Apresentamos fotometria profunda (V ~ 25,5) nas bandas V e I obtidas com a Wide Field and Planetary Camera 2 a bordo do telesc opio espacial Hubble para 7 campos distantes ~5º do centro da Grande Nuvem de Magalhães. Ajustamos isócronas aos diagramas cor-magnitude a fim de identficar diferentes populaões estelares nestes campos. Uma população velha (τ > 10¹º anos) foi encontrada em todos os campos. Alguns eventos de elevada formação estelar, com idades entre 2 x 109 e 4 x 109 anos, foram também encontrados em alguns campos localizados na região N/NO. Funções de luminosidade de estrelas de baixa massa (m ≤ 1; 1msol) foram obtidas para todos os campos. Aparentemente não há diferenças na mistura de populações entre os campos como sugerido através do teste Kolmogorov-Smirnov aplicados as funções de luminosidade. Finalmente, derivamos perfis de densidade para estrelas velhas e de idade intermediária. O primeiro apresenta uma inclinação levemente maior quando comparado com o último.

Made available in DSpace on 2015-03-03T15:16:26Z (GMT). No. of bitstreams: 1 PedroCF_TESE.pdf: 3741158 bytes, checksum: 14276162d36c87d8680aa0cc51164df9 (MD5) Previous issue date: 2014-02-13 / Conselho Nacional de Desenvolvimento Cient?fico e Tecnol?gico / A possible approach to the cosmological coincidence problem is to allow dark matter and dark energy to interact with each other also nongravitationally. Two general classes of interaction were considered in this thesis, characterized by a constant interaction parameter ( or ?). Their ability to address the coincidence problem was appraised and was shown that some models are capable to alleviate the problem. It is estimated the average accuracy required to distinguish interacting cosmological models from the conventional CDM scenario using the cosmic expansion rate H(z) data. The analysis is performed at two levels: through Monte Carlo simulations based on an interaction model, in which H(z) samples with different accuracies are generated, and through a semianalytic method that calculates the error propagation of the parameters or ? as a function of the error in H(z). It is shown that the semianalytical approach agrees with simulations and that to detect an interaction using H(z) data only, these must reach an accuracy better than 1% if the parameter is of the order of recent determinations (10?2). This means that, among the planned surveys, the Wide Field Infrared Survey Telescope has the best chance to detect an interaction, though at a low significance level. To determine more precisely the existence of an interaction it would be needed to combine the expansion data with other type of observation / Uma abordagem poss?vel para o problema da coincid?ncia cosmol?gica ? permitir que a mat?ria escura e a energia escura interajam uma com a outra tamb?m de forma n?o gravitacional. Nesta tese s?o consideradas duas classes gerais para tal intera??o, caracterizadas por um par?metro de intera??o constante ( ou ?). Sua capacidade de solucionar o problema da coincid?ncia ? avaliada e ? mostrado que alguns modelos s?o capazes de aliviar o problema. Em seguida, ? determinada a precis?o m?dia necess?ria para distinguir modelos cosmol?gicos com intera??o do Modelo Padr?o CDM usando dados da taxa de expans?o c?smica H(z). Esta an?lise ? realizada em dois n?veis: por meio de simula??es de Monte Carlo baseadas em modelos com intera??o, em que amostras de H(z) com diferentes precis?es s?o geradas, e atrav?s de um m?todo semianal?tico que calcula a propaga??o de erros dos par?metros ou ? em fun??o do erro em H(z). Mostra-se que a abordagem semianal?tica concorda com as simula??es e que para detectar uma intera??o usando somente dados de H(z) estes devem atingir uma precis?o melhor do que 1% se o par?metro for da ordem daquele indicado pelas determina??es mais recentes ( 10?2). Isso significa que, dentre os projetos observacionais planejados, o Wide Field Infrared Survey Telescope tem a melhor chance de detectar uma intera??o, embora em um n?vel de signific?ncia baixo. Para determinar de forma mais segura a exist?ncia de uma intera??o seria preciso combinar os dados da expans?o com outros tipos de observa??es.

For this project, a historical statistical analysis of the Amplitude of Mass Fluctuations ($\sigma_8$) and Hubble's Constant ($H_0$) parameters in the Standard Cosmological Model was carried out to determine whether or not the given error bars truly represent the dispersion of values. It was found through analysis of the Chi-Squared ($\chi^2$) values of the data that for $\sigma_8$ (60 data points and $\chi^2$ between 183.167 and 189.037) that the associated probability Q is extremely low, with $Q = 1.5597*10^{-15}$ for the weighted average and $Q = 1.2107*10^{-14}$ for the best fit of the data. This was also the case for the $\chi^2$ values (163 data points and $\chi^2$ between 484.3977 and 575.655) of $H_0$, where $Q = 4.2176*10^{-34}$ for the linear fit of the data and $Q = 1.0342*10^{-47}$ for the weighted average of the data. Through further analysis, it is shown in question, a linear fit is a better estimate of the data than the weighted average. The general conclusion is that the statistical error bars have been underestimated (in around 20\% of the measurements), or the systematic errors were not properly taken into account.

In recent years, the increasingly precise constraints on the value of the Hubble constant, H0, have highlighted a discrepancy between the results arising from early-time and late-time measurements. A potential solution to this so-called Hubble tension is the hypothesis that we reside in a cosmic void, i.e. an underdense cosmic neighbourhood characterized by a faster local expansion rate. In this thesis, we model this scenario through the Lemaître-Tolman-Bondi formalism for an isotropic but inhomogeneous universe containing matter, curvature and a cosmological constant, which we denote by ΛLTB. We numerically implement this framework with two different formulations for the local matter density profile, respectively based upon a more realistic Gaussian ansatz and the idealized scenario of the so-called Oppenheimer-Snyder model. We then constrain the background cosmology and the void parameters involved in each case through a Markov Chain Monte Carlo analysis with a combination of recent data sets: the Pantheon Sample of type Ia supernovae, a collection of baryon acoustic oscillations data points from different galaxy surveys and the distance priors extracted from the latest Planck data release. For both models, the resulting bounds on the investigated parameter space suggest a preference for a -13% density drop with a size of approximately 300 Mpc, interestingly matching the prediction for the so-called KBC void already identified on the basis of independent analyses using galaxy distributions. We quantify the level of improvement on the Hubble tension by analyzing the ΛLTB constraints on the B-band absolute magnitude of the supernovae, which provides the calibration for the local measurements of H0. Since no significant difference is observed with respect to an analogous fit performed with the standard ΛCDM model, we conclude that the potential presence of a local void does not resolve the tension.

The structure of the plasma in Jupiter’s vast magnetosphereis complicated and not fully understood. One way to study the plasma is to look at auroral emissions from the moonIo as it moves through different regions of the plasma torus that surrounds Jupiter. In this paper, the correlation between aurorabrightness on Io and the plasma density at the position of the moon is investigated. If a correlation exists, auroral emissonson Io could be used as a diagnostic for the current state ofJupiter’s plasma environment. For this purpose, a model of the Io plasma torus is developed, combining ideas from different existing models. The model is compared with observations of aurorae on Io made by the Hubble Space Telescope. Io’s position at the time of the observations is obtained with SPICE, a software developed by NASA. A moderate correlation is found when using the whole data set of observations. However, a strong correlation is found for observations on the dusk side of Jupiter. Strong correlations are also found when studying individual years and epochs. / Strukturen på plasman i Jupiters vidsträckta magnetosfär är komplicerad och inte fullständigt känd. Ett sätt att studera plasman är att undersöka ljuset från polarsken på månen Io då den passerar genom olika regioner av det torusformade plasmamolnet som omsluter Jupiter. I denna artikel undersöks korrelationen mellan polarskenets ljusstyrka och plasmans densitiet kring månens position. Om ett sådant samband finns skulle ljusstyrkan hos månens polarsken kunna användas som diagnostik för plasmans aktuella tillstånd. För detta ändamål utvecklas en modell av plasmatorusen genom att kombinera ide´er från flera tidigare modeller. Modellen jämförs sedan med observationer av polarskenet på Io genomförda med rymdteleskopet Hubble. Månens position vid de olika tidpunkterna bestäms med hjälp av SPICE, en mjukvara utvecklad av NASA. En måttligt stark korrelation uppnås när hela datamängden används. När däremot endast data från Jupiters gryningssida används uppnås en korrelation. Det hittas även starka samband när enskilda år studeras. / Kandidatexjobb i elektroteknik 2022, KTH, Stockholm

No description available.

Several studies have been conducted with the aimof finding water plumes at Jupiter’s moon Europa. The possibleevidence of plumes is important for two future space missions,the JUpiter ICy moons Explorer (JUICE) and the Europa clippermission. Multiple observations of Europa in transit of Jupiterhave been obtained with the Hubble Space Telescope (HST).In an analysis by Sparks et al. 2016 three plume candidateswere found. Later on, in the report Sparks et al. 2017 anadditional candidate was found at a similar location as a previouscandidate, potentially making the evidence of plume existencestronger. In 2020 Giono et al. reproduced the results from Sparkset al. 2016 and found uncertainties in the method that hadbeen used when finding these plume candidates. First Giono etal. claim that the position of Europa in the observation wasinadequately determined. Also, positive outliers had not beenconsidered when analyzing the z-statistic. In this study, thealgorithm developed by Giono et al. has been used to reproducethe results from Sparks et al. 2017 where additional evidence forplume activity was presented. The algorithm was then applied tothe previous observation, where plume activity had been foundin the same location. Lastly, the two observations were mergedinto one image and the algorithm was applied once again. Theresults of the z-statistic from the observations gave large negativeoutliers which can be considered as plumes. However, positive andnegative outliers had similar significance for the two independentobservations which somewhat diminishes the evidence. Also,misalignment between model and observation generates distortedstatistics. The statistical uncertainties and fluctuations can easilybe mistaken as evidence of plume existence. / Flera studier har utförts med syftet attupptäcka vattenplymer på Jupiters måne Europa. Det eventuellabeviset för att plymer existerar är viktigt för två framtidarymduppdrag, JUpiter ICy moons Explorer (JUICE) och Europaclipper mission. Flera observationer av när Europa passerarframför Jupiter har erhållits av Hubbleteleskopet (HST). I enanalys av Sparks et al. 2016 har tre kandidater för plymerhittats. I rapporten av Sparks et al. 2017 hittades ytterligare enkandidat på ungefär samma ställe, vilket potentiellt kunde stärkabeviset för att det var plymer. År 2020 reproducerade Giono et alresultaten från Sparks et al. 2016 och hittade brister i metodennär dessa plymkandidater hittades. Först pöangterar de att Europas position i observationen var felaktig. Dessutom togs detinte hänsyn till positiva avvikelser när z-statistiken betraktades.I den här rapporten har algoritmen som skapades av Gionoet al. använts för att reproducera resultaten från Sparks et al.2017 där ytterligare bevis för plymer presenterades. Algoritmenapplicerades sedan på den föregående observationen där bevis förplymer hade hittats i samma område. Därefter slogs dessa bilderihop och analyserades som en bild. Resultatet av z-statistikenfrån observationerna gav stora negativa avvikelser vilket kanses som en plym av vattenånga. Dock eftersom positiva ochnegativa avvikelser hade liknande signifikans för de två enskildaobservationerna försvagas beviset för att plymer skulle existera.Dessutom genererar lokala fel mellan modell och observation enförvrängd statistik där statistiska osäkerheter och fluktuationerenkelt kan misstas som bevis för att vattenplymer existerar / Kandidatexjobb i elektroteknik 2021, KTH, Stockholm

Les deux méthodes principales pour mesurer la constante de Hubble, soit le taux d’expansion actuel de l’Univers, trouvent des valeurs différentes. L’une d’elle s’appuie lourdement sur le modèle cosmologique aujourd’hui accepté pour décrire le cosmos et l’autre, sur une mesure directe. Le désaccord éveille donc des soupçons sur l’existence d’une nouvelle physique en dehors de ce modèle. Si une autre méthode, indépendante des deux en conflit, soutenait une des deux valeurs, cela orienterait les efforts des cosmologistes pour résoudre la tension. Les lentilles gravitationnelles fortes comptent parmi les méthodes candidates. Ce phénomène se produit lorsqu’une source lumineuse s’aligne avec un objet massif le long de la ligne de visée d’un télescope. La lumière dévie de sa trajectoire sur plusieurs chemins en traversant l’espace-temps déformé dans le voisinage de la masse, résultant en une image déformée, gros- sie et amplifiée. Dans le cas d’une source lumineuse ponctuelle, deux ou quatre images se distinguent nettement. Si cette source est aussi variable, une de ses fluctuations apparaît à différents moments sur chaque image, puisque chaque chemin a une longueur différente. Le délai entre les signaux des images dépend intimement de la constante de Hubble. Or, cette approche fait face à de nombreux défis. D’abord, elle requiert plusieurs jours à des spécialistes pour exécuter la méthode de Monte-Carlo par chaînes de Markov (MCMC) qui évalue les paramètres d’un seul système de lentille à la fois. Avec les détections de milliers de systèmes prévues par l’observatoire Rubin dans les prochaines années, cette approche est inconcevable. Elle introduit aussi des simplifications qui risquent de biaiser l’inférence, ce qui contrevient à l’objectif de jeter la lumière sur le désaccord entre les mesures de la constante de Hubble. Ce mémoire présente une stratégie basée sur l’inférence par simulations pour remédier à ces problèmes. Plusieurs travaux antérieurs accélèrent la modélisation de la lentille grâce à l’ap- prentissage automatique. Notre approche complète leurs efforts en entraînant un estimateur neuronal de ratio à déterminer la distribution de la constante de Hubble, et ce, à partir des produits de la modélisation et des mesures de délais. L’estimateur neuronal de ratio s’exécute rapidement et obtient des résultats qui concordent avec ceux de l’analyse traditionnelle sur des simulations simples, qui ont une cohérence statistique acceptable et qui sont non-biaisés. / The two main methods to measure the Hubble constant, the current expansion rate of the Universe, find different values. One of them relies heavily on today’s accepted cosmological model describing the cosmos and the other, on a direct measurement. The disagreement thus arouses suspicions about the existence of new physics outside this model. If another method, independent of the two in conflict, supported one of the two values, it would guide cosmologists’ efforts to resolve the tension. Strong gravitational lensing is among the candidate methods. This phenomenon occurs when a light source aligns with a massive object along a telescope line of sight. When crossing the curved space-time in the vicinity of the mass, the light deviates from its trajectory on several paths, resulting in a distorted and magnified image. In the case of a point light source, two or four images stand out clearly. If this source is also variable, the luminosity fluctuations will appear at different moments on each image because each path has a different length. The time delays between the image signals depend intimately on the Hubble constant. This approach faces many challenges. First, it requires several days for specialists to perform the Markov Chain Monte-Carlo (MCMC) which evaluates the parameters of a single lensing system at a time. With the detection of thousands of lensing systems forecasted by the Rubin Observatory in the coming years, this method is inconceivable. It also introduces simplifications that risk biasing the inference, which contravenes the objective of shedding light on the discrepancy between the Hubble constant measurements. This thesis presents a simulation-based inference strategy to address these issues. Several previous studies have accelerated the lens modeling through machine learning. Our approach complements their efforts by training a neural ratio estimator to determine the distribution of the Hubble constant from lens modeling products and time delay measurements. The neural ratio estimator results agree with those of the traditional analysis on simple simulations, have an acceptable statistical consistency, are unbiased, and are obtained significantly faster.

International Telemetering Conference Proceedings / October 25-28, 1993 / Riviera Hotel and Convention Center, Las Vegas, Nevada / The Hubble Space Telescope (HST) Observatory Management System (HSTOMS), located at the Goddard Space Flight Center (GSFC), provides telemetry, command, analysis and mission planning functions in support of the HST spacecraft. The Telemetry and Command System (TAC) is an aging system that performs National Aeronautics and Space Administration (NASA) Communications (Nascom) block and telemetry processing functions. Future maintainability is of concern because of the criticality of this system element. HSTOMS has embarked on replacing the TAC by using functional elements developed by the Microelectronics Systems Branch of the GSFC. This project, known as the Transportable TAC (TTAC) because of its inherent flexibility, is addressing challenges that have resulted from applying recent technological advances into an existing operational environment. Besides presenting a brief overview of the original TAC and the new TTAC, this paper also describes the challenges faced and the approach to overcoming them.

Foram analisados espectros óticos de fenda longa de 29 galáxias que hospedam núcleos ativos (AGNs), sendo 6 galáxias Seyfert 1, 18 galáxias Seyfert 2, 4 Rádio-galáxias de linhas estreitas (NLRG) e 1 Rádio-galáxia de linhas largas (BLRG). Estas galáxias apresentam emissão por gás de alta excitação que se estende em alguns casos a 10 kpc do núcleo. O objetivo do presente trabalho consiste em estudar e caracterizar as propriedades físicas da região estendida de linhas estreitas (ENLR) destes objetos bem como propriedades da fonte central. A distribuição radial de parâmetros que caracterizam o gás emissor em cada galáxia, tais como brilho superficial das linhas de emissão, densidade do gás, massa, extinção e excitação são obtidos. Estes valores característicos são comparados entre as diferentes classes de atividade nuclear presentes em nossa amostra, bem como às propriedades de galáxias normais com o mesmo tipo de Hubble quando possível. Nós encontramos que a massa de gás ionizado é consistente com a hipótese de que o gás é “originado” na fotoionização pela fonte central das nuvens de HI préexistentes na galáxia hospedeira. Os valores observados das razões entre as linhas estreitas de emissão são comparados com os obtidos através de modelos de fotoionização gerados com o código MAPPINGS Ic, obtendo os parâmetros do modelo – densidade, índice espectral da distribuição de energia e da metalicidade do gás – que melhor reproduzem as observações. Observamos que a variação da abundância química do gás é necessária para explicar o espalhamento nos valores observados. Adicionalmente, comparamos os valores observados com os obtidos com modelos de choques gerados por Dopita & Sutherland. Investigamos também a influência da emissão proveniente de regiões HII ao espectro observado – a qual concluímos ser importante particularmente nas regiões emissoras mais distantes do que 2 kpc do núcleo. Nós determinamos a luminosidade ionizante da fonte central nos AGNs usando a aproximação de que as nuvens de gás são limitadas por radiação, e obtivemos os correspondentes valores para o fator de cobertura do gás. Esta luminosidade ionizante foi então comparada com a luminosidade observada em raios-X na banda 2 –10 keV, através de aproximações para a distribuição espectral de energia (SED). Para 9 galáxias Seyfert 2 a luminosidade observada está disponível, e verificamos que nosso método recupera a luminosidade do AGN em raios-X – assim como obtida dos dados do satélite ASCA – bem como identifica os 3 casos Compton espessos. Por fim, investigamos a natureza do contínuo infravermelho (IR) médio e distante – comparandose a luminosidade observada no IR, calculada a partir dos fluxos IRAS, com a luminosidade predita para um toro que envolve a fonte central absorvendo a radiação incidente e re-emitindo esta no infravermelho. Encontramos que a luminosidade observada no IR é consistente com a luminosidade predita para o torus.