Depuis leur découverte en 1912, l'origine des rayons cosmiques, composés à 90% de protons, n'est toujourspas connue. Les vestiges de supernovae sont de bons candidats à la production des rayons cosmiquesgalactiques.Pour étudier les sites de production des protons, sensibles aux champ magnétiques, nous nousappuyons sur les rayons gamma (neutres et stables).L'onde de choc créée par l'explosion de la supernova se propage dans un milieu interstellairedense, les nuages moléculaires, pouvant être concidéré comme une cible pour les protons accélérés.L'objectif de ce travail est de rechercher des sites d'émission gamma en coïncidence avec des vestiges etdes nuages moléculaires.Nous avons utilisé pour cela les données du télescope spatial Fermi-LAT et du télescopes au solH.E.S.S.L'analyse conjointe des données a permis de tirer profit des points forts de chaque intrument.La production d'images de la région du ciel étudié est primordiale en astronomie.Nous avons tenté d'améliorer la production des images obtenues avec l'imageur H.E.S.S. en proposant uneméthode de lissage différente de celle employée actuellement. / Since their discovery in 1912, the cosmic rays origin is still unknown.Supernovae remnants (SNR) are good candidates to product Galactic cosmic rays.Because protons are sensitive to magnetic field, we lean on gamma rays, neutrals and stables particles.The shock wave of the SNR go through the interstellar medium which can be dense: the molecular clouds.They can be seen as target for accelerated protons.The objective of this work is to search for gamma-ray emission in coincidence with remnants and molecularclouds.We analysed data from Fermi-LAT space telescope and H.E.S.S., a Tcherenkov ground based telescope.The data joined analysis allow us to get the strong point out of each instrument.The sky view produced from the data is very important in astronomy.We tryied to improve the smoothing method of the images performed in H.E.S.S. analysis.

Les étoiles de type solaire se forment par l'effondrement d'un nuage moléculaire, durant lequel la matière s'organise autour de l'étoile en formation sous la forme d'un disque, appelé disque protoplanétaire. Dans ce disque se forment les planètes, comètes et autres objets du système stellaire. La nature de ces objets peut donc avoir un lien avec l'histoire de la matière du disque.J'ai étudié l'évolution chimique et physique de cette matière, du nuage au disque, à l'aide du code de chimie gaz-grain Nautilus.Une étude de sensibilité à divers paramètres du modèle (comme les abondances élémentaires et les paramètres de chimie de surface) a été réalisée. Notamment, la mise à jour des constantes de vitesse et des rapports de branchement des réactions de notre réseau chimique s'est avérée influente sur de nombreux points, comme les abondances de certaines espèces chimiques, et la sensibilité du modèle à ses autres paramètres.Plusieurs modèles physiques d'effondrement ont également été considérés. L'approche la plus complexe et la plus consistante a été d'interfacer notre code de chimie avec le code radiatif magnétohydrodynamique de formation stellaire RAMSES, pour modéliser en trois dimensions l'évolution physique et chimique de la formation d'un jeune disque. Notre étude a démontré que le disque garde une trace de l'histoire passée de la matière, et sa composition chimique est donc sensible aux conditions initiales. / Low mass stars, like our Sun, are born from the collapse of a molecular cloud. The matter falls in the center of the cloud, creating a protoplanetary disk surrounding a protostar. Planets and other solar system bodies will be formed in the disk.The chemical composition of the interstellar matter and its evolution during the formation of the disk are important to better understand the formation process of these objects.I studied the chemical and physical evolution of this matter, from the cloud to the disk, using the chemical gas-grain code Nautilus.A sensitivity study to some parameters of the code (such as elemental abundances and parameters of grain surface chemistry) has been done. More particularly, the updates of rate coefficients and branching ratios of the reactions of our chemical network showed their importance, such as on the abundances of some chemical species, and on the code sensitivity to others parameters.Several physical models of collapsing dense core have also been considered. The more complex and solid approach has been to interface our chemical code with the radiation-magneto-hydrodynamic model of stellar formation RAMSES, in order to model in three dimensions the physical and chemical evolution of a young disk formation. Our study showed that the disk keeps imprints of the past history of the matter, and so its chemical composition is sensitive to the initial conditions.

A two-dimensional hydrodynamic numerical model is extended and applied to simulate the interaction between stellar winds and the interstellar medium (ISM). In particular, the stellar wind evolution of O- and B-type stars is calculated. First, the evolution of a stellar wind into the ambient interstellar medium and also a more dense molecular cloud are considered for the case of no relative motion between the star and the interstellar medium. This interaction results in a cavity being blown into the ISM. Of importance in this work is the boundary radius (astropause) of the stellar wind and also the location where the outflow speed decreases from supersonic to subsonic speeds, called the termination shock. Different parameters like ISM density, outflow speed and mass-loss rate were varied to study the effect these have on the computed astropause (AP) and termination shock (TS) radii. The evolution of these structures is presented up to a simulation time of 1 My. However, stars are not stationary relative to the ISM, and the evolution of stellar winds into the interstellar medium including relative motion is also considered. It is shown that the positions of the TS and AP are dependent on the mass-loss rate and stellar wind outflow speed of the star and the interstellar medium density and relative speed. When these massive stars reach the end of their life, they end their life in a supernova explosion. The explosion results in a blast wave moving outward, called the forward shock (FS) and a reverse shock (RS) also forms which moves inward. Previous work done by Ferreira and de Jager (2008) to simulate supernova remnant (SNR) evolution, was only done for the case of evolution into the undisturbed ISM (no cavity). In this work, the evolution of SNR is simulated taking also into account the pre-existing cavity blown out by the stellar winds of these massive stars. The results of this study showed that the evolution of the SNR is definitely influenced by the presence of a stellar wind cavity even if the cavity is only a few pc in extent. / Thesis (MSc (Space Physics))--North-West University, Potchefstroom Campus, 2011.

A two-dimensional hydrodynamic numerical model is extended and applied to simulate the interaction between stellar winds and the interstellar medium (ISM). In particular, the stellar wind evolution of O- and B-type stars is calculated. First, the evolution of a stellar wind into the ambient interstellar medium and also a more dense molecular cloud are considered for the case of no relative motion between the star and the interstellar medium. This interaction results in a cavity being blown into the ISM. Of importance in this work is the boundary radius (astropause) of the stellar wind and also the location where the outflow speed decreases from supersonic to subsonic speeds, called the termination shock. Different parameters like ISM density, outflow speed and mass-loss rate were varied to study the effect these have on the computed astropause (AP) and termination shock (TS) radii. The evolution of these structures is presented up to a simulation time of 1 My. However, stars are not stationary relative to the ISM, and the evolution of stellar winds into the interstellar medium including relative motion is also considered. It is shown that the positions of the TS and AP are dependent on the mass-loss rate and stellar wind outflow speed of the star and the interstellar medium density and relative speed. When these massive stars reach the end of their life, they end their life in a supernova explosion. The explosion results in a blast wave moving outward, called the forward shock (FS) and a reverse shock (RS) also forms which moves inward. Previous work done by Ferreira and de Jager (2008) to simulate supernova remnant (SNR) evolution, was only done for the case of evolution into the undisturbed ISM (no cavity). In this work, the evolution of SNR is simulated taking also into account the pre-existing cavity blown out by the stellar winds of these massive stars. The results of this study showed that the evolution of the SNR is definitely influenced by the presence of a stellar wind cavity even if the cavity is only a few pc in extent. / Thesis (MSc (Space Physics))--North-West University, Potchefstroom Campus, 2011.