The first stars in the Universe are thought to have formed in high dark matter density minihalos about 200 million years after the Big Bang. If these stars were able to contract dark matter into their stellar core while forming, some of them might have turned into dark stars (DSs) powered by the heat from dark matter annihilation. The possibilities for detection of DSs with the upcoming James Webb Space Telescope (JWST), scheduled for launch in 2021, is investigated in this work. With DS models generated in Spolyar et al. (2009) and atmosphere spectra from Gustafsson et al. (2008), spectral analysis has been carried out in MATLAB to find the unique colors of DSs compared to galaxies generated in Zackrisson et al. (2017) at z ≈ 7 − 11. It was found that lower temperature DSs (Teff ≤ 7800K) are distinguishable from galaxies and that they would be bright enough to be detected with the JWST provided a magnification factor of µ ≈ 160−1000 with the use of gravitational lensing. More recent DS models reveal that the DS of temperature Teff = 7800K is detectable even without the use of gravitational lensing. However, the probability of finding one today is really small due to DSs’ presumably short lifetime. The results of this work are hoped to give a better understanding of the properties of DSs and to increase the probability of finding one in the large imaging survey carried out by the JWST. / De första stjärnorna i universum antas ha bildats i minihalos med hög densitet av mörk materia omkring 200 miljoner år efter Big Bang. Om dessa stjärnor kunde dra till sig mörk materia under sitt bildande kan vissa av dem ha utvecklats till mörka stjärnor (s.k. dark stars) med mörk materia som energikälla. I detta arbete undersöks möjligheterna att upptäcka dem med det kommande James Webb Space Teleskopet (JWST) som planeras för uppskjutning år 2021. Med dark starmodeller genererade i Spolyar et al. (2009) och atmosfärspektra från Gustafsson et al. (2008) har spektralanalys utförts i MATLAB för att hitta vilka dark stars som går att urskilja från galaxer genererade i Zackrisson et al. (2017) vid z ≈ 7−11. Det visade sig att dark stars med låg temperatur (Teff ≤ 7800K) är urskiljbara och att de flesta av dessa dark stars, vid en förstoringsfaktor av µ ≈ 160−1000 vid användning av gravitationell linsning, är tillräckligt ljusstarka för att kunna detekteras. Jämfört med senare dark star-modeller skulle även Teff = 7800K DSs kunna detekteras utan användning av gravitaionell linsning. Sannolikheten att hitta en dark star är fortfarande väldigt liten på grund av dess förmodade korta livstid. Resultaten av detta arbete hoppas kunna ge en bättre förståelse för egenskaperna hos mörka stjärnor samt öka sannolikheten för detektion med JWST.

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.

Gamma-ray bursts (GRBs) are short, intense flashes of 0.1-1 MeV electromagnetic radiation that are routinely observed by Earth orbiting satellites. The sources of GRBs are known to be extragalacitic and located at cosmological distances. Due to the extremely high isotropic equivalent energies of GRBs, which are on the order of Eiso~1054 erg, the gamma-ray emission is believed to be collimated, making them observable only when they are directed towards Earth. The favored progenitor models of GRBs are also believed to emit gravitational waves that would be observable by the current generation of ground-based interferometric gravitational wave detectors. The LIGO (Laser Interferometer Gravitational-Wave Observatory) and Virgo instruments operated near design sensitivity and collected more than a year of triple coincident data during the S5/VSR1 science run, which spanned the two year interval between November 2005 and October 2007. During this time, GRB detections were being made by the NASA/Goddard Swift Burst Alert Telescope at a rate of approximately 0.3 per day, producing a collection of triggers that has since been used in a coincident GRB-GW burst search with data from the LIGO-Virgo interferometer network. This dissertation describes the search for gravitational waves using the times and locations of 123 below-threshold potential GRB triggers from Swift over the same time period. Although most of the below-threshold triggers are likely false alarms, there is reason to believe that some are the result of actual faintly-observed GRB events. Recent GRB observations indicate that the local rate of low-luminosity GRBs is much higher than previously believed. This result, combined with the possibility of discovering a rare nearby GRB event accompanied by gravitational waves, is what motivates this search. The analysis results indicate no evidence for gravitational waves associated with any of the below-threshold triggers. A median distance lower limit of ~16 Mpc was derived for a typical neutron star-black hole coalescence progenitor assumption.

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.

Orientador: Carlos Ourivio Escobar / Tese (doutorado) - Universidade Estadual de Campinas, Instituto de Fisica Gleb Wataghin / Made available in DSpace on 2018-08-04T21:20:16Z (GMT). No. of bitstreams: 1 Sato_Ricardo_D.pdf: 12445347 bytes, checksum: de6912545351fe42a3693e16ebbbcaa6 (MD5) Previous issue date: 2005 / Resumo: Desde antes de sua descoberta, o estudo dos raios cósmicos e de seus efeitos tem mobilizado intensamente teóricos e experimentais. Hoje, um dos grandes desafios é a explicação da existência dos raios cósmicos de altíssimas energias, que chegam a ultrapassar 1020 eV ~ 16 J. Com o intuito de investigar a faixa mais energética do espectro, em particular energias superiores a 1019 eV, onde o fluxo é da ordem de 1 evento por quilômetro quadrado por ano, encontra-se em construção, mas já em operação, o Observatório Pierre Auger, a ser constituído por duas grandes redes de detectores que cobrirão 3.000 km2 cada uma, o que equivale a praticamente duas vezes a área da cidade de São Paulo (1.523, 986 km2, segundo dados do IBGE). Em cada sítio, serão adotadas duas técnicas independentes e complementares de detecção dos chuveiros atmosféricos extensos: observação direta das partículas que chegam ao solo e registro da luz de fluorescência produzida pela passagem da cascata. Os detectores de fluorescência consistem de telescópios de Schmidt, com uma lente corretora em sua abertura. O presente trabalho mostra os estudos desenvolvidos desde a concepção da lente até o seu desempenho nos telescópios, envolvendo a definição do perfil, a investigação das possíveis vantagens de seu uso, a escolha do material, o método de produção e os testes ópticos para a avaliação da qualidade. O uso da lente possibilitou o aumento da área de coleta de luz em praticamente duas vezes, sem deteriorar a resolução óptica do telescópio, o que permite fazer estimativas melhores dos parâmetros relevantes do chuveiro, como a energia e a profundidade em que ocorre o máximo do chuveiro / Abstract: Since before its discovery, the study of cosmic rays and its effect has deeply stimulated theorists and experimentalists. Today, one of the great challenge is a explanation of the existence of the ultra high energy cosmic rays, that overcome energies of 1020 eV ~ 16 J. With the goal to investigate the most energetic part of the spectrum, in particular energies above 1019 eV, where the flux is about 1 event per square kilometer per year, the Pierre Auger Observatory is under operation and construction. It will be composed by two large groups of detectors covering 3,000 km2 each one, what is equivalent twice São Paulo city area (1.523,986 kmM2, according to IBGE data). In each site, two independent and complementary detection techniques of extensive air showers will be used: direct observation of the particles which reach the ground and the measurement of the fluorescence light produced by the cascade. The fluorescence detectors consist of Schmidt telescopes with a corrector lens at its aperture. The present work shows the studies developed from the lens conception to its performance in the telescopes, involving the definition of the profile, investigation of its possible advantages, material choice, production method and the optical tests to evaluate quality. Using the lens, it is possible to double the effective light collection area, without deteriorate the telescope optical resolution. It enables a better determination of important shower parameters like the energy and shower maximum / Doutorado / Teorias Especificas e Modelos de Interação ; Sistematica de Particulas ; Raios Cosmicos / Doutor em Ciências

The small-body populations of the distant Solar System inform our understanding of the structure, formation, and evolution of the Solar System. The orbits of these Trans-Neptunian Objects (TNOs) act as tracers for dynamical activities either ongoing or past. The distributions of TNO sizes are set by, and so probe, the conditions of the formation and evolution of the Solar System. Using data from surveys on the Canada-France-Hawaii Telescope, I constrain the size distribution of a TNO subpopulation: the scattering TNOs. The scattering TNOs are chosen as they have orbits that come in closer to the Sun, therefore allowing smaller TNOs to be detected. The characteristics of size distribution for the small-sized TNOs is an important, and only recently observable, constraint on the formation of this population. I find that the H-distribution is consistent with models where TNOs form as large (50 km - 100 km) aggregates from the proto-planetary nebula. A recent discovery of apparent clustering in the orbits of some TNOs has led to the hypothesis of an additional and unseen planet in the distant Solar System. I examine the formation implications and consequences of such a planet, and the biases in the detected sample used to infer the planet's existence. Via a combination of dynamical simulations, survey simulations, and statistical comparisons of the observed TNOs, I explore the additional planet hypothesis to determine if there exists strong evidence for an additional planet in our Solar System. I find that there is currently no strong evidence for the clustering of orbits in the observed sample and that the proposed additional planet does not produce such a signature in models. / Graduate

Though there has been a considerable amount of work investigating the early stages of low-mass star formation in recent years, the general theory is only broadly understood and several open questions remain. Specifically, the dominant physical mechanisms which connect large-scale molecular cloud structures, intermediate-scale filamentary gas flows, and small-scale collapsing prestellar envelopes in the interstellar medium are poorly constrained. Even for an individual forming protostar, the evolution of the mass accretion rate from the envelope onto the central object is debated with little observational evidence to help guide the theoretical framework. In addition, with the development of new technology such as the continuum imaging instrument in operation at the James Clerk Maxwell Telescope (JCMT), the Submillimetre Common User Bolometer Array 2 (SCUBA-2), the best practices for data reduction and image calibration for ground-based, submillimetre wavelength observations are still being investigated. In this dissertation, I address facets of these open questions in five main projects with an overarching focus on the flow of material from the largest to the smallest scales in a molecular cloud. By performing synthetic observations of a numerical simulation of a turbulent molecular cloud, I investigate the nature of prestellar envelopes and find evidence of larger mass reservoirs that form filamentary structures and feed cluster formation. Then, after robustly investigating and suggesting improvements for ground-based, submillimetre data reduction techniques, I continue to probe the connection between larger and smaller scales by characterising structure fragmentation in the Southern Orion A Molecular Cloud from the perspective of 850 m continuum data. Finally, I follow star forming material to even smaller scales by exploring the evolution of the mass accretion rate onto individual protostars. This examination has required designing and implementing unprecedented spatial alignment and flux calibration techniques at 850 m. Using these newly calibrated images, I am able to identify several candidate sources that show evidence for submillimetre variability, suggesting changes in protostellar accretion rates over several year timescales. / Graduate

Extragalactic charged particles, each with energies rising up to and beyond 1 Joule, have been studied for almost a century. Yet, no precise evidence have proven to show where they might originate from as their energy levels rise above the current familiar acceleration sources in outer space. The highly energetic particles have been given the name Ultra-High Energy Cosmic Rays (UHECR) and investigations of particle properties such as primary energy, mass composition and direction can be made through indirect measurements of the interaction between the UHECR and Earth's atmosphere. The considered interaction induces an Extensive Air Shower (EAS) which emits fluorescent light in the Ultraviolet (UV) range. The probability of detecting such events is, however, as low as a few particles per km2 per century. Making observations more sufficient therefore requires larger detection volumes. By introducing the Mini-EUSO instrument, a telescope of which the main purpose is to measure the UV-light radiated from the Earth in the wavelength range of 300-400 nm, allows just for this. To be accommodating the International Space Station and targeting Earth in the nadir direction, the Mini-EUSO instrument will allow for a higher exposure to the interactions than what is currently available. The use of two Fresnel lenses provides the instrument with a large field of view (±22o) and the detections are made through multiple photomultiplier tubes. The scope of this thesis is to evaluate the main detector of the Mini-EUSO instrument (i.e. the UV-detector) through ground-based tests. The procedures involved in the evaluation have consisted of; validating the statistical distributions of the signals, implementing dark field and flat field calibrations, and radiations measurements with three kinds of radiation sources. The data from the tests were provided during two periods and the visualization was made by adapting an already existing piece of code, using Python and ROOT Cern, to perform step by step procedures such that all operations are overlooked properly. The analysis showed that the implementation of the dark field and flat field procedures improved the original image significantly. It also showed that both the lower and higher photon count values in a pixel indeed gave the expected statistical behaviours, with a Poissonian distribution for low values and a Gaussian distribution for higher values. The flat fielding screen did however show unknown fluctuations in the emitted light and further tests have to be implemented to assure its functionality. Under proper covering, almost no dark current was found, however, observation tests showed that the borders of the Multi-Anode Photomultiplier Tubes (MAPMTs) gave higher photon count values than the center part even when they were emitted with Lambertian light.

High resolution imaging of wide fields has been a prerogative of space telescopes for decades. Multi-conjugate adaptive optics (MCAO) is a key technology for the future of ground-based astronomy, especially as we approach the era of ELTs, where the large apertures will provide diffraction limits that will significantly surpass even the James Webb Space Telescope. NFIRAOS will be the first light MCAO system for the Thirty Meter Telescope and to support its development I have worked on HeNOS, its test bench integrated in Victoria at NRC Herzberg. I have aligned the optics, tested the electronic hardware, calibrated the subsystems (cameras, deformable mirrors, light sources, etc.) and characterized the system parameters. Development and support for future MCAO instruments also involves data analysis, a critical process in delivering the expected performance of any scientific instrument. To develop a strategy for optimal stellar photometry with MCAO, I have observed the Galactic globular cluster NGC 1851 with GeMS, the MCAO system on the 8-meter Gemini South telescope. From near-infrared images of this target in two bands, I have found the optimal parameters to employ in the profile-fitting photometry and calibration. As testimony to the precision of the results, I have obtained the deepest near-infrared photometry of a crowded field from the ground and used it to determine the age of the cluster with a method recently proposed that exploits the bend in the lower main sequence. The precise color-magnitude diagram also allows us to clearly observe the double subgiant branch for the first time from the ground, caused by the multiple stellar populations in the cluster. As the only facility MCAO system, GeMS is an important instrument that serves to illuminate the challenges of obtaining accurate photometry using such a system. By coupling the knowledge acquired from an instrument already on-sky with experiments in the lab on a prototype of a future system, I have addressed new challenges in photometry and astrometry, like the promising technique of point spread function reconstruction. This thesis informs the development of appropriate data processing techniques and observing strategies to ensure the ELTs deliver their full scientific promise over extended fields of view. / Graduate

Une nouvelle architecture robotique parallèle de télescope d'observation spatial actif a été développée préalablement à cette thèse. Afin de pouvoir améliorer le réglage optique du télescope, la structure robotique doit pouvoir être auto-étalonnée dans l'espace, à partir des informations disponibles (mesures proprioceptives, images, etc). Dans un premier temps, les hypothèses nécessaires pour assurer le bon déroulement de l'étalonnage sont analysées. Cette étude théorique, appuyée par des exemples, permet de définir des conditions nécessaires à l'étalonnage. Ces conditions permettent de déterminer les précisions nécessaires sur les paramètres du modèle et l'amplitude maximale du bruit de mesure admissible pour l'étalonnage. Avec ces valeurs, un critère d'arrêt pour les algorithmes d'étalonnage ayant une réelle signification physique peut être obtenu. De plus, une normalisation de la matrice d'identification est proposée, ce qui permet l'analyse de ses valeurs singulières pour détecter les problèmes d'identifiabilité des paramètres. Dans une deuxième partie, nous nous intéressons à la modélisation du télescope d'observation. Plusieurs modèles de déformation des articulations flexibles du télescope sont proposés, en considérant par exemple les équations de la théorie des poutres ou l'équilibre statique de la plate-forme. Ces modèles sont ensuite comparés expérimentalement par une analyse des résultats d'étalonnage photogrammétrique. Cette analyse permet aussi d'observer une déformation de la plate-forme mobile qui peut être approchée par l'intermédiaire de deux modèles. / A new parallel robotic architecture has previously been developed for an active space telescope. The telescope needs to be calibrated in order to improve its optical quality. This also has to be done automatically in space with the available information (propriocetive measures, images, etc) which is referred as self-calibration. First, the necessary hypothesis for calibration are analyzed. This theoretical study, illustrated with examples, leads to the definition of the necessary conditions for an efficient calibration. With those conditions, the required accuracy of the model parameters and the maximal measurement noise allowed for calibration can be calculated. A physically meaningful stop criterion for the identification algorithm can also be derived and a normalization of the identification Jacobian matrix is proposed, which permits the analysis of its singular values in order to detect identifiability problems. Concerning the telescope modeling, three kinematic models taking into account the telescope flexure joint behaviors are proposed, for example using the beam theory or the static equilibrium of the mobile platform. Those models are compared through an analysis of the calibration results using photogrammetry. This analysis highlights a deformation of the mobile platform of the telescope, that was considered using two models. Thus, the kinematic model of the telescope is composed of both a model for the flexure joints and a model approaching the mobile platform deformation. This model was validated with the calibration results of photogrammetry.