This thesis considers the various morphologies of radio supernova remnants (SNRs), and attempts to determine whether their appearance results from the properties of the progenitor star and its supernova explosion, or from the structure of the interstellar medium (ISM) and ambient magnetic field into which a SNR consequently expands. High-resolution observations of Supernova 1987A show a young remnant whose appearance and evolution are completely dominated by the structure of its progenitor wind. A statistical study of the Galactic population of bilateral SNRs demonstrates that the symmetry axes of these remnants run parallel to the Galactic Plane. This result can be explained by the interaction of main sequence stellar wind-bubbles with the ambient magnetic field; expansion of SNRs into the resulting elongated cavities results in a bilateral appearance with the observed alignment. Radio observations of SNR G296.8-00.3 show a double-ringed morphology which is best explained by expansion either into an anisotropic main-sequence progenitor wind or into multiple cavities in the ISM. Data on SNRs G309.2-00.6 and G320.4-01.2 (MSH 15-52) make a strong case that the appearance of both remnants is significantly affected by collimated outflows from a central source; for G309.2-00.6 the source itself is not detected, but for G320.4-01.2 there is now compelling evidence that the remnant is associated with and is interacting with the young pulsar PSR B1509-58. I conclude that, while the youngest SNRs are shaped by their progenitor's circumstellar material, the appearance of most SNRs reflects the properties of the local ISM and magnetic field. Remnants which interact with an associated pulsar or binary system appear to be rare, and are easily distinguished by their unusual and distorted morphologies.

La thèse présentée ici concerne la recherche et l'étude de jeunes vestiges de supernova à partir des observations menées avec l'instrument IBIS/ISGRI à bord du satellite européen gamma INTEGRAL. Ce travail de recherche porte sur deux thèmes principaux que sont<br />la nucléosynthèse et l'accélération de particules. Le premier thème est abordé par l'étude des raies émises lors de la décroissance radioactive du 44Ti, élément à courte durée de vie (Tau ~ 86 ans) exclusivement produit aux premiers instants du phénomène de supernova, et le deuxième par l'étude de l'émission continue non-thermique sous-jacente, preuve<br />observationnelle de l'accélération de particules au sein des vestiges de supernova. <br /><br />Le manuscrit est divisé en quatre parties. La première partie porte sur une présentation générale des<br />supernovae des points de vue observationnel et théorique. La deuxième partie décrit le satellite INTEGRAL et les principaux instruments à bord, les méthodes d'imagerie et de détection avec l'instrument IBIS/ISGRI, ainsi que mon investissement personnel sur<br />le développement d'outils spécifiques liés à l'analyse de données : la correction en énergie des évènements, cruciale pour l'étude des raies gamma comme celles issues de la décroissance du 44Ti, la recherche des pixels bruyants, importante pour l'étude de l'émission non-thermique à basse énergie autour de 20 keV,<br />la création de cartes de fond mesuré sur IBIS/ISGRI, et la mise en place d'une chaine de traitement alternative. Je présente également une méthode pour estimer le flux et la significativité d'une source étendue observée par un instrument à masque codé comme IBIS/ISGRI, ainsi qu'une première application de cette méthode sur l'amas de Coma. Les résultats obtenus sur les vestiges des<br />supernovae historiques tels que Cassiopeia A, Tycho, et Vela Junior sont exposés dans la troisième partie. Le premier chapitre de la dernière partie pose la problématique des jeunes vestiges de supernova manquants et présente une étude de la détectabilité des<br />supernovae dans le domaine visible, à partir d'un modèle d'extinction interstellaire galactique. Le deuxième chapitre rapporte les résultats de la recherche de jeunes vestiges de supernova dans le plan galactique par l'intermédiaire des raies de décroissance du 44Ti ainsi que par une approche multi-longueur d'onde, du domaine radio (VLA) à la nouvelle fenêtre d'observation au TeV (HESS). Je discusse également les contraintes apportées sur la fréquence des explosions et sur les<br />taux de production de cet élément, vis-à-vis des observations IBIS/ISGRI et de l'abondance solaire du 44Ca.

Thesis (Ph. D.)--University of Washington, 2000. / Vita. Includes bibliographical references (p. 183-190).

Reproduction de : Thèse de doctorat : Physique des particules : Lyon 1 : 2005. / Titre provenant de l'écran titre. 134 réf. bibliogr.

Theoretical models predict that some of the first stars ended their lives as extremely energetic pair-instability supernovae (PISNe). With energies approaching 10⁵³ ergs, these supernovae are expected to be within the detection limits of the upcoming James Webb Space Telescope (JWST), allowing observational constraints to be placed on the properties of the first stars. We estimate the source density of PISNe using a semi-analytic halo mass function based approach, accounting for the effects of feedback from star formation on the PISN rate using cosmological simulations. We estimate an upper limit of ~0.2 PISNe per JWST field of view at any given time. Feedback can reduce this rate significantly, e.g., lowering it to as little as one PISN per 4000 JWST fields of view for the most pessimistic explosion models. We also find that the main obstacle to observing PISNe from the first stars is their scarcity, not their faintness; exposures longer than a few times 10⁴ s will do little to increase the number of PISNe found. Given this we suggest a mosaic style search strategy for detecting PISNe from the first stars. Even rather high redshift PISNe are unlikely to be missed by moderate exposures, and a large number of pointings will be required to ensure a detection. / text

published_or_final_version / Physics / Master / Master of Philosophy

The ESSENCE survey discovered 213 type Ia supernovae at redshifts 0.10 < z < 0.81 between 2002 and 2008. We present their R and I band light curve measurements, obtained using the MOSAIC II imager at the CTIO 4 m, along with rapid response spectroscopy for each object from a range of large aperture ground based telescopes. We detail our program to obtain quantitative classifications and precise redshifts from our spectroscopic follow-up of each object. We describe our efforts to improve the precision of the calibration of the CTIO 4 m natural photometric system. We use several empirical metrics to measure our internal photometric consistency and our absolute calibration of the survey. We assess the effect of various sources of systematic error on our measured fluxes, and estimate that the total systematic error budget from the photometric calibration is ~1%. We combine 108 ESSENCE SNIa that pass stringent quality cuts with a compilation of 441 SNIa from 3 year results presented by the Supernova Legacy Survey and Baryon Acoustic Oscillation measurements from the Sloan Digital Sky Survey to produce preliminary cosmological constraints employing the SNIa . This constitutes the largest sample of well-calibrated, spectroscopically confirmed SNIa to date. Assuming a flat Universe, we obtain a joint constraint of \(\Omega_M = 0.266^{+0.026}_{-0.016}(stat 1\sigma)\), and \(w = -1.112^{+0.069}_{-0.072}(stat 1\sigma)\). These measurements are consistent with a cosmological constant. / Physics

In this thesis, the hydrodynamics of massive star interiors are explored. Our primary theoretical tool is multi-dimensional hydrodynamic simulation using realistic initial conditions calculated with the one-dimensional stellar evolution code, TYCHO. The convective shells accompanying oxygen and carbon burning are examined, including models with single as well as multiple, simultaneously burning shells. A convective core during hydrogen burning is also studied in order to test the generality of the flow characteristics. Two and three dimensional models are calculated. We analyze the properties of turbulent convection, the generation of internal waves in stably stratified layers, and the rate and character of compositional mixing at convective boundaries.

Core-collapse supernovae are some of the most energetic events in the Universe, they herald the birth of neutron stars and black holes, are a major site for nucleosynthesis, influence galactic hydrodynamics, and trigger further star formation. As such, it is important to understand the mechanism of explosion. Moreover, observations imply that asymmetries are, in the least, a feature of the mechanism, and theory suggests that multi-dimensional hydrodynamics may be crucial for successful explosions. In this dissertation, we present theoretical investigations into the multi-dimensional nature of the supernova mechanism. It had been suggested that nuclear reactions might excite non-radial g-modes (the ε-mechanism) in the cores of progenitors, leading to asymmetric explosions. We calculate the eigenmodes for a large suite of progenitors including excitation by nuclear reactions and damping by neutrino and acoustic losses. Without exception, we find unstable g-modes for each progenitor. However, the timescales for growth are at least an order of magnitude longer than the time until collapse. Thus, the ε-mechanism does not provide appreciable amplification of non-radial modes before the core undergoes collapse. Regardless, neutrino-driven convection, the standing accretion shock instability, and other instabilities during the explosion provide ample asymmetry. To adequately simulate these, we have developed a new hydrodynamics code, BETHE-hydro that uses the Arbitrary Lagrangian-Eulerian (ALE) approach, includes rotational terms, solves Poisson’s equation for gravity on arbitrary grids, and conserves energy and momentum in its basic implementation. By using time dependent arbitrary grids that can adapt to the numerical challenges of the problem, this code offers unique flexibility in simulating astrophysical phenomena. Finally, we use BETHE-hydro to investigate the conditions and criteria for supernova explosions by the neutrino mechanism. We find that a critical luminosity/ mass-accretion-rate condition distinguishes non-exploding from exploding models in hydrodynamic 1D and 2D simulations. Importantly, the critical luminosity for 2D simulations is found to be ∼70% of the critical luminosity for 1D simulations. We identify the specifics ofmulti-dimensional hydrodynamic simulations that enable explosions at lower neutrino luminosities in 2D and discuss how these results might foreshadow successful explosions by eventual 3D radiation-hydrodynamic simulations.

Supernovae of Type Ia, SNe Ia, are currently the most powerful tool of modern cosmology, but their progenitor scenario is not yet well constrained. Recent studies of SN Ia rates in radio-loud early-type galaxies, and members of rich clusters, suggest a possible influence on SN Ia explosions outside of the established correlation with the age of the parent galaxy's stellar population (via the current specific star formation rate, sSFR). These rates were used to show that the characteristics of SN Ia progenitor systems may be inconsistent with theoretical expectations of the most popular scenarios. The astrophysical question of this thesis is: do parent galaxy and environment influence the rates and properties of Type Ia supernovae, and, if so, how? Towards this end, we combine the database of Type Ia supernovae from the Canada-France-Hawaii Telescope's Supernova Legacy Survey with publicly available catalogs including: galaxy photometric and spectroscopic redshifts, radio and infrared sources, and members of galaxy groups and clusters. This is the most comprehensive set of multi-wavelength host properties and environment parameters for intermediate redshift Type Ia supernovae yet compiled. We present the SNLS SN Ia rate per unit mass in a variety of parent galaxy and environment samples. We also statistically assess the probability of discrepancies between our rates, those of previous works at low redshift, rates in the general population of galaxies, and predictions of established empirical SN Ia rate models. In general, we do not find statistically significant evidence for SN Ia rate enhancements over the general population in galaxies which are radio-loud, infrared-bright, or associated with galaxy groups and clusters. In cases where we do find a suggestive rate enhancement, it is always with less than 2-sigma confidence. These rates agree with established empirical rate models, which in turn are consistent with theoretical expectations of the most plausible progenitor scenarios. Furthermore, we find the properties of SNLS SNe Ia in these types of hosts and environments are consistent with the predictions of these scenarios. We conclude that, aside from the established correlation with host sSFR, no conclusive evidence is observed with SNLS data for strictly environmental effects on SN Ia rates. This supports their continued status as cosmological standard candles.