Thermonuclear (Type Ia) supernovae are excellent distance indicators, due to their uniform peak brightness. They are also important contributors to the chemical evolution of galaxies since their explosions supply large amounts of iron peak elements to the interstellar medium. However, there is no consensus on the progenitor systems of these supernovae. As a result, different delay times from the formation of the binary system to the supernova have been proposed. Whether the observed rate of supernova Type Ia in early-type galaxies supports a progenitor channel with one or two degenerate objects has been disputed. While the predominant old population found in early-type galaxies supports longer delay times, the presence of recent star formation might indicate the opposite. In this work, we employ a double-burst model to account for the relative contribution of both populations. We show that for a DTD ∝ t^−1, convolved with star formation histories that are relevant for early-type galaxies, the supernova rate is independent of a host galaxy’s colour. Our results indicate that a DTD with no cutoff is preferred, thus favoring the double-degenerate scenario. / Graduate

Dans la décennie précédente les supernovae se sont imposées comme une des sondes les plus puissantes pour reconstruire l'histoire globale de l'Univers. Cependant la standardisation des supernovae de type Ia est toujours une relation empirique. De futures expériences, tel que JDEM, sont prévues pour apporter une meilleure caractérisation de l'équation d'état de l'énergie noire responsable de l'accélération de l'Univers. Ces expériences nécessiterons un contrôle des erreurs systématiques pour assurer aux conclusions futures de n'être pas dominées par des effets non liés à la cosmologie. L'évolution des supernovae avec le redshift ou la présence de sous-classes parmi elles peuvent être à l'origine de ce type de systématiques. Ainsi une meilleure compréhension des propriétés des supernovae et de leur environnement pourrait apporter, une meilleure compréhension de leur standardisation, finalement une meilleure description des supernovae en tant qu'objets astrophysiques. Cette étude apporte également des informations traitant de la simulation de missions spatiales telles que JDEM / Over the past decade supernovae have emerged as one of the most powerful tools for reconstructing the global history of the Universe. However type Ia supernovae are still empirical tools. Future experiments, as JDEM, are planned to better characterize the equation of state of the dark energy leading to the observed acceleration thousands of objects. These experiments will need to carefully control systematic errors to ensure future conclusions are not dominated by effects unrelated to cosmology. The evolution of N Ia with redshift or the presence of subclasses among them can be at the origin of that kind os systematics. So a better understanding of the properties of supernovae in their host galaxies could provide information about the correlation between supernovae and their environment, a better understanding of their standardization, finally a better description of supernovae as astrophisical object. this study can also provide informations for more realistic simultations of a space mission like JDEM

While the progenitors of Type Ia supernovae (SNe Ia) have long been thought to be thermonuclear explosions of white dwarf stars, what triggers the explosion are still a topic of debate. This thesis considers constraints on single-degenerate progenitors of SNe Ia based on the presence of a Roche-lobe filling companion. The ejecta strips material from the companion, that maybe detectable via Hα emission during the nebular phase. Using the full structure from simulations produces line widths are larger than those produced in simple models. The structure formed by the ejecta-companion interaction produce a broken reverse shock that may be visible in X-rays via the Fe K&alpha; line at the age of Tycho's supernova remnant (SNR). If the similar structures in Tycho’s SNR are produced this way then the companion star must have been massive, with M ~ 2 M_&odot;. Detections of circumstellar material within the supernova provides another way to indirectly probe the companion star. Mass loss through winds or novae are expected to shape the circumsteller medium for single-degenerate progenitors and the velocities, v ~ 100 km s^-1 appear to be consistent with recurrent nova shells, a model that is tested by analysing simulations of RS Ophiuchi. Models of RS Ophiuchi can explain the absorption lines seen around the 2006 outburst if the mass loss is 10⁻⁶ M_&odot; yr<sup>-1,/sup>. The circumsteller medium is shown to produce in the velocity and relative strengths of the features seen in SN 2006X. However, whether density in the shells is high enough to produce the required recombination timescale and to overcome ionization by &gamma;-rays for shells at 5 × 10¹⁶ cm remains uncertain.

Modern problems in astrophysics tend to require large, complex computational frameworks to solve many aspects of the system simultaneusly. Calculation of the energy production through nuclear reactions is typically one of those aspects. The use of standard nuclear burning algorithms will take up the majority of the computational time with all but the smallest of networks. The explicit asymptotic method has shown promise in computing large networks faster than existing methods in various environments while retaining accuracy. The purpose of this thesis is to show that this method can be successfully used to solve complex systems using a network of realistic size in a reasonable amount of time, and to investigate some problems in the flame propagation for a Type Ia, which have never been investigated with a realistic network.

In the standard model of cosmology, the universe is currently dominated by dark energy in the form of the cosmological constant that drives the expansion to accelerate. While the cosmological constant hypothesis is consistent with all current data, models with dynamical behaviour of dark energy are still allowed by observations. Uncertainty also remains over whether the underlying assumption of a homogeneous and isotropic universe is valid, or if large-scale inhomogeneities in the matter distribution can be the cause of the apparent late-time acceleration.This thesis investigates inhomogeneous cosmological models in which dark energy clusters or where we live inside an underdense region in a matter-dominated universe. In both of these scenarios, we expect directional dependences in the redshift-luminosity distance relation of type Ia supernovae. Dynamical models of dark energy predict spatial variations in the dark energy density. Searches for angular correlated fluctuations in the supernova peak magnitudes, as expected if dark energy clusters, yield results consistent with no dark energy fluctuations. However, the current observational limits on the amount of correlation still allow for quite general dark energy clustering occurring in the linear regime. Inhomogeneous models where we live inside a large, local void in the matter density can possibly explain the apparent acceleration without invoking dark energy. This scenario is confronted with current cosmological distance measurements to put constraints on the size and depth of the void, as well as on our position within it. The model is found to explain the observations only if the void size is of the order of the visible universe and the observer is located very close to the center, in violation of the Copernican principle. / At the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 4: Accepted.

Modern problems in astrophysics tend to require large, complex computational frameworks to solve many aspects of the system simultaneusly. Calculation of the energy production through nuclear reactions is typically one of those aspects. The use of standard nuclear burning algorithms will take up the majority of the computational time with all but the smallest of networks. The explicit asymptotic method has shown promise in computing large networks faster than existing methods in various environments while retaining accuracy. The purpose of this thesis is to show that this method can be successfully used to solve complex systems using a network of realistic size in a reasonable amount of time, and to investigate some problems in the flame propagation for a Type Ia, which have never been investigated with a realistic network.

Studying how SN Ia rates (SNR) correlate with host galaxy properties is an important step in understanding the exact nature of SN Ia. Taking a sample of SNe and galaxies from the SDSS, we obtain the optimum parameter values for the A+B model for SNR, which states that SNR scale linearly with mass and star formation rate of the host, and compare them with previous work. We then proceed to show that the A+B model deviates very significantly from the SNR behaviour in our sample, demonstrate that no reasonable values for A and B could possibly match the observations, and investigate the possibility of a third-parameter correction to the generic A+B model. We find that several hypothesised models seem to match the distribution of SNRs in our sample; however, discriminating between them is a difficult task. We interpret the above to be an indicator that a new parameter may need to be taken into account when modelling SNR, and we present metallicity as a possible candidate for the new parameter. Also, by investigating decomposed bulge + disk components of the host galaxies, we find that the spatial positions of SNe Ia are correlated with bulge luminosity, but not with galaxy total luminosity or disk luminosity. It is also shown that SNe do not preferentially occur in bulge-dominated galaxies. Our interpretation of these results is that SNe arise from a population having a spatial distribution which correlates very well with bulge luminosity, but does not usually contribute to bulge luminosity. / Graduate

Vers la fin des années 1990, l’utilisation des supernovae de type Ia (SNe Ia) comme indicateurs de distance a permis de mettre en évidence l’expansion accélérée de l’univers. Depuis lors, des campagnes d’observations de grandes envergures ont permis d’augmenter de façon significative le nombre de SNe Ia observées, mais les incertitudes systématiques liées à la qualité des échantillons de SNe Ia proches restent un facteur limitant sur la précision des mesures actuelles. C’est dans le but de réduire ces incertitudes que le projet the Nearby Supernova Factory (SNfactory), à l’aide d’un instrument spectro-photométrique dédié à l’observation des SNe Ia (the Supernova Integral Field Spectrograph), a collecté depuis 2004 plus de 3000 spectres de près de 200 SNe Ia proches. Une des limitations actuelles de leur utilisation, outre les aspects liés aux problèmes d’inter-calibration entre les différentes expériences, est celle du mélange des différentes composantes de leurs variabilités lors de la standardisation empirique de leur module de distance. Une meilleure séparation de ces composantes, ainsi que la découverte de nouveaux indicateurs de distance, font partie des améliorations que peut apporter un échantillon spectral de SNe Ia proches tel que celui de la collaboration SNfactory. Cette thèse de doctorat, effectuée à l’Institut de Physique Nucléaire de Lyon et au Lawrence Berkeley National Laboratory, s’inscrit directement dans cette problématique, en se concentrant sur la mesure d’indicateurs spectraux sur l’échantillon spectral de la collaboration Snfactory. Le plan de cette thèse est le suivant : La première partie présente le contexte scientifique ainsi que l’échantillon de SNe Ia de la collaboration SNfactory utilisé dans les analyses. La deuxième partie se concentre sur la méthode de mesure d’indicateurs spectraux appliquée à l’échantillon spectrale présenté, ainsi que sur une étude de leur sensibilité à l’extinction par le milieu interstellaire. La troisième partie est une étude des corrélations des indicateurs spectraux et de leur utilisation pour la standardisation des Sne Ia. Dans la dernière partie, une utilisation de ces indicateurs spectraux pour la détermination d’une loi d’extinction moyenne est présentée / One of the current limitations of type Ia supernovae used as distance indicators is themixing of their different sources of variabilitiy during the empirical standardization of their distance modulus. Using the nearby SNe Ia spectral sample observed by the Nearby Supernovae Collaboration with the instrument SNIFS (Supernovae Intergral Field Sperctrograph), this thesis mainly focuses on this problematic using spectral indicators measurements. The first part of the thesis presents the scientific context as well as the sample used in the analysis. The second part focus on the spectral indicators measurement and their properties in the presence of interstellar dust extinction. The third part is a study of spectral indicators correlations and their use as standardization parameters. In the last part, we use these spectral indicators to construct a mean extinction law for type Ia supernovae

Les supernovae de type Ia (SNe Ia) sont de puissants indicateurs de distance cosmologique. Elles sont à l'origine de la découverte de l'énergie noire dans l'univers et restent aujourd'hui la meilleure méthode pour contraindre son équation d'état. Cependant, nous ignorons toujours le phénomène exact donnant naissance à ces supernovae. Notamment, nous ne connaissons pas l'influence de l'évolution des paramètres stellaires avec le redshift sur la luminosité de ces objets et donc sur les ajustements cosmologiques. De récentes études ont mis en évidence évidence des biais environnementaux ayant un impact significatif sur les mesures des paramètres cosmologiques. Cependant, ces études analysent les hôtes des SNe Ia dans leur globalité en négligeant les variations pourtant connues des propriétés stellaires et gazeuses au sein de ces galaxies. ! Dans cette thèse je montre comment les données de spectrographie à champ intégral de la collaboration The Nearby Supernova Factory permettent l'étude de l'environnement immédiat (~kpc) de la SNe Ia. Dans une première partie, j'introduis les bases physiques et le contexte scientifique dans lesquels ma thèse s'inscrit. Dans la seconde partie, je commence par détailler les techniques d'extraction des données environnementales locales et, une fois ces données extraites, je développe la mesure du taux de formation stellaire environnant les SNe Ia à partir du signal Hα. Dans mon analyse, je montre comment les propriétés des SNe Ia, et notamment leur luminosité standardisée, dépendent de la présence de formation stellaire à proximité. Ce biais, duquel découlent les biais environnementaux précédemment évoqués, a un impact significatif sur la cosmologie. En se basant sur les évolutions des propriétés stellaires des galaxies, je construit un modèle d'évolution de la luminosité moyenne des SNe Ia en fonction du redshift pour estimer cet impact; les données de la littérature semblent confirmer mes hypothèses. Ces résultats ont été publiés dans le journal européen Astronomy & Astrophysics (Rigault et al. 2013). Dans une troisième partie, je présente des analyses supplémentaires sur l'environnement local des SNe Ia et je suggère de nouvelles approches. ! Cette thèse a mis en évidence un biais environnemental important sur les propriétés des SNe Ia que seule l'analyse locale permet d'aborder. Cette découverte est une étape importante dans la compréhension de ces objets et dans l'amélioration de leur utilisation cosmologique / Type Ia supernovae (SNe Ia) are powerful cosmological distance indicators. They were key tools for the discovery of the accelerating expansion of the Universe and today they remain the strongest demonstrated technique for measuring the dark-energy equation of state. However, a major issue remains: despite decades of study, their progenitors are as yet undetermined. Notably, we still ignore the influence of the redshift-evolution of stellar properties on the absolute luminosity of the SNe Ia and therefore on the fitted cosmological parameters. Recent studies have highlighted potential biases correlated with the global properties of their host galaxies, large enough to induce systematic errors into cosmological measurements if not properly treated. However, those studies analyse hosts of Type Ia supernovae globally thus neglecting the known stellar and gas property variations across galaxies. ! In this thesis, I show how integral field spectroscopy data from the Nearby Supernova Factory allow the study of the local environment of the SNe Ia (~kpc). In the first part of this document, I introduce the physical principals and the scientific context of this work. In a second part, I start by detailing the technical extraction tools developed in order to extract the local host properties. Then, I show how one could measure the star formation activity in the SN vicinity from those data. I focus the analysis on this star formation activity and notably I show how the SNe Ia properties -- particularly their standardised Hubble residuals -- depend on the local host environment, which corresponds to a significant cosmological bias. I finish this second part by introducing a simple model based on the known evolution of the galactic star formation activity. This model enables me to estimate the potential influence of the aforementioned environmental bias on cosmology. I also show that this model can be tested using public data and a first analyses tend to confirm our hypotheses. Those results have been published in Astronomy & Astrophysics (Rigault et al. 2013). The third and last part of the document introduces new approaches and future work perspectives. ! In this thesis, I have highlighted significant environmental biases in SNe Ia properties, thanks to the local approach. However, those biases are less an issue for the cosmological analyses using Type Ia supernovae than a new opportunity to improve them as cosmological probes. ! This Document is written in French. The figures are in English

<p>Type Ia supernovae can be used as distance indicators for probing the expansion history of the Universe. The method has proved to be an efficient tool in cosmology and played a decisive role in the discovery of a yet unknown energy form, dark energy, that drives the accelerated expansion of the Universe. The work in this thesis addresses the nature of dark energy, both by presenting existing data, and by predicting opportunities and difficulties related to possible future data.</p><p>Optical and infrared measurements of type Ia supernovae for different epochs in the cosmic expansion history are presented along with a discussion of the systematic errors. The data have been obtained with several instruments, and an optimal method for measuring the lightcurve of a background contaminated source has been used. The procedure was also tested by applying it on simulated images.</p><p>The future of supernova cosmology, and the target precision of cosmological parameters for the proposed SNAP satellite are discussed. In particular, the limits that can be set on various dark energy scenarios are investigated. The possibility of distinguishing between different inverse power-law quintessence models is also studied. The predictions are based on calculations made with the Supernova Observation Calculator, a software package, introduced in the thesis, for simulating the light propagation from distant objects. This tool has also been used for investigating how SNAP observations could be biased by gravitational lensing, and to what extent this would affect cosmology fitting. An alternative approach for estimating cosmological parameters, where lensing effects are taken into account, is also suggested. Finally, it is investigated to what extent strongly lensed core-collapse supernovae could be used as an alternative approach for determining cosmological parameters.</p>