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

L'effet de lentille gravitationnelle, qui se traduit par une deformation des images nous parvenant de galaxies lointaines, constitue l'une des techniques les plus prometteuse pour répondre aux nombreuses questions portant sur la nature de l'énergie sombre et de la matière noire. Cet effet de lentille étant sensible à la masse totale, il permet de sonder directement la distribution de matière noire, qui resterait autrement invisible. En mesurant la forme d'un grand nombre de galaxies lointaines, il est possible d'estimer statistiquement les déformations causées par l'effet de lentille gravitationnelles puis d'en inférer la distribution de masse à l'origine de ces deformations. La reconstruction de ces cartes de masses constitue un problème inverse qui se trouve être mal posé dans un certain nombre de situations d'interêt, en particulier lors de la reconstruction de la carte de masse aux petites échelles ou en trois dimensions. Dans ces situations, il devient impossible de reconstruire une carte sans l'ajout d'information a priori.Une classe particulière de méthodes, basées sur un a priori de parcimonie, s'est révélé remarquablement efficace pour résoudre des problèmes inverses similaires pour un large champ d'applications tels que la géophysique et l'imagerie médicale. Le but principal de cette these est donc d'adapter ces techniques de régularisation parcimonieuses au problème de la cartographie de la matière noire afin de developper une nouvelle generation de méthodes. Nous développons en particulier de nouveaux algorithmes permettant la reconstruction de carte masses bi-dimensionnelles de haute resolution ainsi que de cartes de masses tri-dimensionnelles. Nous appliquons de plus les mêmes méthodes de régularisation parcimonieuse au problème de la reconstruction du spectre de puissance des fluctuations primordiales de densités à partir de mesures du fond diffus cosmologique, ce qui constitue un problème inverse particulièrement difficile a résoudre. Nous développons un nouvel algorithme pour résoudre ce problème, que nous appliquons aux données du satellite Planck.Enfin, nous investiguons de nouvelles méthodes pour l'analyse de relevés cosmologiques exprimés en coordonnées sphériques. Nous développons une nouvelle transformée en ondelettes pour champs scalaires exprimés sur la boulle 3D et nous comparons différentes méthodes pour l'analyse cosmologique de relevés de galaxies spectroscopiques. / Gravitational lensing, that is the distortion of the images of distant galaxies by intervening massive objects, has been identified as one of the most promising probes to help answer questions relative to the nature of dark matter and dark energy. As the lensing effect is caused by the total matter content, it can directly probe the distribution of the otherwise invisible dark matter. By measuring the shapes of distant galaxies and statistically estimating the deformations caused by gravitational lensing, it is possible to reconstruct the distribution of the intervening mass. This mass-mapping process can be seen as an instance of a linear inverse problem, which can be ill-posed in many situations of interest, especially when mapping the dark matter on small angular scales or in three dimensions. As a result, recovering a meaningful mass-map in these situations is not possible without prior information. In recent years, a class of methods based on a so-called sparse prior has proven remarkably successful at solving similar linear inverse problems in a wide range of fields such as medical imaging or geophysics. The primary goal of this thesis is to apply these sparse regularisation techniques to the gravitational lensing problem in order to build next-generation dark matter mass-mapping tools. We propose in particular new algorithms for the reconstruction of high-resolution 2D mass-maps and 3D mass-maps and demonstrate in both cases the effectiveness of the sparse prior. We also apply the same sparse methodologies to the reconstruction the primordial density fluctuation power spectrum from measurements of the Cosmic Microwave Background which constitutes another notoriously difficult inverse problem. We apply the resulting algorithm to reconstruct the primordial power spectrum using data from the Planck satellite. Finally, we investigate new methodologies for the analysis of cosmological surveys in spherical coordinates. We develop a new wavelet transform for the analysis of scalar fields on the 3D ball. We also conduct a comparison of methods for the 3D analysis of spectroscopic galaxy survey.

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No description available.

<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)

Gravitationslinsen bewirken Ablenkung, Verzögerung und Verzerrung von Signalen im Universum. Jedes Signal wird mindestens schwach durch Gravitationsfelder gelinset, und bei starker Linsenbildung entstehen mehrere Bilder, wenn Quelle und Linse genau ausgerichtet sind. Die Beobachtung von Linsen bei elektromagnetischen Quellen ermöglicht Einblicke in die Materieverteilung von Galaxien bis hin zu Sternen. Linsenbildung ist entscheidend für die Interpretation astronomischer Daten und hat Anwendungen in Astrophysik, Kosmologie und fundamentaler Physik. Mit Fortschritten in der Gravitationswellen-(GW)-Astronomie erlangt GW-Linsenbildung Aufmerksamkeit. Ihre niedrige Frequenz und Phasenkohärenz ergänzen elektromagnetische Beobachtungen und eröffnen neue Phänomene. Diese Arbeit erforscht GW-Linsenbildung in schwachen und starken Regimen und mögliche Anwendungen. In der starken Linsenbildung untersuchen wir kontinuierliche Wellen von rotierenden Neutronensternen (NS), die durch Sgr A*, das zentrale Schwarze Loch der Milchstraße, gelinset werden. Wir zeigen, dass sich Linsenparameter jenseits des Einstein-Radius rekonstruieren lassen. Unter günstigen Annahmen könnten NSs, die von Sgr A* gelinset werden, von künftigen Detektoren beobachtet werden und Einblicke ins galaktische Zentrum bieten. Der zweite Teil untersucht Wellenoptik-Effekte im schwachen Linsenregime, entwickelt Methoden zur Lösung des Beugungsintegrals und wendet diese auf spezifische Linsenmodelle an. Künftige Detektoren wie LISA könnten diese Effekte auch bei großen Linsen-Quellen-Abständen erkennen. Mithilfe realistischer Modelle von dunkler und baryonischer Materie schätzen wir, dass LISA Signaturen von Galaxien, supermassereichen Schwarzen Löchern und dunklen Materiehalos erkennen könnte. Diese Arbeit ebnet den Weg für künftige Entdeckungen in der GW-Linsenbildung und unterstreicht ihr Potenzial, die Astrophysik und Kosmologie zu bereichern. / Gravitational lensing causes deflection, delay, and distortion of signals in the universe. Every signal is at least weakly lensed by gravitational fields, and strong lensing creates multiple images when the source and lens are precisely aligned. Observing lensing from electromagnetic sources provides insights into the distribution of matter, from galaxies to stars. Lensing is crucial for interpreting astronomical data and has applications in astrophysics, cosmology, and fundamental physics. With advances in gravitational wave (GW) astronomy, GW lensing has gained interest. Their low frequency and phase coherence complement electromagnetic observations and reveal new phenomena. This work explores GW lensing in weak and strong regimes and potential applications. In strong lensing, we investigate continuous waves from rotating neutron stars (NS) lensed by Sgr A*, the central black hole of the Milky Way. We show that lensing parameters beyond the Einstein radius can be reconstructed. Under favorable assumptions, NSs lensed by Sgr A* could be observed by future detectors, providing insights into the galactic center. The second part examines wave-optics effects in the weak lensing regime, developing methods to solve the diffraction integral and applying them to specific lens models. Future detectors like LISA could detect these effects even at large lens-source separations. Using realistic models of dark and baryonic matter, we estimate that LISA may detect signatures of galaxies, supermassive black holes, and dark matter halos. This work paves the way for future discoveries in GW lensing and highlights its potential to advance astrophysics and cosmology.

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.