This thesis presents the study of four aspects of high energy astronomy.The first part of my thesis is dedicated to an aspect of instrument development for imaging atmospheric Cherenkov telescopes, namely the Level 2 trigger system of the High Energy Stereoscopic System (H.E.S.S.). My work on the project focused on the algorithm development and the Monte Carlo simulations of the trigger system and overall instrument (Moudden, Barnacka, Glicenstein et al. 2011a; Moudden, Venault, Barnacka et al. 2011b). The hardware implementation of the system is described andits expected performances are then evaluated. The H.E.S.S. array has been used to observe the blazar PKS 1510-089.The second part of my thesis deals with the data analysis and modeling of broad-band emission of this particular blazar. In part II of my thesis, I am presenting the analysis of the H.E.S.S. data: the light curve and spectrum of PKS 1510-089, together with the FERMI data and a collection of multi-wavelength data obtained with various instruments. I am presenting the model of PKS 1510-089 observations carried out during a flare recorded by H.E.S.S.. The model is based on a single zone internal shock scenario.The third part of my thesis deals with blazars observed by the FERMI-LAT, but from the point of view of other phenomena: a strong gravitational lensing. This part of my thesis shows the first evidence for gravitational lensing phenomena in high energy gamma-rays. This evidence comes from the observation of a gravitational lens system induced echo in the light curve of the distant blazar PKS 1830-211. Traditionalmethods for the estimation of time delays in gravitational lensing systems rely on the cross-correlation of the light curves from individual images. In my thesis, I used 300 MeV-30 GeV photons detected by the Fermi-LAT instrument. The FERMI-LAT instrument cannot separate the images of known lenses. The observed light curve is thus the superposition of individual image light curves. The FERMI-LAT instrument has the advantage of providing long, evenly spaced, time series with very low photonnoise. This allows to use directly Fourier transform methods. A time delay between the two compact images of PKS 1830-211 has been searchedfor both by the autocorrelation method and a new method: the "double power spectrum". The double power spectrum shows a 4.2 σ evidence for a time delay of 27.1±0.6 days (Barnacka et al. 2011), consistent with the results from Lovell et al. (1998) and Wiklind & Combes (2001).The last part of my thesis concentrates on another lensing phenomena called "femtolensing". The search for femtolensing effects has been used to derive limits on the primordial black holes abundance. The abundance of primordial black holes is currently significantly constrained in a wide range of masses. The weakest limits are established for the small mass objects, where the small intensity of the associated physical phenomenon provides a challenge for current experiments. I have usedgamma-ray bursts with known redshifts detected by the FERMI Gamma-ray Burst Monitor (GBM) to search for the femtolensing effects caused by compact objects. The lack of femtolensing detection in the GBM data provides new evidence that primordial black holes in the mass range 5 × 10^17 - 10^20 g do not constitute a major fraction of dark matter (Barnacka et al. 2012). My Ph.D. studies have been carried out jointly between the Nicolaus Copernicus Astronomical Center of the Polish Academy of Sciences, in Warsaw in Poland and the IRFU institute of the Commissariat à l'énergie atomique et aux énergies alternatives(CEA) Saclay in France.

Thesis (Ph. D.)--Ohio State University, 2007. / Title from first page of PDF file. Includes bibliographical references (p. 157-163).

Thesis (MEng)--University of Stellenbosch, 2000. / ENGLISH ABSTRACT: In this thesis we addressed some issues concerning the automation of the detection, processing and the analysis of gravitational microlensing events, which are currently being used in the search for extra-solar planets. We were provided with a series of data images containing a microlensing event. Using these images we address several practical problems: registration, background subtraction and some PSF modelling. Registration is accomplished by using the intersection points of circular arcs drawn around stellar objects. After which the influence of the sky background is removed by using the watershedding algorithm and plane fitting. Our analysis is based on relative brightness - to counter seeing, the brightness of stars are calculated by isolating the objects from the background and summing over the area. A brightness variation curve is plotted and the trend of the lensing event and the posi tion of a blip are extracted using wavelets, calculating general trends and LOESS. The trend of the brightness variation curve can be used for both identification and classification of various events. It can also be used for the identification and classification of variable stars. Blip analysis is used to detect the presence of a planet (or dark body) in the vicinity of the source. / AFRIKAANSE OPSOMMING: Hierdie tesis beskryf tegnieke om die identifikasie, prosessering en analise van gravitasie mikro-lens gebeure te outomatiseer. Die analise van hierdie gebeure is belangrik aangesien dit gebruik word vir die opsporing van planete buite ons sonnestelsel. Om gebruik te maak van 'n reeks beelde wat een van hierdie gebeure vertoon moet ons die volgende probleme aanspreek: beeld registrasie, verwydering van die agtergrond en die modulering van die verspreiding van die lig van 'n puntbron deur die atmosfeer. Ons verkry registrasie deur die berekening van die snypunte van sirkels met middelpunte by sekere voorwerpe op die beeld. Na registrasie kan ons die invloed van die agtergrond bepaal deur gebruik te maak van die waterskeidingsalgoritme. Dit stelons in staat om die relatiewe helderheid van die voorwerpe ondersoek deur die voorwerpe te isoleer en te sommeer oor die area van 'n voorwerp. 'n Grafiese voorstelling van die helderhede dui vir ons die relatiewe variasies in die helderhede van die mikrolens objek tussen die beelde aan. Ons ondersoek die vorm van die kromme asook die moontlike voorkoms van 'n 'blip' deur middel van wavelet analiese en die LOESS metode. Die vorm van die kromme word gebruik vir die identifikasie en klassifikasie van die verskillende mikro-lens gebeure en kan uitgebrei word om ook veranderlike sterre te ondersoek. Die teenwoordighied van 'n 'blip' op die data wys op die moontlik teenwoordigheid van 'n planeet nabyaan die bron wat ons ondersoek.

La présente thèse porte sur quatre aspects différents de l’astronomie des hautes énergies.La première partie de ma thèse est dédiée à un développement instrumental pour les télescopes Cherenkov imageurs, le système de déclenchement de niveau 2 du télescope de 28 mètres du réseau H.E.S.S. (High Energy Stereoscopic System). Mon travail s’est focalisé sur l’invention d’algorithmes et les simulations Monte-Carlo du système de déclenchement, ainsi que la comparaison de la reconstruction au niveau de la carte de déclenchement à la reconstruction ”hors-ligne” (Moudden,Barnacka, Glicenstein et al. 2011a; Moudden, Venault, Barnacka et al. 2011b). Je décris le système et j’évalue ses performances.Le réseau H.E.S.S. a observé le blazar PKS1510-089. La deuxième partie de ma thèse traite de l’analyse des données et la modélisation de l’émission large bande de ce blazar. C’est un exemple de quasar radio à spectre plat (FSRQ), pour lequel il n’est attendu aucune émission aux très hautes énergiesJ’ai modélisé les données observées pendant un "flare” de PKS1510-089. Ce modèle est basé sur un scénario de choc interne à une zone.Le troisième chapitre de ma thèse est une étude d’un autre phénomène affectant potentiellement les blazars observés par FERMI-LAT: l’effet de lentille gravitationnelle fort. Cette partie de ma thèse montre le premier indice de présence d’un effet de lentille gravitationnelle dans le domaine des photons de haute énergie. Cet indice provient de l’observation d’un écho dans la courbe de lumière du blazar distant PKS1830-211, qui est une lentille gravitationnelle connue. Les méthodes d’estimation des retards temporels dans les systèmes de lentille gravitationnelles reposent sur la corrélation croisée des courbes de lumière individuelles. Dans l’analyse présentée dans cette thèse, j’ai utilisé des photons de 300 MeV à 30 GeV détectés par l’instrument FERMI-LAT. L’instrument FERMI-LAT ne peut pas séparer spatialement les images des lentilles gravitationnelles fortes connues. La courbe de lumière observée est donc la superposition des courbes de lumière des images individuelles. Les données du FERMI-LAT ont l’avantage d’être des séries temporelles régulièrement espacées,avec un bruit de photons très bas. Cela permet d’utiliser directement les méthodes de transformées de Fourier. Un retard temporel entre les images compactes de PKS1830-211 a été recherché par deux méthodes : une méthode d’auto-corrélation et la méthode du ”double spectre”. La méthode du double spectre fournit un signal de 27 ± 0.6jours (statistique) avec une significativité de 4.2 σ. Ce résultat est compatible avec ceux de Lovell et al (1998) et Wiklind et Combes (2001).La dernière partie de ma thèse est consacrée à un effet de lentille différent, le ”femtolensing”. La recherche d’effets de femtolensing a été utlisée pour obtenir des limites sur l’abondance de trous noirs primordiaux. Celle-ci a été contrainte de manière significative dans un large domaine de masses. Les limites les moins contraignantes ont été établies pour les objets de faible masse, pour lesquels la détection représente un défi expérimental. J’ai utilisé les sursauts gamma de redshift connus d´etectés par le Fermi Gamma Ray Burst Monitor (GBM) pour rechercher d’éventuels effets de femtolensing produits par des objets compacts sur la ligne de visée. L’absence de ces effets de femtolensing montre que des trous noirs primordiaux de masse comprises entre 5×10^17 et 10^20 g ne constituent pas une fraction importante de la matière noire. J’ai effectué mes études de thèse en co-tutelle entre le Centre Astronomique Nicolaus Copernicus de l’académie des sciences polonaise, à Varsovie et l’Institut de Recherches sur les Lois fondamentales de l’Univers du CNRS à Saclay, en France. / This thesis presents the study of four aspects of high energy astronomy.The first part of my thesis is dedicated to an aspect of instrument development for imaging atmospheric Cherenkov telescopes, namely the Level 2 trigger system of the High Energy Stereoscopic System (H.E.S.S.). My work on the project focused on the algorithm development and the Monte Carlo simulations of the trigger system and overall instrument (Moudden, Barnacka, Glicenstein et al. 2011a; Moudden, Venault, Barnacka et al. 2011b). The hardware implementation of the system is described andits expected performances are then evaluated. The H.E.S.S. array has been used to observe the blazar PKS 1510-089.The second part of my thesis deals with the data analysis and modeling of broad-band emission of this particular blazar. In part II of my thesis, I am presenting the analysis of the H.E.S.S. data: the light curve and spectrum of PKS 1510-089, together with the FERMI data and a collection of multi-wavelength data obtained with various instruments. I am presenting the model of PKS 1510-089 observations carried out during a flare recorded by H.E.S.S.. The model is based on a single zone internal shock scenario.The third part of my thesis deals with blazars observed by the FERMI-LAT, but from the point of view of other phenomena: a strong gravitational lensing. This part of my thesis shows the first evidence for gravitational lensing phenomena in high energy gamma-rays. This evidence comes from the observation of a gravitational lens system induced echo in the light curve of the distant blazar PKS 1830-211. Traditionalmethods for the estimation of time delays in gravitational lensing systems rely on the cross-correlation of the light curves from individual images. In my thesis, I used 300 MeV-30 GeV photons detected by the Fermi-LAT instrument. The FERMI-LAT instrument cannot separate the images of known lenses. The observed light curve is thus the superposition of individual image light curves. The FERMI-LAT instrument has the advantage of providing long, evenly spaced, time series with very low photonnoise. This allows to use directly Fourier transform methods. A time delay between the two compact images of PKS 1830-211 has been searchedfor both by the autocorrelation method and a new method: the “double power spectrum”. The double power spectrum shows a 4.2 σ evidence for a time delay of 27.1±0.6 days (Barnacka et al. 2011), consistent with the results from Lovell et al. (1998) and Wiklind & Combes (2001).The last part of my thesis concentrates on another lensing phenomena called ”femtolensing”. The search for femtolensing effects has been used to derive limits on the primordial black holes abundance. The abundance of primordial black holes is currently significantly constrained in a wide range of masses. The weakest limits are established for the small mass objects, where the small intensity of the associated physical phenomenon provides a challenge for current experiments. I have usedgamma-ray bursts with known redshifts detected by the FERMI Gamma-ray Burst Monitor (GBM) to search for the femtolensing effects caused by compact objects. The lack of femtolensing detection in the GBM data provides new evidence that primordial black holes in the mass range 5 × 10^17 – 10^20 g do not constitute a major fraction of dark matter (Barnacka et al. 2012). My Ph.D. studies have been carried out jointly between the Nicolaus Copernicus Astronomical Center of the Polish Academy of Sciences, in Warsaw in Poland and the IRFU institute of the Commissariat à l’énergie atomique et aux énergies alternatives(CEA) Saclay in France.

The principal observational contribution of this thesis is an innovative technique, using spatially resolved spectroscopy of highly magnified, gravitationally lensed galaxies, to study their internal structure and kinematics at redshift, z≥1 on sub-galactic scales. The scientific objective is to measure the important, but poorly understood, role of star formation and associated feedback on galaxy evolution. With Gemini GMOS-IFU observations of CFRS03+1077, a lensed galaxy at z=2.94, we determined surface brightness and integration time requirements for spatially resolved kinematics with spectra in the visible region (< 1 micron). For reasonable exposure times the presence of a strong emission line is key, limiting the redshift range to < 1.5 for [OII]3727Å. To tackle the lack of suitable lenses for such studies, we designed a lens search algorithm suitable for multi-color photometric data (with a minimum of 2 colors). Our method uses a two-step approach, first automatically identifying galaxy clusters and groups as high likelihood lensing regions, followed by a dedicated visual search for lensed arcs in pseudo-color images of sub-regions centered on these candidates. By using the color-position clustering of elliptical galaxies in high density environments, the algorithm efficiently isolates candidates with a completeness ≥ 80% for z ≤ 0.6 in Monte-Carlo simulations. Implemented on the CFHT Legacy Survey-Wide fields with available g, r and i photometry, the present yield is 9 lenses (8 new and 1 previously known) from 104 deg². With Gemini GMOS, we confirmed two lensed galaxies with strong [OII]3727Å emission suitable for IFU spectroscopy. The follow-up of both systems, the confirmation of remaining lenses and the application of the lens detector to the remaining 91 square degrees of CFHTLS-Wide are ongoing. In a complementary project, we aim to understand non-linear structure formation within the Λ-CDM framework by characterizing the mass distributions and mass/light ratios of galaxy groups; these structures (where 60% of all galaxies reside), have masses representative of the critical break between cluster and field galaxy mass scales. We use strong gravitational lensing to constrain the mass in the inner core, with velocity dispersion measurements from MOS spectroscopy to map the mass distribution up to the scale of the virial radius. The formalism supporting this approach as well as the tools for analysis (including an efficient B-spline based method for flat fielding and sky subtraction of sky limited spectra) are presented in this thesis. The deflectors of 6 lenses in our catalog resemble galaxy groups suitable for this study. One group, for which the observations are complete, is compatible with either NFW or Hernquist profile; these results will be corroborated with observations of other candidates in forthcoming observing programs. The objective is to amalgamate our results with mass measurements from weak lensing and X-ray observations from our Strong Lensing Legacy Survey (SL2S) collaborators to build a comprehensive picture of the dark matter profile and thus constrain theoretical predictions of mass assembly in galaxy groups.

Quasar microlensing is a relatively newly explored phenomenon, which is ideally suited for studying the spatial distribution of emission from the innermost accretion disc. By now we know many macrolensed quasars, in which we can observe multiple images formed by the deflection of light in the gravitational field of an intervening galaxy. In case one of these images passes directly through the stellar population of the galaxy, it can be additionally microlensed by individual stars. The gravitational field of these stars forms a caustic network for light passing by. When a quasar accretion disc crosses behind this network, induced changes can be observed in the light curve as well as in the spectrum. In the first part of this thesis we study the statistics of the time intervals between successive caustic crossings. In the second part we use a fully relativistic Kerr-metric thin-disc model for studying the light curve of a fold-caustic crossing and its dependence on the accretion- disc parameters. In the last part we simulate changes in the X-ray iron-line profile during a fold-caustic crossing. We find characteristic spectral features formed on the line, and derive their analytical description. Finally, we map the maximum strength of microlensing-generated peaks on the spectral line for different...

Despite the many successes of the current standard model of cosmology on the largest physical scales, it relies on two phenomenologically motivated constituents, cold dark matter and dark energy, which account for approximately 95% of the energy-matter content of the universe. From a more fundamental point of view, however, the introduction of a dark energy (DE) component is theoretically challenging and extremely fine-tuned, despite the many proposals for its dynamics. On the other hand, the concept of cold dark matter (CDM) also suffers from several issues such as the lack of direct experimental detection, the question of its cosmological abundance and problems related to the formation of structure on small scales. A perhaps more natural solution might be that the gravitational interaction genuinely differs from that of general relativity, which expresses itself as either one or even both of the above dark components. Here we consider different possibilities on how to constrain hypothetical modifications to the gravitational sector, focusing on the subset of tensor-vector-scalar (TeVeS) theory as an alternative to CDM on galactic scales and a particular class of chameleon models which aim at explaining the coincidences of DE. Developing an analytic model for nonspherical lenses, we begin our analysis with testing TeVeS against observations of multiple-image systems. We then approach the role of low-density objects such as cosmic filaments in this framework and discuss potentially observable signatures. Along these lines, we also consider the possibility of massive neutrinos in TeVeS theory and outline a general approach for constraining this hypothesis with the help of cluster lenses. This approach is then demonstrated using the cluster lens A2390 with its remarkable straight arc. Presenting a general framework to explore the nonlinear clustering of density perturbations in coupled scalar field models, we then consider a particular chameleon model and highlight the possibility of measurable effects on intermediate scales, i.e. those relevant for galaxy clusters. Finally, we discuss the prospects of applying similar methods in the context of TeVeS and present an ansatz which allows to cast the linear perturbation equations into a more convenient form.

Made available in DSpace on 2014-12-17T15:15:03Z (GMT). No. of bitstreams: 1 RoseCS.pdf: 2067725 bytes, checksum: e198ed9a88482d8df2676d67728edee7 (MD5) Previous issue date: 2007-05-23 / Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior / The recent observational advances of Astronomy and a more consistent theoretical framework turned Cosmology in one of the most exciting frontiers of contemporary science. In this thesis, homogeneous and inhomogeneous Universe models containing dark matter and different kinds of dark energy are confronted with recent observational data. Initially, we analyze constraints from the existence of old high redshift objects, Supernovas type Ia and the gas mass fraction of galaxy clusters for 2 distinct classes of homogeneous and isotropic models: decaying vacuum and X(z)CDM cosmologies. By considering the quasar APM 08279+5255 at z = 3.91 with age between 2-3 Gyr, we obtain 0,2 < OM < 0,4 while for the j3 parameter which quantifies the contribution of A( t) is restricted to the intervalO, 07 < j3 < 0,32 thereby implying that the minimal age of the Universe amounts to 13.4 Gyr. A lower limit to the quasar formation redshift (zJ > 5,11) was also obtained. Our analyzes including flat, closed and hyperbolic models show that there is no an age crisis for this kind of decaying A( t) scenario. Tests from SN e Ia and gas mass fraction data were realized for flat X(z)CDM models. For an equation of state, ?J(z) = ?Jo + ?JIZ, the best fit is ?Jo = -1,25, ?Jl = 1,3 and OM = 0,26, whereas for models with ?J(z) = ?Jo+?Jlz/(l+z), we obtain?Jo = -1,4, ?Jl = 2,57 and OM = 0,26. In another line of development, we have discussed the influence of the observed inhomogeneities by considering the Zeldovich-Kantowski-DyerRoeder (ZKDR) angular diameter distance. By applying the statistical X2 method to a sample of angular diameter for compact radio sources, the best fit to the cosmological parameters for XCDM models are OM = O, 26,?J = -1,03 and a = 0,9, where ?J and a are the equation of state and the smoothness parameters, respectively. Such results are compatible with a phantom energy component (?J < -1). The possible bidimensional spaces associated to the plane (a , OM) were restricted by using data from SNe Ia and gas mass fraction of galaxy clusters. For Supernovas the parameters are restricted to the interval 0,32 < OM < 0,5(20") and 0,32 < a < 1,0(20"), while to the gas mass fraction we find 0,18 < OM < 0,32(20") with alI alIowed values of a. For a joint analysis involving Supernovas and gas mass fraction data we obtained 0,18 < OM < 0,38(20"). In general grounds, the present study suggests that the influence of the cosmological inhomogeneities in the matter distribution need to be considered with more detail in the analyses of the observational tests. Further, the analytical treatment based on the ZKDR distance may give non-negligible corrections to the so-calIed background tests of FRW type cosmologies / Os recentes avan?os observacionais da Astronomia e um arcabou?o te?rico cada vez mais consistente, transformaram a Cosmologia numa das mais excitantes ?reas da ci?ncia contempor?nea. Nesta tese, modelos homog?neos e inomog?neos contendo mat?ria escura e diferentes tipos de energia escura s?o confrontados com dados observacionais recentes. Inicialmente, analisamos os v?nculos oriundos da exist?ncia de objetos velhos em altos redshifts, Supernovas do tipo Ia e fra??o de massa do g?s em aglomerados de gal?xias para 2 classes distintas de modelos homog?neos: decaimento do v?cuo e X(z)CDM. Considerando o quasar APM 08279 + 5255, em z = 3, 91 e idade entre 2 - 3 bilh?es de anos, obtemos 0,2 < &#937;M < 0,4 enquanto o par?metro (3, quantificando a contribui??o de A(t), est? restrito ao intervalo 0,07 < &#946; < 0,32; implicando numa idade m?nima para o universo de 13,4 bilh?es de anos. Um limite inferior para o redshift de forma??o do quasar (zf > 5,11) foi tamb?m obtido. Nossas an?lises, incluindo modelos planos, fechados e hiperb?licos, mostram que n?o existe uma crise de idade para esses cen?rios com A(t). Os testes com dados de SNe Ia e fra??o de massa do g?s foram realizados com modelos do tipo X(z)CDM plano. Para uma equa??o de estado, w(z) = Wo+WIZ, obtemos como melhor ajuste Wo = -1,25, WI = 1,3 e &#937;M = 0,26, enquanto nos models com w(z) = wo+wlz/(l+z), o melhor ajuste ? Wo = -1,4, WI = 2,57 e OM = 0,26. Em outra linha de desenvolvimento, discutimos as influ?ncias das inomogeneidades observadas considerando a dist?ncia de di?metro angular proposta por Zeldovich-Kantowski-Dyer-Roeder (ZKDR). Aplicando o m?todo estat?stico X2 para uma amostra de dados de di?metros angulares de fontes de r?dio compactas, o melhor ajuste para os par?metros cosmol?gicos nos modelos XCDM foram 11M = 0,26, ?) = -1,03 e a = 0,9, onde ?) e a s?o os par?metros da equa??o de estado e de aglomeramento, respectivamente. Esses resultados s?o compat?veis com uma componente do tipo energia fantasma (phantom energy, ?) < -1). Os poss?veis espa?os bidimensionais associados ao plano (a , 11M) foram tamb?m restritos utilizando dados de SN e Ia e fra??o de massa do g?s em aglomerados de gal?xias. No teste de Supernovas os par?metros de interesse est?o restritos aos intervalos 0,32 < 11M < 0,5(20') e 0,32 < a < 1,0(20'), enquanto para fra??o de massa do g?s temos 0,18 < 11M < 0,32(20') e todos os valores de a s?o permitidos. Na an?lise conjunta envolvendo supernovas e fra??o de massa do g?s foi obtido 0,18 < 11M < 0,38(20'). Em linhas gerais, o presente estudo sugere que a influ?ncia das inomogeneidades cosmol?gicas na distribui??o de mat?ria precisam ser consideradas com mais detalhe ao se analisar os testes cosmol?gicos. Al?m disso, o tratamento anal?tico baseado na dist?ncia ZKDR pode fornecer corre??es importantes para os chamados testes de background em cosmologias do tipo FRW