published_or_final_version / abstract / Physics / Master / Master of Philosophy

The Canadian astrophysics program rapidly developed between 1903 and 1914, leading to the wartime construction of what was hoped to be the world’s largest research telescope. The institution opened in Victoria British Columbia in 1918 with fanfare. Throughout the 1920s, the new Dominion Astrophysical Observatory (DAO) contributed to discoveries on the frontiers of astrophysics, while educating residents of Victoria about astronomy. In a history often overshadowed by the advent of cosmology in the 1920s, the discoveries of Victoria’s astronomers produced lasting insight into the size and scale of our own galaxy. Accordingly, historians of astronomy have probed the scientific accomplishments of Canadian astronomers, devoting relatively little attention to the regional importance of these scientific facilities. The Victoria observatory itself developed into a widely visited tourism destination as staff astronomers regularly engaged in public education initiatives. This study utilizes newspaper sources, scientific papers, and contemporary publications in assessing the cultural relationship between the DAO, Victorians, and Canadians, while examining the significance of the scientific research conducted with the world’s second largest telescope. In doing so it engages themes of public interest in the achievements of the institution, and Victoria’s civic identity as an emerging tourism destination. / Graduate / 0334 / 0585 / danielgposey@gmail.com

This work aims to obtain the fusion excitation function for the 16O+16O system through gamma-spectroscopy measurements and gamma-charged particle coincidence, using the Saci-Perere system mounted at the end of the 30A beamline of the Open Laboratory of Nuclear Physics of the University of São Paulo (LAFN). Tests with the gamma-charged particle detection system indicated its unfeasibility due to the short measurement time and lose of the neutron channel. To overcome this problem, a new experimental setup was used. Two $\\gamma$-ray detectors were placed at 55º and 125º and a surface barrier detector was placed at 130º to monitor the 16O nuclei backscattered. The partial fusion cross sections related to the exit channels from the 16O+16O fusion reaction were measured by detecting their characteristic gamma rays at Ecm= 8.27, 9.27, 10.77 and 12.27 MeV. Three difficulties were faced during and after the experiment: carbon contamination of the target, natural background and low beam intensity. Efforts were made to successfully overcome these difficulties. The relative normalization was made by two ways, using the gamma-rays at 279 keV(197Au) and 536 keV(100Mo), and their results agree very well with each other. The total fusion cross section was obtained by summing the partial cross sections for each beam energy. Its absolute normalization was performed with the total theoretical fusion cross section obtained using coupled channel calculations, using the zero point motion model (ZPM), at Ecm= 12.27 MeV. With the total fusion cross section we calculated the astrophysical S-factor, and both results are in good agreement with the literature. / O objetivo deste trabalho é obter uma função de excitação para o sistema 16O+16O através de medidas de espectroscopia-gamma e coincidência gamma-partícula carregada, utilizando o sistema Saci-Perere montado no final da linha de feixe 30A do Laboratório Aberto de Física Nuclear da Universidade de São Paulo (LAFN). Testes com o sistema de detecção gamma-partícula carregada indicaram sua inviabilidade devido ao curto tempo de medida e a perda do canal de nêutrons. Para superarmos este problema, uma nova configuração experimental foi utilizada. Dois detectores de radiação gamma foram posicionados a 55º e 125º e um detector de barreira de superfície foi posicionado a 130º para monitorar os núcleos de 16O retroespalhados. As seções de choque parciais relativas aos canais de saída da reação de fusão 16O+16O foram medidas através da detecção de seus raios-gamma característicos para Ecm= 8.27, 9.27, 10.77 e 12.27 MeV. Três dificuldades foram encontradas ao longo e após o experimento: contaminação do alvo por carbono, radiação natural de fundo e baixa intensidade do feixe. Esforços foram direcionados com sucesso para superar estas dificuldades. A normalização relativa foi realizada por dois caminhos, utilizando os raios-gamma a 279 keV(197Au) e a 536 keV(100Mo), e seus resultados concordam muito bem. A seção de choque de fusão total foi obtida somando as seções de choque parciais para cada energia de feixe medida. Sua normalização absoluta foi feita usando a seção de choque de fusão teórica total obtida com cálculos de canais acoplados, utilizando o modelo (ZPM), para Ecm= 12.27 MeV. De posse da seção de choque de fusão total calculamos o fator S-astrofísico, e ambos os resultados concordam bem com a literatura.

Je présente et j'analyse dans ma thèse des observations de l'émission dans l'infrarouge proche de transitions rovibrationelles de H2 dans des régions de formation stellaire. Le sujet principal de ce travail concerne de nouvelles observations du nuage moléculaire d'Orion (OMC1) et en particulier de la région BN-KL. Les données sont constituées d'images des raies individuelles de H2 obtenues à haute résolution spatiale avec le Telescope Canada-France-Hawaii et avec l'ESO VLT. Grâce à la haute résolution spatiale du VLT il est possible d'analyser en détail (jusq'à 60 UA ~0.''13) des objets individuels dans cette région. De plus, j'ai analysé l'émission de H2 et [FeII] dans des écoulements (« outflows ») présents dans deux nuages sombres (les globules de Bok BHR71 et BHR137) ainsi que dans un « blob » à haute excitation dans le grand nuage de Magellan (N159-5). Ici les données sont constituées de spectres en fente longue obtenus à l'ESO-VLT. Pour réaliser ce travail j'ai tout d'abord calculé une grille complète de modèles de chocs composée de ~25 000 simulations (correspondant à 400 Go, environ). Ces modèles qui sont les plus récents comportent un grand nombre de paramètres libres qui peuvent être ajustés. Une grande partie demon travail a été d'analyser les résultats de cette grille avant de les mettre en ligne. En effet les résultats ne sont pas tous crédibles, et il m'a donc fallu de développer des méthodes pour les vérifier. Mais avec une bonne compréhension du modèle et un solide sens de la physique des chocs, il est maintenant assez facile d'interpréter les données sur H2 et [FeII]. Les modèles me permettent ensuite de prédire les conditions physiques à grande échelle dans OMC1, par exemple la densité, la vitesse des chocs, l'intensité du champ magnétique, etc. En général la densité du milieu avant le choc est ~105-107 cm-3 et la vitesse de choc est dans la gamme 10-40 km.s-1. Un autre résultat très intéressant de mon travail est le développement d'une nouvelle méthode pour analyser les chocs en arc (« bow shocks ») observés à une haute résolution spatiale. Pour un choc en arc isolé je prédis une vitesse de choc de ~50 km.s-1 et une densité avant le choc de 5×105 cm-3. La vitesse 3D a été mesurée très récemment à 55 km.s-1. Cela donne une confirmation indépendante de nos résultats.

The main focus of this thesis is the investigation of an interesting new population of massive passively evolving galaxies found at high redshifts. We use a sample of these galaxies at redshifts 1<z<2 drawn from the Gemini Deep Deep Survey sample and measure their structural parameters based on the Hubble Space Telescope imaging in the rest frame visible and ultraviolet wavelength range. Our analysis shows that a fraction of these systems are very compact, with effective radii of R_e<1 kpc, even when observed in rest frame visible light. The average size of these objects is 2-5 times smaller than the typical size of an early-type galaxy of similar mass found locally. We combine the results from our morphological analysis with data from published spectroscopic samples of quiescent systems with known structural parameters. Analysis of these data for galaxies over the redshift range 0<z<2.5 shows that passively evolving galaxies are continuously and gradually growing in size. We also find smooth evolution of the stellar mass density within the central kiloparsec of these systems. The stellar mass density grows by a factor of 3 from z=0 to z~2.5. None of the models proposed to drive the structural evolution of early-type objects can explain all the observed aspects of this process. Because these massive compact galaxies have such small angular sizes, future studies of these systems will benefit from adaptive optics. In order to compile a large statistical sample of these objects suitable for adaptive optics follow-up, we first need to find a large number of targets with nearby bright natural guide stars. As a first step in this process, we describe the properties of a set of one square degree regions of the sky we have located that have a rare combination of high stellar surface density and low levels of extinction. We demonstrate that the adaptive optics-related properties of these fields are in some cases orders of magnitude better than those of existing deep fields.

The main focus of this thesis is the investigation of an interesting new population of massive passively evolving galaxies found at high redshifts. We use a sample of these galaxies at redshifts 1<z<2 drawn from the Gemini Deep Deep Survey sample and measure their structural parameters based on the Hubble Space Telescope imaging in the rest frame visible and ultraviolet wavelength range. Our analysis shows that a fraction of these systems are very compact, with effective radii of R_e<1 kpc, even when observed in rest frame visible light. The average size of these objects is 2-5 times smaller than the typical size of an early-type galaxy of similar mass found locally. We combine the results from our morphological analysis with data from published spectroscopic samples of quiescent systems with known structural parameters. Analysis of these data for galaxies over the redshift range 0<z<2.5 shows that passively evolving galaxies are continuously and gradually growing in size. We also find smooth evolution of the stellar mass density within the central kiloparsec of these systems. The stellar mass density grows by a factor of 3 from z=0 to z~2.5. None of the models proposed to drive the structural evolution of early-type objects can explain all the observed aspects of this process. Because these massive compact galaxies have such small angular sizes, future studies of these systems will benefit from adaptive optics. In order to compile a large statistical sample of these objects suitable for adaptive optics follow-up, we first need to find a large number of targets with nearby bright natural guide stars. As a first step in this process, we describe the properties of a set of one square degree regions of the sky we have located that have a rare combination of high stellar surface density and low levels of extinction. We demonstrate that the adaptive optics-related properties of these fields are in some cases orders of magnitude better than those of existing deep fields.

This thesis was motivated by the promise that some physical aspects of astrophysical jets and collimation processes can be scaled to laboratory parameters through hydrodynamic scaling laws. The simulation of astrophysical jet phenomena with laser-produced plasmas was attractive because the laser-target interaction can inject energetic, repeatable plasma into an external environment. Novel laboratory simulations of astrophysical jets involved constructing and using the YOGA laser, giving a 1064 nm, 8 ns pulse laser with energies up to 3:7 - 0:2 J. Laser-produced plasmas were characterized using Schlieren, interferometry and ICCD photography for their use in simulating jet and magnetosphere physics. The evolution of the laser-produced plasma in various conditions was compared with self-similar solutions and HYADES computer simulations. Millimeter-scale magnetized collimated out-flows were produced by a centimeter scale cylindrically symmetric electrode conguration triggered by a laser-produced plasma. A cavity with a flared nozzle surrounded the center electrode and the electrode ablation created supersonic uncollimated flows. This flow became collimated when the center electrode changed from an anode to a cathode. The plasma jets were in axially directed permanent magnetic fields with strengths up to 5000 Gauss. The collimated magnetized jets were 0.1-0.3 cm wide, up to 2.0 cm long, and had velocities of ~ 4:0 x 10⁶ cm/s. The dynamics of the evolution of the jet were compared qualitatively and quantitatively with fluxtube simulations from Bellan's formulation [6] giving a calculated estimate of ~ 2:6 x 10⁶ cm=s for jet evolution velocity and evidence for jet rotation. The density measured with interferometry was 1.9 ± .2 x 10¹⁷ cm⁻³ compared with 2.1 x10¹⁶ cm⁻³ calculated with Bellan's pressure balance formulation [6]. Kinks in the jet column were produced consistent with the Kruskal-Shafranov condition which allowed stable and symmetric jets to form with the background magnetic fields. The Euler number for the laboratory jet was 9 compared with an estimate of 40 for young stellar object jets [135] which demonstrated adequate scaling between the two frames. A second experiment was performed concerning laboratory simulations of magnetospheres with plasma winds impinging on permanent magnetic dipoles. The ratio of the magnetopause measured with ICCD photography to the calculated magnetopause standoff distance was ~2. / text

Thesis (M. Phil.)--University of Hong Kong, 2007. / Title proper from title frame. Also available in printed format.

Cosmic black holes can act as agents of particle acceleration. We study properties of a system consisting of a rotating black hole immersed in a large-scale organized magnetic field. Electrically charged particles in the immediate neighborhood of the horizon are influenced by strong gravity acting together with magnetic and induced electric components. We relax several constraints which were often imposed in previous works: the magnetic field does not have to share a common symmetry axis with the spin of the black hole but they can be inclined with respect to each other, thus violating the axial symmetry. Also, the black hole does not have to remain at rest but it can instead perform fast translational motion together with rotation. We demonstrate that the generalization brings new effects. Starting from uniform electro-vacuum fields in the curved spacetime, we find separatrices and identify magnetic neutral points forming in certain circumstances. We suggest that these structures can represent signatures of magnetic reconnection triggered by frame-dragging effects in the ergosphere. We further investigate the motion of charged particles in these black hole magnetospheres. We concentrate on the transition from the regular motion to chaos, and in this context we explore the characteristics of chaos in...

Orientador: Orlando Luis Goulart Peres / Dissertação (mestrado) - Universidade Estadual de Campinas, Instituto de Física Gleb Wataghin / Made available in DSpace on 2018-08-17T22:10:39Z (GMT). No. of bitstreams: 1 Picoreti_Renan_M.pdf: 2695409 bytes, checksum: 33f93ce114e33774d72d40191bbac72b (MD5) Previous issue date: 2011 / Resumo: Neutrinos Astrofísicos são produzidos quando prótons ou núcleos, acelerados numa fonte astrofísica, interagem com a matéria nas imediações gerando méons que decaem fracamente produzindo neutrinos. Remanescentes de Supernovas, Núcleos Ativos de Galáxias (AGN) e Explosões de Raios Gama (GRB) são alguns dos candidatos a fontes, e a detecção desses neutrinos pode fornecer informações tanto sobre esses objetos astrofísicos quanto sobre a física de neutrinos. Neste trabalho, supomos, de forma simplificada, que nas fontes são produzidos mésons ¶ ± num espectro de lei de potência da energia, 8 E¶ -a . Calculando-se os espectros de produção dos neutrinos gerados na cadeia de decaimento, obtém-se, no limite em que as partículas são ultrarrelativísticas, uma razão entre sabores de neutrinos muônicos e eletrônicos que é função do expoente do espectro inicial, a, dos píons. Calculamos uma correção a essa razão devido a termos proporcionais à massa do elétron, geralmente desprezada na literatura, e verificamos a validade da razão na aproximação ultrarrelativística. Entre produção e detecção, a razão entre sabores deve se modificar devido ao fenômeno da oscilação de neutrinos. Assim, discutimos a possibilidade de, através da detecção destes neutrinos e da medição da razão entre os sabores, inferir-se propriedades da produção dos neutrinos na fonte ou mesmo verificar-se a existência de novos fenômenos da física de neutrinos, em especial, o decaimento de neutrinos / Abstract: Astrophysical Neutrinos are produced when protons or nuclei, accelerated in a astrophysical source, interact with the surrounding matter generating weakly decaying mesons that decay producing neutrinos. Supernova Remnants, Active Galactic Nuclei (AGN) and Gamma-ray Bursts (GRB) are some of the candidates to such sources, and the detection of those neutrinos may provide information about these astrophysical objects and about neutrino physics. In this work, we suppose, in a simplified manner, that the sources produce ¶ ± mesons with a power law spectrum, 8¶ -a .Upon calculation of the neutrino production spectra on the pion decay chain, it is obtained, on the ultra-relativistic limit, the flavor ratio between muon and electron neutrinos as a function of the slope of the initial pion spectrum. We calculated a correction to this flavor ratio due to non-vanishing electron mass, usually disregarded, and we verified if the ultra-relativistic limit is reasonable. Between neutrino production and detection, the flavor ratio is modified due to the neutrino flavor oscillation. Thus, we discuss the possibility of inferring the source properties or new neutrino physics phenomena, such as neutrino decay, through the detection of astrophysical neutrinos and the measurement of its flavor ratio / Mestrado / Física das Particulas Elementares e Campos / Mestre em Física