Reproduction de : Thèse de doctorat : Astrophysique : Toulouse 3 : 2007. / Titre provenant de l'écran-titre. Bibliogr. à la fin des chapitres.

Not available / text

Thesis (Ph. D.)--University of Hawaii at Manoa, 2004. / Includes bibliographical references. / Also available by subscription via World Wide Web / xxxiii, 335 leaves, bound ill. 29 cm

Thesis (Ph.D.)--McMaster University (Canada), 1988. / Source: Dissertation Abstracts International, Volume: 49-08, Section: B, page: 3250.

Thesis (Ph.D.) - Universidad de Valencia, 1999. / Introductory pages in Spanish. Thesis is in English. Includes subject index, pages 177 - 178.

Thesis (Ph. D.)--University of Wisconsin--Madison, 1975. / Typescript. Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references.

Thesis (Ph. D.)--University of Hawaii at Manoa, 2004. / Includes bibliographical references.

Thesis (Ph. D.)--University of Texas at Austin, 2006. / Vita. Includes bibliographical references.

abstract: 3D models of white dwarf collisions are used to assess the likelihood of double-degenerate mergers as progenitors for Type Ia supernovae (henceforth SNIa) and to identify observational signatures of double-degenerate collisions. Observations of individual SNIa, SNIa rates in different galaxy types, and double white dwarf binary systems suggest that mergers or collisions between two white dwarfs play a role in the overall SNIa population. Given the possibility of two progenitor systems (single-degenerate and double-degenerate), the sample of SNIa used in cosmological calcula- tions needs to be carefully examined. To improve calculations of cosmological parameters, the development of calibrated diagnostics for double-degenerate progenitor SNIa is essential. Head-on white dwarf collision simulations are used to provide an upper limit on the Ni-56 production in white dwarf collisions. In chapter II, I explore zero impact parameter collisions of white dwarfs using the Eulerian grid code FLASH. The initial 1D white dwarf profiles are created assuming hydrostatic equilibrium and a uniform composition of 50% C-12 and 50% O-16. The masses range from 0.64 to 0.81 solar masses and have an isothermal temperature of 10^7 K. I map these 1D models onto a 3D grid, where the dimensions of the grid are each eight times the white dwarf radius, and the dwarfs are initially placed four white dwarf radii apart (center to center). To provide insight into a larger range of physical possibilities, I also model non-zero impact parameter white dwarf collisions (Chapter III). Although head-on white dwarf collisions provide an upper limit on Ni-56 production, non-zero impact parameter collisions provide insight into a wider range of physical scenarios. The initial conditions (box size, initial separation, composition, and initial temperature) are identical to those used for the head-on collisions (Chapter II) for the same range of masses. For each mass pair- ing, collision simulations are carried out at impact parameters b=1 and b=2 (grazing). Finally, I will address future work to be performed (Chapter IV). / Dissertation/Thesis / Ph.D. Astrophysics 2012

Visando aprimorar as medidas de distâncias cosmológicas feitas com a observação de supernovas de tipo Ia (SNIas), nós realizamos dois estudos: primeiro, verificamos as relações entre as propriedades das SNIas e de seus ambientes; segundo, avaliamos os dados de supernovas que poderiam ser obtidos com um mapeamento (survey) fotométrico do céu em filtros de banda estreita. Na primeira parte deste trabalho, nós utilizamos dados do Sloan Digital Sky Survey para confirmar as relações publicadas na literatura entre as propriedades das SNIas e a taxa de formação estelar de suas galáxias hospedeiras: SNIas em galáxias passivas tendem a ser mais breves, mais luminosas após correções, e sua cor influencia menos a sua magnitude quando comparadas a SNIas em galáxias ativas. Nós então analisamos SNIas em aglomerados ricos de galáxias e concluímos que elas são ainda mais breves do que a SNIa média em galáxias passivas. Essa característica está relacionada com a idade mais alta das galáxias passivas em ambientes densos e com a preferência dessas galáxias em hospedar SNIas bastante breves. As demais características das SNIas foram consideradas compatíveis com SNIas de campo dentro da precisão alcançada. Esse tipo de estudo deve impactar a determinação de distâncias uma vez que, em diversos casos, SNIas em redshifts diferentes habitam ambientes diferentes. O segundo tema desta tese trata de estudar as características de um novo método fotométrico aplicado às supernovas: o imageamento em filtros de banda estreita. Utilizando simulações de fotometria e tomando como base o projeto Javalambre Physics of the accelerating universe Astrophysical Survey (J-PAS), mostramos que um mapeamento realista em filtros de banda estreita é capaz de produzir amostras massivas de SNIas em redshifts intermediários (0 < z < 0;5) com baixa contaminação (3% ou menos), com um redshift fotométrico altamente preciso (sz =0;005) e com boa precisão na parametrização de suas curvas de luz. Além disso, filtros de banda estreita são capazes de resolver quase todas as características espectrais das supernovas. Junto com a rica informação que esse mapeamento pode prover sobre as galáxias observadas, esse tipo de projeto deve trazer contribuições significativas para o melhor entendimento das supernovas e das relações com seus ambientes. / Aiming at improvements in cosmological distance measurements performed with type Ia supernovae (SNe Ia) observations, we carried out two studies: first, we analyzed the relationships between the properties of SNe Ia and those of their environments; second, we assessed what kind of SNe data could be attained by a photometric survey using narrowband filters. In the first part of this work we used data from the Sloan Digital Sky Survey to confirm previously reported relations between SNe Ia properties and their hosts star formation rate: SNe Ia in passive galaxies tend to be briefer, more luminous after corrections and their colors do not impact their magnitudes as much when compared to SNe Ia in active galaxies. We then analyzed the properties of SNe Ia inside rich galaxy clusters and concluded that they are even briefer than the average SNe Ia in passive galaxies. This characteristic is related to the older age of passive galaxies in dense regions and their preference for hosting very brief SNe Ia. Other properties of these SNe Ia were considered compatible under the precision attained. This kind of study may influence distance determinations since, in many cases, SNe Ia at different redshifts populate different environments. On the second part of this work we studied the characteristics of a new photometric method applied to supernovae: the narrowband filter imaging of the sky. Using photometry simulations and taking the Javalambre Physics of the accelerating universe Astrophysical Survey (J-PAS) project as our fiducial survey, we showed that a realistic narrowband survey is capable of producing massive SNe Ia samples at intermediate redshifts (0 < z < 0;5) with low contamination rate (3% or less), a highly precise photometric redshift (sz = 0;005) and a good precision on their light curve parametrization. Moreover, narrowband filters are able to resolve almost every supernova spectral feature. Together with the rich galaxy information this kind of survey can provide, it should present significant contributions to the better understanding of supernovae and their relationships with their environments.