevance of the concept of indistinguishability in determining the states of equilibrium of self-gravitating systems in general, suggesting an association of this concept with the mixing level of the system. We implement this association in a combinatorial analysis and study the consequences for the determination of the distribution function and the density profile. This association also raises some questions about the validity of the Vlasov equation during the process of violent relaxation.

<p>Most of the matter in the Universe appears to be in some form which does not emit or absorb light. While evidence for the existence of this dark matter has accumulated over the last seventy years, its nature remains elusive. In this thesis, quasars and low surface brightness galaxies (LSBGs) are used to investigate the properties of the dark matter. </p><p>Quasars are extremely bright light sources which can be seen over vast distances. These cosmic beacons may be used to constrain dark matter in the form of low-mass, compact objects along the line of sight, as such objects are expected to induce brightness fluctuations in quasars through gravitational microlensing effects. Using a numerical microlensing model, we demonstrate that the uncertainty in the typical size of the optical continuum-emitting region in quasars represents the main obstacle in this procedure. We also show that, contrary to claims in the literature, microlensing fails to explain the observed long-term optical variability of quasars. Here, quasar distances are inferred from their redshifts, which are assumed to stem from the expansion of the Universe. Some astronomers do however defend the view that quasar redshifts could have a different origin. A number of potential methods for falsifying claims of such non-cosmological redshifts are proposed. </p><p>As the ratio of dark to luminous matter is known to be unusually high in LSBGs, these objects have become the prime targets for probing dark matter halos around galaxies. Here, we use spectral evolutionary models to constrain the properties of the stellar populations in a class of unusually blue LSBGs. Using rotation curve data obtained at the ESO Very Large Telescope, we also investigate the density profiles of their dark halos. We find our measurements to be inconsistent with the predictions of the currently favoured cold dark matter scenario.</p>